Showing 1–50 of 210 results for author: Estrada, J

Regression with Observational Multilayered Network Data

Authors: Juan Estrada, Kim Huynh, David Jacho-Chavez, Leonardo Sanchez-Aragon

Abstract: A novel method to estimate social effect coefficients in the popular so-called linear-in-means regression model in the Social Sciences is presented here that utilizes non-experimental multidimensional network data. The procedure can accommodate social interactions that correlate with the error in the model by making use of a different set of network links among the same observations that are exoge… ▽ More A novel method to estimate social effect coefficients in the popular so-called linear-in-means regression model in the Social Sciences is presented here that utilizes non-experimental multidimensional network data. The procedure can accommodate social interactions that correlate with the error in the model by making use of a different set of network links among the same observations that are exogenous in the traditional sense. In particular, the full observability of a two-layered multiplex network data structure is assumed here to propose a new Generalized 3-Stage Least Squares (G3SLS) estimator that is consistent, asymptotically normally distributed, and also easy to implement using widely-used existing statistical software because of its closed-form definition. The underlying assumptions are general enough to accommodate common problems with observational data such as measurement error, simultaneity, and unobserved heterogeneity. Monte Carlo exercises confirm the good small sample performance of the proposed G3SLS estimator in these scenarios. An empirical application finds positive and significant peer effects in citations among research articles published in top general-interest journals in economics. △ Less

Submitted 2 August, 2026; originally announced August 2026.

Comments: Forthcoming in 'Econometrics and Statistics'

Estimating Peer Influence in Multilayer Networks

Authors: Weihua An, Pablo Estrada, Juan Estrada, David Jacho-Chavez

Abstract: This paper proposes a model-based empirical method to identify influential individuals in risky behaviors. To determine the most influential individuals, we estimate peer influence using observational cross-sectional data from multiple social connections. Our empirical strategy employs the observed characteristics of distant individuals across multiple social networks as instruments to address the… ▽ More This paper proposes a model-based empirical method to identify influential individuals in risky behaviors. To determine the most influential individuals, we estimate peer influence using observational cross-sectional data from multiple social connections. Our empirical strategy employs the observed characteristics of distant individuals across multiple social networks as instruments to address the endogeneity arising from homophily. Using Add Health data, we find positive peer effects from friends and classmates on both cigarette smoking and marijuana use. Based on the estimated peer effects, we characterize the influencers in our sample. △ Less

Submitted 2 August, 2026; originally announced August 2026.

Comments: 32 pages, 3 figures, 12 tables

Journal ref: Social Networks, 2026, (86), pp. 252-265

Estimating Social Effects with Randomized and Observational Network Data

Authors: TszKin Julian Chan, Juan Estrada, Kim Huynh, David Jacho-Chavez, Chungsang Tom Lam, Leonardo Sanchez-Aragon

Abstract: This paper introduces an innovative approach to identifying and estimating the parameters of interest in the widely recognized linear-in-means regression model under conditions where the initial randomization of peers determines the observed network. We assert that peers who are initially randomized do not produce social effects. However, after randomization, agents can endogenously develop signif… ▽ More This paper introduces an innovative approach to identifying and estimating the parameters of interest in the widely recognized linear-in-means regression model under conditions where the initial randomization of peers determines the observed network. We assert that peers who are initially randomized do not produce social effects. However, after randomization, agents can endogenously develop significant connections that potentially generate peer influences. We present a moment condition that compiles local heterogeneous identifying information for all agents within the population. Under the assumption of $ψ$-dependence in the endogenous network space, we propose a Generalized Method of Moments (GMM) estimator, which is proven to be consistent, asymptotically normally distributed, and straightforward to implement using commonly available statistical software due to its closed-form expression. Monte Carlo simulations demonstrate the GMM estimator's strong small-sample performance. An empirical analysis utilizing data from Hong Kong high school students reveals substantial positive spillover effects on math test scores among study partners in our sample, provided that their seatmates were exogenously assigned by their teachers. △ Less

Submitted 2 August, 2026; originally announced August 2026.

Comments: 42 pages (main manuscript), 34 pages (supplemental materials)

Journal ref: Journal of Econometric Methods, Volume 13, Number 2, Pages 205-224, October 2024

In situ cryogenic characterization of proton damage in thick p-channel skipper CCDs

Authors: Brandon M. Roach, Brenda Cervantes Vergara, Alex Drlica-Wagner, Phoenix Alpine, Ana Martina Botti, Claudio Chavez, Julian Cuevas-Zepeda, Juan Estrada, Guillermo Fernandez Moroni, Nora Hoch, Stephen E. Holland, Blas Irigoyen Gimenez, Agustin Lapi, Santiago Perez, Nathan Saffold, Javier Tiffenberg, Yikai Wu

Abstract: Skipper charge-coupled devices (CCDs) are an offshoot of standard silicon pixel detectors and are capable of performing repeated non-destructive charge measurements, enabling deeply sub-electron readout noise. This capability has opened the door to single-photon counting from the near-infrared ($\sim$1.1\,$μ$m) to the soft X-ray (several keV), making these devices strong candidates for future astr… ▽ More Skipper charge-coupled devices (CCDs) are an offshoot of standard silicon pixel detectors and are capable of performing repeated non-destructive charge measurements, enabling deeply sub-electron readout noise. This capability has opened the door to single-photon counting from the near-infrared ($\sim$1.1\,$μ$m) to the soft X-ray (several keV), making these devices strong candidates for future astronomical instruments operating in the photon-starved limit. Furthermore, the p-channel architecture used to fabricate Skipper CCDs on n-type silicon has been demonstrated to have an increased hardness to the intense radiation environment of space. Building upon previous irradiation campaigns on room-temperature sensors, here we describe the first radiation-hardness tests of p-channel skipper CCDs at their cryogenic operating temperatures. We assess the performance of the floating-gate output stage and global CCD parameters (charge transfer inefficiency, dark current, hot pixels, and charge traps). We find that these devices maintain excellent performance after displacement damage doses equivalent to ${\sim}$10 years at the Earth/Sun L2 Lagrange point, demonstrating for the first time that these sensors remain radiation-hard in realistic deep-space thermal and radiation environments. △ Less

Submitted 24 June, 2026; originally announced June 2026.

Comments: 33 pages, 9 figures. Prepared for submission to JATIS

Report number: FERMILAB-PUB-26-0399-PPD

Limits of constant-parameter constitutive models for hydrogels under inertial cavitation

Authors: Tianyi Chu, Joseph Beckett, Zhiren Zhu, Jonathan B. Estrada, Spencer H. Bryngelson

Abstract: Mechanical characterization of soft materials at high strain rates is challenging due to their high compliance, nonlinear viscoelastic behavior, and potentially history-dependent responses. Inertial microcavitation rheometry (IMR) addresses this challenge by coupling laser-induced cavitation (LIC) experiments with numerical simulations of bubble dynamics models to infer constitutive models and mat… ▽ More Mechanical characterization of soft materials at high strain rates is challenging due to their high compliance, nonlinear viscoelastic behavior, and potentially history-dependent responses. Inertial microcavitation rheometry (IMR) addresses this challenge by coupling laser-induced cavitation (LIC) experiments with numerical simulations of bubble dynamics models to infer constitutive models and material parameters. Both IMR and its variants infer parameters that depend on the chosen fitting window, which suggests that a constant-parameter constitutive model is insufficient to describe the full cavitation event. We use this window dependence to identify when the constant-parameter assumption fails, rather than to report a single effective parameter set. The constitutive parameters are estimated over moving, overlapping windows using a modified iterative ensemble Kalman smoother with multiple data assimilation (MIEnKS-MDA). Within the neo-Hookean Kelvin--Voigt (NHKV) constitutive model, we obtain time-resolved estimates of the constitutive response in polyacrylamide (PAAm) hydrogels with different crosslinker concentrations. The inferred shear modulus and viscosity generally decrease and then plateau during cavitation, while exhibiting relatively weak temperature sensitivity. For gelatin gels, by contrast, the inferred property evolution shows a pronounced temperature dependence, with distinct trends at low and high temperatures. Moreover, both the apparent shear modulus and viscosity exhibit significant variations during the first two bubble collapses. These results show that time-resolved parameter estimation within the prescribed NHKV constitutive structure can diagnose where the constant-parameter model assumption falls short during cavitation, thereby guiding the development of improved physics-based models of complex bubble--material interactions. △ Less

Submitted 11 June, 2026; originally announced June 2026.

Characterization of Spurious Charge in SENSEI Skipper-CCDs

Authors: Yikai Wu, Ansh Desai, Sho Uemura, Ana M. Botti, Brenda A. Cervantes-Vergara, Fernando Chierchie, Alex Drlica-Wagner, Rouven Essig, Juan Estrada, Erez Etzion, Guillermo Fernandez Moroni, Miqueas Gamero, Stephen E. Holland, Ian Lawson, Steffon Luoma, Nathan A. Saffold, Miguel Sofo-Haro, Javier Tiffenberg, Tomer Volansky

Abstract: Skipper Charge-Coupled Devices (Skipper-CCDs) are a leading technology in the search for sub-GeV dark matter and coherent elastic neutrino-nucleus scattering. A key background for rare-event searches with these detectors arises from "spurious charge" -- single-electron events generated when charges are transferred through the active region to the serial register, and across the serial register to… ▽ More Skipper Charge-Coupled Devices (Skipper-CCDs) are a leading technology in the search for sub-GeV dark matter and coherent elastic neutrino-nucleus scattering. A key background for rare-event searches with these detectors arises from "spurious charge" -- single-electron events generated when charges are transferred through the active region to the serial register, and across the serial register to the readout stage. We present a characterization of spurious charge in both the active region and the serial register of SENSEI Skipper-CCDs, and show that, in a well-shielded low-background environment, the dominant contribution originates in the serial register during Skipper readout, when horizontal clocks are held at constant voltage between pixel transfers. Motivated by this finding, we develop a "tri-level" clocking scheme in which the held-low phase is raised to an intermediate voltage during readout to suppress trap-mediated charge generation. Using the SENSEI detector near the MINOS cavern, we measure a serial-register single-electron density of $(2.9 \pm 0.1) \times 10^{-5}$ electrons/pixel/image under standard SENSEI readout conditions, reduced to $(4.0 \pm 0.4) \times 10^{-6}$ electrons/pixel/image with tri-level clocking -- a factor of $\sim$7 improvement. This technique offers a promising path to lower backgrounds in current and future Skipper-CCD experiments. △ Less

Submitted 28 May, 2026; originally announced May 2026.

Comments: 10 pages + references, 9 figures

Report number: FERMILAB-PUB-26-0349-PPD

PIU: Proximity-guided Identity Unlearning in ID-Conditioned Diffusion Models

Authors: Jose Edgar Hernandez Cancino Estrada, Mauro Díaz Lupone, Žiga Emeršič, Vitomir Štruc, Peter Peer, Darian Tomašević

Abstract: Identity-conditioned diffusion models enable high-quality and identity-consistent face generation, but they also raise severe privacy concerns, as models may continue to synthesize individuals despite their right to be forgotten. While machine unlearning has been extensively studied for concept and data removal, identity unlearning remains largely unexplored, particularly in models conditioned dir… ▽ More Identity-conditioned diffusion models enable high-quality and identity-consistent face generation, but they also raise severe privacy concerns, as models may continue to synthesize individuals despite their right to be forgotten. While machine unlearning has been extensively studied for concept and data removal, identity unlearning remains largely unexplored, particularly in models conditioned directly on identity embeddings rather than text prompts. In this work, we study identity unlearning in Arc2Face, a state-of-the-art identity-conditioned latent diffusion model for face generation, and introduce Proximity-guided Identity Unlearning (PIU), an anchor-guided framework for identity unlearning. Specifically, we formulate identity removal as an identity replacement objective that reassigns the source identity to a selected anchor identity in the learned identity space, and we complement it with a proximity-based anchor selection strategy motivated by the geometry of ArcFace representations. We further show that effective unlearning can be achieved through localized fine-tuning of a small subset of identity-sensitive cross-attention layers. Experiments across many target identities show that our framework effectively suppresses generation of the target identity while preserving realism and identity consistency for retained identities, as validated by improved performance on unlearning and image-quality metrics, together with qualitative evaluation. The source code for the PIU framework is publicly available at https://github.com/edgarcancinoe/piu_unlearning . △ Less

Submitted 21 May, 2026; originally announced May 2026.

The DAMSA Experiment

Authors: Prithak Bhattarai, Andrew Brandt, Alan Bross, Bradley Brown, Samriddha Chakraborty, Haohui Che, Bhupal Dev, Bhaskar Dutta, Juan V. Estrada, Eric Garcia, Anthony Gomez, Gajendra Gurung, Brian Joshua Gomez Hernandez, Wooyoung Jang, Jay Hyun Jo, Krzysztof Jodłowski, Doojin Kim, Eunsu Kim, Hyunyong Kim, Shin Hyung Kim, Young-Kee Kim, Jing Liu, Chang-Seong Moon, Donna Naples, David Nygren , et al. (19 additional authors not shown)

Abstract: DAMSA (DArk Messenger Searches at an Accelerator) is a novel short-baseline accelerator/beam dump experiment aimed at probing short-lived physics processes, including searches for evidence of a dark sector of particle physics and well-motivated rare Standard Model signals. Motivated by open questions in neutrino physics and the absence of conclusive evidence for conventional weakly interacting mas… ▽ More DAMSA (DArk Messenger Searches at an Accelerator) is a novel short-baseline accelerator/beam dump experiment aimed at probing short-lived physics processes, including searches for evidence of a dark sector of particle physics and well-motivated rare Standard Model signals. Motivated by open questions in neutrino physics and the absence of conclusive evidence for conventional weakly interacting massive particles, DAMSA targets MeV-to-sub-GeV dark-sector messengers with feeble couplings that can be produced in abundance at a beam dump/target. By employing an ultra-short baseline, DAMSA is uniquely positioned to overcome the beam-dump "ceiling" that limits sensitivity to fast decaying particles in longer-baseline experiments. The conceptual design emphasizes a beam-dump production scheme combined with a compact detector optimized for rare decays while mitigating intense neutron-induced backgrounds, inherent to high-power proton beams. To validate the experimental strategy and detector technologies, the DAMSA Path-Finder (DPF) proof-of-concept experiment is also proposed, focusing on axion-like particles decaying to two photons, as the benchmark physics case and operating with 8 GeV electron beams at SLAC Linac-to-ESA (LESA) facility. Successful realization of DPF will establish the feasibility of the DAMSA approach, enabling a broad and powerful program to explore short-lived new physics and precision Standard Model processes in a previously inaccessible regime. This paper outlines the technical details of DAMSA's physics goals, key experimental challenges, and how to overcome them. △ Less

Submitted 30 April, 2026; originally announced April 2026.

Comments: 35 pages, 26 figures. arXiv admin note: substantial text overlap with arXiv:2601.15255

Report number: NIMA-D-26-00502

MAS-CCD: New technique for measuring low-level charge content based on the multiple amplifier architecture

Authors: Miqueas E. Gamero, Guillermo Fernández Moroni, Fernando Chierchie, Agustin J. Lapi, Blas J. Irigoyen Gimenez, Juan Estrada, Javier Tiffenberg

Abstract: Low-noise detectors are a key technology for the next generation of astronomical instruments aimed at spectroscopy of faint objects and the search for exoplanets. In this context, the multiple-amplifier sensing charge-coupled device (MAS-CCD) emerges as a promising technology for future scientific instruments. A critical parameter affecting the performance of these devices is spurious charge, prod… ▽ More Low-noise detectors are a key technology for the next generation of astronomical instruments aimed at spectroscopy of faint objects and the search for exoplanets. In this context, the multiple-amplifier sensing charge-coupled device (MAS-CCD) emerges as a promising technology for future scientific instruments. A critical parameter affecting the performance of these devices is spurious charge, produced by the clocking of the gates. Its measurement is typically challenging with existing methods. In practice, the optimization of this parameter often relies on empirical procedures that require significant time and careful consideration of the trade-off with full-well capacity. In this work, we present a new technique to estimate spurious charge based on covariance analysis of the output amplifiers of the MAS-CCD, which measures the same charge packet in different amplifiers at different times. The method enables fast and precise measurements of spurious charge under operating conditions where conventional approaches are difficult to apply. We develop the theoretical framework of the method and validate the model through simulations. The results demonstrate the feasibility of this approach and suggest that it could serve as a basis for reliable large-scale characterization of sensor performance. △ Less

Submitted 14 April, 2026; originally announced April 2026.

Report number: FERMILAB-PUB-26-0148

X-ray Response of the Fully-Depleted, p-Channel SiSeRO-CCD

Authors: Julian Cuevas-Zepeda, Joseph Noonan, Claudio Chavez, Miguel Sofo-Haro, Nathan Saffold, Juan Estrada, Kevan Donlon, Chris Leitz, Steve Holland

Abstract: We present an X-ray characterization of a fully depleted, 725 $μ$m thick p-channel SiSeRO-CCD. Measurements with a $^{55}$Fe source yield an energy resolution of $54 \pm 0.9$ eV ($14.6 \pm 0.25 e^{-}$) at 5.9 keV for single-pixel events, indicating that the SiSeRO amplifier preserves the intrinsic charge resolution of the CCD under multi-sample non-destructive readout. Characterization with a… ▽ More We present an X-ray characterization of a fully depleted, 725 $μ$m thick p-channel SiSeRO-CCD. Measurements with a $^{55}$Fe source yield an energy resolution of $54 \pm 0.9$ eV ($14.6 \pm 0.25 e^{-}$) at 5.9 keV for single-pixel events, indicating that the SiSeRO amplifier preserves the intrinsic charge resolution of the CCD under multi-sample non-destructive readout. Characterization with a $^{241}$Am source extends the response to higher-energy photons, with reconstructed spectral features observed between 9-26 keV and the 59.5 keV $γ$ emission. These measurements, together with a muon-derived diffusion calibration, show that charge transport and diffusion are consistent with interactions spanning the full sensor depth. These results demonstrate that the SiSeRO-CCD simultaneously achieves sub-electron noise performance and efficient charge collection in a thick, fully depleted silicon detector. This combination enables X-ray spectroscopy across a broad energy range while maintaining sensitivity to faint signals. △ Less

Submitted 6 June, 2026; v1 submitted 2 April, 2026; originally announced April 2026.

Report number: FERMILAB-PUB-26-0218-PPD

A Sub-electron-noise Skipper-CCD Readout ASIC with Improved Channel-to-channel Isolation and an Integrated Cryogenic Voltage Reference

Authors: Fabricio Alcalde Bessia, Claudio Chavez, Troy England, Hongzhi Sun, Andrew Lathrop, Davide Braga, Miguel Sofo-Haro, Juan Estrada, Farah Fahim

Abstract: The MIDNA application specific integrated circuits (ASICs) are a series of skipper-CCD readout chips fabricated in a 65 nm low-power CMOS process that implement a correlated double sampling signal processing chain based on dual-slope integrators. They are capable of working from room to cryogenic temperatures, down to 84 K. The present iteration of the ASIC has been fabricated including several de… ▽ More The MIDNA application specific integrated circuits (ASICs) are a series of skipper-CCD readout chips fabricated in a 65 nm low-power CMOS process that implement a correlated double sampling signal processing chain based on dual-slope integrators. They are capable of working from room to cryogenic temperatures, down to 84 K. The present iteration of the ASIC has been fabricated including several design updates and the addition of an on-chip voltage reference, resulting in improved performance. This work presents the main vulnerabilities solved, the changes carried out, and the resulting performance benefits. Measurements with a skipper-CCD and the ASIC at 140 K showed that the single-electron resolution can be reached by averaging the measured charge in the analog domain using the analog pile-up technique with a readout noise as low as 0.11 erms of equivalent charge for 1200 samples. The channel-to-channel crosstalk was also characterized showing values better than -62 dB. △ Less

Submitted 19 March, 2026; originally announced March 2026.

Comments: Submitted to IEEE Instrumentation and Measurements. 8 pages, 10 figures, previous publication: arXiv:2304.13088

Report number: FERMILAB-PUB-25-0752-ETD-PPD

Latin American HECAP Physics Briefing Book 2025

Authors: Mario A. Acero, Alexis A. Aguilar-Arevalo, Belén Andrada, Andrés Baquero Larriva, Mauro Cambiaso, Edgar Carrera, Melissa Cruz, Lucía Duarte, Juan Estrada, Alberto Gago, Esteban Jimenez, Diana López Nacir, José A. López, Marta Losada, Fernando Monticelli, Deywis Moreno, Martjin Mulders, Luis A. Núñez, Arturo S. Pineda, Juan Ponciano, Farinaldo Queiroz, Rogerio Rosenfeld, Sandro F. de Souza, Martin Alfonso Subieta Vasquez, Maria Elena Tejeda-Yeomans , et al. (2 additional authors not shown)

Abstract: The first process for the Latin American Strategy Forum for Research Infrastructure for High Energy, Cosmology and Astroparticle Physics (LASF4RI-HECAP) came to a conclusion in October 2020, with a Physics Briefing Book (PBB) presented in (2104.06852). Here we present an updated PBB, the result of the first update of LASF4RI-HECAP. The update process began with a call for White Papers from the HEC… ▽ More The first process for the Latin American Strategy Forum for Research Infrastructure for High Energy, Cosmology and Astroparticle Physics (LASF4RI-HECAP) came to a conclusion in October 2020, with a Physics Briefing Book (PBB) presented in (2104.06852). Here we present an updated PBB, the result of the first update of LASF4RI-HECAP. The update process began with a call for White Papers from the HECAP community. The submitted contributions were presented at the III LASF4RI for HECAP Symposium: Update of the Strategic Plan, held at ICTP-SAIFR in São Paulo in August 26-29, 2024, with the participation of the Preparatory Group, High Level Strategy Group, Funding Agencies and representatives of similar efforts from around the globe. This updated PBB was written by the Preparatory Group based mainly on 46 White Papers submitted by the community and is organized around seven working groups: Astronomy, Astrophysics and Astroparticle Physics; Cosmology; Dark Matter; Neutrinos; Electroweak and Strong Interactions, Higgs Physics, CP and Flavour Physics and BSM; Instrumentation and Computing; Advanced Training and Capacity Building. It is intended to provide the essential input for the creation of a long-term HECAP strategy in the region. △ Less

Submitted 6 March, 2026; originally announced March 2026.

DESI DR2 Baryon Acoustic Oscillations from the Lyman Alpha Forest Multipoles

Authors: N. G. Karaçaylı, A. Cuceu, J. Aguilar, S. Ahlen, S. Bailey, S. BenZvi, D. Bianchi, A. Brodzeller, D. Brooks, T. Claybaugh, A. de la Macorra, Biprateep Dey, P. Doel, J. Estrada, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, A. X. Gonzalez-Morales, G. Gutierrez, C. Hahn, H. K. Herrera-Alcantar, K. Honscheid, C. Howlett , et al. (33 additional authors not shown)

Abstract: We present an alternative measurement of the Baryon Acoustic Oscillation (BAO) using the Legendre multipole representation of the Ly$α$ forest correlation functions from the second data release (DR2) of the Dark Energy Spectroscopic Instrument survey. Compressing the auto- and cross-correlation functions into Legendre multipoles yields a positive-definite covariance matrix without any smoothing --… ▽ More We present an alternative measurement of the Baryon Acoustic Oscillation (BAO) using the Legendre multipole representation of the Ly$α$ forest correlation functions from the second data release (DR2) of the Dark Energy Spectroscopic Instrument survey. Compressing the auto- and cross-correlation functions into Legendre multipoles yields a positive-definite covariance matrix without any smoothing -- unlike the baseline DR2 analysis -- thanks to a significantly reduced data vector size. We introduce the statistical corrections required to debias the finite-sample covariance matrix estimate and demonstrate that monopole and quadrupole terms for both auto- and cross-correlations can be used even when the correlation functions are distorted by continuum errors and contaminated by metals. This formalism has slightly diminished the constraining power of the BAO scale, while considerably weakening constraints on nuisance parameters. We measure the isotropic BAO scale with $0.93\%$ precision at $z_\mathrm{eff}=2.35$, the Hubble parameter $H(z_\mathrm{eff})=(239.5\pm3.4)~(147.09~\mathrm{Mpc}/r_d) ~\mathrm{km~s}^{-1}~\text{Mpc}^{-1}$, and the transverse comoving distance $D_M(z_\mathrm{eff})=(5.80 \pm 0.10)~(r_d/147.09~\mathrm{Mpc})$~Gpc for a given value of the sound horizon ($r_d$). Our BAO results are entirely consistent with the baseline DR2 analysis. △ Less

Submitted 30 June, 2026; v1 submitted 4 March, 2026; originally announced March 2026.

Comments: 15 pages, 7 figures

Finite-time thermal refrigerator in interacting Bose-Einstein Condensates

Authors: Joaquín I. Ganly, Julián Amette Estrada, Franco Mayo, Augusto J. Roncaglia, Pablo D. Mininni

Abstract: We study a finite-time thermodynamic refrigeration cycle realized numerically in three-dimensional, weakly interacting Bose-Einstein condensates (BECs). The setup consists of three spatially separated condensates -- system, piston, and reservoir -- coupled through time-dependent potential barriers that implement compression, expansion, and contact strokes. Finite-temperature initial states are gen… ▽ More We study a finite-time thermodynamic refrigeration cycle realized numerically in three-dimensional, weakly interacting Bose-Einstein condensates (BECs). The setup consists of three spatially separated condensates -- system, piston, and reservoir -- coupled through time-dependent potential barriers that implement compression, expansion, and contact strokes. Finite-temperature initial states are generated with the Stochastic Ginzburg-Landau equation, and the subsequent dynamics are evolved using the truncated Gross-Pitaevskii equation. To measure temperatures we use a momentum-space thermometry method that provides estimates for each condensate. We find that despite mass transfer and sound excitations, the protocol achieves successful cooling during consecutive cycles: the first cycle lowers its temperature by ~20%, and a second cycle yields additional, though reduced, cooling, reaching a final ~27% cooling from the initial state. Our results show that interacting BECs can sustain finite-time quantum thermal cycles under realistic conditions, and provide a platform for exploring different refrigeration schemes, optimized control protocols, and shortcuts to adiabaticity. △ Less

Submitted 26 February, 2026; originally announced February 2026.

Comments: 9 pages, 7 figures

Report number: 013315

X-ray characterization of fully-depleted p-channel Skipper-CCDs for the DarkNESS mission

Authors: Phoenix Alpine, Ana M. Botti, Brenda A. Cervantes-Vergara, Claudio R. Chavez, Fernando Chierchie, Alex Drlica-Wagner, Juan Estrada, Erez Etzion, Michael Lembeck, Pilar López Maggi, Joseph Noonan, Brandon Roach, Nathan Saffold, Javier Tiffenberg

Abstract: The Dark matter Nanosatellite Equipped with Skipper Sensors (DarkNESS) mission is a 6U CubeSat designed to search for X-ray lines from decaying dark matter using Skipper-CCDs. Thick, fully-depleted p-channel Skipper-CCDs provide low readout noise and high quantum efficiency for 1-10 keV X-rays, but their X-ray performance has not yet been demonstrated in the space environment. DarkNESS will operat… ▽ More The Dark matter Nanosatellite Equipped with Skipper Sensors (DarkNESS) mission is a 6U CubeSat designed to search for X-ray lines from decaying dark matter using Skipper-CCDs. Thick, fully-depleted p-channel Skipper-CCDs provide low readout noise and high quantum efficiency for 1-10 keV X-rays, but their X-ray performance has not yet been demonstrated in the space environment. DarkNESS will operate in low-Earth orbit, where trapped protons induce displacement damage in the sensor that increases charge-transfer inefficiency and degrades the X-ray energy resolution. This work measures the X-ray line response of Skipper-CCDs before and after proton irradiation and quantifies the associated degradation. A sensor was exposed to 217 MeV protons at a fluence of 8.4 x 10^10 protons cm^-2, corresponding to a displacement-damage dose more than an order of magnitude above the three-year expectation for representative mid-inclination and Sun-synchronous low-Earth orbits. A 55Fe source was used to compare the energy resolution of the beam-exposed quadrant to adjacent unexposed quadrants and a non-irradiated reference sensor. These measurements provide a quantitative assessment of radiation-induced spectral degradation in Skipper-CCDs and enable an estimate of the end-of-life X-ray energy resolution expected for DarkNESS operation in low-Earth orbit. △ Less

Submitted 2 February, 2026; originally announced February 2026.

DAMSA Experiment Conceptual Design White Paper

Authors: Prithak Bhattarai, Andrew Brandt, Alan Bross, Bradley Brown, Samriddha Chakraborty, Haohui Che, Bhupal Dev, Bhaskar Dutta, Juan V. Estrada, Eric Garcia, Anthony Gomez, Gajendra Gurung, Brian Joshua Gomez Hernandez, Wooyoung Jang, Jay Hyun Jo, Krzysztof Jodłowski, Doojin Kim, Eunsu Kim, Hyunyong Kim, Shin Hyung Kim, Young-Kee Kim, Jing Liu, Chang-Seong Moon, Donna Naples, David Nygren , et al. (19 additional authors not shown)

Abstract: DAMSA (DArk Messenger Searches at an Accelerator) is a novel short-baseline accelerator experiment aimed at probing short-lived physics processes, including searches for evidence of a dark sector of particle physics and well-motivated Standard Model signals. Motivated by open questions in neutrino physics and the absence of conclusive evidence for conventional weakly interacting massive particles,… ▽ More DAMSA (DArk Messenger Searches at an Accelerator) is a novel short-baseline accelerator experiment aimed at probing short-lived physics processes, including searches for evidence of a dark sector of particle physics and well-motivated Standard Model signals. Motivated by open questions in neutrino physics and the absence of conclusive evidence for conventional weakly interacting massive particles, DAMSA targets MeV-to-sub-GeV dark-sector messengers with feeble couplings that can be produced in abundance at the PIP-II LINAC. By employing an ultra-short baseline of order one meter, DAMSA is uniquely positioned to overcome the beam-dump "ceiling" that limits sensitivity to promptly decaying particles in longer-baseline experiments. The conceptual design emphasizes a beam-dump production scheme combined with a compact detector optimized for rare decays while mitigating intense neutron-induced backgrounds inherent to high-power proton beams. To validate the experimental strategy and detector technologies, the Little DAMSA Path-Finder (LDPF) proof-of-concept experiment is proposed, focusing on axion-like particles decaying to two photons and operating with 300 MeV electron beams at FAST. Successful realization of LDPF will establish the feasibility of the DAMSA approach, enabling a broad and powerful program to explore short-lived new physics and precision Standard Model processes in a previously inaccessible regime. This conceptual design document outlines the technical details of DAMSA's physics goals, the beam facility proposals, key experimental challenges and how to overcome them, and the proposed experimental staging campaigns. △ Less

Submitted 19 February, 2026; v1 submitted 21 January, 2026; originally announced January 2026.

Comments: Corrected duplicate plot in Figure 15, appended author list. 41 pages, 30 figures

Dark Energy Survey Year 6 Results: Cosmological Constraints from Galaxy Clustering and Weak Lensing

Authors: DES Collaboration, T. M. C. Abbott, M. Adamow, M. Aguena, A. Alarcon, S. S. Allam, O. Alves, A. Amon, D. Anbajagane, F. Andrade-Oliveira, S. Avila, D. Bacon, E. J. Baxter, J. Beas-Gonzalez, K. Bechtol, M. R. Becker, G. M. Bernstein, E. Bertin, J. Blazek, S. Bocquet, D. Brooks, D. Brout, H. Camacho, G. Camacho-Ciurana, R. Camilleri , et al. (147 additional authors not shown)

Abstract: We present cosmology results combining galaxy clustering and weak gravitational lensing measured in the full six years (Y6) of observations by the Dark Energy Survey (DES) covering $\sim$5000 deg$^2$. We perform a large-scale structure analysis using three two-point correlation functions (3$\times$2pt): (i) cosmic shear from 140 million source galaxy shapes, (ii) galaxy clustering of 9 million len… ▽ More We present cosmology results combining galaxy clustering and weak gravitational lensing measured in the full six years (Y6) of observations by the Dark Energy Survey (DES) covering $\sim$5000 deg$^2$. We perform a large-scale structure analysis using three two-point correlation functions (3$\times$2pt): (i) cosmic shear from 140 million source galaxy shapes, (ii) galaxy clustering of 9 million lens galaxy positions, and (iii) galaxy-galaxy lensing from their cross-correlation. We model the data in flat $Λ$CDM and $w$CDM cosmologies. The combined analysis yields $S_8\equiv σ_8 (Ω_{\rm m}/0.3)^{0.5} = 0.789^{+0.012}_{-0.012}$ and matter density $Ω_{\rm m} = 0.333^{+0.023}_{-0.028}$ in $Λ$CDM (68\% CL), where $σ_8$ is the clustering amplitude. These constraints show a (full-space) parameter difference of 1.8$σ$ from a combination of cosmic microwave background (CMB) primary anisotropy datasets from Planck 2018, ACT-DR6, and SPT-3G DR1. Projected only into $S_8$ the difference is $2.6σ$. In $w$CDM the Y6 3$\times$2pt results yield $S_8 = 0.782^{+0.021}_{-0.020}$, $Ω_{\rm m} = 0.325^{+0.032}_{-0.035}$, and dark energy equation-of-state parameter $w = -1.12^{+0.26}_{-0.20}$. For the first time, we combine all DES dark-energy probes: 3$\times$2pt, SNe Ia, BAO and Clusters. In $Λ$CDM this combination yields a $2.8σ$ parameter difference from the CMB. When combining DES 3$\times$2pt with other low-redshift datasets (DESI DR2 BAO, DES SNe Ia, SPT clusters), we find a 2.3$σ$ parameter difference with CMB. A joint fit of Y6 3$\times$2pt, CMB, and those low-redshift datasets produces the tightest $Λ$CDM constraints to date: $S_8 = 0.806^{+0.006}_{-0.007}$, $Ω_{\rm m} = 0.302^{+0.003}_{-0.003}$, $h = 0.683^{+0.003}_{-0.002}$, and $\sum m_ν< 0.14$ eV (95\% CL). In $w$CDM, this combination yields $w = -0.981^{+0.021}_{-0.022}$. △ Less

Submitted 29 January, 2026; v1 submitted 20 January, 2026; originally announced January 2026.

Comments: See https://www.darkenergysurvey.org/des-y6-cosmology-results-papers/ for the full DES Y6 3x2pt cosmology release. Version with minor typos fixed

Microbubble surface instabilities in a strain stiffening viscoelastic material

Authors: Sawyer Remillard, Bachir A. Abeid, Timothy L. Hall, Jonathan R. Sukovich, Jacob Baker, Jin Yang, Jonathan B. Estrada, Mauro Rodriguez Jr

Abstract: Understanding the dynamics of instabilities along fluid-solid interfaces is critical for the efficacy of focused ultrasound therapy tools (e.g., histotripsy) and microcavitation rheometry techniques. Non-uniform pressure fields generated by either ultrasound or a focused laser can cause non-spherical microcavitation bubbles. Previous perturbation amplitude evolution models in viscoelastic material… ▽ More Understanding the dynamics of instabilities along fluid-solid interfaces is critical for the efficacy of focused ultrasound therapy tools (e.g., histotripsy) and microcavitation rheometry techniques. Non-uniform pressure fields generated by either ultrasound or a focused laser can cause non-spherical microcavitation bubbles. Previous perturbation amplitude evolution models in viscoelastic materials either assume pure radial deformation or have inconsistent kinematic fields between the fluid and solid contributions. We derive a kinematically-consistent theoretical model for the evolution of surface perturbations. The model captures the non-linear kinematics of a strain-stiffening viscoelastic material surrounding a non-spherical bubble. The model is validated for (i) small, approximately linear radial oscillations and (ii) large inertial oscillations using laser-induced microcavitation experiments in a soft hydrogel. For the former, the bubble is allowed to reach mechanical equilibrium, and then surface perturbations are excited using ultrasound forcing. For the latter, the microbubble forms small bubble surface perturbations at its maximum radius that grow during collapse. The model's dominant surface perturbation mode scales linearly with equilibrium radius and matches experiments. Similarly, the model's perturbation amplitude evolution sufficiently constrains the rheometry problem and is experimentally validated. △ Less

Submitted 7 January, 2026; originally announced January 2026.

Light-tight skipper-CCDs for X-ray detection in space

Authors: Ana M. Botti, Yikai Wu, Brenda Cervantes, Claudio Chavez, Juan Estrada, Stephen E. Holland, Nathan Saffold, Javier Tiffenberg, Sho Uemura

Abstract: Skipper Charge-Coupled Devices (skipper-CCDs) are pixelated silicon detectors with deep sub-electron resolution. Their radiation hardness and capability to reconstruct energy deposits with unprecedented precision make them a promising technology for space-based X-ray astronomy. In this scenario, optical and near-infrared photons may saturate the sensor, distorting the reconstructed signal. We pres… ▽ More Skipper Charge-Coupled Devices (skipper-CCDs) are pixelated silicon detectors with deep sub-electron resolution. Their radiation hardness and capability to reconstruct energy deposits with unprecedented precision make them a promising technology for space-based X-ray astronomy. In this scenario, optical and near-infrared photons may saturate the sensor, distorting the reconstructed signal. We present a light-tight shield for skipper-CCDs to suppress optical backgrounds while preserving X-ray detection efficiency. We deposited thin aluminum layers on the CCD surface using an e-beam evaporator and evaluated their blinding performance across wavelengths from 650 to 1000 nm using a monochromator, as well as the X-ray transmission using an $^{55}$Fe source. We find that 50 and 100 nm layers provide >99.6% light suppression, with no efficiency loss for 5.9 and 6.4 keV X-rays. In addition, we used Geant4 simulations to extend these results to a broader energy range and quantify the efficiency loss for different aluminum thicknesses. Results show that thin aluminum coatings are an effective, low-cost solution for optical suppression in skipper-CCDs intended for X-ray detection and space instrumentation. △ Less

Submitted 8 May, 2026; v1 submitted 31 December, 2025; originally announced January 2026.

Comments: 9 pages, 11 figures

Report number: FERMILAB-PUB-25-0963-PPD

Journal ref: 2026 PASP 138 055002

Hadronic contributions to $a_μ$ within Resonance Chiral Theory

Authors: Emilio J. Estrada, Alejandro Miranda, Pablo Roig

Abstract: We review the recent progress achieved, using Resonance Chiral Theory, in the hadronic contributions to the muon anomalous magnetic moment. These include the hadronic vacuum polarization, either using $e^+e^-$ or $τ$ decays into hadron final states as input; and the hadronic light-by-light part, where in addition to previous results on the lightest pseudoscalar and tensor-poles contributions, we f… ▽ More We review the recent progress achieved, using Resonance Chiral Theory, in the hadronic contributions to the muon anomalous magnetic moment. These include the hadronic vacuum polarization, either using $e^+e^-$ or $τ$ decays into hadron final states as input; and the hadronic light-by-light part, where in addition to previous results on the lightest pseudoscalar and tensor-poles contributions, we first present the evaluation of the pseudoscalar box using this formalism. We also discuss the scalar, axial-pole and other subleading pieces. The results obtained are consistent with the White Paper 2 values, with comparable precision. △ Less

Submitted 10 December, 2025; originally announced December 2025.

Comments: 32 pages, 1 figure, 1 table. Invited review. Version accepted for publication in EPJ ST

Journal ref: Eur. Phys. J. Spec. Top. (2026) (s11734-026-02147-8)

Hierarchical Bayesian constitutive model selection for high-strain-rate soft material characterization

Authors: Victor Sanchez, Sawyer Remillard, Bachir A. Abeid, Lehu Bu, Spencer H. Bryngelson, Jin Yang, Jonathan B. Estrada, Mauro Rodriguez Jr

Abstract: The high-fidelity characterization of soft, tissue-like materials under ultra-high-strain-rate conditions is critical in engineering and medicine. Still, it remains challenging due to limited optical access, sensitivity to initial conditions, and experimental variability. Microcavitation techniques (e.g., laser-induced microcavitation) have emerged as a viable method for determining the mechanical… ▽ More The high-fidelity characterization of soft, tissue-like materials under ultra-high-strain-rate conditions is critical in engineering and medicine. Still, it remains challenging due to limited optical access, sensitivity to initial conditions, and experimental variability. Microcavitation techniques (e.g., laser-induced microcavitation) have emerged as a viable method for determining the mechanical properties of soft materials in the ultra-high-strain-rate regime (higher than 10^3 s^{-1}); however, they are limited by measurement noise and uncertainty in parameter estimation. A hierarchical Bayesian model selection method is employed using the Inertial Microcavitation Rheometry (IMR) technique to address these limitations. With this method, the parameter space of different constitutive models is explored to determine the most credible constitutive model that describes laser-induced microcavitation bubble oscillations in soft, viscoelastic, transparent hydrogels. The target data/evidence is computed using a weighted Gaussian likelihood with a hierarchical noise scale, which enables the quantification of uncertainty in model plausibility. Physically informed priors, including range-invariant, stress-based parameter priors, a model-redundancy prior, and a Bayesian Information Criterion motivated model prior, penalize complex models to enforce Occam's razor. Using a precomputed grid of simulations, the probabilistic model selection process enables an initial guess for the Maximum A Posteriori (MAP) material parameter values. Synthetic tests recover the ground-truth models and expected parameters. Using experimental data for gelatin, fibrin, polyacrylamide, and agarose, MAP simulations of credible models reproduce the data. Moreover, a cross-institutional comparison of 10% gelatin indicates consistent constitutive model selection. △ Less

Submitted 20 November, 2025; originally announced November 2025.

Tailored robotic training improves hand function and proprioceptive processing in stroke survivors with proprioceptive deficits: A randomized controlled trial

Authors: Andria J. Farrens, Luis Garcia-Fernandez, Raymond Diaz Rojas, Jillian Obeso Estrada, Dylan Reinsdorf, Vicky Chan, Disha Gupta, Joel Perry, Eric Wolbrecht, An Do, Steven C. Cramer, David J. Reinkensmeyer

Abstract: Precision rehabilitation aims to tailor movement training to improve outcomes. We tested whether proprioceptively-tailored robotic training improves hand function and neural processing in stroke survivors. Using a robotic finger exoskeleton, we tested two proprioceptively-tailored approaches: Propriopixel Training, which uses robot-facilitated, gamified movements to enhance proprioceptive processi… ▽ More Precision rehabilitation aims to tailor movement training to improve outcomes. We tested whether proprioceptively-tailored robotic training improves hand function and neural processing in stroke survivors. Using a robotic finger exoskeleton, we tested two proprioceptively-tailored approaches: Propriopixel Training, which uses robot-facilitated, gamified movements to enhance proprioceptive processing, and Virtual Assistance Training, which reduces robotic aid to increase reliance on self-generated feedback. In a randomized controlled trial, forty-six chronic stroke survivors completed nine 2-hour sessions of Standard, Propriopixel or Virtual training. Among participants with proprioceptive deficits, Propriopixel ((Box and Block Test: 7 +/- 4.2, p=0.002) and Virtual Assistance (4.5 +/- 4.4 , p=0.068) yielded greater gains in hand function (Standard: 0.8 +/- 2.3 blocks). Proprioceptive gains correlated with improvements in hand function. Tailored training enhanced neural sensitivity to proprioceptive cues, evidenced by a novel EEG biomarker, the proprioceptive Contingent Negative Variation. These findings support proprioceptively-tailored training as a pathway to precision neurorehabilitation. △ Less

Submitted 31 October, 2025; originally announced November 2025.

Comments: Main manuscript: 38 pages (double spaced, with references), 6 figures, 2 tables and collated supplemental materials (17 pages, double spaced)

Charge Trap Analysis in a SENSEI Skipper-CCD: Understanding Low-Energy Backgrounds in Rare-Event Searches

Authors: Agustin Brusco, Bruno Sivilotti, Ana M. Botti, Brenda Cervantes, Ansh Desai, Rouven Essig, Juan Estrada, Erez Etzion, Guillermo Fernandez Moroni, Stephen E. Holland, Ian Lawson, Steffon Luoma, Santiago E. Perez, Dario Rodrigues, Javier Tiffenberg, Sho Uemura, Yikai Wu

Abstract: Skipper Charge-Coupled Devices (Skipper-CCDs) are ultra-low-threshold detectors capable of detecting energy deposits in silicon at the eV scale. Increasingly used in rare-event searches, one of the major challenges in these experiments is mitigating low-energy backgrounds. In this work, we present results on trap characterization in a silicon Skipper-CCD produced in the same fabrication run as the… ▽ More Skipper Charge-Coupled Devices (Skipper-CCDs) are ultra-low-threshold detectors capable of detecting energy deposits in silicon at the eV scale. Increasingly used in rare-event searches, one of the major challenges in these experiments is mitigating low-energy backgrounds. In this work, we present results on trap characterization in a silicon Skipper-CCD produced in the same fabrication run as the SENSEI experiment at SNOLAB. Lattice defects contribute to backgrounds in rare-event searches through single-electron charge trapping. To investigate this, we employ the charge-pumping technique at different temperatures to identify dipoles produced by traps in the CCD channel. We fully characterize a fraction of these traps and use this information to extrapolate their contribution to the single-electron background in SENSEI. We find that this subpopulation of traps does not contribute significantly but more work is needed to assess the impact of the traps that can not be characterized. △ Less

Submitted 27 October, 2025; originally announced October 2025.

Report number: FERMILAB-PUB-25-0780-PPD

SENSEI: A Search for Diurnal Modulation in sub-GeV Dark Matter Scattering

Authors: Itay M. Bloch, Ana M. Botti, Mariano Cababie, Gustavo Cancelo, Brenda A. Cervantes-Vergara, Miguel Daal, Ansh Desai, Alex Drlica-Wagner, Rouven Essig, Juan Estrada, Erez Etzion, Guillermo Fernandez Moroni, Stephen E. Holland, Jonathan Kehat, Ian Lawson, Steffon Luoma, Aviv Orly, Santiago E. Perez, Dario Rodrigues, Nathan A. Saffold, Silvia Scorza, Miguel Sofo-Haro, Kelly Stifter, Javier Tiffenberg, Sho Uemura , et al. (6 additional authors not shown)

Abstract: Dark matter particles with sufficiently large interactions with ordinary matter can scatter in the Earth's atmosphere and crust before reaching an underground detector. This Earth-shielding effect can induce a directional dependence in the dark matter flux, leading to a sidereal daily modulation in the signal rate. We perform a search for such a modulation using data from the SENSEI experiment, ta… ▽ More Dark matter particles with sufficiently large interactions with ordinary matter can scatter in the Earth's atmosphere and crust before reaching an underground detector. This Earth-shielding effect can induce a directional dependence in the dark matter flux, leading to a sidereal daily modulation in the signal rate. We perform a search for such a modulation using data from the SENSEI experiment, targeting MeV-scale dark matter. We achieve an order-of-magnitude improvement in sensitivity over previous direct-detection bounds for dark-matter masses below 1 MeV, assuming the Standard Halo Model with a Maxwell--Boltzmann velocity distribution, and constrain the amplitude of a general daily modulation signal to be below 6.8 electrons per gram per day. △ Less

Submitted 23 October, 2025; originally announced October 2025.

Comments: 6 pages, 3, figures, + Supplemental Materials (4 pages, 4 figures) + References

Stability of vortex lattices in rotating flows

Authors: Julián Amette Estrada, Alexandros Alexakis, Marc E. Brachet, Pablo D. Mininni

Abstract: Vortex lattices -- highly ordered arrays of vortices -- are known to arise in quantum systems such as type II superconductors and Bose-Einstein condensates. More recently, similar arrangements have been reported in classical rotating fluids. However, the mechanisms governing their formation, stability, and eventual breakdown remain poorly understood. We explore the dynamical stability of vortex la… ▽ More Vortex lattices -- highly ordered arrays of vortices -- are known to arise in quantum systems such as type II superconductors and Bose-Einstein condensates. More recently, similar arrangements have been reported in classical rotating fluids. However, the mechanisms governing their formation, stability, and eventual breakdown remain poorly understood. We explore the dynamical stability of vortex lattices in three-dimensional rotating flows. To that end we construct controlled initial conditions consisting of vortex lattices superimposed on turbulent backgrounds. We then characterize their evolution across different Rossby numbers and domain geometries. By introducing an Ekman drag we are able to reach a steady state where vortex lattices persist with near constant amplitude up until spontaneous breakup of the lattice, or an equivalent of ``melting,'' occurs. We examine an ensemble of runs in order to determine the mean lifetime of the lattice as a function of the system parameters. Our results reveal that the stability of the lattices is a memory-less random process whose mean life-time depends sensitively on the system parameters that if finely tuned can lead to very long lived lattice states. These metastable states exhibit statistical properties reminiscent of critical systems and can offer insight into long-lived vortex patterns observed in planetary atmospheres. △ Less

Submitted 7 October, 2025; originally announced October 2025.

From Legacy to Leadership Intelligent Radio Network Planning Framework for Cell-Free Massive MIMO in B5G6G Era

Authors: Valdemar Farré, David Vega, Juan Estrada, Juan A. Vásquez Peralvo, Symeon Chatzinotas

Abstract: The proliferation of cell-free Massive MIMO represents a transformative shift in wireless network architecture, addressing critical limitations of conventional distributed Massive MIMO systems. This paper presents an intelligent radio network planning framework that bridges legacy 5G infrastructures with future B5G/6G networks through cell-free architectures. By leveraging operational insights fro… ▽ More The proliferation of cell-free Massive MIMO represents a transformative shift in wireless network architecture, addressing critical limitations of conventional distributed Massive MIMO systems. This paper presents an intelligent radio network planning framework that bridges legacy 5G infrastructures with future B5G/6G networks through cell-free architectures. By leveraging operational insights from existing 5G deployments, we systematically address coverage optimization, and capacity enhancement. Our scalable framework enables seamless evolution from legacy designs to next-generation cell-free systems. Through extensive simulations in dense urban environments, we demonstrate substantial improvements: 45% spectral efficiency gains, 30% interference reduction, and significantly enhanced uniform coverage. The proposed framework provides network operators with a practical roadmap for transitioning from traditional cellular architectures to demanding B5G/6G requirements while maximizing existing infrastructure investments. △ Less

Submitted 29 September, 2025; originally announced September 2025.

Comments: arXiv admin comment: This version has been removed by arXiv administrators: The full text has been removed following publication in IEEE Xplore

Automating Sensor Characterization with Bayesian Optimization

Authors: J. Cuevas-Zepeda, C. Chavez, J. Estrada, J. Noonan, B. D. Nord, N. Saffold, M. Sofo-Haro, R. Spinola e Castro, S. Trivedi

Abstract: The development of novel instrumentation requires an iterative cycle with three stages: design, prototyping, and testing. Recent advancements in simulation and nanofabrication techniques have significantly accelerated the design and prototyping phases. Nonetheless, detector characterization continues to be a major bottleneck in device development. During the testing phase, a significant time inves… ▽ More The development of novel instrumentation requires an iterative cycle with three stages: design, prototyping, and testing. Recent advancements in simulation and nanofabrication techniques have significantly accelerated the design and prototyping phases. Nonetheless, detector characterization continues to be a major bottleneck in device development. During the testing phase, a significant time investment is required to characterize the device in different operating conditions and find optimal operating parameters. The total effort spent on characterization and parameter optimization can occupy a year or more of an expert's time. In this work, we present a novel technique for automated sensor characterization that aims to accelerate the testing stage of the development cycle. This technique leverages closed-loop Bayesian optimization (BO), using real-time measurements to guide parameter selection and identify optimal operating states. We demonstrate the method with a novel low-noise CCD, showing that the machine learning-driven tool can efficiently characterize and optimize operation of the sensor in a couple of days without supervision of a device expert. △ Less

Submitted 16 January, 2026; v1 submitted 25 September, 2025; originally announced September 2025.

Report number: FERMILAB-PUB-25-0671-CSAID-PPD

A compact, low-power epithermal neutron counter for lunar water detection

Authors: Julian Cuevas-Zepeda, Phoenix Alpine, Brenda A. Cervantes-Vergara, Claudio Chavez, Juan Estrada, Erez Etzion, Guillermo Fernandez-Moroni, Nathan Saffold, Miguel Sofo-Haro, Javier Tiffenberg

Abstract: The detection and characterization of lunar water are critical for enabling sustainable human and robotic exploration of the Moon. Orbital neutron spectrometers, such as instruments on Lunar Prospector and the Lunar Reconnaissance Orbiter, have revealed hydrogen-rich regions near the poles but are limited by coarse spatial resolution and low counting efficiency. We present a compact, lightweight,… ▽ More The detection and characterization of lunar water are critical for enabling sustainable human and robotic exploration of the Moon. Orbital neutron spectrometers, such as instruments on Lunar Prospector and the Lunar Reconnaissance Orbiter, have revealed hydrogen-rich regions near the poles but are limited by coarse spatial resolution and low counting efficiency. We present a compact, lightweight, and low-power epithermal neutron detector based on boron-coated silicon imagers, designed to probe subsurface hydrogen at decimeter scales from mobile platforms such as lunar rovers. This instrument leverages the high neutron capture cross-section of $^{10}$B to convert epithermal neutrons into detectable $α$ and $^{7}$Li ions in a fully-depleted silicon imager, providing a unique event topology to identify neutrons while suppressing backgrounds. Monte Carlo simulations demonstrate that a 3 $μ$m boron layer achieves optimal neutron detection efficiency, further enhanced with polyethylene moderation to improve sensitivity to the 0.4 eV-500 keV epithermal energy range. For a 10 cm$^2$ active area, the detector achieves sensitivity to H$_2$O weight fractions as low as 0.01 wt % in a 15 minute measurement. This scalable, portable, low-mass design is well-suited for integration into upcoming Artemis and commercial lunar rovers, providing a transformative capability for in-situ resource prospecting and ground-truth validation of orbital measurements. △ Less

Submitted 4 September, 2025; originally announced September 2025.

Report number: FERMILAB-PUB-25-0634-PPD

Variation-matching sensitivity-based virtual fields for hyperelastic material model calibration

Authors: Denislav P. Nikolov, Zhiren Zhu, Jonathan B. Estrada

Abstract: Accurate identification of nonlinear material parameters from three-dimensional full-field deformation data remains a challenge in experimental mechanics. The virtual fields method (VFM) provides a powerful, computationally efficient approach for material model calibration, however, its success depends critically on the choice of virtual fields and the informativeness of available kinematic data.… ▽ More Accurate identification of nonlinear material parameters from three-dimensional full-field deformation data remains a challenge in experimental mechanics. The virtual fields method (VFM) provides a powerful, computationally efficient approach for material model calibration, however, its success depends critically on the choice of virtual fields and the informativeness of available kinematic data. In this work, we advance the state-of-the-art discrete formulation of the sensitivity-based virtual fields (SBVF) method by systematically developing and comparing alternative variational and analytical SBVFs within a strain-invariant-based modeling framework. A central contribution of this work is the implementation and assessment of variation-based SBVFs (vSBVFs), formulated using directional Gâteaux derivatives, as well as virtual fields derived from analytical differentiation (aSBVFs) which provide explicit, model-tailored virtual displacement fields for parameter identification. Using simulated noisy volumetric datasets, we demonstrate that vSBVFs and aSBVFs enable procedural, automated construction of optimal virtual fields for each material parameter, substantially enhancing the robustness and efficiency of calibration without the need for manual field selection or high temporal resolution in the data acquisition. We quantify data richness -- the effective diversity of sampled kinematic states -- showing that increased data richness via sample geometry and loading protocols leads to improved parameter identifiability. These findings establish a pathway for automated, noise-robust material model calibration suitable for future deployment with experimental full-field imaging of soft, complex materials, and provide a foundation for optimizing shape topology and extending to viscoelastic and anisotropic behaviors. △ Less

Submitted 3 September, 2025; originally announced September 2025.

Investigation of Low-Energy Particle Remnants in High-Energy Collisions at the LHC with a Skipper-CCD detector

Authors: Brenda A. Cervantes-Vergara, Santiago E. Perez, Nicola Bacchetta, Nuria Castello-Mor, Juan Estrada, Marcos Fernandez Garcia, Petra Merkel, Maria Perez Martinez, Dario Rodrigues, Javier Tiffenberg, Rocio Vilar Cortabitarte

Abstract: We deployed MOSKITA $\sim$33 m away from the CMS collision point, the first skipper-CCD detector probing low-energy particles produced in high-energy collisions at the Large Hadron Collider (LHC). In this work, we search for beam-related events using data collected in 2024 during beam-on and beam-off periods. The dataset corresponds to integrated luminosities of 113.3 fb$^{-1}$ and 1.54 nb$^{-1}$… ▽ More We deployed MOSKITA $\sim$33 m away from the CMS collision point, the first skipper-CCD detector probing low-energy particles produced in high-energy collisions at the Large Hadron Collider (LHC). In this work, we search for beam-related events using data collected in 2024 during beam-on and beam-off periods. The dataset corresponds to integrated luminosities of 113.3 fb$^{-1}$ and 1.54 nb$^{-1}$ for the proton-proton and Pb-Pb collision periods, respectively. We report observed event rates in a model-independent framework across two ionization regions: $\leq20e^-$ and $>20e^-$. For the low-energy region, we perform a likelihood analysis to test the null hypothesis of no beam-correlated signal. We found no significant correlation during proton-proton and Pb-Pb collisions. For the high-energy region, we present the energy spectra for both collision periods and compare event rates for images with and without luminosity. We observe a slight increase in the event rate following the Pb-Pb collisions, coinciding with a rise in the single-electron rate, which will be investigated in future work. Using the low-energy proton-proton results, we place 95% C.L. constraints on the mass-millicharge parameter space of millicharged particles. Overall, the results in this work demonstrate the viability of skipper-CCD technology to explore new physics at high-energy colliders and motivate future searches with more massive detectors. △ Less

Submitted 8 August, 2025; originally announced August 2025.

Report number: FERMILAB-PUB-25-0568-CMS-PPD

Low Activity Tritium Detection in CCDs Using Deep Learning Techniques

Authors: E. Rofors, R. Heller, R. J. Cooper, J. Estrada, G. Moroni, B. Nachman, K. Spears

Abstract: This study explores the use of charge-coupled devices (CCDs) for detecting low-energy beta particles from tritium decay - a critical signal for nuclear safety, nuclear nonproliferation, and environmental monitoring. We employ a dual approach utilizing both measured CCD data and detailed Geant4 simulations. Our analysis compares classical techniques with advanced deep learning methods, including co… ▽ More This study explores the use of charge-coupled devices (CCDs) for detecting low-energy beta particles from tritium decay - a critical signal for nuclear safety, nuclear nonproliferation, and environmental monitoring. We employ a dual approach utilizing both measured CCD data and detailed Geant4 simulations. Our analysis compares classical techniques with advanced deep learning methods, including convolutional neural networks (CNNs), autoencoders trained exclusively on tritium data, and preliminary studies on boosted decision trees (BDTs). The CNN, trained on mixed signal/background datasets, demonstrates superior classification performance, while the autoencoder shows the potential of unsupervised, background-agnostic strategies when background characteristics are poorly defined. These results highlight the excellent sensitivity achievable thanks to the background rejection made possible by information-rich CCD data, paving the way for improved portable tritium monitoring. △ Less

Submitted 7 November, 2025; v1 submitted 1 August, 2025; originally announced August 2025.

Community Report from the 2025 SNOLAB Future Projects Workshop

Authors: M. D. Diamond, P. Abbamonte, A. Arvanitaki, D. M. Asner, D. Balut, D. Baxter, C. Blanco, D. Boreham, M. Boulay, B. Broerman, T. Brunner, E. Caden, A. Chavarria, M. Chen, J. P. Davis, A. Drlica-Wagner, J. Estrada, N. Fatemighomi, J. Foster, D. Freedman, C. Gao, J. Hall, S. Hall, W. Halperin, M. Hirschel , et al. (32 additional authors not shown)

Abstract: SNOLAB hosts a biannual Future Projects Workshop (FPW) with the goal of encouraging future project stakeholders to present ideas, concepts, and needs for experiments or programs that could one day be hosted at SNOLAB. The 2025 FPW was held in the larger context of a 15-year planning exercise requested by the Canada Foundation for Innovation. This report collects input from the community, including… ▽ More SNOLAB hosts a biannual Future Projects Workshop (FPW) with the goal of encouraging future project stakeholders to present ideas, concepts, and needs for experiments or programs that could one day be hosted at SNOLAB. The 2025 FPW was held in the larger context of a 15-year planning exercise requested by the Canada Foundation for Innovation. This report collects input from the community, including both contributions to the workshop and contributions that could not be scheduled in the workshop but nonetheless are important to the community. △ Less

Submitted 7 August, 2025; v1 submitted 15 July, 2025; originally announced July 2025.

Comments: 83 pages, 15 figures

Report number: SNOLAB-STR-2025-006

Characterization of the Cherenkov Photon Background for Low-Noise Silicon Detectors in Space

Authors: Manuel E. Gaido, Javier Tiffenberg, Alex Drlica-Wagner, Guillermo Fernandez-Moroni, Bernard J. Rauscher, Fernando Chierchie, Dario Rodrigues, Lucas Giardino, Juan Estrada, Agustin J. Lapi

Abstract: Future space observatories that seek to perform imaging and spectroscopy of faint astronomical sources will require ultra-low-noise detectors that are sensitive over a broad wavelength range. Silicon charge-coupled devices (CCDs), such as EMCCDs, skipper CCDs, multi-amplifier sensing (MAS) CCDs, and single-electron sensitive read out (SiSeRO) CCDs have demonstrated the ability to detect and measur… ▽ More Future space observatories that seek to perform imaging and spectroscopy of faint astronomical sources will require ultra-low-noise detectors that are sensitive over a broad wavelength range. Silicon charge-coupled devices (CCDs), such as EMCCDs, skipper CCDs, multi-amplifier sensing (MAS) CCDs, and single-electron sensitive read out (SiSeRO) CCDs have demonstrated the ability to detect and measure single photons from X-ray energies to near the silicon band gap (~1.1 $μ$m), making them candidate technologies for this application. In this context, we study a relatively unexplored source of low-energy background coming from Cherenkov radiation produced by energetic cosmic rays traversing a silicon detector. We present a model for Cherenkov photon production and absorption that is calibrated to laboratory data, and we use this model to characterize the residual background rate for ultra-low-noise silicon detectors in space. We study how the Cherenkov background rate depends on detector thickness, variations in solar activity, and the contribution of heavy cosmic ray species (Z > 2). We find that for thick silicon detectors, such as those required to achieve high quantum efficiency at long wavelengths, the rate of cosmic-ray-induced Cherenkov photon production is comparable to other detector and astrophysical backgrounds. We apply our Cherenkov background model to simulated spectroscopic observations of extra-solar planets, and we find that thick detectors continue to outperform their thinner counterparts at longer wavelengths despite a larger Cherenkov background rate. Furthermore, we find that minimal masking of cosmic-ray tracks continues to maximize the signal-to-noise ratio of very faint sources despite the existence of extended halos of Cherenkov photons. △ Less

Submitted 7 December, 2025; v1 submitted 30 June, 2025; originally announced July 2025.

Comments: 14 pages, 10 figures (see also arXiv:2410.06261). Updated to match published version

Report number: FERMILAB-PUB-25-0427-LDRD-PPD

Journal ref: PASP 137, 095001 (2025)

The many faces of rotating quantum turbulence

Authors: Julian Amette Estrada, Marc E. Brachet, Pablo D. Mininni

Abstract: Quantum turbulence shares many similarities with classical turbulence in the isotropic and homogeneous case, despite the inviscid and quantized nature of its vortices. However, when quantum fluids are subjected to rotation, their turbulent dynamics depart significantly from the classical expectations. We explore the phenomenology of rotating quantum turbulence, emphasizing how rotation introduces… ▽ More Quantum turbulence shares many similarities with classical turbulence in the isotropic and homogeneous case, despite the inviscid and quantized nature of its vortices. However, when quantum fluids are subjected to rotation, their turbulent dynamics depart significantly from the classical expectations. We explore the phenomenology of rotating quantum turbulence, emphasizing how rotation introduces new regimes with no classical analogs. We review recent theoretical, experimental, and numerical developments, and present new numerical results that map out distinct dynamical regimes arising from the interplay of rotation, quantization, non-linearities, and condensed matter regimes. In particular, we show the importance of distinguishing the dynamics of rotating quantum fluids in the slowly rotating, rapidly rotating, and low Landau level regimes. The findings have implications for the dynamics of liquid helium, atomic Bose-Einstein condensates, and neutron stars, and show how rotating quantum fluids can serve as a unique platform bridging turbulence theory and condensed matter physics revealing novel states of out-of-equilibrium quantum matter. △ Less

Submitted 19 June, 2025; originally announced June 2025.

Dynamic Beyond 5G and 6G Connectivity: Leveraging NTN and RIS Synergies for Optimized Coverage and Capacity in High-Density Environments

Authors: Valdemar Farré, Juan Estrada, David Vega, Luis F Urquiza-Aguiar, Juan A. Vásquez Peralvo, Symeon Chatzinotas

Abstract: The increasing demand for reliable, high-capacity communication during large-scale outdoor events poses significant challenges for traditional Terrestrial Networks (TNs), which often struggle to provide consistent coverage in high-density environments. This paper presents a novel 6G radio network planning framework that integrates Non-Terrestrial Networks (NTNs) with Reconfigurable Intelligent Sur… ▽ More The increasing demand for reliable, high-capacity communication during large-scale outdoor events poses significant challenges for traditional Terrestrial Networks (TNs), which often struggle to provide consistent coverage in high-density environments. This paper presents a novel 6G radio network planning framework that integrates Non-Terrestrial Networks (NTNs) with Reconfigurable Intelligent Surfaces (RISs) to deliver ubiquitous coverage and enhanced network capacity. Our framework overcomes the limitations of conventional deployable base stations by leveraging NTN architectures, including Low Earth Orbit (LEO) satellites and passive RIS platforms seamlessly integrated with Beyond 5G (B5G) TNs. By incorporating advanced B5G technologies such as Massive Multiple Input Multiple Output (mMIMO) and beamforming, and by optimizing spectrum utilization across the C, S, and Ka bands, we implement a rigorous interference management strategy based on a dynamic SINR model. Comprehensive calculations and simulations validate the proposed framework, demonstrating significant improvements in connectivity, reliability, and cost-efficiency in crowded scenarios. This integration strategy represents a promising solution for meeting the evolving demands of future 6G networks. △ Less

Submitted 12 June, 2025; originally announced June 2025.

Comments: 6 pages, 6 figures, 11 tables

DarkNESS: A skipper-CCD NanoSatellite for Dark Matter Searches

Authors: Phoenix Alpine, Samriddhi Bhatia, Ana M. Botti, Brenda A. Cervantes-Vergara, Claudio R. Chavez, Fernando Chierchie, Alex Drlica-Wagner, Rouven Essig, Juan Estrada, Erez Etzion, Roni Harnik, Terry Kim, Michael Lembeck, Qi Lim, Bernard J. Rauscher, Nathan Saffold, Javier Tiffenberg, Sho Uemura, Hailin Xu

Abstract: The Dark matter Nanosatellite Equipped with Skipper Sensors (DarkNESS) deploys a recently developed skipper-CCD architecture with sub-electron readout noise in low Earth orbit (LEO) to investigate potential signatures of dark matter (DM). The mission addresses two interaction channels: electron recoils from strongly interacting sub-GeV DM and X-rays produced through decaying DM. Orbital observatio… ▽ More The Dark matter Nanosatellite Equipped with Skipper Sensors (DarkNESS) deploys a recently developed skipper-CCD architecture with sub-electron readout noise in low Earth orbit (LEO) to investigate potential signatures of dark matter (DM). The mission addresses two interaction channels: electron recoils from strongly interacting sub-GeV DM and X-rays produced through decaying DM. Orbital observations avoid attenuation that limits ground-based measurements, extending sensitivity reach for both channels. The mission proceeds toward launch following laboratory validation of the instrument. A launch opportunity has been secured through Firefly Aerospace's DREAM 2.0 program, awarded to the University of Illinois Urbana-Champaign (UIUC). This will constitute the first use of skipper-CCDs in space and evaluate their suitability for low-noise X-ray and single-photon detection in future space observatories. △ Less

Submitted 22 May, 2025; originally announced May 2025.

Comments: Submitted to Advances in Space Research. arXiv admin note: text overlap with arXiv:2412.12084

Report number: FERMILAB-PUB-25-0354-PPD

Accelerating Bayesian Optimal Experimental Design via Local Radial Basis Functions: Application to Soft Material Characterization

Authors: Tianyi Chu, Jonathan B. Estrada, Spencer H. Bryngelson

Abstract: We develop a computational approach that significantly improves the efficiency of Bayesian optimal experimental design (BOED) using local radial basis functions (RBFs). The presented RBF--BOED method uses the intrinsic ability of RBFs to handle scattered parameter points, a property that aligns naturally with the probabilistic sampling inherent in Bayesian methods. By constructing accurate determi… ▽ More We develop a computational approach that significantly improves the efficiency of Bayesian optimal experimental design (BOED) using local radial basis functions (RBFs). The presented RBF--BOED method uses the intrinsic ability of RBFs to handle scattered parameter points, a property that aligns naturally with the probabilistic sampling inherent in Bayesian methods. By constructing accurate deterministic surrogates from local neighborhood information, the method enables high-order approximations with reduced computational overhead. As a result, computing the expected information gain (EIG) requires evaluating only a small uniformly sampled subset of prior parameter values, greatly reducing the number of expensive forward-model simulations needed. For demonstration, we apply RBF--BOED to optimize a laser-induced cavitation (LIC) experimental setup, where forward simulations follow from inertial microcavitation rheometry (IMR) and characterize the viscoelastic properties of hydrogels. Two experimental design scenarios, single- and multi-constitutive-model problems, are explored. Results show that EIG estimates can be obtained at just 8% of the full computational cost in a five-model problem within a two-dimensional design space. This advance offers a scalable path toward optimal experimental design in soft and biological materials. △ Less

Submitted 19 May, 2025; originally announced May 2025.

Tensor Meson Pole contributions to the HLbL piece of $a_μ$ within R$χ$T

Authors: Emilio J. Estrada, Pablo Roig

Abstract: We compute the tensor meson pole contributions to the Hadronic Light-by-Light piece of $a_μ$ in the purely hadronic region, using Resonance Chiral Theory. Given the differences between the dispersive and holographic groups determinations, we consider timely to present an alternative evaluation. In our approach, the lightest tensor meson nonet and two vector meson resonance nonets are considered in… ▽ More We compute the tensor meson pole contributions to the Hadronic Light-by-Light piece of $a_μ$ in the purely hadronic region, using Resonance Chiral Theory. Given the differences between the dispersive and holographic groups determinations, we consider timely to present an alternative evaluation. In our approach, the lightest tensor meson nonet and two vector meson resonance nonets are considered in the chiral limit. Disregarding operators with derivatives, only the form factor $\mathcal{F}_1^T$ is non-vanishing, as assumed in the dispersive study. All parameters are determined by imposing a set of short-distance QCD constraints, and the radiative decay widths. In this case, we obtain (in units of $10^{-11}$): $ a_2$-pole: $-\left(1.02(10)_{\rm stat}(^{+0.00}_{-0.12})_{\rm syst}\right)$, $f_2$-pole: $-\left(3.2(3)_{\rm stat}(^{+0.0}_{-0.4})_{\rm syst}\right)$ and $f_2^\prime$-pole: $-\left(0.042(13)_{\rm stat}\right)$, which add up to $a_μ^{a_2+f_2+f_2^\prime \rm -pole}=-\left(4.3^{+0.3}_{-0.5}\right)$, in close agreement with the holographic result when truncated to $\mathcal F_1^T$ only. However, with an ad-hoc extended Lagrangian, that also generates $\mathcal F_3^T$, as in the holographic approach, we have found: $ a_2$-pole: $+0.47(1.43)_{\rm norm}(3)_{\rm stat}(^{+0.06}_{-0.00})_{\rm syst}$, $f_2$-pole: $+1.18(4.18)_{\rm norm}(12)_{\rm stat}(^{+0.24}_{-0.00})_{\rm syst}$ and $f_2^\prime$-pole: $+0.040(78)_{\rm norm}(2)_{\rm stat}$, summing to $a_μ^{a_2+f_2+f_2^\prime \rm - pole}=+1.7(4.4)$, which agree with these recent determinations within uncertainties (dominated by the $\mathcal F_3^T$ normalization). We point out that $RχT$ generates all form factors, the contributions to $a_μ$ of $\mathcal F_{2,4,5}$ cannot be evaluated in the current basis, preventing for the moment a complete calculation of $a_μ^{\rm T-poles}$ within our framework. △ Less

Submitted 23 November, 2025; v1 submitted 1 April, 2025; originally announced April 2025.

Comments: REVTEX, 27 pages, 8 figures, 2 tables. Mass corrections included and code error corrected in TFF3. Appendix for the computation of TFF3 at zero virtuality within R$χ$T included. Version accepted for publication in JHEP

Journal ref: JHEP01(2026)070

The Spectroscopic Stage-5 Experiment

Authors: Robert Besuner, Arjun Dey, Alex Drlica-Wagner, Haruki Ebina, Guillermo Fernandez Moroni, Simone Ferraro, Jaime Forero-Romero, Klaus Honscheid, Pat Jelinsky, Dustin Lang, Michael Levi, Paul Martini, Adam Myers, Nathalie Palanque-Delabrouille, Swayamtrupta Panda, Claire Poppett, Noah Sailer, David Schlegel, Arman Shafieloo, Joseph Silber, Martin White, Timothy Abbott, Lori Allen, Santiago Avila, Roberto Avilés , et al. (85 additional authors not shown)

Abstract: The existence, properties, and dynamics of the dark sectors of our universe pose fundamental challenges to our current model of physics, and large-scale astronomical surveys may be our only hope to unravel these long-standing mysteries. In this white paper, we describe the science motivation, instrumentation, and survey plan for the next-generation spectroscopic observatory, the Stage-5 Spectrosco… ▽ More The existence, properties, and dynamics of the dark sectors of our universe pose fundamental challenges to our current model of physics, and large-scale astronomical surveys may be our only hope to unravel these long-standing mysteries. In this white paper, we describe the science motivation, instrumentation, and survey plan for the next-generation spectroscopic observatory, the Stage-5 Spectroscopic Experiment (Spec-S5). Spec-S5 is a new all-sky spectroscopic instrument optimized to efficiently carry out cosmological surveys of unprecedented scale and precision. The baseline plan for Spec-S5 involves upgrading two existing 4-m telescopes to new 6-m wide-field facilities, each with a highly multiplexed spectroscopic instrument capable of simultaneously measuring the spectra of 13,000 astronomical targets. Spec-S5, which builds and improves on the hardware used for previous cosmology experiments, represents a cost-effective and rapid approach to realizing a more than 10$\times$ gain in spectroscopic capability compared to the current state-of-the-art represented by the Dark Energy Spectroscopic Instrument project (DESI). Spec-S5 will provide a critical scientific capability in the post-Rubin and post-DESI era for advancing cosmology, fundamental physics, and astrophysics in the 2030s. △ Less

Submitted 7 May, 2025; v1 submitted 10 March, 2025; originally announced March 2025.

Comments: 27 pages, 14 figures

Measurement of Photons Emitted by High-Energy Charged Particles as Background in Single-Photon Resolving Image Sensors

Authors: Guillermo Fernandez Moroni, Fernando Chierchie, Lucas Giardino, Javier Tiffenberg, Juan Estrada

Abstract: This work introduces an advanced technique optimized for detecting photons generated by charged particles, leveraging Skipper-CCD sensors. By analyzing background sources and detection efficiencies, the technique achieves strong agreement between experimental results and Cherenkov-based simulations. It also provides a robust framework for investigating secondary photon production in environments w… ▽ More This work introduces an advanced technique optimized for detecting photons generated by charged particles, leveraging Skipper-CCD sensors. By analyzing background sources and detection efficiencies, the technique achieves strong agreement between experimental results and Cherenkov-based simulations. It also provides a robust framework for investigating secondary photon production in environments with high fluxes of ionizing particles, such as those anticipated in space-based astronomical instruments. These secondary photons present a critical challenge as background noise for next-generation single-photon resolving imagers used to study faint celestial objects. Furthermore, the method exhibits significant potential for broader applications, including exploring photon generation in various substrate materials and examining their transport through multiple interfaces. △ Less

Submitted 6 March, 2025; originally announced March 2025.

Characterization of proton-induced damage in thick, p-channel skipper-CCDs

Authors: Brenda A. Cervantes-Vergara, Santiago E. Perez, Claudio R. Chavez, Fernando Chierchie, Brandon Roach, Juan Estrada, Alex Drlica-Wagner

Abstract: In this work, we characterize the radiation-induced damage in two thick, p-channel skipper-CCDs irradiated unbiased and at room temperature with 217-MeV protons. We evaluate the overall performance of the sensors and demonstrate their single-electron/single-photon sensitivity after receiving a fluence on the order of 10$^{10}$~protons/cm$^2$. Using the pocket-pumping technique, we quantify and cha… ▽ More In this work, we characterize the radiation-induced damage in two thick, p-channel skipper-CCDs irradiated unbiased and at room temperature with 217-MeV protons. We evaluate the overall performance of the sensors and demonstrate their single-electron/single-photon sensitivity after receiving a fluence on the order of 10$^{10}$~protons/cm$^2$. Using the pocket-pumping technique, we quantify and characterize the proton-induced defects from displacement damage. We report an overall trap density of 0.134~traps/pixel for a displacement damage dose of $2.3\times10^7$~MeV/g. Three main proton-induced trap species were identified, V$_2$, C$_i$O$_i$ and V$_n$O$_m$, and their characteristic trap energies and cross sections were extracted. We found that while divacancies are the most common proton-induced defects, C$_i$O$_i$ defects have a greater impact on charge integrity at typical operating temperatures because their emission-time constants are comparable or larger than typical readout times. To estimate ionization damage, we measure the characteristic output transistor curves. We found no threshold voltage shifts after irradiation. Our results highlight the potential of skipper-CCDs for applications requiring high-radiation tolerance and can be used to find the operating conditions in which effects of radiation-induced damage are mitigated. △ Less

Submitted 22 February, 2025; originally announced February 2025.

Journal ref: JINST 20 P07005, 2025

Multiple-Amplifier Sensing Charged-Coupled Device: Model and improvement of the Node Removal Efficiency

Authors: Blas J. Irigoyen Gimenez, Miqueas E. Gamero, Claudio R. Chavez Blanco, Agustin J. Lapi, Fernando Chierchie, Guillermo Fernandez Moroni, Juan Estrada, Javier Tiffenberg, Alex Drlica-Wagner

Abstract: The Multiple Amplifier Sensing Charge-Coupled Device (MAS-CCD) has emerged as a promising technology for astronomical observation, quantum imaging, and low-energy particle detection due to its ability to reduce the readout noise without increasing the readout time as in its predecessor, the Skipper-CCD, by reading out the same charge packet through multiple inline amplifiers. Previous works identi… ▽ More The Multiple Amplifier Sensing Charge-Coupled Device (MAS-CCD) has emerged as a promising technology for astronomical observation, quantum imaging, and low-energy particle detection due to its ability to reduce the readout noise without increasing the readout time as in its predecessor, the Skipper-CCD, by reading out the same charge packet through multiple inline amplifiers. Previous works identified a new parameter in this sensor, called the Node Removal Inefficiency (NRI), related to inefficiencies in charge transfer and residual charge removal from the output gates after readout. These inefficiencies can lead to distortions in the measured signals similar to those produced by the charge transfer inefficiencies in standard CCDs. This work introduces more details in the mathematical description of the NRI mechanism and provides techniques to quantify its magnitude from the measured data. It also proposes a new operation strategy that significantly reduces its effect with minimal alterations of the timing sequences or voltage settings for the other components of the sensor. The proposed technique is corroborated by experimental results on a sixteen-amplifier MAS-CCD. At the same time, the experimental data demonstrate that this approach minimizes the NRI effect to levels comparable to other sources of distortion the charge transfer inefficiency in scientific devices. △ Less

Submitted 21 February, 2025; originally announced February 2025.

Report number: FERMILAB-PUB-25-0089-PPD

Readout Optimization of Multi-Amplifier Sensing Charge-Coupled Devices for Single-Quantum Measurement

Authors: Ana M. Botti, Brenda A. Cervantes-Vergara, Claudio R. Chavez, Fernando Chierchie, Alex Drlica-Wagner, Juan Estrada, Guillermo Fernandez Moroni, Stephen E. Holland, Blas J. Irigoyen Gimenez, Agustin J. Lapi, Edgar Marrufo Villalpando, Miguel Sofo Haro, Javier Tiffenberg, Sho Uemura, Kenneth Lin, Armin Karcher, Julien Guy, Peter E. Nugent

Abstract: The non-destructive readout capability of the Skipper Charge Coupled Device (CCD) has been demonstrated to reduce the noise limitation of conventional silicon devices to levels that allow single-photon or single-electron counting. The noise reduction is achieved by taking multiple measurements of the charge in each pixel. These multiple measurements come at the cost of extra readout time, which ha… ▽ More The non-destructive readout capability of the Skipper Charge Coupled Device (CCD) has been demonstrated to reduce the noise limitation of conventional silicon devices to levels that allow single-photon or single-electron counting. The noise reduction is achieved by taking multiple measurements of the charge in each pixel. These multiple measurements come at the cost of extra readout time, which has been a limitation for the broader adoption of this technology in particle physics, quantum imaging, and astronomy applications. This work presents recent results of a novel sensor architecture that uses multiple non-destructive floating-gate amplifiers in series to achieve sub-electron readout noise in a thick, fully-depleted silicon detector to overcome the readout time overhead of the Skipper-CCD. This sensor is called the Multiple-Amplifier Sensing Charge-Coupled Device (MAS-CCD) can perform multiple independent charge measurements with each amplifier, and the measurements from multiple amplifiers can be combined to further reduce the readout noise. We will show results obtained for sensors with 8 and 16 amplifiers per readout stage in new readout operations modes to optimize its readout speed. The noise reduction capability of the new techniques will be demonstrated in terms of its ability to reduce the noise by combining the information from the different amplifiers, and to resolve signals in the order of a single photon per pixel. The first readout operation explored here avoids the extra readout time needed in the MAS-CCD to read a line of the sensor associated with the extra extent of the serial register. The second technique explore the capability of the MAS-CCD device to perform a region of interest readout increasing the number of multiple samples per amplifier in a targeted region of the active area of the device. △ Less

Submitted 21 February, 2025; v1 submitted 14 February, 2025; originally announced February 2025.

Report number: FERMILAB-CONF-24-0991-PPD

Journal ref: Proceedings Volume 13103, X-Ray, Optical, and Infrared Detectors for Astronomy XI; 1310311 (2024). Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Towards a quantum realization of the ampere using single-electron resolution Skipper-CCDs

Authors: Miqueas Gamero, Agustin Lapi, Blas Irigoyen Gimenez, Fernando Chierchie, Guillermo Fernandez Moroni, Brenda Cervantes-Vergara, Javier Tiffenberg, Juan Estrada, Eduardo Paolini, Gustavo Cancelo

Abstract: This paper presents a proof-of-concept demonstration of the Skipper-CCD, a sensor with single-electron counting capability, as a promising technology for implementing an electron-pump-based current source. Relying on its single-electron resolution and built-in charge sensing, it allows self-calibration of the charge packets. This article presents an initial discussion of how low ppm and high curre… ▽ More This paper presents a proof-of-concept demonstration of the Skipper-CCD, a sensor with single-electron counting capability, as a promising technology for implementing an electron-pump-based current source. Relying on its single-electron resolution and built-in charge sensing, it allows self-calibration of the charge packets. This article presents an initial discussion of how low ppm and high current realizations can be achieved with this technology. We report experimental results that illustrate the key functionalities in manipulating both small and large electron charge packets, including a comparison of the charge generated, self-measured, and drained by the sensor against measurements from an electrometer. These results were obtained using a standard sensor and readout electronics without specific optimizations for this application. The objective is to explore the potential of Skipper-CCD for realizing an electron-based current source. △ Less

Submitted 11 February, 2025; originally announced February 2025.

Comments: 18 pages, 11 figures with 13 image files, 1 table

Report number: FERMILAB-PUB-25-0036-PPD-V

DarkNESS: developing a skipper-CCD instrument to search for Dark Matter from Low Earth Orbit

Authors: Phoenix Alpine, Samriddhi Bhatia, Fernando Chierchie, Alex Drlica-Wagner, Rouven Essig, Juan Estrada, Erez Etzion, Roni Harnik, Michael Lembeck, Nathan Saffold, Sho Uemura

Abstract: The DarkNESS (Dark Matter Nano-satellite Equipped with Skipper Sensors) mission aims to deploy a skipper-CCD CubeSat Observatory to search for dark matter (DM) from Low Earth Orbit. This mission will employ novel skipper-CCDs to investigate O(keV) X-rays from decaying DM, as well as electron recoils from strongly-interacting sub-GeV DM. The DarkNESS mission will be the first space deployment of sk… ▽ More The DarkNESS (Dark Matter Nano-satellite Equipped with Skipper Sensors) mission aims to deploy a skipper-CCD CubeSat Observatory to search for dark matter (DM) from Low Earth Orbit. This mission will employ novel skipper-CCDs to investigate O(keV) X-rays from decaying DM, as well as electron recoils from strongly-interacting sub-GeV DM. The DarkNESS mission will be the first space deployment of skipper-CCDs, and the DarkNESS team is developing a skipper-CCD instrument that is compatible with the CubeSat platform. DarkNESS has recently progressed from laboratory validation to a Critical Design Review (CDR) phase, with a launch opportunity anticipated in late 2025. The implementation of the DarkNESS skipper-CCD payload on the CubeSat platform will pave the way for future demonstrators of space-based imagers for X-ray and single-electron counting applications. △ Less

Submitted 16 December, 2024; originally announced December 2024.

Report number: FERMILAB-FN-1265-PPD

Vortex lattice melting and critical temperature shift in rotating Bose-Einstein condensates

Authors: Julian Amette Estrada, Marc E. Brachet, Pablo D. Mininni

Abstract: We investigate a shift in the critical temperature of rotating Bose-Einstein condensates mediated by the melting of the vortex lattice. Numerical simulations reveal that this temperature exhibits contrasting behavior depending on the system configuration: a negative shift occurs for fixed trap potentials due to the expansion of the condensate, while a positive shift is observed for fixed volumes,… ▽ More We investigate a shift in the critical temperature of rotating Bose-Einstein condensates mediated by the melting of the vortex lattice. Numerical simulations reveal that this temperature exhibits contrasting behavior depending on the system configuration: a negative shift occurs for fixed trap potentials due to the expansion of the condensate, while a positive shift is observed for fixed volumes, where vortex lattice rigidity suppresses thermal fluctuations. We introduce a vortex-energy model that captures the role of vortex interactions, the positional energy of the vortex lattice, as well as the phase transition and how the vortex lattice disappears. The findings provide insights into the thermodynamic properties of rotating condensates and the dynamics of vortex lattice melting, offering potential parallels with other quantum systems such as type-II superconductors. △ Less

Submitted 6 December, 2024; originally announced December 2024.

Proton-box contribution to $a_μ^{\rm{HLbL}}$

Authors: Emilio J. Estrada, Juan Manuel Márquez, Diego Portillo-Sánchez, Pablo Roig

Abstract: We analyze the proton$\text{-}$box contribution to the hadronic light$\text{-}$by$\text{-}$light part of the muon's anomalous magnetic moment, which is the first reported baryonic contribution to this piece. We follow the quark$\text{-}$loop analysis, incorporating the relevant data$\text{-}$driven and lattice proton form factors. Although the heavy mass expansion would yield a contribution of… ▽ More We analyze the proton$\text{-}$box contribution to the hadronic light$\text{-}$by$\text{-}$light part of the muon's anomalous magnetic moment, which is the first reported baryonic contribution to this piece. We follow the quark$\text{-}$loop analysis, incorporating the relevant data$\text{-}$driven and lattice proton form factors. Although the heavy mass expansion would yield a contribution of $\mathcal{O}(10^{-10})$, the damping of the form factors in the regions where the kernel peaks, explains our finding $a_μ^{\rm{p-box}}=1.82 (7)\times 10^{-12}$, two orders of magnitude smaller than the forthcoming uncertainty on the $a_μ$ measurement and on its Standard Model prediction. △ Less

Submitted 8 May, 2025; v1 submitted 11 November, 2024; originally announced November 2024.

Comments: 19 pages, 4 figures. Version accepted for publication in Phys. Rev. D

Journal ref: Phys. Rev. D 111, 093008 (2025)

SENSEI at SNOLAB: Single-Electron Event Rate and Implications for Dark Matter

Authors: Itay M. Bloch, Ana M. Botti, Mariano Cababie, Gustavo Cancelo, Brenda A. Cervantes-Vergara, Miguel Daal, Ansh Desai, Alex Drlica-Wagner, Rouven Essig, Juan Estrada, Erez Etzion, Guillermo Fernandez Moroni, Stephen E. Holland, Jonathan Kehat, Ian Lawson, Steffon Luoma, Aviv Orly, Santiago E. Perez, Dario Rodrigues, Nathan A. Saffold, Silvia Scorza, Miguel Sofo-Haro, Kelly Stifter, Javier Tiffenberg, Sho Uemura , et al. (5 additional authors not shown)

Abstract: We present results from data acquired by the SENSEI experiment at SNOLAB after a major upgrade in May 2023, which includes deploying 16 new sensors and replacing the copper trays that house the CCDs with a new light-tight design. We observe a single-electron event rate of $(1.39 \pm 0.11) \times 10^{-5}$ e$^-$/pix/day, corresponding to $(39.8 \pm 3.1)$ e$^-$/gram/day. This is an order-of-magnitude… ▽ More We present results from data acquired by the SENSEI experiment at SNOLAB after a major upgrade in May 2023, which includes deploying 16 new sensors and replacing the copper trays that house the CCDs with a new light-tight design. We observe a single-electron event rate of $(1.39 \pm 0.11) \times 10^{-5}$ e$^-$/pix/day, corresponding to $(39.8 \pm 3.1)$ e$^-$/gram/day. This is an order-of-magnitude improvement compared to the previous lowest single-electron rate in a silicon detector and the lowest for any photon detector in the near-infrared-ultraviolet range. We use these data to obtain a 90% confidence level upper bound of $1.53 \times 10^{-5}$ e$^-$/pix/day and to set constraints on sub-GeV dark matter candidates that produce single-electron events. We hypothesize that the data taken at SNOLAB in the previous run, with an older tray design for the sensors, contained a larger rate of single-electron events due to light leaks. We test this hypothesis using data from the SENSEI detector located in the MINOS cavern at Fermilab. △ Less

Submitted 24 October, 2024; originally announced October 2024.

Report number: FERMILAB-PUB-24-0767-PPD, YITP-SB-2024-25

A multi-channel silicon package for large-scale skipper-CCD experiments

Authors: A. M. Botti, C. Chavez, M. Sofo-Haro, C. S. Miller, F. Chierchie, M. Jonas, M. Lisovenko, H. Gutti, D. Czaplewski, A. Lathrop, J. Tiffenberg, G. Fernandez-Moroni, J. Estrada

Abstract: The next generation of experiments for rare-event searches based on skipper Charge Coupled Devices (skipper-CCDs) presents new challenges for the sensor packaging and readout. Scaling the active mass and simultaneously reducing the experimental backgrounds in orders of magnitude requires a novel high-density silicon-based package that must be massively produced and tested. In this work, we present… ▽ More The next generation of experiments for rare-event searches based on skipper Charge Coupled Devices (skipper-CCDs) presents new challenges for the sensor packaging and readout. Scaling the active mass and simultaneously reducing the experimental backgrounds in orders of magnitude requires a novel high-density silicon-based package that must be massively produced and tested. In this work, we present the design, fabrication, testing, and empirical signal model of a multi-channel silicon package. In addition, we outline the chosen specifications for the ongoing production of 1500 wafers that will add up to a 10 kg skipper-CCD array with 24000 readout channels. △ Less

Submitted 12 January, 2025; v1 submitted 8 October, 2024; originally announced October 2024.

Comments: 11 pages, 14 figures, 2 tables

Report number: FERMILAB-PUB-24-0716-PPD

Cherenkov Photon Background for Low-Noise Silicon Detectors in Space

Authors: Manuel E. Gaido, Javier Tiffenberg, Alex Drlica-Wagner, Guillermo Fernandez-Moroni, Bernard J. Rauscher, Fernando Chierche, Darío Rodrigues, Lucas Giardino, Juan Estrada

Abstract: Future space observatories dedicated to direct imaging and spectroscopy of extra-solar planets will require ultra-low-noise detectors that are sensitive over a broad range of wavelengths. Silicon charge-coupled devices (CCDs), such as EMCCDs, Skipper CCDs, and Multi-Amplifier Sensing CCDs, have demonstrated the ability to detect and measure single photons from ultra-violet to near-infrared wavelen… ▽ More Future space observatories dedicated to direct imaging and spectroscopy of extra-solar planets will require ultra-low-noise detectors that are sensitive over a broad range of wavelengths. Silicon charge-coupled devices (CCDs), such as EMCCDs, Skipper CCDs, and Multi-Amplifier Sensing CCDs, have demonstrated the ability to detect and measure single photons from ultra-violet to near-infrared wavelengths, making them candidate technologies for this application. In this context, we study a relatively unexplored source of low-energy background coming from Cherenkov radiation produced by energetic charged particles traversing a silicon detector. In the intense radiation environment of space, energetic cosmic rays produce high-energy tracks and more extended halos of low-energy Cherenkov photons, which are detectable with ultra-low-noise detectors. We present a model of this effect that is calibrated to laboratory data, and we use this model to characterize the residual background rate for ultra-low noise silicon detectors in space. We find that the rate of cosmic-ray-induced Cherenkov photon production is comparable to other detector and astrophysical backgrounds that have previously been considered. △ Less

Submitted 8 October, 2024; originally announced October 2024.

Comments: SPIE Proceeding; 9 pages, 6 figures

Report number: FERMILAB-CONF-24-0282-LDRD-PPD

Journal ref: Proc. SPIE 13103, X-Ray, Optical, and Infrared Detectors for Astronomy XI, 131031P (2024)