Showing 1–50 of 956 results for author: Zhang, Y

Thermal width shift of $Δ^{++}$ in a pion gas

Authors: Ying Zhang, Peng-Yu Niu, Xin-yue Hu, Kai-Jia Sun, Qian Wang

Abstract: We compute the thermal width shift of the $Δ^{++}$ resonance induced by a pion gas within a nonrelativistic effective field theory framework. The $Δ^{++}$ self-energy is evaluated from pion-forward-scattering diagrams with intermediate proton and $Δ$ states, weighted by the thermal pion distribution. Analytical expressions for the imaginary part of the self-energy yield the temperature-dependent w… ▽ More We compute the thermal width shift of the $Δ^{++}$ resonance induced by a pion gas within a nonrelativistic effective field theory framework. The $Δ^{++}$ self-energy is evaluated from pion-forward-scattering diagrams with intermediate proton and $Δ$ states, weighted by the thermal pion distribution. Analytical expressions for the imaginary part of the self-energy yield the temperature-dependent width correction $δΓ(T)$. The width increases with temperature, reaching approximately $6$~MeV at $T \approx 160$~MeV. When the temperature-dependent $Δ$ and nucleon masses from an NJL-model chiral restoration scenario are incorporated, the width shift becomes non-monotonic, peaking near $T \approx 140$~MeV---a consequence of the competition between collisional broadening and the shrinking $Δ\to Nπ$ phase space as the $N$--$Δ$ mass gap closes. Applying our formalism to STAR data for $Δ^{++}$ in d+Au collisions at $\sqrt{s_{NN}} = 200$~GeV, we extract a temperature $T \approx 300$~MeV at $p_t = 900$~MeV, consistent with the experimental extraction within errors. This value significantly exceeds the hadronic-phase temperature, explicitly demonstrating that the observed $Δ^{++}$ width shift is not solely of pion-gas origin---genuine hot-medium and collective-flow contributions must be substantial. △ Less

Submitted 21 August, 2026; originally announced August 2026.

Probing 5.49 MeV Solar Axions at Xenon Experiments

Authors: Ruofei Feng, Shao-Feng Ge, Oleg Titov, Yongchao Zhang

Abstract: The monochromatic 5.49 MeV solar axions induced by the isovector coupling $g_{3aN}$ can be searched for at the dark matter direct detection experiments. In this paper we estimate the prospects of the relevant axion couplings for axion mass $m_{a} <$ 1 MeV with xenon targets. Given the axion-electron coupling $g_{ae}$, the signal is dominated by the axion-induced $e^+ e^-$ pair production whose cro… ▽ More The monochromatic 5.49 MeV solar axions induced by the isovector coupling $g_{3aN}$ can be searched for at the dark matter direct detection experiments. In this paper we estimate the prospects of the relevant axion couplings for axion mass $m_{a} <$ 1 MeV with xenon targets. Given the axion-electron coupling $g_{ae}$, the signal is dominated by the axion-induced $e^+ e^-$ pair production whose cross section is largely enhanced when the axion mass approaches twice of the electron mass. Furthermore, the cross section depends on the atomic number squared $Z^2$. This allows the next-generation xenon experiments to surpass the current Borexino constraints and provide sensitivities competitive with those of the large neutrino detectors such as JUNO and Hyper-Kamiokande. With an exposure of 200 and 1000 ton$\cdot$yr, the couplings $|g_{3aN} g_{ae}|$ can be probed down to $1.59\times10^{-14}$ and $7.12\times10^{-15}$ at 90% C.L., respectively. If the axion couples to photons, the projected sensitivities on $|g_{3aN}g_{aγ}|$ can touch down to $6.76\times10^{-12}$ GeV$^{-1}$ and $3.02\times10^{-12}$ GeV$^{-1}$, respectively. △ Less

Submitted 16 August, 2026; originally announced August 2026.

Comments: 27 pages, 8 figures and 2 tables

A Bayesian approach to the long-baseline neutrino oscillation sensitivity of DUNE

Authors: DUNE Collaboration, S. Abbaslu, F. Abd Alrahman, A. Abed Abud, R. Acciarri, M. A. Acero, M. R. Adames, G. Adamov, M. Adamowski, K. Adhikari, C. Adriano, K. Agudelo-Jaramillo, F. Akbar, F. Alemanno, N. S. Alex, L. Aliaga Soplin, A. Alqaisi, O. Alterkait, A. Alton, R. Alvarez, T. Alves, A. Aman, H. Amar, R. M. Amarinei, P. Amedo , et al. (1262 additional authors not shown)

Abstract: The sensitivity of the Deep Underground Neutrino Experiment (DUNE) to neutrino oscillation is evaluated using a Bayesian Markov Chain Monte Carlo (MCMC) approach. This analysis uses the same underlying sensitivity inputs as previous DUNE studies [Eur. Phys. J. C 80, 978 (2020)], and therefore does not present updated DUNE sensitivities, but instead explores the additional inferences accessible usi… ▽ More The sensitivity of the Deep Underground Neutrino Experiment (DUNE) to neutrino oscillation is evaluated using a Bayesian Markov Chain Monte Carlo (MCMC) approach. This analysis uses the same underlying sensitivity inputs as previous DUNE studies [Eur. Phys. J. C 80, 978 (2020)], and therefore does not present updated DUNE sensitivities, but instead explores the additional inferences accessible using a Bayesian approach. We present four-dimensional posterior probability distributions of the oscillation parameters, highlighting the breadth of correlation in the parameter space of interest, especially between $\sin^2 θ_{23}$ and $\sin^2 θ_{13}$. We exploit the flexibility of the Bayesian framework to incorporate parameter constraints post hoc and assess the impact of applying a reactor short-baseline $θ_{13}$ constraint. A significant increase in the sensitivity to the $θ_{23}$ octant is found when including the constraint. Posterior distributions of derived quantities can be easily constructed from MCMC results. This work presents the first study of DUNE's sensitivity to the Jarlskog invariant, $J$, a quantity that provides a parametrisation-independent measure of charge-parity violation in the leptonic sector. △ Less

Submitted 4 August, 2026; originally announced August 2026.

Comments: 20 pages, 5 figures

Report number: FERMILAB-PUB-26-0548-LBNF

Photon Gas Thermodynamics in Doubly Special Relativity at the Planck Scale

Authors: Qi Xiong, Xinyi Yang, Guifeng Su, Yi Zhang

Abstract: We investigate the thermodynamics of a photon gas within the Magueijo-Smolin formulation of doubly special relativity, a framework that augments the speed of light with an observer-independent energy scale of the order of the Planck energy. We derive the logarithmic grand partition function, and the complete set of thermodynamic quantities for the photon gas, including the Helmholtz free energy, i… ▽ More We investigate the thermodynamics of a photon gas within the Magueijo-Smolin formulation of doubly special relativity, a framework that augments the speed of light with an observer-independent energy scale of the order of the Planck energy. We derive the logarithmic grand partition function, and the complete set of thermodynamic quantities for the photon gas, including the Helmholtz free energy, internal energy, entropy, pressure, and heat capacity, and perform their numerical evaluation. Our results smoothly reduce to the conventional special relativistic expressions in the limit where the invariant energy scale tends to infinity. For temperatures approaching the Planck scale, the finite cutoff induces a systematic suppression of all thermodynamic functions relative to their standard special-relativistic counterparts. △ Less

Submitted 28 July, 2026; originally announced July 2026.

Comments: 13 pages, 7 figures

Chiral Magnetic Conductivity in the Tight-Binding Model of Dirac Semimetals

Authors: Mustafa Bohra, Yuexiang Zhang, M. A. Zubkov

Abstract: We consider the typical tight - binding model of Dirac semimetal in the presence of both magnetic and electric fields. The electric conductivity reveals dependence on magnetic field. We calculate this dependence in the limit of strong magnetic field, when the given model is described effectively by the one - dimensional SSH model because the dynamics in the plane orthogonal to magnetic field is re… ▽ More We consider the typical tight - binding model of Dirac semimetal in the presence of both magnetic and electric fields. The electric conductivity reveals dependence on magnetic field. We calculate this dependence in the limit of strong magnetic field, when the given model is described effectively by the one - dimensional SSH model because the dynamics in the plane orthogonal to magnetic field is reduced to that of the lowest Landau level (LLL). Considering the small temperature limit we take into account dissipation due to scattering on impurities. The corresponding dissipation rate is calculated explicitly. The obtained results confirm that the source of the magnetoconductivity in this system is chiral magnetic effect. △ Less

Submitted 3 August, 2026; v1 submitted 21 July, 2026; originally announced July 2026.

Comments: Latex, 28 pages

Spacelike-Collinear Scattering by the Method of Regions

Authors: Wen Chen, Einan Gardi, Rourou Ma, Yao Ma, Yang Zhang, Zehao Zhu

Abstract: We study the spacelike-collinear limit of gauge-theory scattering amplitudes using the Method of Regions. The corresponding splitting amplitude violates strict collinear factorisation through its dependence on the non-collinear partons. While the associated colour dependence has long been known, starting at two loops the splitting amplitude also acquires dependence on their kinematics. We show tha… ▽ More We study the spacelike-collinear limit of gauge-theory scattering amplitudes using the Method of Regions. The corresponding splitting amplitude violates strict collinear factorisation through its dependence on the non-collinear partons. While the associated colour dependence has long been known, starting at two loops the splitting amplitude also acquires dependence on their kinematics. We show that this kinematic dependence originates from a unique hidden region present in the asymptotic expansion of the five-point amplitude in the spacelike-collinear limit, but absent in the timelike limit. More generally, we propose that hidden regions provide the mechanism by which crossing-related asymptotic limits cease to be analytically connected. We develop a general algorithm for the systematic identification of hidden regions. Applying it to the five-point amplitude in super Yang-Mills theory, we compute the hidden-region contributions to the complete set of basis integrals and recover the exact kinematically dependent factorisation-violating splitting amplitude. In momentum space, the hidden region is characterised by soft and Glauber loop momenta. This explains why the Wilson-line calculation captures the complete kinematic dependence, thereby accounting for the observed universality across gauge theories. △ Less

Submitted 16 July, 2026; originally announced July 2026.

Comments: 9 pages, 1 figure

Report number: USTC-ICTS/PCFT-26-46

Reconstruction of Primordial Power Spectrum from Gravitational Waves of High-Redshift Black Hole Binaries

Authors: Qianhang Ding, Xinpeng Wang, Masahide Yamaguchi, Ying-li Zhang

Abstract: High-redshift binary black hole (BBH) events are promising candidates for primordial black holes (PBHs) detectable by next-generation gravitational wave (GW) detectors. A redshifted mass distribution of detected PBH candidates can be obtained from GW observations, from which the underlying PBH mass function can be reconstructed. In this work, we develop a framework that applies the gradient-descen… ▽ More High-redshift binary black hole (BBH) events are promising candidates for primordial black holes (PBHs) detectable by next-generation gravitational wave (GW) detectors. A redshifted mass distribution of detected PBH candidates can be obtained from GW observations, from which the underlying PBH mass function can be reconstructed. In this work, we develop a framework that applies the gradient-descent method to the observed redshifted mass distribution and reconstructs the PBH mass function and, subsequently, the primordial power spectrum (PPS) on small scales. As an illustrative application, we analyze BBH events in the LIGO--Virgo--KAGRA (LVK) catalogs under a specified PBH selection criterion. We find a regularization-stable candidate bump-like enhancement of order $\mathcal{O}(10^{-2})$ in the reconstructed PPS, centered around $k_{\mathrm{peak}}\simeq 5.7\times 10^5~\mathrm{Mpc}^{-1}$ under the adopted assumptions. Our results demonstrate the feasibility of reconstructing the small-scale PPS from high-redshift BBH observations with next-generation GW detectors. △ Less

Submitted 13 July, 2026; originally announced July 2026.

Comments: 24 pages, 6 figures, 3 tables

Neutrino mass constraints in the Schwarzschild-de Sitter black-hole dark energy model with ACT DR6 and DESI DR2 data

Authors: Sheng-Han Zhou, Tian-Nuo Li, Guo-Hong Du, Yi-Min Zhang, Zhao-Yu Li, Jing-Fei Zhang, Xin Zhang

Abstract: Recent DESI observations have posed new challenges to $Λ$CDM, showing a preference for dynamical dark energy and yielding neutrino mass constraints within $Λ$CDM that approach the lower bound allowed by neutrino oscillation experiments. In this work, we investigate cosmological constraints on the key neutrino parameters, $\sum m_ν$ and $N_{\rm eff}$, within the Schwarzschild-de Sitter black-hole d… ▽ More Recent DESI observations have posed new challenges to $Λ$CDM, showing a preference for dynamical dark energy and yielding neutrino mass constraints within $Λ$CDM that approach the lower bound allowed by neutrino oscillation experiments. In this work, we investigate cosmological constraints on the key neutrino parameters, $\sum m_ν$ and $N_{\rm eff}$, within the Schwarzschild-de Sitter black-hole dark energy (SdSDE) framework. We use cosmic microwave background (CMB) data from Planck and ACT DR6, baryon acoustic oscillation data from DESI DR2, and type Ia supernova data from DES-Dovekie and PantheonPlus. We find that SdSDE scenarios prefer a positive neutrino mass whenever $\sum m_ν$ is allowed to vary. Using CMB+DESI+DES-Dovekie data, we obtain $\sum m_ν=0.207^{+0.047}_{-0.052}~{\rm eV}$ for SdSDE+$\sum m_ν$, reduced to $\sum m_ν=0.162^{+0.055}_{-0.056}~{\rm eV}$ when $N_{\rm eff}$ is also varied. This arises from the positive correlation between $N_{\rm eff}$ and $\sum m_ν$, together with the systematic preference of SdSDE for values of $N_{\rm eff}$ below the standard value. Furthermore, the best-fit $χ^2$ comparison shows that $Λ$CDM with extended neutrino parameters is strongly preferred over the corresponding SdSDE extension. Overall, the positive neutrino mass preference induced by SdSDE may reflect parameter compensation rather than an improved global fit, a possibility that should be further tested with future high-precision observational data. △ Less

Submitted 3 July, 2026; originally announced July 2026.

Comments: 13 pages, 5 figures

Exploring the neutron momentum distribution in nuclei through $γn \to π^- p$ at an electron-positron collider

Authors: Zi-Wei Yan, Shu-man Hu, Wei Wang, Ji Xu, Fu-Sheng Yu, Ya-Teng Zhang

Abstract: The neutron momentum distribution is essential both for reliably extracting fundamental free neutron observables from nuclear measurements and for probing the tensor force via the high-momentum neutron fraction, which is crucial to the theoretical understanding of short-range correlations (SRCs). In this work, we investigate this distribution by studying the $γn \to π^- p$ process at an electron-p… ▽ More The neutron momentum distribution is essential both for reliably extracting fundamental free neutron observables from nuclear measurements and for probing the tensor force via the high-momentum neutron fraction, which is crucial to the theoretical understanding of short-range correlations (SRCs). In this work, we investigate this distribution by studying the $γn \to π^- p$ process at an electron-positron collider, proposing to utilize the beryllium beam pipe at the Beijing Spectrometer III (BESIII). The cross sections for this process on both deuteron and beryllium targets are calculated within the impulse approximation framework. We also evaluate the effective luminosity of the photon flux from radiative Bhabha scattering, taking into account the distribution of target materials within the BESIII experimental setup. Our results show that tens of thousands of events can be generated at BESIII, offering the potential for precise measurements of the neutron momentum distribution. These findings suggest that electron-positron colliders could play a valuable role in elucidating nuclear structure and advancing our understanding of nonperturbative QCD, offering promising new avenues for both particle and nuclear physics. △ Less

Submitted 1 July, 2026; originally announced July 2026.

Comments: 10 pages, 7 figures, 2 tables

EasyScan_HEP 2: Agent-Ready Parameter Scans for High-Energy Physics

Authors: Yang Xiao, Yuanfang Yue, Yang Zhang

Abstract: AI agents are beginning to reshape the preparation and steering of computational workflows in high-energy physics phenomenology. To accommodate this change, we upgrade EasyScan_HEP to make the construction of parameter-scan configuration files more accessible to AI assistance. EasyScan_HEP 2 exposes agent-facing command-line and machine-readable interfaces, allowing an assistant to translate natur… ▽ More AI agents are beginning to reshape the preparation and steering of computational workflows in high-energy physics phenomenology. To accommodate this change, we upgrade EasyScan_HEP to make the construction of parameter-scan configuration files more accessible to AI assistance. EasyScan_HEP 2 exposes agent-facing command-line and machine-readable interfaces, allowing an assistant to translate natural language requests into an explicit .ini configuration that defines the scan method, external-program workflow, constraints, and outputs. The resulting configuration can be inspected through a local Web UI. The framework also supports AI-assisted extension to new scan methods, as illustrated by the integration of BESTFIT, EMCEE, and DYNESTY. In this way, EasyScan_HEP 2 adapts parameter scans to AI-assisted workflows while preserving reproducibility, transparency, and user control. △ Less

Submitted 30 June, 2026; originally announced June 2026.

Comments: 16 pages, 3 figures

The QCD phase diagram for three-flavor Möbius domain-wall fermions

Authors: Yu Zhang, Yasumichi Aoki, Jishnu Goswami, Shoji Hashimoto, Issaku Kanamori, Takashi Kaneko, Yoshifumi Nakamura

Abstract: We investigate the phase transition of Quantum Chromodynamics (QCD) with three degenerate quark flavors at zero baryon chemical potential. Using Möbius domain-wall fermions as the lattice fermion formulation, we ensure excellent chiral symmetry preservation. Our simulations are performed at three different temporal lattice extents, $N_{t}=6, 8, 12$, with a fixed lattice spacing $a=0.1361(20)$ fm,… ▽ More We investigate the phase transition of Quantum Chromodynamics (QCD) with three degenerate quark flavors at zero baryon chemical potential. Using Möbius domain-wall fermions as the lattice fermion formulation, we ensure excellent chiral symmetry preservation. Our simulations are performed at three different temporal lattice extents, $N_{t}=6, 8, 12$, with a fixed lattice spacing $a=0.1361(20)$ fm, corresponding to temperatures of 242(4), 181(3), and 121(2) MeV, respectively. We explore a range of quark masses and spatial volumes with aspect ratios $N_{s}/N_{t}$ spanning from 2 to 4. By analyzing the mass and volume dependencies of the plaquette, plaquette susceptibility, chiral condensate, chiral susceptibilities, and Binder cumulant, we identify the pseudocritical transition quark masses from our largest lattice volumes. For $N_t=6$, this is 184(10) MeV (determined from the plaquette susceptibility). For $N_t=8$ and 12, the transition points vary slightly depending on whether the total or disconnected chiral susceptibility is used, yielding ranges of 36(1)-39.1(9) MeV and 3.5(3)-3.7(2) MeV, respectively, in the $\overline{\text{MS}}$ scheme at a scale of $μ=2$ GeV. The negligible volume dependence at $N_t=6$ and 8, combined with finite-size scaling analysis at $N_t=12$ revealing volume growth significantly weaker than expected for a first- or second-order phase transition, points to a continuous crossover at these specific quark mass points. Additionally, we study the effects of residual chiral symmetry breaking on the chiral condensate and chiral susceptibilities using two different values of $L_s$. △ Less

Submitted 26 June, 2026; originally announced June 2026.

Comments: 53 pages, 22 figures

Report number: KEK-CP-0412

Bootstrapping two-loop six-gluon amplitudes in QCD

Authors: Sérgio Carrôlo, Dmitry Chicherin, Johannes M. Henn, Qinglin Yang, Yang Zhang

Abstract: The maximally transcendental, or most complicated, terms of gauge-theory scattering amplitudes have long been singled out, following Lipatov and collaborators, as those parts of a QCD amplitude that most closely mirror maximally supersymmetric Yang--Mills theory. We report on a programme that turns this observation into a practical computational tool. We show that the rational prefactors multiplyi… ▽ More The maximally transcendental, or most complicated, terms of gauge-theory scattering amplitudes have long been singled out, following Lipatov and collaborators, as those parts of a QCD amplitude that most closely mirror maximally supersymmetric Yang--Mills theory. We report on a programme that turns this observation into a practical computational tool. We show that the rational prefactors multiplying the highest-weight special functions of planar QCD amplitudes are governed by four-dimensional leading singularities, which can be classified and evaluated using on-shell diagrams. The resulting prefactors are manifestly conformally invariant and admit compact spinor-helicity expressions that hold for arbitrary multiplicity. Combining this input with the recently established two-loop six-particle function space, we set up a symbol bootstrap and determine, for the first time, the maximal-weight symbol of the planar two-loop six-gluon amplitude in massless QCD, first for the ${-}{-}{+}{+}{+}{+}$ helicity configuration and subsequently for all MHV configurations. The answer is fixed uniquely by physical consistency conditions, requires a reduced alphabet of only $137$ symbol letters, and yields as a byproduct previously unknown two-loop triple-collinear and double-soft splitting functions. We summarise the method and the results, and outline the directions they open up. △ Less

Submitted 26 June, 2026; originally announced June 2026.

Comments: 8 pages, 1 figure; talk presented at Loops and Legs in Quantum Field Theory 2026

Report number: MPP-2026-114

CHESS: CHEbyshev pSeudo-Spectral transport for Feynman integral differential equations

Authors: Yuanche Liu, Yang Zhang

Abstract: We present CHESS (CHEbyshev pSeudo Spectrum), a Wolfram Language package for high-precision one-dimensional transport of ε-factorized differential equations for Feynman master integrals. The solver works with the matrix obtained by pulling a differential one-form to a chosen path. This matrix may be supplied directly, or assembled from constant matrices and precomputed scalar pullbacks of the one-… ▽ More We present CHESS (CHEbyshev pSeudo Spectrum), a Wolfram Language package for high-precision one-dimensional transport of ε-factorized differential equations for Feynman master integrals. The solver works with the matrix obtained by pulling a differential one-form to a chosen path. This matrix may be supplied directly, or assembled from constant matrices and precomputed scalar pullbacks of the one-forms. The program combines Chebyshev-Lobatto spectral collocation, sparse matrix assembly, sequential propagation in the ε-expansion, and residue-based regularization of spurious regular singular endpoints. Benchmarks for large multi-scale integral families show rapid node convergence and agreement with independent reference data where such data are available. In the fixed local-series comparison used here, the Chebyshev transports also give shorter wall times; the reported process-tree memory usage is comparable for the smaller parallel runs and lower for the largest benchmark system in that comparison. △ Less

Submitted 25 June, 2026; originally announced June 2026.

Report number: USTC-ICTS/PCFT-26-42

SU(3)-flavor breaking as a structural probe of hidden-charm-strange $0^{--}$ tetraquarks in a color-octet basis

Authors: Bing-Dong Wan, Jun-Hao Zhang, Yan Zhang, Ming-Yang Yuan

Abstract: We study hidden-charm-strange tetraquark candidates with the exotic quantum number $J^{PC}=0^{--}$ to test whether SU(3)-flavor breaking acts as a universal mass shift or as a structural probe of a fixed color-octet current basis. Using $[\bar c c]_{8_c}\otimes[\bar s s]_{8_c}$-type and $[\bar c s]_{8_c}\otimes[\bar s c]_{8_c}$-type color-octet currents within QCD sum rules, we keep the strange-qu… ▽ More We study hidden-charm-strange tetraquark candidates with the exotic quantum number $J^{PC}=0^{--}$ to test whether SU(3)-flavor breaking acts as a universal mass shift or as a structural probe of a fixed color-octet current basis. Using $[\bar c c]_{8_c}\otimes[\bar s s]_{8_c}$-type and $[\bar c s]_{8_c}\otimes[\bar s c]_{8_c}$-type color-octet currents within QCD sum rules, we keep the strange-quark mass and strange condensates explicitly in the operator product expansion through dimension eight so that the strange-sector response can be traced at fixed color and Dirac structure. The hidden-charm-strange system is treated as the primary phenomenological target, while the hidden-bottom-strange sector serves as a stability benchmark. The strange-sector spectrum remains ordered, but the induced charm-sector shifts are grouped rather than uniform, with relatively small shifts for the $[\bar c c]_{8_c}\otimes[\bar s s]_{8_c}$ configurations and substantially larger shifts for the $[\bar c s]_{8_c}\otimes[\bar s c]_{8_c}$ ones. The $[\bar c s]_{8_c}\otimes[\bar s c]_{8_c}$ solutions are shifted toward the $D_s^*\bar D_{s1}$ threshold region, with one overlapping this region within uncertainties and another showing the largest positive SU(3)-breaking shift. Taken together, these features indicate that hidden strangeness can serve as a useful discriminator of internal current structure in the exotic $0^{--}$ sector. △ Less

Submitted 24 June, 2026; originally announced June 2026.

Comments: 21 pages, 9 figures, and 1 table

axionbloch: an Open-Source Python Package for Simulating Axion-Induced Spin Dynamics

Authors: Yuzhe Zhang

Abstract: The interaction of ultralight bosonic dark matter with spins can be interpreted as a pseudomagnetic field acting on normal matter. Such interactions can be modeled as usual magnetic interactions using spin-evolution (Bloch) equations. axionbloch, an open-source Python package for simulating spin dynamics induced by both usual and exotic interactions, is presented. The numerical simulations serve a… ▽ More The interaction of ultralight bosonic dark matter with spins can be interpreted as a pseudomagnetic field acting on normal matter. Such interactions can be modeled as usual magnetic interactions using spin-evolution (Bloch) equations. axionbloch, an open-source Python package for simulating spin dynamics induced by both usual and exotic interactions, is presented. The numerical simulations serve as a tool for deriving axion signal signatures, which are crucial for designing experimental searches and data analysis. Simulations are calibrated against theoretical expectations, ensuring the accuracy of the simulated signals. axionbloch is available at https://github.com/Yuzhe98/AxionBloch, allowing researchers to simulate pseudomagnetic signals under specific configurations of the axion models and experimental setups. The package is documented at http://axionbloch.readthedocs.io/ and includes example scripts for application. △ Less

Submitted 21 June, 2026; originally announced June 2026.

The Muon and Tau Electric Dipole Moments in the B-L Supersymmetric Standard Model

Authors: Wen-Hui Zhang, Jin-Lei Yang, Zhao-Feng Ge, Yu-Li Yan, Yin-Jie Zhang

Abstract: Recently proposed experiments are expected to significantly improve the measurement sensitivities of the electric dipole moments (EDMs) of muon ($d_μ$) and tau ($d_τ$). Given that theoretical predictions for $d_μ$ and $d_τ$ typically surpass those for the electron EDM, this work focuses on studying the contributions from the CP-violating (CPV) effects in the B-L supersymmetric (SUSY) standard mode… ▽ More Recently proposed experiments are expected to significantly improve the measurement sensitivities of the electric dipole moments (EDMs) of muon ($d_μ$) and tau ($d_τ$). Given that theoretical predictions for $d_μ$ and $d_τ$ typically surpass those for the electron EDM, this work focuses on studying the contributions from the CP-violating (CPV) effects in the B-L supersymmetric (SUSY) standard model (B-LSSM) to $d_μ$ and $d_τ$. After considering the corrections from some two-loop diagrams, the contributions in the B-LSSM to the EDMs of charged leptons are presented analytically in general forms. The numerical results show that the traditional $μ$-term in most SUSY models makes dominant contributions to $d_μ$ and $d_τ$, while the B-LSSM specific CPV parameters also induce significant effects. It is found that across a substantial region of the B-LSSM parameter space, $d_μ$ falls well within the projected sensitivity at Phase II of the proposed experiment, and $|d_τ|$ can reach about $10^{-21}e\cdot\text{cm}$. △ Less

Submitted 8 June, 2026; originally announced June 2026.

Comments: 21 pages, 5 figures

Hyperon-Nucleon Spectrometer

Authors: Xiaozhi Bai, Xu Cao, Zhe Cao, Jinhui Chen, Kai Chen, Qibo Chen, Shi Chen, Xin Chen, Yuquan Chen, Zhenyu Chen, Jianping Dai, Heng-Tong Ding, Dongshuo Du, Shuxian Du, Limin Duan, Zhe Duan, Anhui Feng, Jie Feng, Yicheng Feng, Jinlin Fu, Xiaofeng Fu, Chaosong Gao, Liang Ge, Wenwen Ge, Lisheng Geng , et al. (215 additional authors not shown)

Abstract: Chirality lies at the heart of low-energy QCD, governing the symmetry structure that shapes hadron masses and strong interaction dynamics. Among the most compelling open questions tied to chiral dynamics and spontaneous chiral symmetry breaking is the longstanding $Λ$ polarization puzzle, in which $Λ$ hyperons produced in unpolarized hadronic collisions exhibit a surprisingly large transverse pola… ▽ More Chirality lies at the heart of low-energy QCD, governing the symmetry structure that shapes hadron masses and strong interaction dynamics. Among the most compelling open questions tied to chiral dynamics and spontaneous chiral symmetry breaking is the longstanding $Λ$ polarization puzzle, in which $Λ$ hyperons produced in unpolarized hadronic collisions exhibit a surprisingly large transverse polarization that remains theoretically unexplained. This whitepaper presents the proposal for the Hyperon-Nucleon Spectrometer (H-NS) at the High-Intensity heavy-ion Accelerator Facility (HIAF). Leveraging the high energy and high intensity of HIAF's proton and heavy-ion beams, the H-NS experiment will perform systematic studies of hyperon polarization phenomena and their underlying mechanisms in proton-proton ($pp$), proton-nucleus ($pA$), and nucleus-nucleus ($AA$) collisions in the fixed target mode. A wide-range beam energy scan, including proton beams from 3 GeV up to 9.3 GeV (HIAF) and up to 32 GeV (upgraded HIAF), will be conducted to examine the dependence of polarization on collision energy. The spectrometer is designed with specialized detectors capable of high-precision reconstruction of final-state baryon polarizations. Among its many interesting and important measurements, H-NS will simultaneously measure hyperon and proton spin observables to explore the polarization mechanism in hadronic interactions and the spin structure of baryons. Furthermore, the use of $pA$ and $AA$ collisions will enable detailed investigations of cold and hot nuclear matter effects on spin polarization. Its physics program and detector development will significantly benefit the future Electron-ion Collider in China. △ Less

Submitted 4 June, 2026; originally announced June 2026.

Comments: 69 pages, Hyperon-Nucleon Spectrometer (H-NS) white paper

Precision Electroweak Constraints on Neutrinophilic Scalars

Authors: Saeid Foroughi-Abari, Camilla Mupo, Drona Vatsyayan, Yue Zhang

Abstract: Strong self-interaction among the active neutrinos mediated by a neutrinophilic scalar is a well-motivated target of particle physics and cosmological probes. In this article, we present precision electroweak constraints on models for neutrino self-interaction. We first work in the simplified model where the finite radiative corrections are obtained with the guidance of gauge invariance. These cor… ▽ More Strong self-interaction among the active neutrinos mediated by a neutrinophilic scalar is a well-motivated target of particle physics and cosmological probes. In this article, we present precision electroweak constraints on models for neutrino self-interaction. We first work in the simplified model where the finite radiative corrections are obtained with the guidance of gauge invariance. These corrections are logarithmically enhanced for small mediator masses. We point out the importance of neutrino charged-current coupling correction and its impact on the $Δr$ parameter and Fermi constant measurements. This effect was overlooked previously and allows us to derive the leading constraint on the neutrinophilic couplings for mediator mass above a few hundred MeV. We investigate the robustness of the result in a concrete UV completion which further includes a TeV-scale $SU(2)_L$ triplet scalar and find the simplified model constraints continue to hold for a wide range of parameter space. We pin down moving parts in the UV complete model and conditions when the contributions from heavy particle loops are no longer negligible. Our results serve as a useful road map for future explorations of the self-interacting neutrino paradigm. △ Less

Submitted 1 June, 2026; originally announced June 2026.

Comments: 36 pages, 11 figures

Probing the dark axion portal via $J/ψ$ decays at BESIII and STCF

Authors: Zeren Simon Wang, Dazhuang He, Yu Zhang

Abstract: Large numbers of $J/ψ$ mesons can be resonantly produced at BESIII and STCF at the center-of-mass energy $\sqrt{s}=3.097$ GeV. Such $J/ψ$ mesons may undergo rare decays into an axionlike particle (ALP) $a$ and a dark photon $γ'$ in the theoretical framework of the dark axion portal. In this work, we investigate the exclusion reach of the existing BESIII dataset together with the projected sensitiv… ▽ More Large numbers of $J/ψ$ mesons can be resonantly produced at BESIII and STCF at the center-of-mass energy $\sqrt{s}=3.097$ GeV. Such $J/ψ$ mesons may undergo rare decays into an axionlike particle (ALP) $a$ and a dark photon $γ'$ in the theoretical framework of the dark axion portal. In this work, we investigate the exclusion reach of the existing BESIII dataset together with the projected sensitivity of STCF, focusing on the mono-photon signature. We perform Monte Carlo simulations and estimate the exclusion reach in the portal coupling $G_{aγγ'}$ as a function of the ALP and dark-photon masses, taking background events into account. Our results indicate that the existing BESIII dataset already has exclusion sensitivity to previously unexplored regions of the dark axion portal parameter space, while the future STCF can further improve the sensitivity by roughly an order of magnitude. △ Less

Submitted 1 June, 2026; originally announced June 2026.

Comments: 7 pages plus refs, 4 figures

Subcritical bubble prehistory in weak first-order phase transition

Authors: Guangshang Chen, Yang Xiao, Jin Min Yang, Yang Zhang

Abstract: Standard calculations of cosmological first-order phase transitions usually assume critical bubbles to nucleate on a homogeneous symmetric vacuum background. However, this assumption can fail in weak transitions, where thermal fluctuations trigger subcritical bubbles before the standard nucleation temperature $T_n$. Motivated by this possibility, we systematically examine whether the homogeneous n… ▽ More Standard calculations of cosmological first-order phase transitions usually assume critical bubbles to nucleate on a homogeneous symmetric vacuum background. However, this assumption can fail in weak transitions, where thermal fluctuations trigger subcritical bubbles before the standard nucleation temperature $T_n$. Motivated by this possibility, we systematically examine whether the homogeneous nucleation background approximation is self-consistent. By evolving the Gelmini-Gleiser subcritical bubble kinetics and comparing it with the standard critical bubble nucleation picture, we identify the parameter regions in which the background becomes apparently mixed. A detailed scan of these regions shows that sizable subcritical volume fractions arise when the two phases are nearly degenerate at $T_n$, the potential barrier is low, the difference of free energy between the symmetric and broken phases is moderate and the transition strength is weak. Our analysis further yields a simple criterion, $\log_{10}\hat f_ξ(T_n)\simeq -1.95$, for a percent level subcritical bubble volume fraction. Parameter points above this boundary should be treated as mixed background candidates rather than as ordinary homogeneous bounce points. △ Less

Submitted 24 May, 2026; originally announced May 2026.

Comments: 11 pages, 6 figures

Spectroscopy of hidden-heavy tetraquark states with $J^{PC}=0^{--}$ in a color-octet configuration

Authors: Bing-Dong Wan, Jun-Hao Zhang, Yan Zhang, Ming-Yang Yuan

Abstract: Within the QCD sum-rule framework, we investigate hidden-heavy tetraquark channels with the exotic quantum number $J^{PC}=0^{--}$ using four representative local color-octet--octet interpolating currents. The currents include both vector--axialvector and scalar--pseudoscalar Dirac structures. The operator product expansion is carried out up to dimension-eight condensates. The four diagonal sum rul… ▽ More Within the QCD sum-rule framework, we investigate hidden-heavy tetraquark channels with the exotic quantum number $J^{PC}=0^{--}$ using four representative local color-octet--octet interpolating currents. The currents include both vector--axialvector and scalar--pseudoscalar Dirac structures. The operator product expansion is carried out up to dimension-eight condensates. The four diagonal sum rules yield mutually consistent mass estimates in the range $10.8$--$11.1~\mathrm{GeV}$ for the hidden-bottom sector and around $4.3$--$4.6~\mathrm{GeV}$ for the corresponding hidden-charm sector, with the bottom sector exhibiting the clearest Borel stability. Since local tetraquark currents with the same quantum numbers are related by Fierz rearrangements, the current-dependent results do not by themselves imply four distinct states or uniquely defined internal color structures. We also discuss quantum-number-allowed decay channels and emphasize the absence of the lowest pseudoscalar--pseudoscalar heavy-meson modes for a neutral $0^{--}$ state. The results provide theoretical guidance for future experimental searches at Belle II, LHCb, and BESIII. △ Less

Submitted 21 August, 2026; v1 submitted 20 May, 2026; originally announced May 2026.

Comments: Accepted by PRD

Radiative decays of the $Λ(1520)$ as a dynamically generated resonance

Authors: Rui-Xiang Shi, Yu-Bao Zhang, Jun-Xu Lu, Chun-Yan Song, Li-Sheng Geng

Abstract: Inspired by the latest BESIII measurement of the $Λ(1520)\toγΣ^0$ radiative decay, we systematically study the decays $Λ(1520)\toγΛ(Σ^0)$ within the chiral unitary approach, where the $Λ(1520)$ is treated as a dynamically generated resonance from meson-baryon interactions. Compared with previous chiral unitary studies, we adopt dimensional regularization for $S$-wave loop integrals to preserve gau… ▽ More Inspired by the latest BESIII measurement of the $Λ(1520)\toγΣ^0$ radiative decay, we systematically study the decays $Λ(1520)\toγΛ(Σ^0)$ within the chiral unitary approach, where the $Λ(1520)$ is treated as a dynamically generated resonance from meson-baryon interactions. Compared with previous chiral unitary studies, we adopt dimensional regularization for $S$-wave loop integrals to preserve gauge invariance and, for the first time, include Feynman diagrams with photon coupling to intermediate baryons. Our calculated partial decay width $Γ(Λ(1520)\toγΣ^0)$ agrees well with the new BESIII data, whereas the predicted $Γ(Λ(1520)\toγΛ)$ is considerably smaller than the CLAS experimental result. By comparing our results with predictions from various quark models, we discuss the internal nature of the $Λ(1520)$ resonance, highlight its complex component structure, and stress the need for more refined theoretical frameworks and further experimental measurements. △ Less

Submitted 14 May, 2026; originally announced May 2026.

Comments: 8 pages,6 figures,3 tables

Long-lived sterile neutrinos from axionlike particles at the Super Tau-Charm Facility

Authors: Xiaokun Li, Zeren Simon Wang, Yu Zhang, Xiaorong Zhou

Abstract: We study the search prospect of long-lived heavy neutral leptons (HNLs) pair produced in decays of axionlike particles (ALPs) at the proposed Super Tau--Charm Facility (STCF), focusing on the center-of-mass energy of $\sqrt{s}=3.773$ GeV. The ALPs are assumed to originate from $D^\pm$-meson decays in association with a charged pion. We perform both truth-level and detector-level Monte Carlo simula… ▽ More We study the search prospect of long-lived heavy neutral leptons (HNLs) pair produced in decays of axionlike particles (ALPs) at the proposed Super Tau--Charm Facility (STCF), focusing on the center-of-mass energy of $\sqrt{s}=3.773$ GeV. The ALPs are assumed to originate from $D^\pm$-meson decays in association with a charged pion. We perform both truth-level and detector-level Monte Carlo simulations and obtain the expected sensitivity reach to the mixing parameter between the HNL and the electron neutrino, $|V_{eN}|^2$, with a displaced-vertex search at STCF. We find that STCF can probe values of $|V_{eN}|^2$ about one-to-two orders of magnitude beyond the existing bounds. We also perform an approximate reinterpretation of a search for HNLs at the CHARM experiment, which is subject to model-dependent assumptions on the production and kinematic distributions, and find that beam-dump experiments may provide strong complementary constraints. △ Less

Submitted 30 July, 2026; v1 submitted 12 May, 2026; originally announced May 2026.

Comments: v1: 25 pages plus refs, 5 figures; v2: 26 pages plus refs, 5 figures, accepted for publication in Chinese Physics C

An Algorithm for the Symbolic Reduction of Multi-loop Feynman Integrals via Generating Functions

Authors: Bo Feng, Xiang Li, Yuanche Liu, Yanqing Ma, Yang Zhang

Abstract: We develop a generating-function formulation for the symbolic reduction of multi-loop Feynman integrals. In this framework, integration-by-parts identities are rewritten as differential equations for sector-wise generating functions, so the reduction problem can be studied in a non-commutative algebra of differential operators rather than only through relations among individual integrals. This vie… ▽ More We develop a generating-function formulation for the symbolic reduction of multi-loop Feynman integrals. In this framework, integration-by-parts identities are rewritten as differential equations for sector-wise generating functions, so the reduction problem can be studied in a non-commutative algebra of differential operators rather than only through relations among individual integrals. This viewpoint leads to an iterative algorithm that generates candidate equations, extracts symbolic reduction rules, updates the active rule set, and tests completeness on the lattice of integral indices. We illustrate the method with the sunset topology, planar and non-planar massless double-box topologies, representative subsectors, and a degenerate example in which the top sector contains no master integral. Together, these examples show how symbolic reduction rules, descendant equations, and completeness criteria can be organized within a single algebraic framework. △ Less

Submitted 10 May, 2026; originally announced May 2026.

Report number: USTC-ICTS/PCFT-26-25

Genus drop involving non-hyperelliptic curves in Feynman integrals

Authors: Feiyu Yang, Jianyu Gong, Yang Zhang

Abstract: For both theoretical and phenomenological studies, it is important to analyze the function types of Feynman integrals. The phenomenon of genus drop between different representations of hyperelliptic Feynman integrals was discussed in \cite{Marzucca2024Genusdrop}. In this paper, we reformulate the extra-involution mechanism of \cite{Marzucca2024Genusdrop} as a special case of an unramified double c… ▽ More For both theoretical and phenomenological studies, it is important to analyze the function types of Feynman integrals. The phenomenon of genus drop between different representations of hyperelliptic Feynman integrals was discussed in \cite{Marzucca2024Genusdrop}. In this paper, we reformulate the extra-involution mechanism of \cite{Marzucca2024Genusdrop} as a special case of an unramified double covering between algebraic curves, and show that this covering mechanism also explains genus drops accompanied by a curve-type change from non-hyperelliptic to hyperelliptic for a class of three-loop Feynman diagrams. We also demonstrate that within a specific framework, the origin of the discrete spacetime symmetry that leads to the genus drop in hyperelliptic cases is manifest. This work also points out that there exist non-hyperelliptic Feynman integrals that exhibit no apparent genus drop. △ Less

Submitted 8 May, 2026; originally announced May 2026.

Comments: 10 pages, 3 figures

Report number: USTC-ICTS/PCFT-26-27

Search for Sub-GeV Axion-Like Particles at EBES Pilot Run Using 4 GeV Positron Beam at KEK LINAC

Authors: Takahiro Fusayasu, Tomoya Iizawa, Fumihito Ikeda, Akimasa Ishikawa, Masako Iwasaki, Hiroshi Iwase, Takahiro Kawahara, Aoi Masaki, Fusashi Miyahara, Yu Morikawa, Yuichi Okayasu, Toshiyuki Ono, Hidetoshi Otono, Yasuhito Sakaki, Takumi Seino, Yuta Shimasaki, Taikan Suehara, Yosuke Takubo, Shusaku Tsumura, Kosuke Uemura, Yifu Zhang

Abstract: We report the results of a search for sub-GeV axion-like particles (ALPs) using pilot run data from the Electron Beam-dump Experiment at KEK LINAC Switching Yard 3 (EBES). The data were collected in December 2023 with a 4 GeV positron beam and correspond to $1.3\times10^{14}$ positrons on target. In the pilot run setup, a tungsten beam dump and a single PbO calorimeter were used. We consider ALP p… ▽ More We report the results of a search for sub-GeV axion-like particles (ALPs) using pilot run data from the Electron Beam-dump Experiment at KEK LINAC Switching Yard 3 (EBES). The data were collected in December 2023 with a 4 GeV positron beam and correspond to $1.3\times10^{14}$ positrons on target. In the pilot run setup, a tungsten beam dump and a single PbO calorimeter were used. We consider ALP production via the Primakoff process induced by bremsstrahlung photons in the beam dump, followed by the decay $a\toγγ$. The background was estimated with a data-driven method, and a signal region was defined such that the expected background yield is below 0.1 events. No events were observed after unblinding. Upper limits at the 90% confidence level were derived in the ALP mass-coupling plane, extending the experimental coverage into a region of parameter space not explored by previous searches. △ Less

Submitted 7 May, 2026; originally announced May 2026.

Comments: 15 pages, 9 figures

Squeezed spectra and back-to-back correlations of protons and antiprotons at RHIC energies

Authors: Yong Zhang

Abstract: This study constrains the range of in-medium mass modification through a comparison of theoretical calculations with experimental transverse momentum spectra and the yield ratio {\bar{p}}/p of protons and antiprotons. Based on the constrained range and a Gaussian source model with radial ow, the theoretical predictions for the fermion back-to-back correlation (fBBC) of p{\bar{p}} pairs at RHIC ene… ▽ More This study constrains the range of in-medium mass modification through a comparison of theoretical calculations with experimental transverse momentum spectra and the yield ratio {\bar{p}}/p of protons and antiprotons. Based on the constrained range and a Gaussian source model with radial ow, the theoretical predictions for the fermion back-to-back correlation (fBBC) of p{\bar{p}} pairs at RHIC energies are presented. The results reveal a strong sensitivity of the fBBC signal to the assumed source time distribution: a Lorentzian form generates a pronounced high-momentum signal, whereas an α-stable Lévy form leads to a marked low-momentum signal. Moreover, the in-medium mass modification is shown to enhance the yield ratio {\bar{p}}/p. Therefore, events characterized by a larger {\bar{p}}/p ratio are predicted to have a significantly higher probability of exhibiting a detectable fBBC signal. This study may propose a promising new direction for the experimental observation of this phenomenon △ Less

Submitted 6 May, 2026; originally announced May 2026.

Comments: 7 pages, 4 figures

Can LLP detectors probe the reheating temperature? A case study of vector dark matter

Authors: Paulo Areyuna C, Giovanna Cottin, Bastián Díaz Sáez, Zeren Simon Wang, Yu Zhang

Abstract: We study an extension of the singlet-scalar Higgs portal featuring a dark vector $V_μ$ and a real scalar $φ$. The vector is a dark matter (DM) candidate, while $φ$ is long-lived and decays via higher-dimensional operators. We explore the DM production via freeze-in at low and high reheating temperatures. At colliders, the decay $φ\to Z+V$ yields distinctive long-lived particle (LLP) signatures. We… ▽ More We study an extension of the singlet-scalar Higgs portal featuring a dark vector $V_μ$ and a real scalar $φ$. The vector is a dark matter (DM) candidate, while $φ$ is long-lived and decays via higher-dimensional operators. We explore the DM production via freeze-in at low and high reheating temperatures. At colliders, the decay $φ\to Z+V$ yields distinctive long-lived particle (LLP) signatures. We explore the interplay between cosmological constraints and LLP searches at the LHC and FCC-hh, showing that far detectors can probe otherwise inaccessible parameter space and place novel bounds on the reheating temperature. △ Less

Submitted 27 April, 2026; originally announced April 2026.

Comments: 31 pages, 15 figures

Gauge-independent approach to inflation in quadratic gravity

Authors: Adrian Palomares, Ying-li Zhang, Jinsu Kim

Abstract: We investigate the scalar sector of linear cosmological perturbations in quadratic gravity. Working in the Einstein frame, we derive the equations of motion in a gauge-independent manner and express them in terms of three sets of gauge-invariant variables. This approach allows us to distinguish genuine physical effects from gauge artefacts, which is particularly relevant for assessing the stabilit… ▽ More We investigate the scalar sector of linear cosmological perturbations in quadratic gravity. Working in the Einstein frame, we derive the equations of motion in a gauge-independent manner and express them in terms of three sets of gauge-invariant variables. This approach allows us to distinguish genuine physical effects from gauge artefacts, which is particularly relevant for assessing the stability of perturbations in this theory. In the superhorizon limit, we obtain the leading-order behaviour of the relevant gauge-invariant variables and analyse the perturbations in commonly used gauges. We find that the Newtonian gauge exhibits an apparent instability, characterised by the exponential growth of the metric perturbations. However, this growth is non-generic and gauge-dependent; in the other gauges analysed in this work, the perturbations remain well behaved within the perturbative regime. Our analysis also demonstrates how the evolution behaviour of a gauge-invariant variable changes under the frame transformation and clarifies the relation between results obtained in the Jordan and Einstein frames. △ Less

Submitted 8 July, 2026; v1 submitted 24 April, 2026; originally announced April 2026.

Comments: 21 pages, PRD-accepted version

Quark Number Susceptibilities and Conserved Charge Fluctuations in $(2+1)$-flavor QCD with Möbius domain-wall fermions (MDWF)

Authors: Jishnu Goswami, Yasumichi Aoki, Hidenori Fukaya, Shoji Hashimoto, Issaku Kanamori, Takashi Kaneko, Yoshifumi Nakamura, David Ward, Yu Zhang

Abstract: We calculate second- and selected fourth-order conserved-charge fluctuations in $(2+1)$-flavor QCD using Möbius domain-wall fermions (MDWF) along a line of constant physics. Gauge ensembles were generated for two light-to-strange quark-mass ratios, $m_l/m_s=1/10$ and $1/27.4$, corresponding to heavier-than-physical and physical pion masses, respectively. For $m_l/m_s=1/10$, calculations were carri… ▽ More We calculate second- and selected fourth-order conserved-charge fluctuations in $(2+1)$-flavor QCD using Möbius domain-wall fermions (MDWF) along a line of constant physics. Gauge ensembles were generated for two light-to-strange quark-mass ratios, $m_l/m_s=1/10$ and $1/27.4$, corresponding to heavier-than-physical and physical pion masses, respectively. For $m_l/m_s=1/10$, calculations were carried out on lattices with temporal extents $N_τ=12$ and $16$, enabling an assessment of lattice-spacing effects at heavier pion mass. For $m_l/m_s=1/27.4$, calculations were performed at $N_τ=12$, allowing us to study the light-quark-mass dependence down to the physical point. Below the pseudocritical temperature, second-order electric-charge, strangeness, and off-diagonal conserved-charge fluctuations are consistent with QMHRG2020 hadron resonance gas calculations. Across the crossover region, these observables rise rapidly and tend toward their Stefan--Boltzmann limits. Selected fourth-order cumulants were also computed at the physical pion mass. Although these observables are statistically more demanding, several channels with controlled uncertainties permit a first comparison with hadron resonance gas calculations. △ Less

Submitted 24 April, 2026; originally announced April 2026.

Comments: 17 pages, 12 figures

Report number: KEK-CP-0409, OU-HET-1279

Looking for Lights from the Darkness: Signals from MeV-scale Solar Axion-like Particles

Authors: Yu-Cheng Qiu, Yongchao Zhang

Abstract: The axion-like particles $a$ can be produced in the Sun via the process of $p + D \to {}^3{\rm He} +a$, with mass up to 5.5 MeV. The photons in the subsequent decay $a \to γγ$ can deviate significantly from the Sun, or even from roughly the opposite direction of the Sun. The nontrivial angular and spectral distributions of such photons enable us new methods to detect the {\it lights from the darkn… ▽ More The axion-like particles $a$ can be produced in the Sun via the process of $p + D \to {}^3{\rm He} +a$, with mass up to 5.5 MeV. The photons in the subsequent decay $a \to γγ$ can deviate significantly from the Sun, or even from roughly the opposite direction of the Sun. The nontrivial angular and spectral distributions of such photons enable us new methods to detect the {\it lights from the darkness}. In this letter, we consider both the space detection and terrestrial experiments at the South Pole. As a result of the two-body decay and the geometric effects, there exists a critical height for the terrestrial experiments, below which there is no photon for some regions of the parameter space. With the sensitivities of $10^{-16}$ ($10^{-17}$) erg cm$^{-2}$ s$^{-1}$ for the MeV-scale photons in future space and terrestrial experiments, the coupling $g_{aγ}$ of $a$ to photons can be probed up to $3\times10^{-12}$ ($1\times10^{-12}$) GeV$^{-1}$, well surpassing the current supernova limits. △ Less

Submitted 20 April, 2026; originally announced April 2026.

Comments: 8+2 pages, 6+1 figures

Exact Solutions of the SU(2) Yang-Mills Equations from a Static Ansatz

Authors: Yu-Xuan Zhang, Jing-Ling Chen

Abstract: We present a systematic study of static solutions to the source-free SU(2) Yang-Mills equations, in which the gauge potential explicitly depends on spin operators. By employing the \emph{vector potential extraction approach} -- which requires the total angular momentum operator (orbital plus spin) to satisfy the standard angular momentum algebra -- we derive the most general form of the spin vecto… ▽ More We present a systematic study of static solutions to the source-free SU(2) Yang-Mills equations, in which the gauge potential explicitly depends on spin operators. By employing the \emph{vector potential extraction approach} -- which requires the total angular momentum operator (orbital plus spin) to satisfy the standard angular momentum algebra -- we derive the most general form of the spin vector potential $\vec{A}$. This leads to the static ansatz $\{ \vec{A} = [k_1(\hat{r}\times\vecΓ) + k_2\vecΓ + k_3(\vecΓ\cdot\hat{r})\hat{r}]/r, \varphi = f_1(r)\,(\vecΓ\cdot\hat{r}) + f_2(r)\}$, parametrized by three constants $\{k_1, k_2, k_3\}$ and two radial functions $\{f_1(r), f_2(r)\}$. After substituting this static ansatz into the Yang-Mills equations we obtain a set of consistency equations. Solving these equations provides a complete classification of the exact static solutions, including both real and complex families. The known simple SU(2) static solution $\{\vec{A}=\tilde{k} (\hat{r}\times\vecΓ)/r, \varphi=κ/r \}$ is recovered as a special case. Our classification reveals new static configurations that could be valuable for non-perturbative studies and for models where the internal spin couples to non-Abelian gauge fields. △ Less

Submitted 7 June, 2026; v1 submitted 16 April, 2026; originally announced April 2026.

Comments: Main 20 pages + SM 71 pages, 0 figure. Revised version

Gravitational Gertsenshtein-Zeldovich mechanism for the Association between GW190425 and FRB 20190425A

Authors: Shao-Qin Wu, Jing-Rui Zhang, Rong-Gen Cai, Bing Zhang, Yun-Long Zhang

Abstract: The temporal and spatial coincidence between the gravitational wave (GW) event GW190425 and the fast radio burst (FRB) event FRB 20190425A raises the intriguing possibility of a physical connection between the two. The widely discussed possibility invoking the collapse of a supermassive neutron star as the merger product suffers the inconsistency between the model prediction and the measured incli… ▽ More The temporal and spatial coincidence between the gravitational wave (GW) event GW190425 and the fast radio burst (FRB) event FRB 20190425A raises the intriguing possibility of a physical connection between the two. The widely discussed possibility invoking the collapse of a supermassive neutron star as the merger product suffers the inconsistency between the model prediction and the measured inclination angle of the system. Here, we propose a novel physical mechanism to account for the association. We envisage a magnetar located at about 2.5 light hours away from the binary neutron star merger site. The kiloherz GWs generated by the merger are converted into kiloherz electromagnetic (EM) radiation via the Gertsenshtein-Zeldovich (GZ) effect near the magnetar. Subsequent inverse Compton scattering off the kilohertz EM waves by relativistic particles generates the observed gigahertz FRB emission. Our calculation reveals that, with appropriate parameter choices, the properties of FRB 20190425A can be reproduced. △ Less

Submitted 14 April, 2026; originally announced April 2026.

Comments: 6 pages, 1 figure

Searching for apparent baryon number violation in $Λ_c^+$ decays at the Super Tau-Charm Facility

Authors: Zeren Simon Wang, Xin-Ru Tang, Yu Zhang, Yu Zhang, Xiaorong Zhou

Abstract: Observation of baryon number violation (BNV) in laboratory experiments would constitute unambiguous evidence for physics beyond the Standard Model. We propose dedicated searches for \textit{apparent} BNV in charm-baryon decays, $Λ_c^+\to M^+ +$ missing energy ($M=π, K$) where the missing energy stems from a resonance. These channels have not been explored experimentally so far, despite the relativ… ▽ More Observation of baryon number violation (BNV) in laboratory experiments would constitute unambiguous evidence for physics beyond the Standard Model. We propose dedicated searches for \textit{apparent} BNV in charm-baryon decays, $Λ_c^+\to M^+ +$ missing energy ($M=π, K$) where the missing energy stems from a resonance. These channels have not been explored experimentally so far, despite the relatively clean environment potentially provided by near $Λ_c^+\overlineΛ_c^-$ threshold production at $e^+e^-$ colliders. Performing state-of-the-art Monte Carlo simulations for the proposed Super Tau-Charm Facility (STCF), we evaluate the signal efficiencies and derive projected model-independent sensitivities under the assumption of negligible background. We further interpret these sensitivities within two theoretical frameworks: a sterile-neutrino-extended low-energy effective field theory ($ν$LEFT) and R-parity-violating (RPV) supersymmetry. With an integrated luminosity of 1 ab$^{-1}$, STCF can probe new-physics scales of several TeV in the $ν$LEFT description and constrain the RPV model parameter $λ''_{212}/m^2_{\tilde{q}}$ down to about $0.1~\mathrm{TeV}^{-2}$. Our results demonstrate that STCF provides a highly competitive opportunity for probing BNV interactions in rare charm-baryon decays. △ Less

Submitted 12 June, 2026; v1 submitted 13 April, 2026; originally announced April 2026.

Comments: v1, 24 pages plus refs, 7 figures; v2, minor revisions, 25 pages plus refs, 7 figures, accepted for publication in PRD

DREAMuS: Dark matter REsearch with Advanced Muon Source

Authors: Xiang Chen, Zejia Lu, Liangwen Chen, Jun Gao, Shao-Feng Ge, Zhanxu Hao, Yang Hu, Bingzhi Li, Cen Mo, Zhiyu Sun, Huayang Wang, Chonghao Wu, Yu Xu, Xueheng Zhang, Yulei Zhang, Liang Li

Abstract: We propose DREAMuS, a fixed-target experiment at the High Intensity Heavy-Ion Accelerator Facility (HIAF), to search for muon-philic dark matter mediated by light flavor-violating bosons. DREAMuS is designed to probe the parameter space of a muon-philic dark matter (DM) mediated by a light flavor-violating boson, specifically a vector $Z'$ (or a scalar $φ$) which is produced in muon-nucleus intera… ▽ More We propose DREAMuS, a fixed-target experiment at the High Intensity Heavy-Ion Accelerator Facility (HIAF), to search for muon-philic dark matter mediated by light flavor-violating bosons. DREAMuS is designed to probe the parameter space of a muon-philic dark matter (DM) mediated by a light flavor-violating boson, specifically a vector $Z'$ (or a scalar $φ$) which is produced in muon-nucleus interactions and decays into dark matter particles with a distinctive detector signature. Precision tracking and time-of-flight measurements are used to suppress the Standard Model backgrounds. We find that DREAMuS can achieve competitive sensitivity in the GeV-scale muon-philic dark matter parameter space, reaching sensitivity to couplings at the $10^{-4}$, especially in the few-hundred-MeV region.In addition to a $μ^-$ run, we highlight the potential of a complementary $μ^+$ beam option, further improving sensitivity to dark matter below 200 $\mathrm{MeV}$ by an order of magnitude. △ Less

Submitted 11 April, 2026; originally announced April 2026.

Detecting Chiral Gravitational Wave Background with a Dipole Pulsar Timing Array

Authors: Baoyu Xu, Hanyu Jiang, Rong-Gen Cai, Misao Sasaki, Yun-Long Zhang

Abstract: The pulsar timing array (PTA) is a powerful technique for detecting nanohertz gravitational wave backgrounds (GWBs). However, conventional PTAs lack sensitivity to parity violation in the GWB. In this work, we propose a dipole pulsar timing array system (dPTA). By deriving the overlap reduction functions (ORFs) from the cross-correlation of timing signals, we find that this system exhibits sensiti… ▽ More The pulsar timing array (PTA) is a powerful technique for detecting nanohertz gravitational wave backgrounds (GWBs). However, conventional PTAs lack sensitivity to parity violation in the GWB. In this work, we propose a dipole pulsar timing array system (dPTA). By deriving the overlap reduction functions (ORFs) from the cross-correlation of timing signals, we find that this system exhibits sensitivity to chiral GWBs in the nanohertz regime. Furthermore, through numerical calculations of its sensitivity curves, we demonstrate that the dPTA extends the detectable frequency range of PTAs for GWBs from the nanohertz to the microhertz regime. △ Less

Submitted 9 April, 2026; originally announced April 2026.

Comments: 11 pages, 6 figures

Scalars at the Cosmological Collider: Full Shapes of Tree Diagrams and Bispectrum Searches using Planck Data

Authors: Soubhik Kumar, Qianshu Lu, Zhong-Zhi Xianyu, Yisong Zhang

Abstract: The Cosmological Collider (CC) provides a unique opportunity to probe the particle spectrum and fundamental interactions at extremely high energies. Massive particles, via their decay into inflaton quanta, can induce a non-analytic, oscillatory, primordial non-Gaussianity (NG), including the bispectrum. At tree level, three classes of such processes contribute to the bispectrum: 'single exchange',… ▽ More The Cosmological Collider (CC) provides a unique opportunity to probe the particle spectrum and fundamental interactions at extremely high energies. Massive particles, via their decay into inflaton quanta, can induce a non-analytic, oscillatory, primordial non-Gaussianity (NG), including the bispectrum. At tree level, three classes of such processes contribute to the bispectrum: 'single exchange', 'double exchange', and 'triple exchange', depending on the number of massive particle propagators. We provide a unified evaluation of all three diagrams and derive the explicit shape functions for the bispectrum, valid across the entire kinematic space. We perform a search for these three processes with the Planck data, finding no evidence for NG. We also consider simple extensions of the minimal scenario that can counter the exponential suppression of the non-analytic signature, and produce on-shell particles with masses $M\gg H$, the Hubble scale during inflation. In particular, we focus on the 'scalar chemical potential' mechanism and extend our previous search to a wider range of chemical potential ($ω$) and $M$, finding global 1.5$σ$ evidence for non-zero NG for the parameter space $ω- M \simeq 3H$. △ Less

Submitted 8 April, 2026; originally announced April 2026.

Comments: 22 pages, 21 figures. Companion paper to the letter arXiv:2603.15728

Dual Implications of Quark Mass Hierarchies to Flavor Structure

Authors: Ying Zhang

Abstract: To solve the mystery of flavor structure, we demonstrate two implications emerging from the hierarchical masses of quarks: one for the mass matrix itself and one for the CKM mixing. These implications naturally lead to a non-redundant, ordered, and family-unified quark flavor structure, which serves as a candidate to replace the unclear Yukawa interactions of the Standard Model. To solve the mystery of flavor structure, we demonstrate two implications emerging from the hierarchical masses of quarks: one for the mass matrix itself and one for the CKM mixing. These implications naturally lead to a non-redundant, ordered, and family-unified quark flavor structure, which serves as a candidate to replace the unclear Yukawa interactions of the Standard Model. △ Less

Submitted 4 June, 2026; v1 submitted 2 April, 2026; originally announced April 2026.

Comments: 11 pages, 1 figure

The effects of a scalar singlet Leptoquark at the $Z$ factory

Authors: Dazhuang He, Yu Zhang, Hao Sun

Abstract: We evaluate the observability of the effects of a scalar singlet leptoquark (LQ) in $μ$ and $τ$-pair productions at the $Z$ factory. In the scenario addressing the charged-current anomalies, the LQ contributions to $μ$-pair final state are negligible. In contrast, a sizable contribution arises in the $τ$-pair production, which is identical in both $Z$ decay and $e^+e^-$ collider at $Z$ pole. These… ▽ More We evaluate the observability of the effects of a scalar singlet leptoquark (LQ) in $μ$ and $τ$-pair productions at the $Z$ factory. In the scenario addressing the charged-current anomalies, the LQ contributions to $μ$-pair final state are negligible. In contrast, a sizable contribution arises in the $τ$-pair production, which is identical in both $Z$ decay and $e^+e^-$ collider at $Z$ pole. These effects are mainly sensitive to left-handed interaction, showing a maximum deviation of about $-0.7\%$ for both 1\,TeV and 2\,TeV LQ. The suppression of new physics effects from the heavy LQ can be compensated by the enlarged couplings parameter space. For the $τ$-pair production channel, we further specify the coupling constraints corresponding to the expected measurement precision at the future $Z$ factory. Moreover, we provide an analytic function in terms of the LQ mass and couplings to quantify the LQ effects. The differential distributions in the collision process indicate that the LQ effects remain stable throughout the kinematic region. Meanwhile, the measurement sensitivity of the $τ$-pair final state at the future $Z$ factory is expected to impose further constraints on the LQ theory. △ Less

Submitted 24 July, 2026; v1 submitted 30 March, 2026; originally announced March 2026.

Observation of $Λ^+_c\to nπ^+η$ and search for $Λ^+_c\to na_0(980)^+$

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, X. C. Ai, C. S. Akondi, R. Aliberti, A. Amoroso, Q. An, Y. H. An, Y. Bai, O. Bakina, Y. Ban, H. -R. Bao, X. L. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. B. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko , et al. (722 additional authors not shown)

Abstract: By analysing 6.1 ${\rm fb}^{-1}$ of data collected at center-of-mass energies between $\sqrt{s}=4.600$ and 4.843 $\rm GeV$ with the BESIII detector at the BEPCII collider, we observe the decay $Λ_c^+\to nπ^+η$ for the first time with a statistical significance of $9.5σ$. The ratio of branching fractions $\mathcal{B}(Λ_c^+\to nπ^+η)/\mathcal{B}(Λ_c^+\to Λπ^+η)$ is measured to be… ▽ More By analysing 6.1 ${\rm fb}^{-1}$ of data collected at center-of-mass energies between $\sqrt{s}=4.600$ and 4.843 $\rm GeV$ with the BESIII detector at the BEPCII collider, we observe the decay $Λ_c^+\to nπ^+η$ for the first time with a statistical significance of $9.5σ$. The ratio of branching fractions $\mathcal{B}(Λ_c^+\to nπ^+η)/\mathcal{B}(Λ_c^+\to Λπ^+η)$ is measured to be $0.155\pm0.031_{\rm stat.}\pm0.012_{\rm syst.}$ Taking the world average of $\mathcal{B}(Λ_c^+\to Λπ^+η)$ as reference, the absolute branching fraction is calculated to be $\mathcal{B}(Λ_c^+\to nπ^+η)=(2.94\pm0.59_{\rm stat.}\pm0.23_{\rm syst.}\pm0.13_{\rm ref.})\times10^{-3}$. The intermediate process $Λ_c^+\to na_0(980)^+$ is also searched for in the $π^+η$ invariant mass spectrum. Since no significant signal is found, the upper limit on $\mathcal{B}(Λ_c^+\to na_0(980)^+)\times\mathcal{B}(a_0(980)^+\toπ^+η)$ is set to $8.4\times10^{-4}$ at 90\% confidence level. A sophisticated deep learning approach using a Transformer-based architecture is employed to distinguish signals from prevalent hadronic backgrounds, complemented by thorough validation and systematic uncertainty quantification. △ Less

Submitted 7 August, 2026; v1 submitted 30 March, 2026; originally announced March 2026.

Comments: 26 pages, 6 figures

Journal ref: JHEP 08 (2026), 009

Same-sign dimuon probe of charged lepton flavor violation at electron-photon colliders

Authors: Zhong Zhang, Yu Zhang, Zeren Simon Wang

Abstract: Observation of charged lepton flavor violation would constitute unambiguous evidence for physics beyond the Standard Model (SM). We identify a previously unexplored same-sign dimuon signature in electron--photon collisions, $γe^- \to e^+μ^-μ^-$, mediated by an axionlike particle (ALP) with flavor-violating $e$--$μ$ couplings. The absence of irreducible SM backgrounds and the on-shell production of… ▽ More Observation of charged lepton flavor violation would constitute unambiguous evidence for physics beyond the Standard Model (SM). We identify a previously unexplored same-sign dimuon signature in electron--photon collisions, $γe^- \to e^+μ^-μ^-$, mediated by an axionlike particle (ALP) with flavor-violating $e$--$μ$ couplings. The absence of irreducible SM backgrounds and the on-shell production of the ALP render this channel intrinsically clean and highly sensitive, with only small residual backgrounds arising from detector effects. Such collisions can be realized via laser Compton backscattering at $e^+e^-$ colliders including BEPC-II with the BESIII detector, STCF, CEPC, and ILC. We find that STCF, CEPC, and ILC can probe couplings one to two orders of magnitude below existing bounds. This combination of resonant production, vanishing irreducible background, and same-sign topology would be difficult to achieve in conventional $e^+e^-$ or hadron-collider environments, establishing electron--photon collisions as a uniquely powerful probe of charged lepton flavor violation. △ Less

Submitted 30 July, 2026; v1 submitted 26 March, 2026; originally announced March 2026.

Comments: v1: 5+3 pages, 4 figures; v2: 6+4 pages, 4+1 figures, added CEPC sensitivities, accepted for publication in Chinese Physics Letters

Two-loop Six-point Planar Massless Feynman Integrals to Higher $ε$ Orders

Authors: Yuanche Liu, Antonela Matijašić, Tiziano Peraro, Yingxuan Xu, Zihua Yang, Yang Zhang

Abstract: In this work, we calculate two-loop six-point planar massless Feynman integrals at higher orders in the dimensional regulator $ε$, corresponding to higher transcendental weights. In previous works, these integrals were calculated up to weight four for the purpose of two-loop gauge theory amplitudes. Using modern rational reconstruction methods, we identify the complete alphabet with $269$ letters… ▽ More In this work, we calculate two-loop six-point planar massless Feynman integrals at higher orders in the dimensional regulator $ε$, corresponding to higher transcendental weights. In previous works, these integrals were calculated up to weight four for the purpose of two-loop gauge theory amplitudes. Using modern rational reconstruction methods, we identify the complete alphabet with $269$ letters relevant to all weights, derive the analytic canonical differential equation and obtain the symbols up to weight six. As a proof of concept, using a new method with Chebyshev pseudospectral transport, we show that the corresponding pure basis can be efficiently evaluated up to weight six, i.e., to $ \mathcal{O}(ε^2)$ in a physical scattering region. The results of this work can be applied to future three-loop amplitudes and provide new data for the formal study of symbols and cluster algebras. △ Less

Submitted 2 April, 2026; v1 submitted 17 March, 2026; originally announced March 2026.

Comments: more details added on symbols, typo corrected, more reference added, data available at https://bitbucket.org/yzhphy/2l6p_complete_function_space/src/main/version_2026/

Report number: TTP26-009, P3H-26-020, USTC-ICTS/PCFT-26-19

Cosmological Collider Searches beyond the Hubble Scale with Planck Data

Authors: Soubhik Kumar, Qianshu Lu, Zhong-Zhi Xianyu, Yisong Zhang

Abstract: Searches for primordial non-Gaussianity (NG) has the potential to not only reveal the physics of cosmic inflation, but also the structure of fundamental interactions at the highest energies. The cosmological collider (CC) physics program exemplifies this possibility and demonstrates how searches for oscillatory NG can lead to mass-spin spectroscopy of extremely heavy states. Adopting an effective… ▽ More Searches for primordial non-Gaussianity (NG) has the potential to not only reveal the physics of cosmic inflation, but also the structure of fundamental interactions at the highest energies. The cosmological collider (CC) physics program exemplifies this possibility and demonstrates how searches for oscillatory NG can lead to mass-spin spectroscopy of extremely heavy states. Adopting an effective field theory approach, we find the class of Feynman diagrams that can give the largest NG mediated by a heavy scalar particle with mass $M\sim H$, the inflationary Hubble scale. We compute the full shape of the NG and perform the first search for this shape using Planck data, finding no evidence for NG. This search loses its sensitivity as $M\gg H$ since quantum vacuum fluctuations cannot efficiently produce such heavier particles. We then focus on a mechanism where a chemical potential excites on-shell scalar particles with mass $M\gg H$. Computing the full shapes, we perform the first CC search for particles parametrically heavier than $H$ using Planck data. For a range of chemical potential $ω$ and $M$ satisfying $ω-M \simeq 3H$, we find a global $1.7σ$ evidence for non-zero NG, after taking into account the look-elsewhere effect. △ Less

Submitted 16 March, 2026; originally announced March 2026.

Comments: 8 pages, 3 figures

Assessing the robustness of amortized simulation-based inference to transient noise in gravitational-wave ringdowns

Authors: Song-Tao Liu, Tian-Yang Sun, Yu-Xin Wang, Yong-Xin Zhang, Shang-Jie Jin, Jing-Fei Zhang, Xin Zhang

Abstract: Gravitational waves (GW) emitted by binary systems allow us to perform precision tests of general relativity in the strong field regime. Ringdown signals allow for probing black hole mass and spin with high precision in GW astronomy. With improvements in current and next-generation GW detectors, developing likelihood-free parameter inference methods is crucial. This is especially important when fa… ▽ More Gravitational waves (GW) emitted by binary systems allow us to perform precision tests of general relativity in the strong field regime. Ringdown signals allow for probing black hole mass and spin with high precision in GW astronomy. With improvements in current and next-generation GW detectors, developing likelihood-free parameter inference methods is crucial. This is especially important when facing challenges such as non-standard noise, partial data, or incomplete signal models that prevent the use of analytical likelihood functions. In this work, we propose an amortized simulation-based inference strategy to estimate ringdown parameters directly. Specifically, our method is based on amortized neural posterior estimation, which trains a neural density estimator of the posterior for all data segments within the prior range. The results show that our trained amortized network achieves statistically consistent parameter estimates with valid confidence coverage compared to established Markov-chain methods, while offering inference speeds that are orders of magnitude faster. Furthermore, we evaluate the robustness of the method against transient noise contamination. Our analysis reveals that the timing of glitch injection has a decisive impact on estimation bias, particularly during the tail of a signal with sparse information. Glitch strength is positively correlated with estimation error, but has limited effect at low signal-to-noise ratios. Mass and spin parameters are most sensitive to noise. This study not only provides an efficient and accurate inference framework for ringdown analysis but also lays a foundation for developing robust data-processing pipelines for future GW astronomy in realistic noise environments. △ Less

Submitted 12 March, 2026; originally announced March 2026.

Comments: 13 pages, 6 figures

Production of muonic kaon atoms at high-energy colliders

Authors: Xiaofeng Wang, Zebo Tang, Zhangbu Xu, Chi Yang, Wangmei Zha, Yifei Zhang

Abstract: We develop a framework for the formation of exotic muonic kaon atoms ($Kμ$) in semileptonic $D^{0}$ decays, using the effective weak Hamiltonian, a helicity-based treatment of the leptonic current, and a nonrelativistic bound-state projection. The resulting branching ratio, $\mathrm{BR}(D^{0} \to (Kμ)ν_μ)=2.29\times10^{-10}$, is implemented in a ROOT-based code to estimate yields at RHIC, LHC, and… ▽ More We develop a framework for the formation of exotic muonic kaon atoms ($Kμ$) in semileptonic $D^{0}$ decays, using the effective weak Hamiltonian, a helicity-based treatment of the leptonic current, and a nonrelativistic bound-state projection. The resulting branching ratio, $\mathrm{BR}(D^{0} \to (Kμ)ν_μ)=2.29\times10^{-10}$, is implemented in a ROOT-based code to estimate yields at RHIC, LHC, and STCF. We show quantitatively that $Kμ$ atoms-also produced through coalescence in the quark-gluon plasma (QGP)-provide a sensitive probe of low-momentum primordial muons and early time electromagnetic radiation, offering complementary constraints in an otherwise unexplored phase space for thermal dilepton and photon emission. Newly estimated dissociation cross sections in detector material indicate that secondary-vertex reconstruction should be experimentally feasible, allowing clean experimental identification of the atoms. Projected yields from QGP coalescence in LHC and RHIC heavy-ion collisions, and from $D^{0}$ decays in LHC high luminosity $p+p$ collisions indicate that the first observation of $Kμ$ atoms is within reach. △ Less

Submitted 30 April, 2026; v1 submitted 10 March, 2026; originally announced March 2026.

Comments: 12 pages, 2 figures, to be published in Chinese Phys. C

Flash from the Past: New Gamma-Ray Constraints on Light CP-even Scalar from SN1987A

Authors: Yue Yu, Writasree Maitra, P. S. Bhupal Dev, Jean-Franccois Fortin, Steven P. Harris, Kuver Sinha, Yongchao Zhang

Abstract: We derive new constraints on light CP-even scalars using old gamma-ray observations in the direction of SN1987A by the Solar Maximum Mission (SMM) satellite. Light scalars can be abundantly produced in the supernova core via the nucleon bremsstrahlung process, can stream out of the supernova-environment and decay into photons -- either primary photons or secondary photons from lepton-antilepton pa… ▽ More We derive new constraints on light CP-even scalars using old gamma-ray observations in the direction of SN1987A by the Solar Maximum Mission (SMM) satellite. Light scalars can be abundantly produced in the supernova core via the nucleon bremsstrahlung process, can stream out of the supernova-environment and decay into photons -- either primary photons or secondary photons from lepton-antilepton pairs -- thus leading to a gamma-ray signal. From the non-observation of excess photon flux by SMM after the detection of the neutrino burst from SN1987A, we set new constraints on the mixing angle of the CP-even scalar with the Standard Model Higgs boson. △ Less

Submitted 9 March, 2026; originally announced March 2026.

Comments: 15 pages, 11 figures

Entanglement measures and Bell-type spin-correlation observables in tau-lepton pairs at the Super Tau-Charm Facility

Authors: Beizhi Yang, Yu Zhang, Zeren Simon Wang, Xiaorong Zhou

Abstract: Within the framework of quantum field theory and the Standard Model (SM), we investigate the prospects of studying entanglement measures and Bell-type spin-correlation observables in the electroweak process $e^- e^+\to τ^-τ^+$ at the center-of-mass (COM) energies of $\sqrt{s}=3.670,4.630$, and $7.000$ GeV at the proposed Super Tau-Charm Facility (STCF) in China. Focusing on the hadronic decay chan… ▽ More Within the framework of quantum field theory and the Standard Model (SM), we investigate the prospects of studying entanglement measures and Bell-type spin-correlation observables in the electroweak process $e^- e^+\to τ^-τ^+$ at the center-of-mass (COM) energies of $\sqrt{s}=3.670,4.630$, and $7.000$ GeV at the proposed Super Tau-Charm Facility (STCF) in China. Focusing on the hadronic decay channel $τ^\pm\to π^\pm ν$, we determine the spin-correlation coefficients of the $τ^-τ^+$ system within the SM framework using measurable production kinematics, namely the $τ$ velocities and scattering angles in the COM frame. From these correlation coefficients, we construct concurrence and a Bell-type correlation combination as defined in the literature. Assuming an integrated luminosity of 1 ab$^{-1}$ for each considered COM energy, and incorporating realistic detector efficiencies as well as statistical and systematic uncertainties, we estimate the expected sensitivity to these observables at STCF. Our results indicate that, under the SM hypothesis, the corresponding Bell-type correlation combinations could be resolved with high statistical significance at STCF. △ Less

Submitted 5 March, 2026; originally announced March 2026.

Comments: 8 pages plus refs, 4 figures, 4 tables

Probing $D_s^+ \to η^{(\prime)} \ell^+ν_\ell$ semileptonic decay within LCSR under chiral heavy quark effective field theory

Authors: Ruiyu Zhou, Hai-Bing Fu, Yi Zhang, Wei Cheng

Abstract: Motivated by the successful application of Heavy Quark Effective Field Theory in describing decays from heavy to light mesons, this work explores its applicability to the semileptonic decays of charmed mesons. So in this paper we investigate the $D_s^+\to η^{(\prime)} \ell^+ ν_\ell$ transition form factors using the light-cone sum rules approach within the framework of heavy-quark effective field… ▽ More Motivated by the successful application of Heavy Quark Effective Field Theory in describing decays from heavy to light mesons, this work explores its applicability to the semileptonic decays of charmed mesons. So in this paper we investigate the $D_s^+\to η^{(\prime)} \ell^+ ν_\ell$ transition form factors using the light-cone sum rules approach within the framework of heavy-quark effective field theory. To address the large uncertainties arsing from the $η^{(\prime)}$-meson twist-3 distribution amplitudes, we employ the right-handed chiral correlation function. By applying the converging simplified series expansion method, we extrapolate the form factors to the entire physical $q^2$-region. Our analysis yields the branching fractions precise predictions for semi-leptonic decays $D_s^+\to η^{(\prime)}\ell^+ν_\ell$ with : $\mathcal{B}(D_s^+\toη\ell^+ν_\ell)=2.300^{+0.230}_{-0.227}\%$ ($\ell = e$) and $2.249_{-0.206}^{+0.209}\%$ ($\ell = μ$); $\mathcal{B}(D_s^+\toη^\prime \ell^+ν_\ell)=0.861^{+0.095}_{-0.093}\%$ ($\ell = e$) and $0.821^{+0.082}_{-0.080}\%$ ($\ell = μ$). The derived lepton flavor universality ratios $R^η_{μ,e}=0.977^{+0.008}_{-0.006}$ and $R^{η^{\prime}}_{μ,e} = 0.953^{+0.011}_{-0.009}$ are consistent with lasted BESIII experimental measurements. Additionally, the forward-backward asymmetry parameters $\langle \mathcal{A}^η_{\rm FB}\rangle=-0.034^{+0.003}_{-0.003}$ and $\langle \mathcal{A}^{η^\prime}_{\rm FB}\rangle=-0.073^{+0.007}_{-0.008}$ suggest that no significant violation of lepton flavor universality in this decay process. △ Less

Submitted 23 February, 2026; originally announced February 2026.

Comments: 8 pages, 5 figures. Accepted by Physics Letters B

Journal ref: Phys. Lett. B 875 (2026) 140297

Lyα forest bounds on sterile neutrino production via neutrino self-interactions

Authors: Priyank Parashari, Vera Gluscevic, Yue Zhang, Simeon Bird, Mikhail M. Ivanov, Adam He

Abstract: Sterile neutrinos in the keV mass range have long been considered a well-motivated dark matter (DM) candidate. In this work, we explore a sterile neutrino production mechanism through active neutrino self-interactions in the early universe, assuming that they constitute the full DM abundance. We implement a self-consistent treatment of the sterile-neutrino free streaming and the active-neutrino se… ▽ More Sterile neutrinos in the keV mass range have long been considered a well-motivated dark matter (DM) candidate. In this work, we explore a sterile neutrino production mechanism through active neutrino self-interactions in the early universe, assuming that they constitute the full DM abundance. We implement a self-consistent treatment of the sterile-neutrino free streaming and the active-neutrino self-interactions on structure formation, which yield a unique scale-dependent modification to the linear matter power spectrum. We then set bounds on this scenario using a combination of the cosmic microwave background and Ly$α$ forest constraints. Specifically, we utilize the two recent likelihoods derived from eBOSS data: (i) an effective field theory (EFT) based full-shape likelihood and (ii) a compressed likelihood obtained from the PRIYA-simulation emulator. We produce some of the most stringent observational constraints to date on sterile neutrino DM, comparable to the bounds from the most stringent laboratory constraints. △ Less

Submitted 19 February, 2026; originally announced February 2026.

Comments: 13 pages, 7 figures

Report number: MIT-CTP/6004

Probing Light Dark Particles in Neutrino Scattering Experiments

Authors: Ruofei Feng, Shao-Feng Ge, Yongchao Zhang

Abstract: In this work we investigate the production of a dark fermionic particle $χ$ in the neutrino scattering experiments. In the framework of effective field theory, such process can be induced by the effective four-fermion interactions involving neutrinos, the dark particle $χ$ and standard model particles. We perform a comprehensive analysis of all possible Lorentz structures, considering representati… ▽ More In this work we investigate the production of a dark fermionic particle $χ$ in the neutrino scattering experiments. In the framework of effective field theory, such process can be induced by the effective four-fermion interactions involving neutrinos, the dark particle $χ$ and standard model particles. We perform a comprehensive analysis of all possible Lorentz structures, considering representative neutrino experiments with distinct neutrino sources and target particles. In particular, we examine the constraints on the effective couplings for the neutrino-nucleus scattering by the latest COHERENT CsI and CONUS+ data, as well as the prospects at the DUNE near detector from neutrino-electron scattering. It turns out the current COHERENT and CONUS+ constraints on the cutoff scales are less stringent than those from the existing Large Hadron Collider data and the SN1987A observations. However, the DUNE near detector could probe the cutoff scales beyond the existing CHARM II and LEP limits up to roughly 1 TeV, for the dark particle mass up to roughly 50 MeV. Our results demonstrate the complementarity between neutrino experiments and collider searches in probing the dark sector physics. △ Less

Submitted 24 June, 2026; v1 submitted 9 February, 2026; originally announced February 2026.

Comments: 48 pages, 6 figures, and 3 tables, more comments and references, version published in JHEP

Journal ref: JHEP06(2026)236