Showing 1–50 of 116 results for author: Zhou, K

Suppressed Quantum Effects of Weakly Coupled Waves

Authors: Yunjia Bao, Dhong Yeon Cheong, Nicholas L. Rodd, Joey Takach, Lian-Tao Wang, Kevin Zhou

Abstract: Precision experiments increasingly target weakly coupled waves, including axion dark matter and gravitational radiation. Such waves are commonly described as classical fields, yet they could exist in quantum states with no classical counterpart. We exhibit two severe obstructions to detecting nonclassical effects, both independent of the mode occupancy. First, realistic detectors cannot resolve th… ▽ More Precision experiments increasingly target weakly coupled waves, including axion dark matter and gravitational radiation. Such waves are commonly described as classical fields, yet they could exist in quantum states with no classical counterpart. We exhibit two severe obstructions to detecting nonclassical effects, both independent of the mode occupancy. First, realistic detectors cannot resolve the fundamental modes of a field; instead they couple to coarse-grained "effective" modes, which often washes out nonclassical effects. Second, all nonclassical effects are suppressed by extra powers of the weak coupling, making them much harder to detect than the waves themselves. We prove this in general, and explicitly show how the suppression arises for quadrature and number statistics, entanglement, and decoherence. The suppression can in principle be overcome given suitable quantum resources, such as highly squeezed detector states, but the required parameters are far beyond current experimental capabilities. We use the axion cavity haloscope as an explicit example, although our conclusions apply to many ultralight dark matter searches, and rule out proposals to establish the quantization of gravity from observations of gravitational waves. △ Less

Submitted 29 July, 2026; originally announced July 2026.

Comments: 45+18 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

Sensitivity of Neutron Star Observables to Transition Density in Hybrid Equation-of-State Models

Authors: N. K. Patra, Sk Md Adil Imam, Kai Zhou

Abstract: We investigate how the transition density \(ρ_{tr}\) affects hybrid constructions of the neutron-star equation of state (EoS) in which a nucleonic description at low densities is matched to a model-agnostic high-density extension based on a speed-of-sound parametrization. Using four representative nucleonic models--Taylor expansion, \(\frac{n}{3}\) expansion, Skyrme, and relativistic mean-field--b… ▽ More We investigate how the transition density \(ρ_{tr}\) affects hybrid constructions of the neutron-star equation of state (EoS) in which a nucleonic description at low densities is matched to a model-agnostic high-density extension based on a speed-of-sound parametrization. Using four representative nucleonic models--Taylor expansion, \(\frac{n}{3}\) expansion, Skyrme, and relativistic mean-field--built from identical nuclear matter parameters, we isolate the impact of the low-density EoS and the transition density on neutron star observables. We find that, within the present smooth-matching prescription, neutron star properties such as radii and tidal deformabilities retain significant sensitivity to the choice of low-density EoS for commonly adopted transition densities around \(ρ_{tr} \approx 2ρ_0\), even when the same high-density parametrization is employed. This residual dependence arises from differences in the matching conditions at \(ρ_{tr}\), which propagate into the high-density extension, so different low-density inputs lead to different effective high-density EoSs. These findings are robust across two distinct speed-of-sound parametrizations. Quantitatively, the model spread in radius and tidal deformability at $1.4\,M_\odot$ exceeds the current observational uncertainty by factors of $\sim 1.8$ and $\sim 1.4$ at $ρ_{\mathrm{tr}} \approx 2ρ_0$, whereas these factors reduce to $\sim 1.05$ and $\sim 0.4$ at $ρ_{\mathrm{tr}} = ρ_0$. Lowering the transition density, therefore, systematically diminishes the spread among models and leads to more consistent predictions. Our results demonstrate that the widely used choice \(ρ_{tr} \approx 2ρ_0\) does not guarantee model independence in hybrid EoS constructions, and should be treated as an explicit source of systematic uncertainty when inferring dense matter properties from neutron star observations. △ Less

Submitted 13 April, 2026; originally announced April 2026.

Comments: 10 pages, 5 figures, 3 tables

Journal ref: Phys. Rev. D 114, 023047(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

Neural-Network Holographic Model of the QCD Phase Transition under Lattice and HRG Constraints

Authors: De-Xing Zhu, Li-Qiang Zhu, Xun Chen, De-Fu Hou, Kai Zhou

Abstract: Within a neural-network-based holographic framework, we incorporate lattice QCD (LQCD) and Hadron Resonance Gas (HRG) data to train the model and predict the location of the QCD critical endpoint (CEP). The training dataset consists of the entropy density, baryon number susceptibility, and baryon density. The metric warp factor $A(z)$ and the gauge kinetic function $f(z)$ are parameterized by neur… ▽ More Within a neural-network-based holographic framework, we incorporate lattice QCD (LQCD) and Hadron Resonance Gas (HRG) data to train the model and predict the location of the QCD critical endpoint (CEP). The training dataset consists of the entropy density, baryon number susceptibility, and baryon density. The metric warp factor $A(z)$ and the gauge kinetic function $f(z)$ are parameterized by neural networks and determined through the training procedure. The resulting model reproduces the equation of state at vanishing chemical potential in good agreement with both LQCD and HRG data. Extending the analysis to finite chemical potential, we solve the equations of motion and obtain thermodynamic observables consistent with LQCD results at finite density. After incorporating the HRG constraints, the predicted position of the CEP shifts toward larger chemical potentials compared to recent studies. We further employ symbolic regression to derive analytic expressions for $A(z)$ and $f(z)$, providing convenient functional forms for future phenomenological applications. Finally, we perform a data-driven validation using synthetic thermodynamic data generated from an existing analytical holographic model. The neural-network framework reproduces the corresponding CEP location with good accuracy, showing close agreement within numerical uncertainties. △ Less

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

Comments: 21 pages, 5 figures

Observation of $\barΛp\to K^{+}π^{+}π^{-}π^{0}$ and $\barΛp\to K^{+}π^{+}π^{-}2π^{0}$

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. (728 additional authors not shown)

Abstract: Using $(10087 \pm 44) \times 10^6$ $J/ψ$ events collected with the BESIII detector at a center-of-mass energy of $\sqrt{s}=3.097$ GeV, the antihyperon-nucleon annihilation processes $\barΛ p \to K^+ π^+ π^- + kπ^0$ ($k=1,2,3$) are studied at an incident $\barΛ$ momentum of approximately 1.074 GeV/$c$. The reactions $\barΛ p \to K^+ π^+ π^- π^0$ and $\barΛ p \to K^+ π^+ π^- 2π^0$ are observed for t… ▽ More Using $(10087 \pm 44) \times 10^6$ $J/ψ$ events collected with the BESIII detector at a center-of-mass energy of $\sqrt{s}=3.097$ GeV, the antihyperon-nucleon annihilation processes $\barΛ p \to K^+ π^+ π^- + kπ^0$ ($k=1,2,3$) are studied at an incident $\barΛ$ momentum of approximately 1.074 GeV/$c$. The reactions $\barΛ p \to K^+ π^+ π^- π^0$ and $\barΛ p \to K^+ π^+ π^- 2π^0$ are observed for the first time, with corresponding cross sections $σ_{\barΛ p \to K^+ π^+ π^- π^0} = 8.5^{+1.2}_{-1.1} (\rm{stat.}) \pm 0.4 (\rm {syst.})$ mb and $σ_{\barΛ p \to K^+ π^+ π^- 2π^0} = 7.9^{+1.9}_{-1.7} \pm 0.4$ mb. No significant signal is found for $\barΛ p \to K^+ π^+ π^- 3π^0$, and an upper limit of 7.2 mb is set at a 90\% confidence level. An evidence for the $K^{*}(892)^+$ resonance is seen in the $K^+π^0$ invariant mass spectrum $M_{K^+π^0}$ for $k=1$, and the corresponding cross section for $\barΛ p \to K^{*}(892)^+ π^+ π^-$ is measured to be $σ_{\barΛ p \to K^{*}(892)^+ π^+ π^-} = 12.5^{+3.8}_{-3.4} \pm 1.2$ mb. Owing to the limited statistics, possible interference effects are not considered. These findings offer crucial input to deepen our understanding of the antihyperon-nucleon interactions. △ Less

Submitted 15 April, 2026; v1 submitted 1 February, 2026; originally announced February 2026.

Journal ref: Phys. Rev. Lett. 136, 171904 (2026)

Learning the relations between neutron star and nuclear matter properties with symbolic regression

Authors: N. K. Patra, Tuhin Malik, Kai Zhou, Constança Providência

Abstract: The equation of state (EOS) of dense matter in neutron stars (NSs) remains uncertain, particularly at supra-nuclear densities where complex nuclear interactions and the potential presence of exotic matter, like hyperons, come into play. The complex relationships existing between nuclear matter and neutron star properties are investigated. The focus is on their nonlinearities and interdependencies.… ▽ More The equation of state (EOS) of dense matter in neutron stars (NSs) remains uncertain, particularly at supra-nuclear densities where complex nuclear interactions and the potential presence of exotic matter, like hyperons, come into play. The complex relationships existing between nuclear matter and neutron star properties are investigated. The focus is on their nonlinearities and interdependencies. In our analysis, we apply a machine learning algorithm known as symbolic regression, paired with principal component analysis, to datasets generated from Bayesian inference over relativistic mean-field models. A systematic Principal Component Analysis has allowed to break down the percentage contribution of each element or feature in the relationships obtained. This study examines two main models (datasets): the NL model, which includes nucleonic degrees of freedom; and the NL-hyp model, which includes hyperons in addition to nucleons. Our analysis confirms a robust correlation between the tidal deformability of a 1.4 \(M_\odot\) neutron star and $β$-equilibrium pressure at twice the nuclear saturation density. This correlation remains once hyperons are included. The contribution of the different nuclear matter properties at saturation to the radius and tidal deformability was calculated. It was shown that the isovector properties have the largest impact, with a contribution of about 90\%. We also studied the relationship between the proton fraction at different densities and various symmetry energy parameters defined at saturation density. For the hyperon data set, we took into account the effects of the negatively charged hyperon $Ξ$ in order to recover the relationships. Our study reveals the individual impact of various symmetry energy parameters on proton fractions at different densities. △ Less

Submitted 12 January, 2026; originally announced January 2026.

Comments: 11 pages, 4 figures, 3 tables

Quantum Calculations of the Cavity Shift in Electron Magnetic Moment Measurements

Authors: Hannah Day, Roni Harnik, Yonatan Kahn, Shashin Pavaskar, Kevin Zhou

Abstract: The measurement of the anomalous electron magnetic moment $g-2$ through quantum transitions of a single trapped electron is the most stringent test of quantum field theory. These experiments are now so precise that they must account for the effects of the cavity containing the electron. Classical calculations of this "cavity shift" must subtract the electron's divergent self-field, and thus requir… ▽ More The measurement of the anomalous electron magnetic moment $g-2$ through quantum transitions of a single trapped electron is the most stringent test of quantum field theory. These experiments are now so precise that they must account for the effects of the cavity containing the electron. Classical calculations of this "cavity shift" must subtract the electron's divergent self-field, and thus require knowledge of the exact Green's function for the cavity's electromagnetic field. We perform the first fully quantum calculation of the cavity shift in a closed cavity, which instead involves subtracting linearly divergent cavity mode sums and integrals. Using contour integration methods, we find perfect agreement with existing classical results for both spherical and cylindrical cavities, justifying their current use. Moreover, our mode-based results can be naturally generalized to account for systematic effects, necessary to push future measurements to the next order of magnitude in precision. △ Less

Submitted 12 March, 2026; v1 submitted 10 November, 2025; originally announced November 2025.

Comments: 41+16 pages, 7 figures. v2: discussion expanded, matches journal version

Journal ref: JHEP 03 (2026) 038

Search for a hypothetical gauge boson and dark photons in charmonium transitions

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. B. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, H. Cai , et al. (677 additional authors not shown)

Abstract: We report a direct search for a new gauge boson, $X$, with a mass of $17~\text{MeV}/c^2$, which could explain the anomalous excess of $e^+e^-$ pairs observed in the $^8\text{Be}$ nuclear transitions. The search is conducted in the charmonium decays $χ_{cJ}\to X J/ψ~(J=0,1,2)$ via the radiative transition $ψ(3686)\toγχ_{cJ}$ using $\left(2712.4\pm 14.3 \right)\times 10^6$ $ψ(3686)$ events collected… ▽ More We report a direct search for a new gauge boson, $X$, with a mass of $17~\text{MeV}/c^2$, which could explain the anomalous excess of $e^+e^-$ pairs observed in the $^8\text{Be}$ nuclear transitions. The search is conducted in the charmonium decays $χ_{cJ}\to X J/ψ~(J=0,1,2)$ via the radiative transition $ψ(3686)\toγχ_{cJ}$ using $\left(2712.4\pm 14.3 \right)\times 10^6$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider. No significant signal is observed, and the updated upper limit on the coupling strength of charm quark and the new gauge boson, $ε_c$, is set to be $|ε_c|<1.2\times 10^{-2}$ at $90\%$ confidence level. We also report new constraints on the mixing strength $ε$ between the Standard Model photon and dark photon $γ^\prime$ in the mass range from $5~\text{MeV}/c^2$ to $300~\text{MeV}/c^2$. The upper limits at $90\%$ confidence level vary within $(2.5-17.5)\times 10^{-3}$ depending on the $γ^\prime $ mass. △ Less

Submitted 5 February, 2026; v1 submitted 18 October, 2025; originally announced October 2025.

Comments: 12 pages, 4 figures

Journal ref: Phys. Rev. D 113, 032009 (2026)

Intrinsically Quantum Effects of Axion Dark Matter are Undetectable

Authors: Yunjia Bao, Dhong Yeon Cheong, Nicholas L. Rodd, Joey Takach, Lian-Tao Wang, Kevin Zhou

Abstract: Is the usual treatment of axion dark matter as a classical field reliable? We show that the answer is subtle: the axion field could well be in a quantum state that has no complete classical description, but realistic detectors cannot tell the difference. To see this, we solve a fully quantum model of axion detection using quantum optics techniques. We show that intrinsically quantum effects are wa… ▽ More Is the usual treatment of axion dark matter as a classical field reliable? We show that the answer is subtle: the axion field could well be in a quantum state that has no complete classical description, but realistic detectors cannot tell the difference. To see this, we solve a fully quantum model of axion detection using quantum optics techniques. We show that intrinsically quantum effects are washed out by mode averaging or small amounts of noise, and significantly suppressed by the weakness of the axion coupling. Our work exemplifies that there should always be a classical analog for axion dark matter effects, extends to other wave (ultralight) dark-matter candidates, and gives a general method to compute the effects of exotic dark-matter states. △ Less

Submitted 6 October, 2025; originally announced October 2025.

Comments: 10 pages, 1 figure

Determination of CKM matrix element and axial vector form factors from weak decays of quantum-entangled strange baryons

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, H. Cai , et al. (705 additional authors not shown)

Abstract: The electromagnetic structure of the nucleon can be determined from the scattering of electrons off a nucleon target. However, to study its axial structure, neutrino beams are required. The results from these experiments should be extrapolated to zero energy-momentum transfers to access the static properties of the nucleon. For baryons with strange quarks, hyperons, the static limit can instead be… ▽ More The electromagnetic structure of the nucleon can be determined from the scattering of electrons off a nucleon target. However, to study its axial structure, neutrino beams are required. The results from these experiments should be extrapolated to zero energy-momentum transfers to access the static properties of the nucleon. For baryons with strange quarks, hyperons, the static limit can instead be approached in semi-leptonic decays, which give direct access to the weak magnetism and axial-vector coupling strengths that are inaccessible in electromagnetic interactions. The axial-vector coupling as while weak magnetism coupling and the overall normalization, given by form factor $f_1$, are being determined with increased precision from the theory of strong interactions using a first principles formulation on the space--time lattice. Furthermore, the probability of the semi-leptonic hyperon decay is approximately proportional to $|V_{us}|^2\cdot (f_1^2+3g_1^2)$, where $V_{us}$ is the CKM matrix element responsible for the transition between an $s$ and a $u$ quark. Current determinations of $|V_{us}|$ come from kaon decays, but the results are not consistent and could indicate a deviation from CKM matrix unitarity, a tell-tale sign of physics beyond the Standard Model (SM) of elementary particles. Here we determine the absolute branching fraction and weak coupling strengths for $Λ\to p e^-\barν_e$, and $\bar Λ\to \bar p e^+ν_e$. These observables combined with form factors determined from first-principle lattice QCD calculations allow for the extraction of the $|V_{us}|$ value. We demonstrate how $|V_{us}|$ can be extracted with increasing sensitivity using polarized hyperons from entangled, baryon-antibaryon pairs, thus enabling a complementary road to that of meson decays. In addition, the presented experimental method can be used for other semileptonic decays of baryons. △ Less

Submitted 12 September, 2025; v1 submitted 11 September, 2025; originally announced September 2025.

Comments: 24 pages, 4 figures

Thermodynamics of Heavy Quarkonium in a Bayesian Holographic QCD model

Authors: Liqiang Zhu, Ou-Yang Luo, Xun Chen, Kai Zhou, Hanzhong Zhang, Defu Hou

Abstract: Leveraging high-precision lattice QCD data on the equation of state and baryon number susceptibility at vanishing chemical potential, we construct a Bayesian holographic QCD model and systematically analyze the thermodynamic properties of heavy quarkonium in QCD matter under varying temperatures and chemical potentials. We compute the quark-antiquark interquark distance, potential energy, entropy,… ▽ More Leveraging high-precision lattice QCD data on the equation of state and baryon number susceptibility at vanishing chemical potential, we construct a Bayesian holographic QCD model and systematically analyze the thermodynamic properties of heavy quarkonium in QCD matter under varying temperatures and chemical potentials. We compute the quark-antiquark interquark distance, potential energy, entropy, binding energy, and internal energy. We present detailed posterior distribution results of the thermodynamic quantities of heavy quarkonium, including maximum a posteriori (MAP) value estimates and 95\% confidence levels (CL). Through numerical simulations and theoretical analysis, we find that increasing temperature and chemical potential decrease the quark distance, thereby facilitating the dissociation of heavy quarkonium and leading to suppressed potential energy. The increase in temperature and chemical potential also raise the entropy and entropy force, further accelerating the dissociation of heavy quarkonium. The calculated results of binding energy indicate that higher temperature and chemical potential enhance the tendency of heavy quarkonium to dissociate into free quarks. Internal energy also increases with rising temperature and chemical potential. These findings provide significant theoretical insights into the properties of strongly interacting matter under extreme conditions and lay a solid foundation for the interpretation and validation of future experimental data. Finally, we also present the results for the free energy, entropy, and internal energy of single quark. △ Less

Submitted 18 August, 2025; originally announced August 2025.

A Prototype Hybrid Mode Cavity for Heterodyne Axion Detection

Authors: Zenghai Li, Kevin Zhou, Marco Oriunno, Asher Berlin, Sergio Calatroni, Raffaele Tito D'Agnolo, Sebastian A. R. Ellis, Philip Schuster, Sami G. Tantawi, Natalia Toro

Abstract: In the heterodyne approach to axion detection, axion dark matter induces transitions between two modes of a microwave cavity, resulting in a parametrically enhanced signal power. We describe the fabrication and characterization of a prototype normal conducting cavity specifically optimized for heterodyne detection. Corrugations on the cavity walls support linearly polarized hybrid modes which maxi… ▽ More In the heterodyne approach to axion detection, axion dark matter induces transitions between two modes of a microwave cavity, resulting in a parametrically enhanced signal power. We describe the fabrication and characterization of a prototype normal conducting cavity specifically optimized for heterodyne detection. Corrugations on the cavity walls support linearly polarized hybrid modes which maximize the signal power while strongly suppressing noise. We demonstrate tuning mechanisms which allow one mode's frequency to be scanned across a 4 MHz range, while suppressing cross-coupling noise by at least 80 dB. A future superconducting cavity with identical geometry to our prototype would have the potential to probe orders of magnitude beyond astrophysical bounds. △ Less

Submitted 13 March, 2026; v1 submitted 9 July, 2025; originally announced July 2025.

Comments: 23 pages, 11 figures. v2: discussion expanded, matches journal version

Journal ref: NIMA 171474 (2026)

Data-Driven Einstein-Dilaton Model for Pure Yang-Mills Thermodynamics and Glueball Spectrum

Authors: Xun Chen, Yidian Chen, Kai Zhou

Abstract: We develop a machine learning assisted holographic model that consistently describes both the equation of state and glueball spectrum of pure Yang-Mills theory, achieved through neural network reconstruction of Einstein-dilaton gravity. Our framework incorporates key non-perturbative constraints of lattice QCD data: the ground ($0^{++}$) and first-excited ($0^{++*}$) scalar glueball masses pins do… ▽ More We develop a machine learning assisted holographic model that consistently describes both the equation of state and glueball spectrum of pure Yang-Mills theory, achieved through neural network reconstruction of Einstein-dilaton gravity. Our framework incorporates key non-perturbative constraints of lattice QCD data: the ground ($0^{++}$) and first-excited ($0^{++*}$) scalar glueball masses pins down the infrared (IR) geometry, while entropy density data anchors the ultraviolet (UV) behavior of the metric. A multi-stage neural network optimization then yields the full gravitational dual -- warp factor $A(z)$ and dilaton field $Φ(z)$ -- that satisfies both spectroscopic and thermodynamic constraints. The resulting model accurately reproduces the deconfinement phase transition thermodynamics (pressure, energy density, trace anomaly) and predicts higher glueball excitations ($0^{++**}$, $0^{++***}$) consistent with available lattice calculations. This work establishes a new paradigm for data-driven holographic reconstruction, solving the long-standing challenge of unified description of confinement thermodynamics and spectroscopy. △ Less

Submitted 5 December, 2025; v1 submitted 9 July, 2025; originally announced July 2025.

Neural Unfolding of the Chiral Magnetic Effect in Heavy-Ion Collisions

Authors: Shuang Guo, Lingxiao Wang, Kai Zhou, Guo-Liang Ma

Abstract: The search for the chiral magnetic effect (CME) in relativistic heavy-ion collisions (HICs) is challenged by significant background contamination. We present a novel deep learning approach based on a U-Net architecture to time-reversely unfold the dynamics of CME-related charge separation, enabling the reconstruction of the physics signal across the entire evolution of HICs. Trained on the events… ▽ More The search for the chiral magnetic effect (CME) in relativistic heavy-ion collisions (HICs) is challenged by significant background contamination. We present a novel deep learning approach based on a U-Net architecture to time-reversely unfold the dynamics of CME-related charge separation, enabling the reconstruction of the physics signal across the entire evolution of HICs. Trained on the events simulated by a multi-phase transport model with different cases of CME settings, our model learns to recover the charge separation based on final-state transverse momentum distributions at either the quark-gloun plasma freeze-out or hadronic freeze-out. This devises a methodological tool for the study of CME and underscores the promise of deep learning approaches in retrieving physics signals in HICs. △ Less

Submitted 24 October, 2025; v1 submitted 8 July, 2025; originally announced July 2025.

Comments: 9+1 pages, 6+1 figures, final published version

Report number: RIKEN-iTHEMS-Report-25

Journal ref: Chin. Phys. Lett. 42, 110101 (2025)

The neural networks with tensor weights and emergent fermionic Wick rules in the large-width limit

Authors: Guojun Huang, Kai Zhou

Abstract: In this paper, we study complex-valued neural network (CVNNs) with tensor-valued hidden-to-output weights within the framework of neural-network quantum field theory (NN-QFT). For standard CVNNs with scalar weights, we derive the generating functional and identify the exact Gaussian process that arises in the infinite-width limit, together with its associated effective quantum state. When the last… ▽ More In this paper, we study complex-valued neural network (CVNNs) with tensor-valued hidden-to-output weights within the framework of neural-network quantum field theory (NN-QFT). For standard CVNNs with scalar weights, we derive the generating functional and identify the exact Gaussian process that arises in the infinite-width limit, together with its associated effective quantum state. When the last-layer weights are promoted to Clifford-algebra-valued tensors, the network output becomes complex matrix-valued, and a fermion-like sign structure in the large-width correlation functions of the network output is induced. We show that, in the infinite-width limit, correlators with equal numbers of $f^†$ and $f$ obey fermionic Wick rules and can be written as determinants built from a scalar Euclidean kernel $S(x,y)=\langle f^†(x)f(y)\rangle$. This provides a sign-structured extension of NN-QFT at the level of Euclidean correlators and Feynman rules, even though a microscopic Grassmann path integral representation for the network parameters has not yet been constructed. Our analysis thus pushes the NN-QFT correspondence beyond purely bosonic Gaussian fields and suggests a possible route to encoding fermion-like symmetries in neural architectures for QFT correspondence. △ Less

Submitted 31 January, 2026; v1 submitted 7 July, 2025; originally announced July 2025.

Journal ref: Phys. Lett. B 873 (2026) 140146

Precise Measurement of the $Λ$ Electric Dipole Moment through the Entangled Strange Baryon-Antibaryon System

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, H. Cai , et al. (696 additional authors not shown)

Abstract: The dominance of matter over antimatter in the universe has consistently driven the pursuit of new physics beyond the Standard Model that violates charge-parity symmetry. Unlike the well-constrained electrons and neutrons, strange baryons (hyperons) remain a largely unexplored territory, in which interactions between hyperons and particles from new physics could induce a non-trivial electric dipol… ▽ More The dominance of matter over antimatter in the universe has consistently driven the pursuit of new physics beyond the Standard Model that violates charge-parity symmetry. Unlike the well-constrained electrons and neutrons, strange baryons (hyperons) remain a largely unexplored territory, in which interactions between hyperons and particles from new physics could induce a non-trivial electric dipole moment (EDM). However, direct measurements of hyperon EDMs through spin precession are highly challenging due to their short lifetimes. In this paper, we present a novel method to extract the EDM of the lightest hyperon, $Λ$, using the entangled $Λ$$\overlineΛ$ system. Our result is consistent with zero, achieving a three-order-of-magnitude improvement over the previous upper limit established in the 1980s with comparable statistics, providing stringent constraints on potential new physics. △ Less

Submitted 28 June, 2025; v1 submitted 23 June, 2025; originally announced June 2025.

Dense Matter in Neutron Stars with eXTP

Authors: Ang Li, Anna L. Watts, Guobao Zhang, Sebastien Guillot, Yanjun Xu, Andrea Santangelo, Silvia Zane, Hua Feng, Shuang-Nan Zhang, Mingyu Ge, Liqiang Qi, Tuomo Salmi, Bas Dorsman, Zhiqiang Miao, Zhonghao Tu, Yuri Cavecchi, Xia Zhou, Xiaoping Zheng, Weihua Wang, Quan Cheng, Xuezhi Liu, Yining Wei, Wei Wang, Yujing Xu, Shanshan Weng , et al. (60 additional authors not shown)

Abstract: In this White Paper, we present the potential of the enhanced X-ray Timing and Polarimetry (eXTP) mission to constrain the equation of state of dense matter in neutron stars, exploring regimes not directly accessible to terrestrial experiments. By observing a diverse population of neutron stars - including isolated objects, X-ray bursters, and accreting systems - eXTP's unique combination of timin… ▽ More In this White Paper, we present the potential of the enhanced X-ray Timing and Polarimetry (eXTP) mission to constrain the equation of state of dense matter in neutron stars, exploring regimes not directly accessible to terrestrial experiments. By observing a diverse population of neutron stars - including isolated objects, X-ray bursters, and accreting systems - eXTP's unique combination of timing, spectroscopy, and polarimetry enables high-precision measurements of compactness, spin, surface temperature, polarimetric signals, and timing irregularity. These multifaceted observations, combined with advances in theoretical modeling, pave the way toward a comprehensive description of the properties and phases of dense matter from the crust to the core of neutron stars. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Sciences, the eXTP mission is planned to be launched in early 2030. △ Less

Submitted 8 September, 2025; v1 submitted 9 June, 2025; originally announced June 2025.

Comments: accepted for publication in the SCIENCE CHINA Physics, Mechanics & Astronomy

Journal ref: SCIENCE CHINA Physics, Mechanics & Astronomy 68, 119503 (2025)

Determining Spin-Dependent Light Dark Matter Rates from Neutron Scattering

Authors: Asher Berlin, Alexander J. Millar, Tanner Trickle, Kevin Zhou

Abstract: The scattering and absorption rates of light dark matter with electron spin-dependent interactions depend on the target's spin response. We show how this response is encoded by the target's dynamical magnetic susceptibility, which can be measured using neutron scattering. We directly use existing neutron scattering data to compute the dark matter scattering rate in a candidate target material, fin… ▽ More The scattering and absorption rates of light dark matter with electron spin-dependent interactions depend on the target's spin response. We show how this response is encoded by the target's dynamical magnetic susceptibility, which can be measured using neutron scattering. We directly use existing neutron scattering data to compute the dark matter scattering rate in a candidate target material, finding close agreement with the previous first-principles calculation at MeV dark matter masses. Complementary experiments and measurements can extend the reach of this technique to other dark matter models and masses, and identify promising target materials for future experiments. △ Less

Submitted 21 August, 2025; v1 submitted 3 April, 2025; originally announced April 2025.

Comments: 19 pages, 5 figures; updated to match published version

Journal ref: Phys. Rev. D 112, 035021, 2025

Search for the radiative leptonic decay $D^+\toγe^+ν_e$ using Deep Learning

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, H. Cai , et al. (680 additional authors not shown)

Abstract: Using 20.3$~\rm fb^{-1}$ of $e^+e^-$ annihilation data collected at a center-of-mass energy of 3.773$~\rm GeV$ with the BESIII detector, we report an improved search for the radiative leptonic decay $D^+\toγe^+ν_e$. An upper limit on its partial branching fraction for photon energies $E_γ>10~\rm MeV$ was determined to be $1.2\times10^{-5}$ at 90\% confidence level; this excludes most current theor… ▽ More Using 20.3$~\rm fb^{-1}$ of $e^+e^-$ annihilation data collected at a center-of-mass energy of 3.773$~\rm GeV$ with the BESIII detector, we report an improved search for the radiative leptonic decay $D^+\toγe^+ν_e$. An upper limit on its partial branching fraction for photon energies $E_γ>10~\rm MeV$ was determined to be $1.2\times10^{-5}$ at 90\% confidence level; this excludes most current theoretical predictions. A sophisticated deep learning approach, which includes thorough validation and is based on the Transformer architecture, was implemented to efficiently distinguish the signal from massive backgrounds. △ Less

Submitted 22 September, 2025; v1 submitted 20 March, 2025; originally announced March 2025.

Comments: 16 pages, 6 figures

Journal ref: Chinese Phys. C 49, 083001 (2025)

Inferring the Equation of State from Neutron Star Observables via Machine Learning

Authors: N. K. Patra, Tuhin Malik, Helena Pais, Kai Zhou, B. K. Agrawal, Constança Providência

Abstract: We have conducted an extensive study using a diverse set of equations of state (EoSs) to uncover strong relationships between neutron star (NS) observables and the underlying EoS parameters using symbolic regression method. These EoS models, derived from a mix of agnostic and physics-based approaches, considered neutron stars composed of nucleons, hyperons, and other exotic degrees of freedom in b… ▽ More We have conducted an extensive study using a diverse set of equations of state (EoSs) to uncover strong relationships between neutron star (NS) observables and the underlying EoS parameters using symbolic regression method. These EoS models, derived from a mix of agnostic and physics-based approaches, considered neutron stars composed of nucleons, hyperons, and other exotic degrees of freedom in beta equilibrium. The maximum mass of a NS is found to be strongly correlated with the pressure and baryon density at an energy density of approximately 800 MeV.fm$^{-3}$. We have also demonstrated that the EoS can be expressed as a function of radius and tidal deformability within the NS mass range 1-2$M_\odot$. These insights offer a promising and efficient framework to decode the dense matter EoS directly from the accurate knowledge of NS observables. △ Less

Submitted 15 April, 2025; v1 submitted 27 February, 2025; originally announced February 2025.

Comments: 9 pages, 5 figures, 2 tables (Published in Physics Letters B)

Journal ref: Phys. Lett. B (2025)

Ultra fast, event-by-event heavy-ion simulations for next generation experiments

Authors: Manjunath Omana Kuttan, Kai Zhou, Jan Steinheimer, Horst Stoecker

Abstract: We present a novel deep generative framework that uses probabilistic diffusion models for ultra fast, event-by-event simulations of heavy-ion collision output. This new framework is trained on UrQMD cascade data to generate a full collision event output containing 26 distinct hadron species. The output is represented as a point cloud, where each point is defined by a particle's momentum vector and… ▽ More We present a novel deep generative framework that uses probabilistic diffusion models for ultra fast, event-by-event simulations of heavy-ion collision output. This new framework is trained on UrQMD cascade data to generate a full collision event output containing 26 distinct hadron species. The output is represented as a point cloud, where each point is defined by a particle's momentum vector and its corresponding species information (ID). Our architecture integrates a normalizing flow-based condition generator that encodes global event features into a latent vector, and a diffusion model that synthesizes a point cloud of particles based on this condition. A detailed description of the model and an in-depth analysis of its performance is provided. The conditional point cloud diffusion model learns to generate realistic output particles of collision events which successfully reproduce the UrQMD distributions for multiplicity, momentum and rapidity of each hadron type. The flexible point cloud representation of the event output preserves full event-level granularity, enabling direct application to inverse problems and parameter estimation tasks while also making it easily adaptable for accelerating any event-by-event model calculation or detector simulation. △ Less

Submitted 18 December, 2025; v1 submitted 22 February, 2025; originally announced February 2025.

Comments: Matches published version. 17 pages, 9 figures

Journal ref: Phys.Rev.C 112 (2025) 5, 054907

Ponderomotive Effects of Ultralight Dark Matter

Authors: Kevin Zhou

Abstract: I exhibit a new class of quadratic effects of ultralight dark matter. Axions, dark photons, and dilatons can exert rapidly oscillating forces, torques, and mass shifts on Standard Model particles. These effects average to zero at first order, but shift particle properties at second order, in analogy to the ponderomotive force in optics. Remarkably, these effects scale with the square of the amplit… ▽ More I exhibit a new class of quadratic effects of ultralight dark matter. Axions, dark photons, and dilatons can exert rapidly oscillating forces, torques, and mass shifts on Standard Model particles. These effects average to zero at first order, but shift particle properties at second order, in analogy to the ponderomotive force in optics. Remarkably, these effects scale with the square of the amplitude of the dark matter field, even when the field's direct physical effects depend only on its derivatives. I calculate the resulting observables in electron $g_e - 2$ experiments using classical mechanics, recovering results previously derived using field theory. When considered properly, these particular experiments do not beat astrophysical bounds, but other precision experiments may have interesting sensitivity. △ Less

Submitted 3 February, 2025; originally announced February 2025.

Comments: 17 pages

Journal ref: JHEP 05 (2025) 134

Bayesian Inference of the Critical Endpoint in 2+1-Flavor System from Holographic QCD

Authors: Liqiang Zhu, Xun Chen, Kai Zhou, Hanzhong Zhang, Mei Huang

Abstract: We present a Bayesian holographic model constructed by integrating the equation of state and baryon number susceptibility at zero chemical potential from lattice QCD. The model incorporates error estimates derived from lattice data. With this model, we systematically investigate the thermodynamic properties of the 2+1-flavor QCD system. Using Bayesian Inference, we perform precise calibration of t… ▽ More We present a Bayesian holographic model constructed by integrating the equation of state and baryon number susceptibility at zero chemical potential from lattice QCD. The model incorporates error estimates derived from lattice data. With this model, we systematically investigate the thermodynamic properties of the 2+1-flavor QCD system. Using Bayesian Inference, we perform precise calibration of the model parameters and determined the critical endpoint (CEP) position under the maximum a posterior (MAP) estimation to be $(T^{c},μ_{B}^{c})=(0.0859\;\mathrm{GeV},0.742\;\mathrm{GeV})$. Additionally, we predict the CEP positions within 68\% and 95\% confidence levels, yielding $(T^{c},\; μ_{B}^{c})_{68\%}$=$(0.0820\text{--}0.0889, 0.71\text{--}0.77)\;\mathrm{GeV}$ and $(T^{c},\; μ_{B}^{c})_{95\%}$=$(0.0816\text{--}0.0898,\; 0.71\text{--}0.79)\;\mathrm{GeV}$, respectively. Moreover, to validate the reliability and predictive power of our approach, we conduct a comprehensive comparison between our predictions and potential CEP locations proposed by other theoretical models. This work not only establishes a novel Bayesian framework for holographic modeling but also provides valuable insights and theoretical support for exploring phase transitions in strongly-interacting matter under extreme conditions. △ Less

Submitted 29 June, 2025; v1 submitted 29 January, 2025; originally announced January 2025.

Physics-Driven Learning for Inverse Problems in Quantum Chromodynamics

Authors: Gert Aarts, Kenji Fukushima, Tetsuo Hatsuda, Andreas Ipp, Shuzhe Shi, Lingxiao Wang, Kai Zhou

Abstract: The integration of deep learning techniques and physics-driven designs is reforming the way we address inverse problems, in which accurate physical properties are extracted from complex data sets. This is particularly relevant for quantum chromodynamics (QCD), the theory of strong interactions, with its inherent limitations in observational data and demanding computational approaches. This perspec… ▽ More The integration of deep learning techniques and physics-driven designs is reforming the way we address inverse problems, in which accurate physical properties are extracted from complex data sets. This is particularly relevant for quantum chromodynamics (QCD), the theory of strong interactions, with its inherent limitations in observational data and demanding computational approaches. This perspective highlights advances and potential of physics-driven learning methods, focusing on predictions of physical quantities towards QCD physics, and drawing connections to machine learning(ML). It is shown that the fusion of ML and physics can lead to more efficient and reliable problem-solving strategies. Key ideas of ML, methodology of embedding physics priors, and generative models as inverse modelling of physical probability distributions are introduced. Specific applications cover first-principle lattice calculations, and QCD physics of hadrons, neutron stars, and heavy-ion collisions. These examples provide a structured and concise overview of how incorporating prior knowledge such as symmetry, continuity and equations into deep learning designs can address diverse inverse problems across different physical sciences. △ Less

Submitted 9 January, 2025; originally announced January 2025.

Comments: 14 pages, 5 figures, submitted version to Nat Rev Phys

Report number: RIKEN-iTHEMS-Report-25

Journal ref: Nature Reviews Physics (2025)

Toward a foundation model for heavy-ion collision experiments based on point-cloud diffusion

Authors: Manjunath Omana Kuttan, Kai Zhou, Jan Steinheimer, Horst Stoecker

Abstract: A novel point cloud diffusion model for relativistic heavy-ion collisions, capable of ultra-fast generation of complete, event-by-event collision output, is introduced. When trained on UrQMD cascade simulations, the model generates realistic collision event output containing 26 distinct hadron species, as a list of particle momentum vectors along with their particle ID. From solving inverse proble… ▽ More A novel point cloud diffusion model for relativistic heavy-ion collisions, capable of ultra-fast generation of complete, event-by-event collision output, is introduced. When trained on UrQMD cascade simulations, the model generates realistic collision event output containing 26 distinct hadron species, as a list of particle momentum vectors along with their particle ID. From solving inverse problems to accelerating model calculations or detector simulations, the model can be a promising general purpose tool for heavy-ion collisions beneficial to both theoretical studies and experimental applications. △ Less

Submitted 18 December, 2025; v1 submitted 13 December, 2024; originally announced December 2024.

Comments: Matches published version. 8 pages, 6 figures

Journal ref: Phys.Rev.C 112 (2025) 5, L051902

Evidence for Two Excited $Ω^{-}$ Hyperons

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, O. Afedulidis, X. C. Ai, R. Aliberti, A. Amoroso, Y. Bai, O. Bakina, I. Balossino, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann , et al. (650 additional authors not shown)

Abstract: Using $e^+e^-$ collision data corresponding to an integrated luminosity of 19,fb$^{-1}$ collected by the BESIII detector at center-of-mass energies ranging from 4.13 to 4.70,GeV, we report the first evidence for a new excited $Ω^{-}$ hyperon, the $Ω(2109)^{-}$, through the process $e^+ e^- \to Ω(2109)^{-} \barΩ^{+} +c.c.$ with a significance of 4.1 $σ$. The mass and width of $Ω(2109)^{-}$ are meas… ▽ More Using $e^+e^-$ collision data corresponding to an integrated luminosity of 19,fb$^{-1}$ collected by the BESIII detector at center-of-mass energies ranging from 4.13 to 4.70,GeV, we report the first evidence for a new excited $Ω^{-}$ hyperon, the $Ω(2109)^{-}$, through the process $e^+ e^- \to Ω(2109)^{-} \barΩ^{+} +c.c.$ with a significance of 4.1 $σ$. The mass and width of $Ω(2109)^{-}$ are measured to be $2108.5 \pm 5.2_{\rm stat} \pm 0.9_{\rm syst}\,{\rm MeV}/c^{2}$ and $18.3 \pm 16.4_{\rm stat} \pm 5.7_{\rm syst}\,{\rm MeV}$, respectively. We also present evidence for a new production mechanism for the previously identified $Ω(2012)^-$ via the process $e^+ e^- \to Ω(2012)^{-} \barΩ^{+} +c.c.$ with a significance of 3.5 $σ$. △ Less

Submitted 25 April, 2025; v1 submitted 18 November, 2024; originally announced November 2024.

Comments: 8 pages, 2 figures

Journal ref: Phys. Rev. Lett. 134, 131903 (2025)

Observation of a rare beta decay of the charmed baryon with a Graph Neural Network

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, O. Afedulidis, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, I. Balossino, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere , et al. (637 additional authors not shown)

Abstract: The beta decay of the lightest charmed baryon $Λ_c^+$ provides unique insights into the fundamental mechanism of strong and electro-weak interactions, serving as a testbed for investigating non-perturbative quantum chromodynamics and constraining the Cabibbo-Kobayashi-Maskawa (CKM) matrix parameters. This article presents the first observation of the Cabibbo-suppressed decay… ▽ More The beta decay of the lightest charmed baryon $Λ_c^+$ provides unique insights into the fundamental mechanism of strong and electro-weak interactions, serving as a testbed for investigating non-perturbative quantum chromodynamics and constraining the Cabibbo-Kobayashi-Maskawa (CKM) matrix parameters. This article presents the first observation of the Cabibbo-suppressed decay $Λ_c^+ \rightarrow n e^+ ν_{e}$, utilizing $4.5~\mathrm{fb}^{-1}$ of electron-positron annihilation data collected with the BESIII detector. A novel Graph Neural Network based technique effectively separates signals from dominant backgrounds, notably $Λ_c^+ \rightarrow Λe^+ ν_{e}$, achieving a statistical significance exceeding $10σ$. The absolute branching fraction is measured to be $(3.57\pm0.34_{\mathrm{stat.}}\pm0.14_{\mathrm{syst.}})\times 10^{-3}$. For the first time, the CKM matrix element $\left|V_{cd}\right|$ is extracted via a charmed baryon decay as $0.208\pm0.011_{\rm exp.}\pm0.007_{\rm LQCD}\pm0.001_{τ_{Λ_c^+}}$. This work highlights a new approach to further understand fundamental interactions in the charmed baryon sector, and showcases the power of modern machine learning techniques in experimental high-energy physics. △ Less

Submitted 15 January, 2025; v1 submitted 17 October, 2024; originally announced October 2024.

Comments: 27 pages, 5 figures

Journal ref: Nature Commun. 16, 681 (2025)

Observation of the Singly Cabibbo-Suppressed Decay $Λ_c^{+}\to pπ^0$

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, O. Afedulidis, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, I. Balossino, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere , et al. (638 additional authors not shown)

Abstract: Utilizing 4.5${~\rm{fb}}^{-1}$ of $e^+e^-$ annihilation data collected with the BESIII detector at the BEPCII collider at center-of-mass energies between 4.600 and 4.699 GeV, the first observation of the singly Cabibbo-suppressed decay $Λ_c^{+}\to pπ^0$ is presented, with a statistical significance of $5.4σ$. The ratio of the branching fractions of $Λ_c^{+}\to pπ^0$ and $Λ_c^{+}\to pη$ is measured… ▽ More Utilizing 4.5${~\rm{fb}}^{-1}$ of $e^+e^-$ annihilation data collected with the BESIII detector at the BEPCII collider at center-of-mass energies between 4.600 and 4.699 GeV, the first observation of the singly Cabibbo-suppressed decay $Λ_c^{+}\to pπ^0$ is presented, with a statistical significance of $5.4σ$. The ratio of the branching fractions of $Λ_c^{+}\to pπ^0$ and $Λ_c^{+}\to pη$ is measured as $\mathcal{B}(Λ_c^{+}\to pπ^0)/\mathcal{B}(Λ_c^{+}\to pη)=(0.120\pm0.026_{\rm stat.}\pm0.007_{\rm syst.})$. This result resolves the longstanding discrepancy between earlier experimental searches, providing both a decisive conclusion and valuable input for QCD-inspired theoretical models. A sophisticated deep learning approach using a Transformer-based architecture is employed to distinguish the signal from the prevalent hadronic backgrounds, complemented by thorough validation and systematic uncertainty quantification. △ Less

Submitted 17 October, 2024; originally announced October 2024.

Comments: 9 pages, 4 figures

Journal ref: Phys. Rev. D 111, L051101 (2025)

Search for $η_c(2S)\toωω$ and $ωφ$ decays and measurements of $χ_{cJ}\toωω$ and $ωφ$ in $ψ(2S)$ radiative processes

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, O. Afedulidis, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, I. Balossino, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere , et al. (643 additional authors not shown)

Abstract: Using $(2712\pm 14)$ $\times$ 10$^{6}$ $ψ(2S)$ events collected with the BESIII detector at the BEPCII collider, we search for the decays $η_{c}(2S)\toωω$ and $η_{c}(2S)\toωφ$ via the process $ψ(2S)\toγη_{c}(2S)$. Evidence of $η_{c}(2S)\toωω$ is found with a statistical significance of $3.2σ$. The branching fraction is measured to be… ▽ More Using $(2712\pm 14)$ $\times$ 10$^{6}$ $ψ(2S)$ events collected with the BESIII detector at the BEPCII collider, we search for the decays $η_{c}(2S)\toωω$ and $η_{c}(2S)\toωφ$ via the process $ψ(2S)\toγη_{c}(2S)$. Evidence of $η_{c}(2S)\toωω$ is found with a statistical significance of $3.2σ$. The branching fraction is measured to be $\mathcal{B}(η_{c}(2S)\toωω)=(5.65\pm3.77(\rm stat.)\pm5.32(\rm syst.))\times10^{-4}$. No statistically significant signal is observed for the decay $η_{c}(2S)\toωφ$. The upper limit of the branching fraction at the 90\% confidence level is determined to be $\mathcal{B}(ψ(2S)\toγη_{c}(2S),η_{c}(2S)\toωφ)<2.24\times 10^{-7}$. We also update the branching fractions of $χ_{cJ}\to ωω$ and $χ_{cJ}\toωφ$ decays via the $ψ(2S)\toγχ_{cJ}$ transition. The branching fractions are determined to be $\mathcal{B}(χ_{c0}\toωω)=(10.63\pm0.11\pm0.46)\times 10^{-4}$, $\mathcal{B}(χ_{c1}\toωω)=(6.39\pm0.07\pm0.29)\times 10^{-4}$, $\mathcal{B}(χ_{c2}\toωω)=(8.50\pm0.08\pm0.38)\times 10^{-4}$, $\mathcal{B}(χ_{c0}\toωφ)=(1.18\pm0.03\pm0.05)\times 10^{-4}$, $\mathcal{B}(χ_{c1}\toωφ)=(2.03\pm0.15\pm0.12)\times 10^{-5}$, and $\mathcal{B}(χ_{c2}\toωφ)=(9.37\pm1.07\pm0.59)\times 10^{-6}$, where the first uncertainties are statistical and the second are systematic. △ Less

Submitted 13 August, 2024; originally announced August 2024.

Neural Network Modeling of Heavy-Quark Potential from Holography

Authors: Ou-Yang Luo, Xun Chen, Fu-Peng Li, Xiao-Hua Li, Kai Zhou

Abstract: Using Multi-Layer Perceptrons (MLP) and Kolmogorov-Arnold Networks (KAN), we construct a holographic model based on lattice QCD data for the heavy-quark potential in the 2+1 system. The deformation factor $w(r)$ in the metric is obtained using the two types of neural network. First, we numerically obtain $w(r)$ using MLP, accurately reproducing the QCD results of the lattice, and calculate the hea… ▽ More Using Multi-Layer Perceptrons (MLP) and Kolmogorov-Arnold Networks (KAN), we construct a holographic model based on lattice QCD data for the heavy-quark potential in the 2+1 system. The deformation factor $w(r)$ in the metric is obtained using the two types of neural network. First, we numerically obtain $w(r)$ using MLP, accurately reproducing the QCD results of the lattice, and calculate the heavy quark potential at finite temperature and the chemical potential. Subsequently, we employ KAN within the Andreev-Zakharov model for validation purpose, which can analytically reconstruct $w(r)$, matching the Andreev-Zakharov model exactly and confirming the validity of MLP. Finally, we construct an analytical holographic model using KAN and study the heavy-quark potential at finite temperature and chemical potential using the KAN-based holographic model. This work demonstrates the potential of KAN to derive analytical expressions for high-energy physics applications. △ Less

Submitted 3 December, 2024; v1 submitted 7 August, 2024; originally announced August 2024.

Measurement of the branching fraction of $D^+_s\to \ell^+ν_\ell$ via $e^+e^-\to D^{*+}_{s} D^{*-}_{s}$

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, O. Afedulidis, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, I. Balossino, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere , et al. (634 additional authors not shown)

Abstract: Based on $10.64~\mathrm{fb}^{-1}$ of $e^+e^-$ collision data taken at center-of-mass energies between 4.237 and 4.699 GeV with the BESIII detector, we study the leptonic $D^+_s$ decays using the $e^+e^-\to D^{*+}_{s} D^{*-}_{s}$ process. The branching fractions of $D_s^+\to\ell^+ν_{\ell}\,(\ell=μ,τ)$ are measured to be $\mathcal{B}(D_s^+\toμ^+ν_μ)=(0.547\pm0.026_{\rm stat}\pm0.016_{\rm syst})\%$ a… ▽ More Based on $10.64~\mathrm{fb}^{-1}$ of $e^+e^-$ collision data taken at center-of-mass energies between 4.237 and 4.699 GeV with the BESIII detector, we study the leptonic $D^+_s$ decays using the $e^+e^-\to D^{*+}_{s} D^{*-}_{s}$ process. The branching fractions of $D_s^+\to\ell^+ν_{\ell}\,(\ell=μ,τ)$ are measured to be $\mathcal{B}(D_s^+\toμ^+ν_μ)=(0.547\pm0.026_{\rm stat}\pm0.016_{\rm syst})\%$ and $\mathcal{B}(D_s^+\toτ^+ν_τ)=(5.60\pm0.16_{\rm stat}\pm0.20_{\rm syst})\%$, respectively. The product of the decay constant and Cabibbo-Kobayashi-Maskawa matrix element $|V_{cs}|$ is determined to be $f_{D_s^+}|V_{cs}|=(246.5\pm5.9_{\rm stat}\pm3.6_{\rm syst}\pm0.5_{\rm input})_{μν}~\mathrm{MeV}$ and $f_{D_s^+}|V_{cs}|=(252.7\pm3.6_{\rm stat}\pm4.5_{\rm syst}\pm0.6_{\rm input}))_{τν}~\mathrm{MeV}$, respectively. Taking the value of $|V_{cs}|$ from a global fit in the Standard Model, we obtain ${f_{D^+_s}}=(252.8\pm6.0_{\rm stat}\pm3.7_{\rm syst}\pm0.6_{\rm input})_{μν}$ MeV and ${f_{D^+_s}}=(259.2\pm3.6_{\rm stat}\pm4.5_{\rm syst}\pm0.6_{\rm input})_{τν}$ MeV, respectively. Conversely, taking the value for $f_{D_s^+}$ from the latest lattice quantum chromodynamics calculation, we obtain $|V_{cs}| =(0.986\pm0.023_{\rm stat}\pm0.014_{\rm syst}\pm0.003_{\rm input})_{μν}$ and $|V_{cs}| = (1.011\pm0.014_{\rm stat}\pm0.018_{\rm syst}\pm0.003_{\rm input})_{τν}$, respectively. △ Less

Submitted 23 January, 2025; v1 submitted 16 July, 2024; originally announced July 2024.

Comments: 27 pages, 13 figures

Journal ref: Phys. Rev. D 110, 052002 (2024)

Exploring Transport Properties of Quark-Gluon Plasma in Flavor-Dependent Systems with a Holographic Model

Authors: Bing Chen, Xun Chen, Xiaohua Li, Zhou-Run Zhu, Kai Zhou

Abstract: Based on the holographic model, which incorporates the equation of state (EoS) and baryon number susceptibility for different flavors, we calculate the drag force, jet quenching parameter, and diffusion coefficient of the heavy quark at finite temperature and chemical potential. The holographic results for the diffusion coefficient align with lattice data for $N_f = 0$ and $N_f = 2+1$, falling wit… ▽ More Based on the holographic model, which incorporates the equation of state (EoS) and baryon number susceptibility for different flavors, we calculate the drag force, jet quenching parameter, and diffusion coefficient of the heavy quark at finite temperature and chemical potential. The holographic results for the diffusion coefficient align with lattice data for $N_f = 0$ and $N_f = 2+1$, falling within their error margins. The holographic diffusion coefficient for heavy quark in the systems of different flavors \textcolor{red}{is compatible with estimates from ALICE data.} The jet quenching parameter in our model demonstrates strong consistency \textcolor{red}{with the estimations obtained from Bayesian analysis of data from both RHIC and LHC for different flavors.} We can confirm the model provides a good description of the transport properties of QGP. The work reinforces the potential of bottom-up holographic model in advancing our understanding of transport properties of hot and dense quark-gluon plasma. △ Less

Submitted 6 July, 2025; v1 submitted 28 April, 2024; originally announced April 2024.

Search for $C$-even states decaying to $D_{s}^{\pm}D_{s}^{*\mp}$ with masses between $4.08$ and $4.32~\mathrm{GeV}/c^{2}$

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, O. Afedulidis, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, I. Balossino, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere , et al. (638 additional authors not shown)

Abstract: Six $C$-even states, denoted as $X$, with quantum numbers $J^{PC}=0^{-+}$, $1^{\pm+}$, or $2^{\pm+}$, are searched for via the $e^+e^-\toγD_{s}^{\pm}D_{s}^{*\mp}$ process using $(1667.39\pm8.84)~\mathrm{pb}^{-1}$ of $e^+e^-$ collision data collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energy of $\sqrt{s}=(4681.92\pm0.30)~\mathrm{MeV}$. No statistically s… ▽ More Six $C$-even states, denoted as $X$, with quantum numbers $J^{PC}=0^{-+}$, $1^{\pm+}$, or $2^{\pm+}$, are searched for via the $e^+e^-\toγD_{s}^{\pm}D_{s}^{*\mp}$ process using $(1667.39\pm8.84)~\mathrm{pb}^{-1}$ of $e^+e^-$ collision data collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energy of $\sqrt{s}=(4681.92\pm0.30)~\mathrm{MeV}$. No statistically significant signal is observed in the mass range from $4.08$ to $4.32~\mathrm{GeV}/c^{2}$. The upper limits of $σ[e^+e^- \to γX] \cdot \mathcal{B}[X \to D_{s}^{\pm} D_{s}^{*\mp}]$ at a $90\%$ confidence level are determined. △ Less

Submitted 30 August, 2024; v1 submitted 2 April, 2024; originally announced April 2024.

Journal ref: Phys. Rev. D 110, 032017 (2024)

Test of lepton universality and measurement of the form factors of $D^0\to K^{*}(892)^-μ^+ν_μ$

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, O. Afedulidis, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, I. Balossino, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere , et al. (637 additional authors not shown)

Abstract: We report a first study of the semileptonic decay $D^0\rightarrow K^-π^0μ^{+}ν_μ$ by analyzing an $e^+e^-$ annihilation data sample of $7.9~\mathrm{fb}^{-1}$ collected at the center-of-mass energy of 3.773 GeV with the BESIII detector. The absolute branching fraction of $D^0\to K^-π^0μ^{+}ν_μ$ is measured for the first time to be $(0.729 \pm 0.014_{\rm stat} \pm 0.011_{\rm syst})\%$. Based on an a… ▽ More We report a first study of the semileptonic decay $D^0\rightarrow K^-π^0μ^{+}ν_μ$ by analyzing an $e^+e^-$ annihilation data sample of $7.9~\mathrm{fb}^{-1}$ collected at the center-of-mass energy of 3.773 GeV with the BESIII detector. The absolute branching fraction of $D^0\to K^-π^0μ^{+}ν_μ$ is measured for the first time to be $(0.729 \pm 0.014_{\rm stat} \pm 0.011_{\rm syst})\%$. Based on an amplitude analysis, the $S\text{-}{\rm wave}$ contribution is determined to be $(5.76 \pm 0.35_{\rm stat} \pm 0.29_{\rm syst})\%$ of the total decay rate in addition to the dominated $K^{*}(892)^-$ component. The branching fraction of $D^0\to K^{*}(892)^-μ^+ν_μ$ is given to be $(2.062 \pm 0.039_{\rm stat} \pm 0.032_{\rm syst})\%$, which improves the precision of the world average by a factor of 5. Combining with the world average of ${\mathcal B}(D^0\to K^{*}(892)^-e^+ν_e)$, the ratio of the branching fractions obtained is $\frac{{\mathcal B}(D^0\to K^{*}(892)^-μ^+ν_μ)}{{\mathcal B}(D^0\to K^{*}(892)^-e^+ν_e)} = 0.96\pm0.08$, in agreement with lepton flavor universality. Furthermore, assuming single-pole dominance parameterization, the most precise hadronic form factor ratios for $D^0\to K^{*}(892)^{-} μ^+ν_μ$ are extracted to be $r_{V}=V(0)/A_1(0)=1.37 \pm 0.09_{\rm stat} \pm 0.03_{\rm syst}$ and $r_{2}=A_2(0)/A_1(0)=0.76 \pm 0.06_{\rm stat} \pm 0.02_{\rm syst}$. △ Less

Submitted 23 January, 2025; v1 submitted 16 March, 2024; originally announced March 2024.

Comments: 10 pages, 3 figures

Journal ref: Phys. Rev. Lett. 134, 011803 (2025)

Physical Signatures of Fermion-Coupled Axion Dark Matter

Authors: Asher Berlin, Alexander J. Millar, Tanner Trickle, Kevin Zhou

Abstract: In the presence of axion dark matter, fermion spins experience an "axion wind" torque and an "axioelectric" force. We investigate new experimental probes of these effects and find that magnetized analogs of multilayer dielectric haloscopes can explore orders of magnitude of new parameter space for the axion-electron coupling. We also revisit the calculation of axion absorption into in-medium excit… ▽ More In the presence of axion dark matter, fermion spins experience an "axion wind" torque and an "axioelectric" force. We investigate new experimental probes of these effects and find that magnetized analogs of multilayer dielectric haloscopes can explore orders of magnitude of new parameter space for the axion-electron coupling. We also revisit the calculation of axion absorption into in-medium excitations, showing that axioelectric absorption is screened in spin-polarized targets, and axion wind absorption can be characterized in terms of a magnetic energy loss function. Finally, our detailed theoretical treatment allows us to critically examine recent claims in the literature. We find that axioelectric corrections to electronic energy levels are smaller than previously estimated and that the purported electron electric dipole moment due to a constant axion field is entirely spurious. △ Less

Submitted 8 June, 2024; v1 submitted 18 December, 2023; originally announced December 2023.

Comments: 58 pages, 8 figures. v2: discussion expanded, matches journal version

Report number: FERMILAB-PUB-23-779-SQMS-T, SLAC-PUB-17758

Journal ref: JHEP 05 (2024) 314

Phase Transition Study meets Machine Learning

Authors: Yu-Gang Ma, Long-Gang Pang, Rui Wang, Kai Zhou

Abstract: In recent years, machine learning (ML) techniques have emerged as powerful tools for studying many-body complex systems, and encompassing phase transitions in various domains of physics. This mini review provides a concise yet comprehensive examination of the advancements achieved in applying ML to investigate phase transitions, with a primary focus on those involved in nuclear matter studies. In recent years, machine learning (ML) techniques have emerged as powerful tools for studying many-body complex systems, and encompassing phase transitions in various domains of physics. This mini review provides a concise yet comprehensive examination of the advancements achieved in applying ML to investigate phase transitions, with a primary focus on those involved in nuclear matter studies. △ Less

Submitted 4 January, 2024; v1 submitted 13 November, 2023; originally announced November 2023.

Comments: arXiv admin note: text overlap with arXiv:2303.06752

Journal ref: Chinese Physics Letters 40, 122101 (2023)

Observation of the decay $J/ψ\to e^+ e^- η(1405)$ with $η(1405) \to π^0 f_0(980)$

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, X. C. Ai, R. Aliberti, A. Amoroso, M. R. An, Q. An, Y. Bai, O. Bakina, I. Balossino, Y. Ban, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann , et al. (601 additional authors not shown)

Abstract: Using a data sample of $(10087\pm44)\times 10^6$ $J/ψ$ events collected by the BESIII detector in 2009, 2012, 2018 and 2019, the electromagnetic Dalitz process $J/ψ\to e^+ e^- η(1405)$ is observed via the decay $η(1405) \to π^0 f_0(980)$, $f_0(980) \to π^+ π^-$, with a significance of about $9.6σ$. The branching fraction of this decay is measured to be… ▽ More Using a data sample of $(10087\pm44)\times 10^6$ $J/ψ$ events collected by the BESIII detector in 2009, 2012, 2018 and 2019, the electromagnetic Dalitz process $J/ψ\to e^+ e^- η(1405)$ is observed via the decay $η(1405) \to π^0 f_0(980)$, $f_0(980) \to π^+ π^-$, with a significance of about $9.6σ$. The branching fraction of this decay is measured to be ${\mathcal B}(J/ψ\to e^+ e^- π^0 η(1405) \to e^+ e^- π^0 f_0(980) \to e^+ e^- π^0 π^+ π^-)=(2.02\pm0.24(\rm{stat.})\pm0.09(\rm{syst.}))\times 10^{-7}$. The branching-fraction ratio ${\mathcal B}(J/ψ\to e^+ e^- η(1405))$/${\mathcal B}(J/ψ\to γη(1405))$ is determined to be $(1.35\pm0.19(\rm{stat.})\pm0.06(\rm{syst.}))\times10^{-2}$. Furthermore, an $e^+e^-$ invariant-mass dependent transition form factor of $J/ψ\to e^+ e^-η(1405)$ is presented for the first time. The obtained result provides input for different theoretical models, and is valuable for the improved understanding the intrinsic structure of the $η(1405)$ meson. △ Less

Submitted 27 July, 2023; originally announced July 2023.

Comments: 9 pages, 3 figures

Machine learning study to identify collective flow in small and large colliding systems

Authors: Shuang Guo, Han-Sheng Wang, Kai Zhou, Guo-Liang Ma

Abstract: Collective flow has been found to be similar between small colliding systems ($p$ $+$ $p$ and $p$ $+$ A collisions) and large colliding systems (peripheral A $+$ A collisions) at the CERN Large Hadron Collider. In order to study the differences of collective flow between small and large colliding systems, we employ a point cloud network to identify $p$ $+$ Pb collisions and peripheral Pb $+$ Pb co… ▽ More Collective flow has been found to be similar between small colliding systems ($p$ $+$ $p$ and $p$ $+$ A collisions) and large colliding systems (peripheral A $+$ A collisions) at the CERN Large Hadron Collider. In order to study the differences of collective flow between small and large colliding systems, we employ a point cloud network to identify $p$ $+$ Pb collisions and peripheral Pb $+$ Pb collisions at $\sqrt{s_{NN}} =$ 5.02 TeV generated from a multiphase transport model (AMPT). After removing the discrepancies in the pseudorapidity distribution and the $p_{\rm T}$ spectra, we capture the discrepancy in collective flow. Although the verification accuracy of our PCN is limited due to similar event-by-event distributions of elliptic and triangular flow, we demonstrate that collective flow between $p$ $+$ Pb collisions and peripheral Pb $+$ Pb collisions becomes more distinct with increasing final hadron multiplicity and parton scattering cross section. This study not only highlights the potential of PCN techniques in advancing the understanding of collective flow in varying colliding systems, but more importantly lays the groundwork for the future PCN-related research. △ Less

Submitted 29 August, 2024; v1 submitted 16 May, 2023; originally announced May 2023.

Comments: 10 pages, 11 figures, final published version

Journal ref: Phys.Rev.C 110 (2024) 2, 024910

First study of reaction $Ξ^{0}n\rightarrowΞ^{-}p$ using $Ξ^0$-nucleus scattering at an electron-positron collider

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, R. Aliberti, A. Amoroso, M. R. An, Q. An, Y. Bai, O. Bakina, I. Balossino, Y. Ban, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, J. Bloms, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann , et al. (593 additional authors not shown)

Abstract: Using $(1.0087\pm0.0044)\times10^{10}$ $J/ψ$ events collected with the BESIII detector at the BEPCII storage ring, the process $Ξ^{0}n\rightarrowΞ^{-}p$ is studied, where the $Ξ^0$ baryon is produced in the process $J/ψ\rightarrowΞ^0\barΞ^0$ and the neutron is a component of the $^9\rm{Be}$, $^{12}\rm{C}$ and $^{197}\rm{Au}$ nuclei in the beam pipe. A clear signal is observed with a statistical si… ▽ More Using $(1.0087\pm0.0044)\times10^{10}$ $J/ψ$ events collected with the BESIII detector at the BEPCII storage ring, the process $Ξ^{0}n\rightarrowΞ^{-}p$ is studied, where the $Ξ^0$ baryon is produced in the process $J/ψ\rightarrowΞ^0\barΞ^0$ and the neutron is a component of the $^9\rm{Be}$, $^{12}\rm{C}$ and $^{197}\rm{Au}$ nuclei in the beam pipe. A clear signal is observed with a statistical significance of $7.1σ$. The cross section of the reaction $Ξ^0+{^9\rm{Be}}\rightarrowΞ^-+p+{^8\rm{Be}}$ is determined to be $σ(Ξ^0+{^9\rm{Be}}\rightarrowΞ^-+p+{^8\rm{Be}})=(22.1\pm5.3_{\rm{stat}}\pm4.5_{\rm{sys}})$ mb at the $Ξ^0$ momentum of $0.818$ GeV/$c$, where the first uncertainty is statistical and the second is systematic. No significant $H$-dibaryon signal is observed in the $Ξ^-p$ final state. This is the first study of hyperon-nucleon interactions in electron-positron collisions and opens up a new direction for such research. △ Less

Submitted 28 May, 2023; v1 submitted 26 April, 2023; originally announced April 2023.

Comments: 13 pages, 7 figures, with Supplemental Material

STCF Conceptual Design Report: Volume 1 -- Physics & Detector

Authors: M. Achasov, X. C. Ai, R. Aliberti, L. P. An, Q. An, X. Z. Bai, Y. Bai, O. Bakina, A. Barnyakov, V. Blinov, V. Bobrovnikov, D. Bodrov, A. Bogomyagkov, A. Bondar, I. Boyko, Z. H. Bu, F. M. Cai, H. Cai, J. J. Cao, Q. H. Cao, Z. Cao, Q. Chang, K. T. Chao, D. Y. Chen, H. Chen , et al. (413 additional authors not shown)

Abstract: The Super $τ$-Charm facility (STCF) is an electron-positron collider proposed by the Chinese particle physics community. It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of $0.5\times 10^{35}{\rm cm}^{-2}{\rm s}^{-1}$ or higher. The STCF will produce a data sample about a factor of 100 larger than that by the present $τ$-Charm factory -- the BEPCII,… ▽ More The Super $τ$-Charm facility (STCF) is an electron-positron collider proposed by the Chinese particle physics community. It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of $0.5\times 10^{35}{\rm cm}^{-2}{\rm s}^{-1}$ or higher. The STCF will produce a data sample about a factor of 100 larger than that by the present $τ$-Charm factory -- the BEPCII, providing a unique platform for exploring the asymmetry of matter-antimatter (charge-parity violation), in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions, as well as searching for exotic hadrons and physics beyond the Standard Model. The STCF project in China is under development with an extensive R\&D program. This document presents the physics opportunities at the STCF, describes conceptual designs of the STCF detector system, and discusses future plans for detector R\&D and physics case studies. △ Less

Submitted 5 October, 2023; v1 submitted 28 March, 2023; originally announced March 2023.

Journal ref: Front. Phys. 19(1), 14701 (2024)

Exploring QCD matter in extreme conditions with Machine Learning

Authors: Kai Zhou, Lingxiao Wang, Long-Gang Pang, Shuzhe Shi

Abstract: In recent years, machine learning has emerged as a powerful computational tool and novel problem-solving perspective for physics, offering new avenues for studying strongly interacting QCD matter properties under extreme conditions. This review article aims to provide an overview of the current state of this intersection of fields, focusing on the application of machine learning to theoretical stu… ▽ More In recent years, machine learning has emerged as a powerful computational tool and novel problem-solving perspective for physics, offering new avenues for studying strongly interacting QCD matter properties under extreme conditions. This review article aims to provide an overview of the current state of this intersection of fields, focusing on the application of machine learning to theoretical studies in high energy nuclear physics. It covers diverse aspects, including heavy ion collisions, lattice field theory, and neutron stars, and discuss how machine learning can be used to explore and facilitate the physics goals of understanding QCD matter. The review also provides a commonality overview from a methodology perspective, from data-driven perspective to physics-driven perspective. We conclude by discussing the challenges and future prospects of machine learning applications in high energy nuclear physics, also underscoring the importance of incorporating physics priors into the purely data-driven learning toolbox. This review highlights the critical role of machine learning as a valuable computational paradigm for advancing physics exploration in high energy nuclear physics. △ Less

Submitted 1 December, 2023; v1 submitted 27 March, 2023; originally announced March 2023.

Comments: 152 pages,53 figures

Journal ref: Progress in Particle and Nuclear Physics, 104084, 2023

Model dependence of the number of participant nucleons and observable consequences in heavy-ion collisions

Authors: Manjunath Omana Kuttan, Jan Steinheimer, Kai Zhou, Marcus Bleicher, Horst Stoecker

Abstract: The centrality determination and the estimated fluctuations of number of participant nucleons $N_{part}$ in Au-Au collisions at 1.23 $A$GeV beam kinetic energy suffers from severe model dependencies. Comparing the Glauber Monte Carlo (MC) and UrQMD transport models, it is shown that $N_{part}$ is a strongly model dependant quantity. In addition, for any given centrality class, Glauber MC and UrQMD… ▽ More The centrality determination and the estimated fluctuations of number of participant nucleons $N_{part}$ in Au-Au collisions at 1.23 $A$GeV beam kinetic energy suffers from severe model dependencies. Comparing the Glauber Monte Carlo (MC) and UrQMD transport models, it is shown that $N_{part}$ is a strongly model dependant quantity. In addition, for any given centrality class, Glauber MC and UrQMD predicts drastically different $N_{part}$ distributions. The impact parameter $b$ and the number of charged particles $N_{ch}$ on the other hand are much more correlated and give an almost model independent centrality estimator. It is suggested that the total baryon number balance, from integrated rapidity distributions, can be used instead of $N_{part}$ in experiments. Preliminary HADES data show significant differences to both, UrQMD simulations and STAR data in this respect. △ Less

Submitted 13 September, 2023; v1 submitted 14 March, 2023; originally announced March 2023.

Comments: Replaced with the published version

Journal ref: Eur. Phys. J. C 83, 792 (2023)

High energy nuclear physics meets Machine Learning

Authors: Wan-Bing He, Yu-Gang Ma, Long-Gang Pang, Huichao Song, Kai Zhou

Abstract: Though being seemingly disparate and with relatively new intersection, high energy nuclear physics and machine learning have already begun to merge and yield interesting results during the last few years. It's worthy to raise the profile of utilizing this novel mindset from machine learning in high energy nuclear physics, to help more interested readers see the breadth of activities around this in… ▽ More Though being seemingly disparate and with relatively new intersection, high energy nuclear physics and machine learning have already begun to merge and yield interesting results during the last few years. It's worthy to raise the profile of utilizing this novel mindset from machine learning in high energy nuclear physics, to help more interested readers see the breadth of activities around this intersection. The aim of this mini-review is to introduce to the community the current status and report an overview of applying machine learning for high energy nuclear physics, to present from different aspects and examples how scientific questions involved in high energy nuclear physics can be tackled using machine learning. △ Less

Submitted 12 March, 2023; originally announced March 2023.

Comments: 30 pages, 20 figures, mini-review

Interactions of Particles with "Continuous Spin" Fields

Authors: Philip Schuster, Natalia Toro, Kevin Zhou

Abstract: Powerful general arguments allow only a few families of long-range interactions, exemplified by gauge field theories of electromagnetism and gravity. However, all of these arguments presuppose that massless fields have zero spin scale (Casimir invariant) and hence exactly boost invariant helicity. This misses the most general behavior compatible with Lorentz symmetry. We present a Lagrangian forma… ▽ More Powerful general arguments allow only a few families of long-range interactions, exemplified by gauge field theories of electromagnetism and gravity. However, all of these arguments presuppose that massless fields have zero spin scale (Casimir invariant) and hence exactly boost invariant helicity. This misses the most general behavior compatible with Lorentz symmetry. We present a Lagrangian formalism describing interactions of matter particles with bosonic "continuous spin" fields with arbitrary spin scale $ρ$. Remarkably, physical observables are well approximated by familiar theories at frequencies larger than $ρ$, with calculable deviations at low frequencies and long distances. For example, we predict specific $ρ$-dependent modifications to the Lorentz force law and the Larmor formula, which lay the foundation for experimental tests of the photon's spin scale. We also reproduce known soft radiation emission amplitudes for nonzero $ρ$. The particles' effective matter currents are not fully localized to their worldlines when $ρ\neq 0$, which motivates investigation of manifestly local completions of our theory. Our results also motivate the development of continuous spin analogues of gravity and non-Abelian gauge theories. Given the correspondence with familiar gauge theory in the small $ρ$ limit, we conjecture that continuous spin particles may in fact mediate known long-range forces, with testable consequences. △ Less

Submitted 5 April, 2023; v1 submitted 8 March, 2023; originally announced March 2023.

Comments: 96 pages, 6 figures. v2: minor typos fixed, matches journal version

Report number: SLAC-PUB-17726

Journal ref: JHEP 04 (2023) 010

Bottom energy loss and non-prompt $J/ψ$ production in relativistic heavy ion collisions

Authors: Meimei Yang, Shiqi Zheng, Bo Tong, Jiaxing Zhao, Wenyuan Ouyang, Kai Zhou, Baoyi Chen

Abstract: We study the momentum and centrality dependence of the non-prompt $J/ψ$ nuclear modification factors ($R_{AA}$), which comes from the $B$ hadrons decay, in Pb-Pb collisions at the Large Hadron Collider. Bottom quarks are produced in the parton hard scatterings and suffer energy loss in the quark-gluon plasma and the hadronic gas, where the spatial and time evolution of the medium is described with… ▽ More We study the momentum and centrality dependence of the non-prompt $J/ψ$ nuclear modification factors ($R_{AA}$), which comes from the $B$ hadrons decay, in Pb-Pb collisions at the Large Hadron Collider. Bottom quarks are produced in the parton hard scatterings and suffer energy loss in the quark-gluon plasma and the hadronic gas, where the spatial and time evolution of the medium is described with the hydrodynamic equations. Medium-induced elastic scatterings and the radiation in bottom quarks are included in the energy loss of bottom quarks. The hadronization process of bottom quarks is described with the instantaneous coalescence model. After considering both cold and hot nuclear matter effects in Pb-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV, we calculated the $R_{AA}$ and also the elliptic flows of non-prompt $J/ψ$ from the decay of $B$ mesons at different centralities and transverse momentum bins. The $R_{AA}$ and $v_2$ of non-prompt $J/ψ$ sensitive to the hot medium reflect and centrality supply an opportunity to study the bottom quarks energy loss in the hot medium. △ Less

Submitted 30 May, 2023; v1 submitted 13 February, 2023; originally announced February 2023.

Comments: 7 pages, 6 figures

Journal ref: Phys.Rev.C 107, 054917(2023)

Examination of nucleon distribution with Bayesian imaging for isobar collisions

Authors: Yi-Lin Cheng, Shuzhe Shi, Yu-Gang Ma, Horst Stöcker, Kai Zhou

Abstract: Relativistic collision of isobaric systems is found to be valuable in differentiating the nucleon distributions for nuclei with the same mass number. In recent contrast experiment of $^{96}_{44}\text{Ru}+^{96}_{44}\text{Ru}$ versus $^{96}_{40}\text{Zr}+^{96}_{40}\text{Zr}$ collisions at $\sqrt{s_\text{NN}} = 200~\text{GeV}$, the ratios of multiplicity distribution, elliptic flow, triangular flow,… ▽ More Relativistic collision of isobaric systems is found to be valuable in differentiating the nucleon distributions for nuclei with the same mass number. In recent contrast experiment of $^{96}_{44}\text{Ru}+^{96}_{44}\text{Ru}$ versus $^{96}_{40}\text{Zr}+^{96}_{40}\text{Zr}$ collisions at $\sqrt{s_\text{NN}} = 200~\text{GeV}$, the ratios of multiplicity distribution, elliptic flow, triangular flow, and radial flow are precisely measured and found to be significantly different from unity, indicating the difference in the shapes of the isobar pair. In this work, we investigate the feasibility of nuclear structure reconstruction from heavy-ion collision observables. We perform Bayesian Inference with employing the Monte-Carlo Glauber model as an estimator of the mapping from nuclear structure to the final state observables and to provide the mock data for reconstruction. By varying combination of observables included in the mock data, we find it plausible to infer Woods--Saxon parameters from the observables. We also observe that single-system multiplicity distribution for the isobar system, rather than their ratio, is crucial to simultaneously determine the nuclear structure for the isobar system. △ Less

Submitted 28 June, 2023; v1 submitted 10 January, 2023; originally announced January 2023.

Comments: Previously entitled "How does Bayesian analysis infer the nucleon distributions in isobar collisions?"

First Direct Measurement of the Absolute Branching Fraction of $Σ^+ \to Λe^+ ν_{e}$

Authors: BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, R. Aliberti, A. Amoroso, M. R. An, Q. An, Y. Bai, O. Bakina, R. Baldini Ferroli, I. Balossino, Y. Ban, V. Batozskaya, D. Becker, K. Begzsuren, N. Berger, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, J. Bloms, A. Bortone, I. Boyko, R. A. Briere , et al. (579 additional authors not shown)

Abstract: The first direct measurement of the absolute branching fraction of $Σ^+ \to Λe^+ ν_{e}$ is reported based on an $e^+e^-$ annihilation sample of $(10087\pm44) \times 10^6$ $J/ψ$ events collected with the BESIII detector at $\sqrt{s}=3.097$ GeV. The branching fraction is determined to be ${\mathcal B}(Σ^+ \to Λe^+ ν_{e}) = [2.93\pm0.74(\rm stat) \pm 0.13(\rm syst)]\times 10^{-5}$, which is the most… ▽ More The first direct measurement of the absolute branching fraction of $Σ^+ \to Λe^+ ν_{e}$ is reported based on an $e^+e^-$ annihilation sample of $(10087\pm44) \times 10^6$ $J/ψ$ events collected with the BESIII detector at $\sqrt{s}=3.097$ GeV. The branching fraction is determined to be ${\mathcal B}(Σ^+ \to Λe^+ ν_{e}) = [2.93\pm0.74(\rm stat) \pm 0.13(\rm syst)]\times 10^{-5}$, which is the most precise measurement obtained in a single experiment to date and also the first result obtained at a collider experiment. Combining this result with the world average of ${\mathcal B}(Σ^- \to Λe^- \barν_{e})$ and the lifetimes of $Σ^{\pm}$, the ratio, $\frac{Γ(Σ^- \to Λe^- \barν_{e})}{Γ(Σ^+ \to Λe^+ ν_{e})}$, is determined to be $1.06 \pm 0.28$, which is within 1.8 standard deviations of the value expected in the absence of second-class currents that are forbidden in the Standard Model. △ Less

Submitted 10 December, 2022; originally announced December 2022.

Comments: 8 pages, 3 figures

QCD Equation of State of Dense Nuclear Matter from a Bayesian Analysis of Heavy-Ion Collision Data

Authors: Manjunath Omana Kuttan, Jan Steinheimer, Kai Zhou, Horst Stoecker

Abstract: Bayesian methods are used to constrain the density dependence of the QCD Equation of State (EoS) for dense nuclear matter using the data of mean transverse kinetic energy and elliptic flow of protons from heavy ion collisions (HIC), in the beam energy range $\sqrt{s_{\mathrm{NN}}}=2-10 GeV$. The analysis yields tight constraints on the density dependent EoS up to 4 times the nuclear saturation den… ▽ More Bayesian methods are used to constrain the density dependence of the QCD Equation of State (EoS) for dense nuclear matter using the data of mean transverse kinetic energy and elliptic flow of protons from heavy ion collisions (HIC), in the beam energy range $\sqrt{s_{\mathrm{NN}}}=2-10 GeV$. The analysis yields tight constraints on the density dependent EoS up to 4 times the nuclear saturation density. The extracted EoS yields good agreement with other observables measured in HIC experiments and constraints from astrophysical observations both of which were not used in the inference. The sensitivity of inference to the choice of observables is also discussed. △ Less

Submitted 17 November, 2023; v1 submitted 21 November, 2022; originally announced November 2022.

Comments: Replaced with the published version

Journal ref: Phys. Rev. Lett. 131, 202303 (2023)

Discovering QCD-Coupled Axion Dark Matter with Polarization Haloscopes

Authors: Asher Berlin, Kevin Zhou

Abstract: In the presence of QCD axion dark matter, atoms acquire time-dependent electric dipole moments. This effect gives rise to an oscillating current in a nuclear spin-polarized dielectric, which can resonantly excite an electromagnetic mode of a microwave cavity. We show that with existing technology such a "polarization haloscope" can explore orders of magnitude of new parameter space for QCD-coupled… ▽ More In the presence of QCD axion dark matter, atoms acquire time-dependent electric dipole moments. This effect gives rise to an oscillating current in a nuclear spin-polarized dielectric, which can resonantly excite an electromagnetic mode of a microwave cavity. We show that with existing technology such a "polarization haloscope" can explore orders of magnitude of new parameter space for QCD-coupled axions. If any cavity haloscope detects a signal from the axion-photon coupling, an upgraded polarization haloscope has the unique ability to test whether it arises from the QCD axion. △ Less

Submitted 25 August, 2023; v1 submitted 26 September, 2022; originally announced September 2022.

Comments: 11 pages, 2 figures. v2: discussion expanded, matches journal version

Report number: FERMILAB-PUB-22-654-SQMS-T, SLAC-PUB-17702

Journal ref: Phys. Rev. D 108, 035038 (2023)