Mon·Mar 31, 2025Monday·March 31, 2025

1. 01*

   CERN AD/ELENA Antimatter Program

   R. Caravita🇮🇹 · A. Cridland Mathad🇨🇭 · J. S. Hangst🇩🇰 · M. Hori🇬🇧 · B. M. Latacz🇨🇭 · A. Obertelli🇩🇪 · P. Perez🇫🇷 · S. Ulmer🇩🇪 · E. Widmann (on behalf of the Antiproton Decelerator User Community (ADUC))🇦🇹

   The CERN AD/ELENA Antimatter program studies the fundamental charge, parity, time (CPT) reversal invariance through high-precision studies of antiprotons, antihydrogen, and antiprotonic atoms. Utilizing the world-unique Antiproton Decelerator (AD) and the Extra Low Energy Antiproton (ELENA) decelerator, the program supports multiple groundbreaking experiments aimed at testing fundamental symmetries, probing gravity with antimatter, and investigating potential asymmetric antimatter/dark matter interactions. Some experiments focus on precision spectroscopy of antihydrogen, while others conduct the most precise tests of CPT invariance in the baryon sector by comparing proton and antiproton properties. Other efforts are dedicated to measure the ballistic properties of antihydrogen under gravity and performing antiproton-based studies of neutron skins in exotic nuclei. These efforts have led to major breakthroughs, including the first trapped antihydrogen, antihydrogen's first gravitational acceleration measurement, and record-breaking precision CPT-tests in the baryon sector. With continuous advancements in antimatter cooling, trapping, and transport, CERN's program is opening new frontiers in fundamental physics. Future goals, described in this document and reaching to timelines beyond 2040, include further improving the precision of antimatter studies, developing transportable antimatter traps, and advancing our understanding of quantum field theory, gravity, and dark matter interactions. Furthermore, new areas of hadron physics with antiprotons will be explored through studies of the Pontecorvo reaction, antineutron annihilation dynamics and hypernuclei decays. The CERN AD/ELENA Antimatter program remains at the forefront of experimental physics, pushing the limits of precision measurements to unravel the mysteries of the universe.

   nucl-exphysics.atom-ph7 citations
2. 02*

   Multiplicity and net-electric charge fluctuations in central Ar+Sc interactions at 13A, 19A, 30A, 40A, 75A, and 150A GeV/c beam momenta measured by NA61/SHINE at the CERN SPS

   H. Adhikary🇵🇱 · P. Adrich🇵🇱 · K.K. Allison🇺🇸 · N. Amin🇩🇪 · E.V. Andronov · I.-C. Arsene🇳🇴 · M. Bajda🇵🇱 · Y. Balkova🇵🇱 · D. Battaglia🇺🇸 · A. Bazgir🇵🇱 · S. Bhosale🇵🇱 · M. Bielewicz🇵🇱 and 119 other authors

   This paper presents results on multiplicity fluctuations of positively and negatively charged hadrons as well as net-electric charge fluctuations measured in central Ar+Sc interactions at beam momenta 13A, 19A, 30A, 40A, 75A, and 150A GeV/c. The fluctuation analysis is one of the tools to search for the predicted critical point of strongly interacting matter. Results are corrected for the experimental biases and quantified using cumulant ratios. In most instances, multiplicity and net-charge distributions appear narrower than the corresponding Poisson or Skellam distributions. Cumulant ratios are compared with the EPOS1.99 model predictions, which provide a qualitative description that aligns with observations for positively and negatively charged particles. The obtained results are also compared to earlier NA61/SHINE results from inelastic p+p interactions in the same analysis acceptance.

   nucl-exEPJC(2025)·12 citations
3. 03*

   Level-anticrossing in B(E2) anomaly (I)

   Tao Wang🇨🇳 · Yu-xin Cheng🇨🇳 · Dong-kang Li · Xiao-shen Kang🇨🇳 · Suo-chang Jin🇨🇳 · Tie Wang🇨🇳 · Zhi-qi Zhang · Cheng-guang Zhang🇨🇳 · Zhi-xin Zhang🇨🇳

   Recently, a new mechanism for explaining the B(E2) anomaly was given by F. Pan \emph{et al.} (PRC, 110, 054324, 2024), which is realized in the parameter region from the SU(3) symmetry limit to the O(6) symmetry limit, and seems to be not related to the SU(3) symmetry. However, through SU(3) analysis, a new technique proposed recently, we found that it is not so. The new mechanism is related to level-anticrossing phenomenon, which is related to level-crossing phenomenon in the SU(3) symmetry limit. By incorporating previous ideas, we have a more general explanatory framework for the B(E2) anomaly, which is important for understanding some higher-order interactions in the interacting boson model. Through analysis, it is shown that level-anticrossing in this mechanism mainly results from the third-order interaction $[\hat{L}\times {\hat{Q}}_{\chi }\times \hat{L}{]}^{(0)}$. Finally, the B(E2) anomaly in ${}^{170}$Os is also discussed within this general framework.

   ↳ nucl-thnucl-exquant-ph7 citations
4. 04*

   Machine learning based parametrization of the resolution function for the first experimental area (EAR1) of the n_TOF facility at CERN

   Petar Žugec🇭🇷 · Marta Sabate Gilarte🇨🇭 · Michael Bacak🇨🇭 · Vasilis Vlachoudis🇨🇭 · Adria Casanovas🇨🇭 · Francisco Garcia Infantes🇨🇭

   This study addresses a challenge of parametrizing a resolution function of the neutron beam from the neutron time of flight facility n_TOF at CERN. A difficulty stems from a fact that a resolution function exhibits rather strong variations in shape, over approximately 10 orders of magnitude in neutron energy. In order to avoid a need for a manual identification of the appropriate analytical forms - hindering past attempts at its parametrization - we take advantage of the versatile machine learning techniques. In particular, we parametrize it by training a multilayer feedforward neural network, relying on a key idea that such networks act as the universal approximators. The proof of concept is presented for a resolution function for the first experimental area of the n_TOF facility, from the third phase of its operation. We propose an optimal network structure for a resolution function in question, which is also expected to be optimal or near-optimal for other experimental areas and for different phases of n_TOF operation. In order to reconstruct several resolution function forms in common use from a single parametrized form, we provide a practical tool in the form of a specialized C++ class encapsulating the computationally efficient procedures suited to the task. Specifically, the class allows an application of a user-specified temporal spread of a primary proton beam (from a neutron production process at n_TOF) to a desired resolution function form.

   ↳ physics.comp-phnucl-exphysics.ins-detNucl.Sci.Tech.(2025)·1 citation
5. 05*

   Effects of perturbation for transition operator of double-$\beta$ decay on nuclear matrix element, effective axial-vector current coupling, and half-life

   J. Terasaki🇨🇿 · O. Civitarese🇦🇷

   We calculate the nuclear matrix element (NME), effective axial-vector current coupling $g_A^{\mathrm{eff}}$, and half-life of the double-$\beta$ ($\beta \beta$) decay using the transition operator perturbed by the nuclear interaction. The correction terms for the NME are obtained by extending the hadron sector to a higher order in terms of the Rayleigh-Schrödinger perturbation theory. The NME calculations are performed for the neutrinoless $\beta \beta$ ($0\nu \beta \beta$) and the two-neutrino $\beta \beta$ ($2\nu \beta \beta$) decays of ${}^{136}$Xe. The nuclear wave functions are calculated by the quasiparticle random-phase approximation (QRPA) with the Skyrme, the Coulomb, and the contact pairing interactions. Sufficiently large single-particle valence spaces are used. The correction terms for the NME are comparable with the leading term in absolute value, and the sum of the corrections has the opposite sign to that of the leading term. The $g_A^{\mathrm{eff}}$'s for the $\beta \beta$ NME are calculated by a few methods depending on the truncation of the NME and the half-life referred to. Similarities are found between some of these $g_A^{\mathrm{eff}}$'s including those of the $0\nu \beta \beta$ NME. This leads to the conclusion that the value of $g_A^{\mathrm{eff}}$ can indeed be determined by the perturbed transition operator. It is in a comparable range of the $g_A$ for the $2\nu \beta \beta$ NME. The perturbation effect on the $2\nu \beta \beta$ half-life is discussed by comparing the calculated half-lives with the different $g_A$'s and the NME components.

   ↳ nucl-thhep-thnucl-exPRC(2025)·3 citations
6. 06*

   Towards a Quantum Information Theory of Hadronization: Dihadron Fragmentation and Neutral Polarization in Heavy Baryons

   Rebecca von Kuk🇩🇪 · Kyle Lee🇺🇸 · Johannes K. L. Michel🇳🇱 · Zhiquan Sun🇺🇸

   We pioneer the application of quantum information theory to experimentally distinguish between classes of hadronization models. We adapt the CHSH inequality to the fragmentation of a single parton to hadron pairs, a violation of which would rule out classical dynamics of hadronization altogether. Furthermore, we apply and extend the theory of quantum contextuality and local quantum systems to the neutral polarization of a single spin-1 hadronic system, namely the light constituents of excited Sigma baryons ${\Sigma }_{c,b}^{\ast }$ formed in the fragmentation of heavy quarks.

   ↳ hep-phhep-exnucl-exnucl-th+124 citations
7. 07*

   Crossover between the zeptosecond and attosecond physics

   T. Nandi · Yash Kumar🇮🇳 · Adya P. Mishra🇮🇳 · Nishchal R. Dwivedi · Chandra Kumar🇮🇳 · Gajendra Singh🇮🇳 · N.Sowmya · H.C.Manjunatha · Sudhir R. Jain · A.S. Kheifets

   Nuclear orbiting resonances have been revealed at the sub-barrier energies as an atomic phenomenon by means of x-ray spectroscopy experiments. This interpretation is supported by several phenomenological models and theoretical estimates of the nuclear orbiting timescale and cross-section, inelastic scattering cross section including both nuclear and Coulomb excitation, and the Wigner-Smith time delay. We demonstrate that a multi-photon exchange during nuclear orbiting is responsible for an atomic excitation. Furthermore, proximity of the projectile and target nucleus during the nuclear orbiting modifies the effective charge of the projectile. Even though this orbiting induced excitation is triggered in zeptoseconds, it can still be observed in the attosecond time scale because of the Wigner-Smith time delay inherent to autoionization. Thus, we demonstrate the crossover between the zeptosecond and attosecond time scales which are native to nuclear and atomic physics, respectively. Markedly, this crossover may be the reason for x-ray production from ultra short nuclear processes ($\le 10^{-21}$ sec). This explanation is likely to resolve the fission time scale anomaly and can stimulate cross-disciplinary research ranging from solid state to high-energy physics.

   ↳ physics.atom-phnucl-exnucl-th0 citations
8. 08*

   Studies of Directed Flow with Event Plane Method in the HIRFL-CSR External-target Experiment

   Wanlong Wu🇨🇳 · Xionghong He🇨🇳 · Yanyu Ren🇨🇳 · Diyu Shen🇨🇳 · Shusu Shi🇨🇳 · Xu Sun🇨🇳

   The Cooling-Storage-Ring External-target Experiment (CEE) at Heavy Ion Research Facility in Lanzhou (HIRFL) is designed to study the properties of nuclear matter created in heavy-ion collisions at a few hundred MeV/$u$ to 1 GeV/$u$ beam energies, facilitating the research of quantum chromodynamics phase structure in the high-baryon-density region. Collective flow is one of the most important observables in heavy-ion collision experiments to study the bulk behavior of the created matter. Even though the standard event plane method has been widely used for collective flow measurements, it remains crucial to validate and optimize this method for the CEE spectrometer. In this paper, we study the experimental procedures of measuring directed flow in ${}^{238}$U+${}^{238}$U collisions at 500 MeV/$u$ using event planes reconstructed by Multi Wire Drift Chamber and Zero Degree Calorimeter, respectively. Jet AA Microscopic (JAM) transport generator is used to generate events, and the detector response is simulated by the CEE Fast Simulation (CFS) package. Finally, the optimal kinetic region for proton directed flow measurements is discussed for the future CEE experiment.

   ↳ physics.ins-dethep-exnucl-exNucl.Sci.Tech.(2026)·2 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.