Tue·Apr 15, 2025Tuesday·April 15, 2025

1. 01*

   Surface and chemical effects on ${}^{199}$Hg spin polarization relaxation in optically pumped magnetometers

   Steven K. Lamoreaux🇺🇸

   Quantum spin magnetometry using optically pumped ${}^{199}$Hg has been successfully used in many fundamental physics experiments. A serious problem that has not been resolved is the instability of the ${}^{199}$Hg spin relaxation rate in atomic vapor cells under irradiation with 254 nm Hg resonance light. In this paper, previously obtained data are re-analyzed or analyzed for the first time. The effects of impurities of H${}_2$ and O${}_2$ are elucidated, and possible ways to stabilize cells are discussed. Surface states originating from the an der Waals interaction of \hg with fused silica are analyzed and shown to be critical to understanding relaxation mechanisms. A discussion of the possible use of a mixture of N${}_2$O and other gases is presented.

   nucl-exphysics.atom-phAcademia Quantum(2025)·1 citation
2. 02*

   Event-shape dependence of symmetry plane correlations using the Gaussian estimator in Pb-Pb collisions at the LHC using a multiphase transport model

   Sarthak Tripathy🇮🇳 · Suraj Prasad🇮🇳 · Raghunath Sahoo🇮🇳

   The study of symmetry plane correlations (SPCs) can be useful in characterizing the direction of the anisotropic emission of produced particles in the final state. The study of SPCs provides an independent method to understand the transport properties of the system formed in heavy-ion collisions. Similar to anisotropic flow coefficients, which are largely influenced by the initial spatial anisotropy, SPCs also depend upon the participant plane correlations measured using the participating nucleons of the collision overlap region. In this paper, SPCs have been studied in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV using the event generator AMPT. In addition to their behaviour with the changing centrality of the collision, their event shape dependence has also been studied for the first time, using the event shape classifier transverse spherocity. The Gaussian estimator has been used to evaluate the correlations, and these have been compared to the participant plane correlations defined in an analogous way to the symmetry plane correlations, and a qualitative match has been found between them. These event-shape differentiated symmetry plane correlations can be used to deduce the presence of higher-order anisotropies in the initial energy distribution, thus giving insight into the initial geometry of the colliding system, among other applications like model development and model testing using Bayesian analyses.

   nucl-exhep-exhep-phhep-th+1PRD(2025)·7 citations
3. 03*

   Measurement of the helicity-dependent response in quasi-elastic proton knockout from ${}^{40}\mathrm{Ca}$

   Tim Kolar🇮🇱 · Iris Sabo-Napadensky🇮🇱 · Patrick Achenbach🇩🇪 · Mirko Christmann🇩🇪 · Michael Otto Distler🇩🇪 · Luca Doria🇩🇪 · Phillipp Eckert🇩🇪 · Anselm Esser🇩🇪 · Carlotta Giusti🇮🇹 · Jennifer Geimer🇩🇪 · Pepe Gülker🇩🇪 · Matthias Hoek🇩🇪 and 25 other authors

   The role of the electron-helicity-dependent cross-section term and the structure function $f_{01}^{\prime }$ in the quasi-elastic $A(\vec{e},e^{\prime }p)$ process was studied. The $f_{01}^{\prime }$ was measured for proton knockout from the $1{\mathrm{d}}_{3/2}$ shell in ${}^{40}\mathrm{Ca}$ via the ${}^{40}\mathrm{Ca}(\vec{e},e^{\prime }p{)}^{39}{\mathrm{K}}_{g.s.}$ reaction, leaving the residual nucleus in a well-defined state. It requires a longitudinally polarized electron beam and out-of-plane proton detection. This structure function vanishes in the absence of final-state interactions (FSI) involving the ejected proton. Presented are the dependencies of $f_{01}^{\prime }$ on the missing momentum (closely related to the initial proton's Fermi momentum) and the angle between the knocked-out proton and the virtual photon momenta. The role of the spin-orbit interaction in FSI through the $\vec{L}\cdot \vec{S}$ term in a nuclear optical potential is discussed.

   nucl-exPLB(2025)·1 citation
4. 04*

   Precise Measurement of Short-Range Correlations in Nuclei from Bremsstrahlung Gamma Ray Emission in Low-Energy Heavy-Ion Collisions

   Junhuai Xu🇨🇳 · Qinglin Niu🇨🇳 · Yuhao Qin🇨🇳 · Dawei Si🇨🇳 · Yijie Wang🇨🇳 · Sheng Xiao🇨🇳 · Baiting Tian🇨🇳 · Zhi Qin🇨🇳 · Haojie Zhang🇨🇳 · Boyuan Zhang🇨🇳 · Dong Guo🇨🇳 · Minxue Fu🇨🇳 and 24 other authors

   Atomic nuclei and dense nucleonic matter in neutron stars exhibit short-range correlations (SRCs), where nucleons form temporally correlated pairs in proximity beyond mean-field approximation. It is essential to make precision measurement of the fraction of SRC since it carries the signature of underlying quark dynamics in nuclear medium. In this letter, we present the first high-precision measurement of neutron-proton bremsstrahlung $\gamma$-ray emission from the symmetric ${}^{124}\mathrm{Sn}$+${}^{124}\mathrm{Sn}$ reactions at 25 MeV/u. From the observed spectral hardening, the precise SRC fraction in the ${}^{124}\mathrm{Sn}$ nucleus is extracted to be $(20\pm 3)\%$. This result provides a novel, direct and unambiguous evidence of SRCs, and demonstrates that low-energy heavy-ion collisions offers a new approach to studying nuclear structure in connection with quark-level dynamics.

   nucl-exnucl-thPRResearch(2025)·8 citations
5. 05*

   From spin to pseudospin symmetry: The origin of magic numbers in nuclear structure

   C. R. Ding🇨🇳 · C. C. Wang🇨🇳 · J. M. Yao🇨🇳 · H. Hergert🇺🇸 · H. Z. Liang🇯🇵 · S. Bogner🇺🇸

   Magic numbers lie at the heart of nuclear structure, reflecting enhanced stability in nuclei with closed shells. While the emergence of magic numbers beyond 20 is commonly attributed to strong spin-orbit coupling, the microscopic origin of the spin-orbit potential remains elusive, owing to its dependence on the resolution scale and renormalization scheme of nuclear forces. Here, we investigate the evolution of shell structure with varying momentum resolution in nuclear interactions derived from chiral effective field theory, using the similarity renormalization group to link different scales. We uncover a novel transition from spin symmetry to pseudospin symmetry as the resolution scale decreases, during which magic numbers emerge naturally. A similar pattern is found in calculations using relativistic one-boson-exchange potentials, underscoring the robustness of the phenomenon. This establishes a direct connection between realistic nuclear forces with a high resolution scale and effective nuclear forces at coarse-grained scales, offering a first-principles explanation for the origin of magic numbers and pseudospin symmetry in nuclear shell structure, and new insights into the structure of exotic nuclei far from stability.

   ↳ nucl-thnucl-exquant-phPRL(2026)·8 citations
6. 06*

   Extracting Meson Distribution Amplitudes from Nonlocal Euclidean Correlations at Next-to-Next-to-Leading Order

   Yao Ji🇩🇪 · Fei Yao🇺🇸 · Jian-Hui Zhang🇨🇳

   We present the first complete result for the next-to-next-to-leading order (NNLO) hard matching kernel indispensable for a precision extraction of light meson distribution amplitudes from lattice calculations of equal-time nonlocal Euclidean correlation functions. The results are given in both coordinate and momentum space, with the renormalization and matching accomplished in a state-of-the-art scheme. Our results can be used in both large-momentum effective theory and short-distance factorization approaches. Notably, our coordinate space kernel is directly applicable to nonsinglet quark unpolarized and helicity generalized parton distributions as well. We also illustrate the numerical impact of the NNLO matching, using the pion distribution amplitude as an example.

   ↳ hep-phhep-latnucl-exnucl-th7 citations
7. 07*

   Time-dependent random phase approximation for particle-number fluctuations and correlations in deep-inelastic collisions of ${}^{144}$Sm+${}^{144}$Sm and ${}^{154}$Sm+${}^{154}$Sm

   Zepeng Gao🇨🇳 · Kazuyuki Sekizawa🇯🇵 · Long Zhu🇨🇳

   The fluctuation-dissipation mechanism underlying non-equilibrium transport in low-energy heavy-ion reactions remains unclear. Although the time-dependent Hartree-Fock (TDHF) method provides a reasonable description of average reaction outcomes and one-body dissipation, it is known to significantly underestimate fluctuations of observables. The purpose of this work is to investigate deep-inelastic collisions of 144Sm+144Sm and 154Sm+154Sm with microscopic mean-field approaches and to show a predominant role of one-body dissipation as well as one-body fluctuations and correlation in low-energy heavy-ion reactions. Three dimensional TDHF calculations are carried out for 144Sm+144Sm at Ecm=500 MeV and 154Sm+154Sm at Ecm=485 MeV for a range of impact parameters with Skyrme SLy5 energy density functional. Backward time evolutions are performed as well to evaluate fluctuations and correlation in nucleon numbers within time-dependent random phase approximation (TDRPA). With TDRPA we calculate mass- and charge-number fluctuations, as well as the correlation between neutron and proton transfers, for each impact parameter. We demonstrate that TDRPA quantitatively reproduces the experimental \sigma_{AA}^2-TKEL distributions, whereas it systematically underestimates the charge fluctuation, \sigma_{ZZ}. The double-differential cross sections of reaction products are calculated, showing good agreement with the experimental data. We confirm a long-thought characteristic property that the closed-shell structure limits nucleon transfer at small energy losses, based on our microscopic TDHF and TDRPA calculations.

   ↳ nucl-thnucl-exPRC(2025)·8 citations
8. 08*

   Prompt and non-prompt production of charm hadrons in proton-proton collisions at the Large Hadron Collider using machine learning

   Raghunath Sahoo🇮🇳 · Suraj Prasad🇮🇳 · Neelkamal Mallick🇮🇳 · Kangkan Goswami🇮🇳 · Gagan B. Mohanty🇮🇳

   In this contribution, we use machine learning (ML) based models to separate the prompt and non-prompt production of heavy flavour hadrons, such as $D^0$ and J/$\psi$, in proton-proton collisions at LHC energies. For this purpose, we use PYTHIA~8 to generate events, which provides a good qualitative agreement with experimental measurements of charm hadron production. The input features for the ML models are experimentally measurable. The prediction accuracy of the ML models used in this study reaches up to 99\%. The ML models can be useful in providing precise track-level identification, which is not possible in experiments with traditional methods. The contribution also discusses future applications of the ML models to understand the production of prompt and non-prompt heavy quark hadrons.

   ↳ hep-phhep-exhep-thnucl-ex+1J.Subatomic Part.Cosmol.(2025)·0 citations
9. 09*

   Understanding baryon stopping at the BNL Relativistic Heavy Ion Collider top energies

   Niseem Magdy🇺🇸 · Prithwish Tribedy🇺🇸 · Chun Yuen Tsang🇺🇸 · Zhangbu Xu🇺🇸

   The nucleon exhibits a rich internal structure governed by Quantum Chromodynamics (QCD), where its electric charge arises from valence quarks, while its spin and mass emerge from complex interactions among valence quarks, sea (anti-)quarks, and gluons. At the advent of QCD, an alternative hypothesis emerged suggesting, at high energies, the transport of a nucleon's baryon number could be traced by a non-perturbative configuration of gluon fields connecting its three valence quarks, forming a $Y$-shaped topology known as the gluon junction. Recent measurements by the STAR experiment are compatible with this scenario. In light of these measurements, this study aims to explore the mechanisms of baryon transport in high-energy nuclear collisions using the PYTHIA-8 framework, which incorporates a state-of-the-art hadronization model with advanced Color Flow (CF) and Color Reconnection (CR) mechanisms that mimic signatures of a baryon junction. Within this model setup, we investigate (i) the rapidity slope of the net-baryon distributions in photon-included processes ($\gamma$+p) and (ii) baryon over charge transport in the isobaric (Ru+Ru and Zr+Zr) collisions. Our study highlights the importance of the CF and CR mechanisms in PYTHIA-8, which play a crucial role in baryon transport. The results show that the CF and CR schemes significantly affect the isobaric baryon-to-charge ratio, leading to different predictions for baryon stopping and underscoring the need to account for CF and CR effects in comparisons with experimental measurements.

   ↳ hep-phnucl-exnucl-thPRC(2025)·4 citations
10. 10*

    Revisiting the deuteron mass radius via near-threshold ${\rho }^0$, $\omega$ and $\varphi$ meson photoproduction

    Xiaoxuan Lin🇨🇳 · Wei Kou🇨🇳 · Shixin Fu🇨🇳 · Rong Wang🇨🇳 · Chengdong Han🇨🇳 · Xurong Chen🇨🇳

    We present a comprehensive analysis of near-threshold photoproduction of ${\rho }^0$, $\omega$, and $\varphi$ mesons on a deuterium target, utilizing published datasets from DESY and SLAC for ${\rho }^0$ and $\omega$ production, as well as data from the LEPS and CLAS Collaborations for $\varphi$ production. In extracting the deuteron mass radius, we adopt a dipole parametrization for the scalar gravitational form factor, which effectively captures the $|t|$-dependence of the differential cross sections associated with vector meson photoproduction. In addition, results from alternative commonly used form factor parametrizations are also considered and compared. Employing the vector meson dominance (VMD) framework and invoking low-energy Quantum Chromodynamics (QCD) theorems, we extract the deuteron mass radius from near-threshold photoproduction data of ${\rho }^0$, $\omega$, and $\varphi$ mesons. The mass radii obtained from the various datasets are found to be consistent within statistical uncertainties, yielding an average value of $2.03\pm 0.13$ fm under the dipole form assumption. We also provide a detailed discussion of the sensitivity of the extracted radius to different choices of gravitational form factor models. Our result represents a significant improvement in precision compared to earlier estimates based solely on $\varphi$ meson photoproduction, offering new constraints for theoretical models of nuclear structure and deepening our understanding of the mass distribution within the deuteron.

    ↳ hep-phnucl-exnucl-thCPC(2025)·1 citation
11. 11*

    Automated next-to-leading order QCD and electroweak predictions of photon-photon processes in ultraperipheral collisions

    Hua-Sheng Shao🇫🇷 · Lukas Simon🇫🇷

    We present automated next-to-leading order QCD and/or electroweak (EW) predictions for photon-photon processes in ultraperipheral high-energy collisions of protons and ions, extending the capabilities of the MadGraph5_aMC@NLO framework together in combination with the gamma-UPC code. Key aspects of this extension are discussed. We compute QCD and/or EW quantum corrections for several phenomenologically interesting processes at LHC and FCC-hh energies.

    ↳ hep-phhep-exnucl-exnucl-thJHEP(2025)·9 citations
12. 12*

    The HYDRA pion-tracker for hypernuclei studies at R3B

    Lian-Cheng Ji🇩🇪 · Uwe Bonnes🇩🇪 · Mikolaj Cwiok🇵🇱 · Meytal Duer🇩🇪 · Alexandru Enciu🇩🇪 · Piotr Gasik🇩🇪 · Joerg Hehner🇩🇪 · Alexandre Obertelli🇩🇪 · Shinsuke Ota🇯🇵 · Valerii Panin🇩🇪 · Jerome Pibernat🇫🇷 · Dominic Rossi🇩🇪 and 5 other authors

    The HYpernuclei-Decay at R3B Apparatus (HYDRA) tracker is a novel time projection chamber combined with a plastic scintillator wall for timing and trigger purposes. This detector is a low radiation length tracker dedicated to measuring pions from the weak decay of light hypernuclei produced from ion-ion collisions at few GeV/nucleon in the magnetic field of the large-acceptance dipole magnet GLAD at the Reactions with Relativistic Radioactive Beams (R3B) experiment at GSI-FAIR. In this paper, we describe the design of the detector and provide the results of its first characterizations.

    ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2026)·2 citations
13. 13*

    Analogical models to introduce high school students to modern physics: an inquiry-based activity on Rutherford's gold foil experiment

    M. Tuveri🇮🇹 · E. Murgia · V. Fanti

    This study presents the design and the implementation of an inquiry-based reconstruction of Rutherford's gold foil experiment. The activity engaged students in collaborative exploration using a "black box" as an analogical model of the atom. Grounded in constructivist theory and the Focus Action-Reflection (FAR) model to introduce analogies in the in-class context, we explore how analogical reasoning can support high school students in understanding the atomic structure. Data from student worksheets, graphical representations, and group discussions were analyzed using thematic, phenomenographic, and conceptual metaphor analysis. Results indicate that students were able to develop and refine analogical models, reason from empirical evidence, and engage in critical reflection on the epistemological limits of the analogy. While students demonstrated conceptual gains and collaborative problem-solving, the analysis also revealed persistent risks of reifying metaphors or overextending macroscopic analogies to quantum domains. These findings highlight the value - and limitations - of structured analogical modeling in contemporary physics education, and point to the need for teacher training that fosters epistemological awareness and reflective use of models in the classroom.

    ↳ physics.ed-phnucl-exphysics.app-phphysics.hist-ph+1Phys.Educ.(2025)·0 citations
14. 14*

    Exploring the effects of $\alpha$-clustered structure of ${}^{16}O$ nuclei in anisotropic flow fluctuations in ${}^{16}O$-${}^{16}O$ collisions at the LHC within a CGC+Hydro framework

    Suraj Prasad🇮🇳 · Neelkamal Mallick🇮🇳 · Raghunath Sahoo🇮🇳 · Gergely Gabor Barnafoldi🇭🇺

    In this paper, we explore the effects of the presence of clustered nuclear structure of ${}^{16}O$ in the final state elliptic flow fluctuations through ${}^{16}O$-${}^{16}O$ collisions at $\sqrt{s_{\mathrm{NN}}}=7$ TeV within a hybrid model, IPGlasma+MUSIC+iSS+ UrQMD. We compare the results of elliptic flow fluctuations using $\alpha$-clustered nuclear structure to the Woods-Saxon nuclear profile having no clustered structure. We observe a significant difference in the elliptic flow fluctuations, which arise due to the consideration of a clustered nuclear structure of ${}^{16}O$.

    ↳ hep-phhep-exnucl-exnucl-thJ.Subatomic Part.Cosmol.(2026)·0 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.