Tue·May 27, 2025Tuesday·May 27, 2025

1. 01*

   High-precision Penning trap mass measurements of neutron-rich chlorine isotopes at the N=28 shell closure

   H. Erington🇺🇸 · G. Bollen🇺🇸 · G. Dykstra · A. Hamaker🇺🇸 · C. M. Ireland🇺🇸 · C. R. Nicoloff · D. Puentes🇺🇸 · R. Ringle🇺🇸 · S. Schwarz🇺🇸 · C. S. Sumithrarachchi🇺🇸 · A. A. Valverde🇺🇸 · I. T. Yandow🇺🇸

   Although it is known that the $N=28$ spherical shell closure erodes, the strength of the closure with decreasing proton number $Z<20$ is an open question in nuclear structure. In this region of interest, direct high-precision mass measurements of neutron-rich ${}^{43-45}$Cl isotopes were performed at the Low Energy Beam and Ion Trap (LEBIT) when coupled to the National Superconducting Cyclotron Lab. The resulting mass excesses (MEs) are ME(${}^{43}$Cl) = -24114.4(1.7) keV, ME(${}^{44}$Cl) = -20450.8(10.6) keV, and ME(${}^{45}$Cl) = -18240.1(3.7) keV, and improve the uncertainty of these masses by up to a factor of ~40 compared to the previous values reported in the 2020 Atomic Mass Evaluation. Comparison to $\text{ab initio}$ calculations using the Valence-Space In-Medium Similarity Renormalization Group (VS-IMSRG) shows good agreement up to and including the closure.

   nucl-exnucl-thPRC(2025)·0 citations
2. 02*

   Backscattering Study of Electrons from 0.1 to 3.4 MeV

   M. Kanafani (1)🇫🇷 · X. Fléchard (1)🇫🇷 · O. Naviliat-Cuncic (1 and 2 and 3)🇫🇷 · R. Garreau (1)🇫🇷 · T.E. Haugen (2 and 4)🇺🇸 · L. Hayen (1)🇫🇷 · S. Leblond (5)🇫🇷 · E. Liénard (1)🇫🇷 · X. Mougeot (5)🇫🇷 · G. Quéméner (1)🇫🇷 · A. Rani (1)🇫🇷 · J-C. Thomas (6)🇫🇷 · S. Vanlangendonck (7) ((1) Université de Caen Normandie, ENSICAEN, CNRS/IN2P3, LPC Caen, UMR6534, France, (2) Facility for Rare Isotope Beams and Department of Physics and Astronomy, Michigan State University, USA, (3) International Research Laboratory Nuclear Physics and Nuclear Astrophysics, CNRS-MSU, USA, (4) Radiation Physics Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, USA, (5) Université Paris-Saclay, CEA, List, Laboratoire National Henri Becquerel (LNE-LNHB), France, (6) GANIL, CEA/DRF-CNRS/IN2P3, France, (7) KU Leuven, Instituut voor Kern- en Stralingsfysica, Belgium)🇧🇪

   Benchmarking simulation codes for electron transport and scattering in matter is a crucial step for estimating uncertainties in many applications. However, experimental data for electron energies of a few MeV is scarce to make such comparisons. We report here the measurement and the quantitative analysis of backscattering probabilities of electrons in the energy range 0.1 to 3.4~MeV impinging on YAP:Ce scintillator. The setup consists of a $2\times 2\pi$ calorimeter which enables, in particular, the inclusion of large incidence angles. The results are used to benchmark various scattering models incorporated in Geant4, showing relative deviations smaller than 5% between experiment and simulations. They demonstrate the current rather high reliability of the simulations when employing appropriate electromagnetic Physics Lists.

   nucl-exPRC(2026)·2 citations
3. 03*

   Measurement of $\Lambda$ Polarization in the ${\pi }^{-}p\to K^0\Lambda$ Reaction at $p_{{\pi }^{-}}=1.33$ GeV/$c$ toward a New $\Lambda p$ Scattering Experiment

   J-PARC E40 Collaboration: T. Sakao🇯🇵 · K. Miwa🇯🇵 · J. K. Ahn🇰🇷 · Y. Akazawa🇯🇵 · T. Aramaki🇯🇵 · S. Ashikaga🇯🇵 · S. Callier🇫🇷 · N. Chiga🇯🇵 · S. W. Choi🇰🇷 · H. Ekawa🇯🇵 · P. Evtoukhovitch🇷🇺 · N. Fujioka🇯🇵 and 59 other authors

   This paper presents high-precision experimental data of the polarization of the $\Lambda$ hyperon in the ${\pi }^{-}p\to K^0\Lambda$ reaction, measured in the angular range $0.6<\cos {\theta }_{K0}^{CM}<1.0$ with a fine bin width of $d\cos {\theta }_{K0}^{CM}=0.05$. The data were obtained from the J-PARC E40 experiment at the K1.8 beamline in the J-PARC Hadron Experimental Facility. The observed average polarization of $\Lambda$ in the range $0.60<\cos {\theta }_{K0}^{CM}<0.85$ was $0.932\pm 0.058(\text{stat})\pm 0.028(\text{syst})$, demonstrating the successful extraction of precise polarization observables. This result provides essential experimental input for partial wave analysis (PWA) of dynamical coupled-channel (DCC) models, which aim to uncover the underlying mechanisms of $N^{\ast }$ resonances that emerge in intermediate states of $\pi N$ and $\gamma N$ interactions. Besides, it indicates the feasibility of a strongly polarized $\Lambda$ beam suitable for future $\Lambda p$ scattering experiments (e.g., J-PARC E86).

   nucl-exPTEP(2026)·0 citations
4. 04*

   Electric dipole polarizability constraints on neutron skin and symmetry energy

   P. von Neumann-Cosel (1,2)🇩🇪 · A. Tamii (3) ((1) Institut für Kernphysik, Technische Universität Darmstadt, Germany, (2) Norwegian Nuclear Research Center and Department of Physics, University of Oslo, Norway, (3) Research Center for Nuclear Physics, University of Osaka, Japan)🇯🇵

   We review the experimental knowledge on the dipole polarizability (DP) of nuclei and its relation to the neutron skin thickness and properties of the neutron-rich matter equation of state (EOS). The discussion focuses on recent experiments using relativistic Coulomb excitation in inelastic proton scattering at extreme forward angles covering a mass range from ${}^{40}$Ca to ${}^{208}$Pb. Constraints on the neutron skins and the density dependence of the symmetry energy are derived from systematic comparison to calculations based on density functional theory (DFT) and ab initio methods utilizing interactions derived from chiral effective field theory ($\chi$EFT). The results consistently favor a soft EOS around or slightly below the saturation point. An outlook is given on possible improvements of the precision achievable in stable nuclei and studies of exotic neutron-rich unstable nuclei with upcoming experimental facilities.

   nucl-exnucl-thFront.in Phys.(2025)·7 citations
5. 05*

   Study of $p_{\mathrm{T}}$-differential radial flow in blast-wave model

   Swati Saha🇮🇳 · Ranbir Singh🇮🇳 · Bedangadas Mohanty🇮🇳

   The transverse momentum-differential radial flow observable $v_0(p_{\mathrm{T}})$, recently proposed and measured by the ATLAS and ALICE collaborations, provides a novel tool to probe radial expansion dynamics in high-energy heavy-ion collisions. In this work, we conduct a detailed study of $v_0(p_{\mathrm{T}})$ using a blast-wave model that incorporates hydrodynamic-like expansion and thermal emission. We introduce event-by-event fluctuations in the transverse expansion velocity and kinetic freeze-out temperature using Gaussian probability distributions. Our results show that increasing the mean expansion velocity leads to a clear mass ordering in $v_0(p_{\mathrm{T}})$, while fluctuations in both expansion velocity and freeze-out temperature significantly enhance the magnitude of $v_0(p_{\mathrm{T}})$, particularly at higher $p_{\mathrm{T}}$. We fit blast-wave model calculations for identified hadrons ($\pi$, K, and p) to recent ALICE data from Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV using a Bayesian parameter estimation framework. The extracted mean transverse expansion velocity decreases, while the kinetic freeze-out temperature increases, from central to peripheral collisions. Additionally, the freeze-out temperatures inferred from $v_0(p_{\mathrm{T}})$ are systematically higher than those obtained from conventional $p_{\mathrm{T}}$-spectra fits, likely due to the reduced sensitivity of $v_0(p_{\mathrm{T}})$ to resonance decay contributions.

   nucl-exhep-exhep-phnucl-thPRC(2025)·16 citations
6. 06*

   Lattice QCD Benchmark of Proton Helicity and Flavor-Dependent Unpolarized Transverse Momentum-Dependent Parton Distribution Functions at Physical Quark Masses

   Dennis Bollweg🇺🇸 · Xiang Gao🇺🇸 · Swagato Mukherjee🇺🇸 · Yong Zhao🇺🇸

   We present the first lattice QCD calculations of the isovector helicity transverse momentum-dependent parton distribution function (TMDPDF) and the flavor-dependent unpolarized TMDPDFs for up and down quarks in the proton. Our computations utilize domain-wall fermion discretization with physical quark masses. Employing Coulomb-gauge-fixed quark correlation functions within the large-momentum effective theory framework, we access nonperturbative transverse quark separations $b_T$ up to approximately 1 fm, corresponding to transverse momenta as low as 200 MeV. Based on the quasi-TMD factorization theorem, we construct renormalization-group-invariant ratios that are equal to the corresponding light-cone TMDPDF ratios. At moderate $x$, our results reveal that the isovector helicity and unpolarized TMDPDFs exhibit nearly identical transverse structure up to a normalization factor, and the unpolarized distributions display only mild flavor dependence. These findings not only support key trends observed in recent global analyses but also provide robust, nonperturbative constraints that can distinguish between different parameterizations. This work establishes a first-principles benchmark for TMDPDFs, offering valuable input for ongoing and future experimental efforts to map the proton's three-dimensional structure.

   ↳ hep-lathep-exhep-phnucl-ex+1PRL(2025)·10 citations
7. 07*

   First measurement of ${\Sigma }^{+}n\to \Lambda p$ and ${\Sigma }^{+}n\to {\Sigma }^{0}p$ cross sections via ${\Sigma }^{+}$-nucleus scattering at an electron-positron collider

   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 and 692 other authors

   Using $(1.0087\pm 0.0044)\times 10^{10}$ $J/\psi$ events collected with the BESIII detector at the BEPCII storage ring, the reactions ${\Sigma }^{+}n\to \Lambda p$ and ${\Sigma }^{+}n\to {\Sigma }^{0}p$ are studied, where the ${\Sigma }^{+}$ baryon is produced in the process $J/\psi \to {\Sigma }^{+}{\bar{\Sigma }}^{-}$ and the neutron is a component of the ${}^9\mathrm{Be}$, ${}^{12}\mathrm{C}$ and ${}^{197}\mathrm{Au}$ nuclei in the beam pipe. Clear signals of these two reactions are observed for the first time. Their cross sections are measured to be $\sigma ({\Sigma }^{+}+{}^9\mathrm{Be}\to \Lambda +p+X)=(45.2\pm 12.1_{\mathrm{stat}}\pm 7.2_{\mathrm{sys}})$ mb and $\sigma ({\Sigma }^{+}+{}^9\mathrm{Be}\to {\Sigma }^0+p+X)=(29.8\pm 9.7_{\mathrm{stat}}\pm 6.9_{\mathrm{sys}})$ mb for a ${\Sigma }^{+}$ average momentum of $0.992$ GeV/$c$, within a range of $\pm 0.015$ GeV/$c$, where $X$ represents the residual nucleus. This is the first study of ${\Sigma }^{+}$-nucleon scattering at an electron-positron collider.

   ↳ hep-exnucl-exPRC(2026)·10 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.