Fri·Nov 22, 2024Friday·November 22, 2024

1. 01*

   Scaling Properties of $\varphi$-Meson and Light Charged Hadron Production in Small and Large Systems at PHENIX

   Rachid Nouicer (for the PHENIX Collaboration)🇺🇸

   Recent results on the identified charged-hadron (${\pi }^{\pm }$, $K^{\pm }$, $p$, $\bar{p}$) production at midrapidity region ($|\eta |<$ 0.35) have been measured by the PHENIX experiment in $p+\mathrm{Al}$, ${}^3\mathrm{He}+\mathrm{Au}$, $\mathrm{Cu}+\mathrm{Au}$ collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV and $\mathrm{U}+\mathrm{U}$ collisions at $\sqrt{s_{{}_{NN}}}$ = 193 GeV. These measurements are presented through the invariant transverse-momentum ($p_T$) and transverse-mass ($m_T$) spectra for different collision centralities. The averaged freeze-out temperature value for different systems was found to be $166.1\pm 2.2$ MeV, and do not exhibit any dependence on the collision centrality and $⟨N_{\mathrm{part}}⟩$ values. The particle ratios of $K/\pi$ and $p/\pi$ have been measured in different centrality ranges of large and small collision systems. The values of $K/\pi$ ratios measured in all considered collision systems were found to be consistent with those measured in $p$$+$$p$ collisions. Furthermore, the identified charged-hadron nuclear-modification factors ($R_{AB}$) are also presented. Enhancement of proton $R_{AB}$ values over meson $R_{AB}$ values was observed in central ${}^3\mathrm{He}+\mathrm{Au}$, $\mathrm{Cu}+\mathrm{Au}$, and $\mathrm{U}+\mathrm{U}$ collisions. The proton $R_{AB}$ values measured in $p+\mathrm{Al}$ collision system were found to be consistent with $R_{AB}$ values of $\varphi$, ${\pi }^{\pm }$, $K^{\pm }$, and ${\pi }^0$ mesons, suggesting that the size of the system produced in $p+\mathrm{Al}$ collisions is too small for recombination to cause a noticeable increase in proton production.

   nucl-exEPJ Web Conf.(2025)·0 citations
2. 02*

   Measurement of two-neutrino double electron capture half-life of ${}^{124}$Xe with PandaX-4T

   PandaX Collaboration: Zihao Bo🇨🇳 · Wei Chen🇨🇳 · Xun Chen🇨🇳 · Yunhua Chen🇨🇳 · Zhaokan Cheng🇨🇳 · Xiangyi Cui🇨🇳 · Yingjie Fan🇨🇳 · Deqing Fang🇨🇳 · Zhixing Gao🇨🇳 · Lisheng Geng🇨🇳 · Karl Giboni🇨🇳 · Xunan Guo🇨🇳 and 89 other authors

   Detailed studies of two-neutrino double electron capture (2$\nu$DEC) is a crucial step towards searching for the neutrino-less mode to explore the Majorana nature of neutrinos. We have measured precisely the half-life of the 2$\nu$DEC process in ${}^{124}$Xe, utilizing a total exposure of 1.73 tonne$\cdot$year from the commissioning run and the first science run of the PandaX-4T experiment. A time-dependent background model in the $\mathcal{O}$(10 keV) energy is constructed for the first time in PandaX-4T data. With an unbinned maximum likelihood fit, we determine the half-life of the 2$\nu$DEC process to be $(1.03\pm 0.15_{\mathrm{stat}}\pm 0.08_{\mathrm{sys}})\times 10^{22}$yr. Furthermore, we have evaluated the branching ratio for both electrons captured from the $K$ shell ($KK$) to be $(65\pm 5)\%$, which aligns with the ${}^{124}$Xe nuclear model calculations within 1.8$\sigma$.

   nucl-exJHEP(2025)·16 citations
3. 03*

   Transverse spin effects and light-quark dipole moments at lepton colliders

   Xin-Kai Wen🇨🇳 · Bin Yan🇨🇳 · Zhite Yu🇺🇸 · C.-P. Yuan🇺🇸

   We propose to probe light-quark dipole interactions at lepton colliders using the azimuthal asymmetry of a collinear dihadron pair $(h_1{h}_2)$ produced in association with another hadron $h^{\prime }$. This asymmetry, arising from quantum interference in the quark spin space, is exclusively sensitive to dipole interactions at the leading power of the new physics scale and simultaneously probes both the real and imaginary components of the dipole couplings. By combining all possible channels of $h^{\prime }$, this method allows for disentangling the up and down quark dipole moments and has the potential to significantly strengthen current constraints by one to two orders of magnitude.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2025)·16 citations
4. 04*

   Proton-neutron pair correlations in neutron-rich nuclei

   Kenichi Yoshida🇯🇵

   [Background] Nuclear pairing is a well-established many-body correlation, particularly among like particles in a spin-singlet state. However, the strength of spin-triplet proton-neutron (pn) pairing in nuclei has remained a long-standing and unresolved issue. [Purpose] The relative strength of spin-triplet pn pairing compared to spin-singlet one is investigated by introducing and analyzing the polarizability of the response to pn pair transfers. [Method] The nuclear energy-density functional method is employed. The ground state of the target nucleus is described using the Hartree-Fock-Bogoliubov approximation, which accounts for the conventional superfluidity of like-particle pairs. The response to pn pair transfers is then analyzed using the pn quasiparticle random-phase approximation. [Results] The spin-singlet pn-pair correlation is strongest at $N=Z$ and decreases monotonically with the increasing number of excess neutrons, whereas the spin-triplet pn-pair correlation is shown to depend non-monotonically on the neutron number and can be enhanced in cases where the pn-pair transfers involving the $\pi j_{>}\otimes \nu j_{<}$ configuration occur at low energy. [Conclusions] The shell effect, which uniquely appears in spin-triplet pn-pair correlation, serves as a key indicator of the strength of pn-pair correlations.

   ↳ nucl-thnucl-ex1 citation
5. 05*

   Direct-photon production in inelastic and high-multiplicity proton-proton collisions at $\sqrt{s}=$ 13 TeV

   ALICE Collaboration

   In this letter, we present the first measurement of direct photons at the transverse momentum of $1<p_{\mathrm{T}}<6$ GeV/$c$ at midrapidity $|\eta |<0.8$ in inelastic and high-multiplicity proton--proton collisions at a centre-of-mass energy of $\sqrt{s}=$ 13 TeV. The fraction of virtual direct photons in the inclusive virtual photon spectrum is obtained from a fit to the dielectron invariant mass spectrum. In the limit of zero invariant mass, this fraction is equal to the relative contribution of real direct photons in the inclusive real photon spectrum. Contributions from decays of light-flavour neutral mesons are estimated using independent measurements in proton-proton collisions at the same energy and the same event class. For the first time at the LHC energies, a direct-photon signal is observed at low $p_{\mathrm{T}}$ in both inelastic and high-multiplicity event classes, with a significance of 3.2$\sigma$ and 1.9$\sigma$ in terms of standard deviations, correspondingly. The yield of direct photons in inelastic pp collisions is compared to perturbative QCD calculations. The integrated photon yield is studied as a function of charged-particle multiplicity and is compared to the results from other experiments and theoretical calculations. The results show a significant increase of direct-photon yield with charged-particle multiplicity.

   ↳ hep-exnucl-exPLB(2025)·6 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.