Wed·Jul 2, 2025Wednesday·July 2, 2025

1. 01*

   Analysis of spectral modification of $\varphi$ mesons at finite density using a transport approach in the 12 GeV pA reactions

   KEK-PS E325 Collaboration: Masaya Ichikawa (1 and 2)🇯🇵 · Philipp Gubler (1)🇯🇵 · Junsei Chiba (2)🇯🇵 · Hideto En'yo (3)🇯🇵 · Yoshinori Fukao (4)🇯🇵 · Haruhiko Funahashi (4)🇯🇵 · Hideki Hamagaki (5)🇯🇵 · Masaharu Ieiri (2)🇯🇵 · Masaya Ishino (4)🇯🇵 · Hiroki Kanda (4)🇯🇵 · Masaaki Kitaguchi (4)🇯🇵 · Satoshi Mihara (4)🇯🇵 and 16 other authors

   The hadron spectrum at finite density is an important observable for exploring the origin of hadron masses. In the KEK-PS E325 experiment, the di-electron decays of phi mesons inside and outside nuclei were measured using 12 GeV pA reactions. In the previous analysis, a significant excess was observed on the low-mass side of the phi meson peak in the data for slow-moving phi mesons ($\beta \gamma =p_{\varphi }/m_{\varphi }<1.25$) with the Cu target, and in-medium vector meson spectral modification was verified. We newly employed the PHSD transport approach to take into account the time evolution of spatial density distribution of the target nuclei. Consistent with the previous analysis, a significant excess was observed in the present analysis as well. It was found that incorporating momentum dependence into the spectral modification leads to better agreement with the experimental results. For the slow-moving $\varphi$ mesons with the Cu target, the newly obtained modification parameters are consistent with those from the previous analysis within the uncertainties.

   nucl-exPTEP(2025)·6 citations
2. 02*

   Energy dependence of rescattering effect on vector mesons spin alignment at RHIC

   Zihan Liu🇨🇳 · Ziyang Li🇨🇳 · Wangmei Zha🇨🇳 · Zebo Tang🇨🇳

   Spin alignment of vector mesons in heavy-ion collisions provides a novel probe of quark polarization and hadronization mechanism in quark-gluon plasma. Hadronic rescattering may affect the measured spin alignment of vector mesons due to non-uniform rescattering probability in non-central heavy-ion collisions. Using the UrQMD model, we systematically investigated the hadronic rescattering effect on the measurement of ${\rho }_{00}$, the spin alignment parameter, for $K^{\ast 0}$, $\varphi$, and ${\rho }^0$ mesons in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 7.7 - 200 GeV. Our results reveal that the measurable ${\rho }_{00}-1/3$ remains unaffected for $\varphi$, while shows significantly negative (positive) deviations for $K^{\ast 0}$ and ${\rho }^0$ with respect to the reaction (production) plane. Quantitatively, the maximum deviation reaches $-0.0056$ ($0.0268$) for $K^{\ast 0}$ and $-0.0122$ ($0.0414$) for ${\rho }^0$ with respect to the reaction (production) plane. Notably, the deviations in ${\rho }_{00}$ for both $K^{\ast 0}$ and ${\rho }^0$ increase monotonically with increasing collision energy. These findings underscore the critical necessity of accounting for rescattering effects when interpreting spin alignment measurements of short-lived vector mesons in heavy-ion collisions.

   nucl-exhep-exhep-thnucl-thPLB(2026)·3 citations
3. 03*

   Collectivity of rotational motion in ${}^{220}$Rn and ${}^{226}$Ra

   Artur Dobrowolski🇵🇱 · Katarzyna Mazurek🇵🇱 · Krzysztof Pomorski🇵🇱

   Calculations to reconstruct rotational level patterns in the ${}^{220}$Rn and ${}^{226}$Ra nuclei have been performed using a collective quadrupole+octupole approach with microscopic mass tensor and moments of inertia dependent on deformation and pairing degrees of freedom. The main objective is to quantitatively confirm the known experimental observations that the Rn nucleus passes from octupole vibrational to octupole deformed with increasing rotation frequency, while the Ra nucleus is relatively weakly affected by collective rotation, being octupole deformed from the beginning. The collective potential in a nine-dimensional collective space is determined using the macroscopic-microscopic method with Strutinsky and the BCS with an approximate particle number projection microscopic corrections. The corresponding Hamiltonian is diagonalized based on the projected solutions of the harmonic oscillators coupled with Wigner functions. Such an orthogonalized basis is additionally symmetrized with respect to the so-called intrinsic symmetrization group, specifically dedicated to the collective space used, to ensure the uniqueness of the Hamiltonian eigen-solutions in the laboratory frame. The response of the pairing and deformation degrees of freedom to external rotation is discussed in the variational approach, where the total energy is minimized by the deformation and pairing variables. Consequently, the corresponding microscopic moments of inertia increase with collective spin (Coriolis {\it antiparing} effect), resulting in effectively lower rotational energy levels I${}^{\pi }$ with respect to pure classical-rotor pattern I(I+1). The obtained comparison of experimental and theoretical rotational energy level schemes, dipole, quadrupole and octupole transition probabilities of B(E$\lambda$) in ${}^{220}$Rn and ${}^{226}$Ra is satisfactory.

   ↳ nucl-thnucl-exPRC(2025)·1 citation
4. 04*

   Interplay of prompt and non-prompt photons in photon-triggered jet observables

   Chathuranga Sirimanna🇺🇸 · Yasuki Tachibana🇯🇵 · Abhijit Majumder🇺🇸 · Aaron Angerami🇺🇸 · Ritu Arora🇺🇸 · Steffen Bass🇺🇸 · Yi Chen🇺🇸 · Ritoban Datta🇺🇸 · Lipei Du🇨🇦 · Raymond Ehlers🇺🇸 · Hannah Elfner🇩🇪 · Rainer J. Fries🇺🇸 and 40 other authors

   Prompt photons are important yet challenging to observe in relativistic heavy-ion collisions, as they are produced in the early stages and traverse almost the entire QGP medium without interaction. Experimental analyses typically employ isolation cuts, in the hope to identify prompt photons. Most theoretical studies consider only events with actual prompt photons, assuming no contribution from isolated non-prompt photons to reduce computational cost. For the first time, we present a study that compares simulation results generated using inclusive (bremsstrahlung) and prompt-photon events with multiple experimental observables for both $p-p$ and $Pb-Pb$ collisions at $5.02$ TeV. Simulations are carried out using the multi-stage JETSCAPE framework tuned to describe the quenching of jets and hadrons. Isolated non-prompt photons are generated in hard photon bremsstrahlung, where the photon is radiated at a sufficient angle to the jet. Several photon triggered jet and jet substructure observables show significant contributions from inclusive photons, yielding an improvement in comparison with experimental data. Novel photon triggered jet substructure observables are also expected to show new structures, yet to be detected in experiment. This effort examines the significance of isolated non-prompt photons using parameters tuned for a simultaneous description of the leading hadron and jet spectrum, and thus provides an independent verification of the multistage evolution framework.

   ↳ hep-phnucl-exnucl-thEPJ Web Conf.(2025)·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.