Tue·Dec 12, 2023Tuesday·December 12, 2023

1. 01*

   High sensitivity of a future search for P-odd/T-odd interactions on the 0.75 eV $p$-wave resonance in $\vec{n}{+}^{139}\overrightarrow{\mathrm{La}}$ forward transmission determined using pulsed neutron beam

   R. Nakabe🇯🇵 · C. J. Auton🇯🇵 · S. Endo🇯🇵 · H. Fujioka🇯🇵 · V. Gudkov🇺🇸 · K. Hirota🇯🇵 · I. Ide🇯🇵 · T. Ino🇯🇵 · M. Ishikado🇯🇵 · W. Kambara🇯🇵 · S. Kawamura🇯🇵 · A. Kimura🇯🇵 and 18 other authors

   Neutron transmission experiments can offer a new type of highly sensitive search for time-reversal invariance violating (TRIV) effects in nucleon-nucleon interactions via the same enhancement mechanism observed for large parity violating (PV) effects in neutron-induced compound nuclear processes. In these compound processes, the TRIV cross-section is given as the product of the PV cross-section, a spin-factor $\kappa$, and a ratio of TRIV and PV matrix elements. We determined $\kappa$ to be $0.59\pm 0.05$ for ${}^{139}$La+$n$ using both $(n,\gamma )$ spectroscopy and ($\vec{n}{+}^{139}\overrightarrow{\mathrm{La}}$) transmission. This result quantifies for the first time the high sensitivity of the ${}^{139}$La 0.75~eV $p$-wave resonance in a future search for P-odd/T-odd interactions in ($\vec{n}{+}^{139}\overrightarrow{\mathrm{La}}$) forward transmission.

   nucl-exhep-exPRC(2024)·4 citations
2. 02*

   Evidence of isospin-symmetry violation in high-energy collisions of atomic nuclei

   NA61/SHINE Collaboration: 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 142 other authors

   Strong interactions preserve an approximate isospin symmetry between up ($u$) and down ($d$) quarks, part of the more general flavor symmetry. In the case of $K$ meson production, if this isospin symmetry were exact, it would result in equal numbers of charged ($K^{+}$ and $K^{-}$) and neutral ($K^0$ and ${\overline{K}}^0$) mesons in the final state. Here, we report results on the relative abundance of charged over neutral $K$ meson production in argon and scandium nuclei collisions at a center-of-mass energy of 11.9 GeV per nucleon pair. We find that the production of $K^{+}$ and $K^{-}$ mesons at mid-rapidity is $(18.4\pm 6.1)\%$ higher than that of the neutral $K$ mesons. Although with large uncertainties, earlier data on nucleus-nucleus collisions in the collision center-of-mass energy range $2.6<\sqrt{s_{NN}}<200$~\GeV are consistent with the present result. Using well-established models for hadron production, we demonstrate that known isospin-symmetry breaking effects and the initial nuclei containing more neutrons than protons lead only to a small (few percent) deviation of the charged-to-neutral kaon ratio from unity at high energies. Thus, they cannot explain the measurements. The significance of the flavor-symmetry violation beyond the known effects is 4.7$\sigma$ when the compilation of world data with uncertainties quoted by the experiments is used. New systematic, high-precision measurements and theoretical efforts are needed to establish the origin of the observed large isospin-symmetry breaking.

   nucl-exhep-exNature Commun.(2025)·42 citations
3. 03*

   Constraining nucleon effective masses with flow and stopping observables from the S$\pi$RIT experiment

   C.Y. Tsang · M. Kurata-Nishimura · M.B. Tsang · W.G. Lynch · Y.X. Zhang · J. Barney · J. Estee · G. Jhang · R. Wang · M. Kaneko · J.W. Lee · T. Isobe and 43 other authors

   Properties of the nuclear equation of state (EoS) can be probed by measuring the dynamical properties of nucleus-nucleus collisions. In this study, we present the directed flow ($v_1$), elliptic flow ($v_2$) and stopping (VarXZ) measured in fixed target Sn + Sn collisions at 270 AMeV with the S$\pi$RIT Time Projection Chamber. We perform Bayesian analyses in which EoS parameters are varied simultaneously within the Improved Quantum Molecular Dynamics-Skyrme (ImQMD-Sky) transport code to obtain a multivariate correlated constraint. The varied parameters include symmetry energy, $S_0$, and slope of the symmetry energy, $L$, at saturation density, isoscalar effective mass, $m_s^{\ast }/m_N$, isovector effective mass, $m_v^{\ast }/m_N$ and the in-medium cross-section enhancement factor $\eta$. We find that the flow and VarXZ observables are sensitive to the splitting of proton and neutron effective masses and the in-medium cross-section. Comparisons of ImQMD-Sky predictions to the S$\pi$RIT data suggest a narrow range of preferred values for $m_s^{\ast }/m_N$, $m_v^{\ast }/m_N$ and $\eta$.

   nucl-exnucl-thPLB(2024)·17 citations
4. 04*

   Effect of hadronic interaction on the flow of $K^{\ast 0}$

   Tribhuban Parida🇮🇳 · Sandeep Chatterjee🇮🇳 · Md. Nasim🇮🇳

   We explore the implications of the late stage hadronic rescattering phase on the flow of $K^{\ast 0}$. The model calculations are done using a (3+1)-dimensional hybrid framework, incorporating both hydrodynamic evolution and hadronic transport that is calibrated to agree with bulk observables including the elusive rapidity differential $v_1$ of light-flavor hadrons. We find that the late stage hadronic rescattering phase causes significant qualitative modification of the $K^{\ast 0}$ $v_1$ resulting in $\frac{d{v}_1}{dy}(K^{\ast 0})-\frac{d{v}_1}{dy}(K^{+})$ and $\frac{d{v}_1}{dy}(\varphi )-\frac{d{v}_1}{dy}(K^{+})$ to have opposite signs with the effect being more pronounced in central collisions as compared to peripheral ones due to the larger multiplicity as well as longer duration of the hadronic phase. Further, this effect is enhanced in low-energy collisions owing to a stronger breaking of boost invariance. On the contrary, the influence of the hadronic phase on the $K^{\ast 0}$ elliptic flow $v_2$ is found to be less significant and quantitative.

   ↳ nucl-thhep-phnucl-exPRC(2024)·7 citations
5. 05*

   Constraints on initial baryon stopping and equation of state from directed flow

   Lipei Du🇨🇦 · Chun Shen🇺🇸 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

   Our investigation focuses on the rapidity-dependent directed flow, $v_1(y)$, of identified hadrons in Au+Au collisions across a broad range of $\sqrt{s_{\mathrm{NN}}}$ from 7.7 to 200 GeV. Employing a (3+1)-dimensional hybrid framework, our study successfully reproduces the characteristic features of the measured $v_1(y)$ for both mesons and baryons across the considered beam energies. Notably, our analysis reveals the constraining power of baryonic $v_1(y)$ on the initial baryon stopping mechanism. Together with mesonic $v_1(y)$, the directed flow serves as a crucial tool for probing the equation of state governing dense nuclear matter at finite chemical potentials.

   ↳ nucl-thhep-exhep-phnucl-exEPJ Web Conf.(2024)·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.