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

• DOI: 10.15120/gsi-2024-00734
• Publication Date: 2024-06-01
• Authors: Tsang, C. Y.; Kurata-Nishimura, M.; Tsang, M. B.; Lynch, W. G.; Zhang, Y. X.; Barney, J.; Estee, J.; Jhang, G.; Wang, R.; Kaneko, M.; Lee, J. W.; Isobe, T.; Murakami, T.; Ahn, D. S.; Atar, L.; Aumann, T.; Baba, H.; Boretzky, K.; Brzychczyk, J.; Cerizza, G.; Chiga, N.; Fukuda, N.; Gasparic, I.; Hong, B.; Horvat, A.; Ieki, K.; Inabe, N.; Kim, Y. J.; Kobayashi, T.; Kondo, Y.; Lasko, P.; Lee, H. S.; Leifels, Y.; Łukasik, J.; Manfredi, J.; McIntosh, A. B.; Morfouace, P.; Nakamura, T.; Nakatsuka, N.; Nishimura, S.; Otsu, H.; Pawłowski, P.; Pelczar, K.; Rossi, D.; Sakurai, H.; Santamaria, C.; Sato, H.; Scheit, H.; Shane, R.; Shimizu, Y.; Simon, H.; Snoch, A.; Sochocka, A.; Sumikama, T.; Suzuki, H.; Suzuki, D.; Takeda, H.; Tangwancharoen, S.; Törnqvist, H.; Togano, Y.; Xiao, Z. G.; Yennello, S. J.; Zhang, Y.
• Keywords: Nuclear Theory (nucl-th); Nuclear Theory; Physics; QC1-999; FOS: Physical sciences; Nuclear Experiment (nucl-ex); info:eu-repo/classification/ddc/530; Nuclear Experiment; 530

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$π$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, $m_{s}^*/m_{N}$, isovector effective mass, $m_{v}^{*}/m_{N}$ and the in-medium cross-section enhancement factor $η$. 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$π$RIT data suggest a narrow range of preferred values for $m_{s}^*/m_{N}$, $m_{v}^{*}/m_{N}$ and $η$.