Proton rapidity distributions have been measured by the NA49 collaboration in 40 and 158 GeV/nucleon Pb+Pb collisions as function of collision centrality. We find that the shape and the yield per wounded nucleon in the mid-rapidity region vary little with centrality and are similar to the distributions obtained from inelastic p+p interactions. This observation is satisfactorily described by the transport models HSD and UrQMD, although there are significant differences in the details of the spectral shape between the experimental data and the models as well as between the models. The approximate invariance of the normalized proton spectrum in the vicinity of mid-rapidity suggests that multiple nucleon-nucleon interactions in nuclear collisions at SPS energies have little effect on the spectra of those final state protons which are slowed down the most.
Three typical algorithms of Pauli blocking in the quantum molecular dynamics type models are investigated in the nuclear matter, the nucleus and the heavy ion collisions. The calculations in nuclear matter show that the blocking ratios obtained with the three algorithms are underestimated 13-25\% compared to the analytical values of blocking ratios. For the finite nucleus, the spurious collisions occur around the surface of the nucleus owing to the defects of Pauli blocking algorithms. In the simulations of heavy ion collisions, the uncertainty of stopping power from different Pauli blocking a…
With the newly updated version of the ultrarelativistic quantum molecular dynamics (UrQMD) model, a systematic investigation of the effects of in-medium nucleon-nucleon ($NN$) elastic cross section on the collective flow and the stopping observables in $^{197}\text{Au}+^{197}\text{Au}$ collisions at beam energies from 40 to 150 MeV/nucleon is performed. Simulations with the medium correction factor $\mathcal{F}=σ^{\text{in-medium}}_{NN}/σ^{\text{free}}_{NN}=0.2,~0.3,~0.5$, and the one obtained with the FU3FP1 parametrization which depends on both the density and the momentum are compared to th…
Within a Boltzmann transport model, we demonstrate correlation between stopping observables and shear viscosity in central nuclear collisions at intermediate energies (on the order of 10 to 1000 MeV/nucleon). The correlation allows us to assess the viscosity of nuclear matter, by tuning the in-medium nucleon-nucleon cross section in our transport model to agree with nuclear stopping data. We also calculate the ratio of shear viscosity to entropy density to determine how close the system is to the universal quantum lower limit proposed in the context of ultrarelativistic heavy ion collisions.
Two Key Day-One Observables in Electron-Nucleus Collisions at the Upcoming Electron-Ion Collider and Their Implications for Baryon Number Carrier Investigations
Institute of Theoretical Physics, State Key Laboratory of Quantum Optics Technologies and Devices & Collaborative Innovation Center of Extreme Optics, Shanxi University（山西大学理论物理研究所、量子光学技术与器件国家重点实验室及极端光学协同创新中心）；Laboratory of High Energy Physics, Physical-Technical Institute of Uzbekistan Academy of Sciences（乌兹别克斯坦科学院物理技术研究所高能物理实验室）；Department of Natural Sciences, National University of Science and Technology MISIS (NUST MISIS), Almalyk Branch（国立科技大学米西思（NUST MISIS）阿尔马雷克分校自然科学系）
We review the recent baryon chiral perturbation theory results for the nucleon polarisabilities that describe the different regimes of nucleon Compton scattering --- real, virtual, and doubly virtual. We stress the importance of the empirical verification of the theory in the context of the calculation of the inelastic nucleon structure corrections, such as the two-photon exchange contributions. We also discuss the recently obtained constraints that relate the different regimes of nucleon Compton scattering and can provide additional information on the nucleon structure.
