# Nuclear Physics & RIKEN Theory Seminar

## "Hydrodynamics at large baryon densities: Understanding proton vs. anti-proton $v_2$ and other puzzles"

#### Presented by Jan Steinheimer-Froschauer, University of Frankfurt/Lawrence Berkeley National Laboratory

Friday, July 20, 2012, 2:00 pm — Small Seminar Room, Bldg. 510

Using hydrodynamics we explore the effects of the initial state, baryon stopping and baryon number transport on various observables such as spectra, elliptic flow and particle yields for heavy ion collisions at beam energies from $\sqrt{s_{NN}}=7.7$ to $200$ GeV. In our setup the transition from the equilibrated hydrodynamical phase to the final transport phase occurs over a broad range of
temperatures/densities. Even though particle yields, extracted at this transition, can be described well by a single temperature freeze out we observe a correlation of particle mass, average transition temperature and flow velocity which allows us to successfully describe the measured non-monotonic behavior of the effective slope parameter as a function of particle mass. Furthermore we show that observed phenomena such as the centrality dependent freeze out parameters as well the asymmetry in particle/antiparticle $v_2$ at large baryon densities can be explained by a collective hydrodynamic expansion, once baryon stopping and baryon number conservation are properly taken into account. We will further discuss how the various
stages of the collision contribute to the $p_{\bot}$ spectra and the mass dependence of $T_{eff}$.