Speaker
Description
At the energies reached in heavy-ion collisions at RHIC, a dense and strongly interacting medium is formed. During the collision, the system reaches a point of maximal compression that may cross the boundary where hadronic degrees of freedom transition into quarks and gluons. This transition modifies the initial conditions of the fireball.
In this talk, I present a simple model of higher net-proton fluctuations that propagates fluctuations from the quark recombination stage to the final state. I show that the emergence of quark degrees of freedom in the early stages of the collision leads to the suppression of the kurtosis of net-proton number, usually interpreted as a signal for the QCD critical point. At the same time, lower-order cumulants remain largely unaffected due to faster equilibration.
This model provides a revised baseline for net-proton fluctuations that incorporates effects both due to the initial-state and the equilibration dynamics during the hadronic phase. A comparison of the Beam Energy Scan data with this new baseline supports the dominance of quark degrees of freedom at high energies and of hadronic degrees of freedom at low energies, but does not indicate the presence of a QCD critical point.
