Extracting the isospin dependent equation of state from RHIC √s = 200 GeV hadron yields.

The statistical hadronization model has been successful in extracting information at chemical freeze-out in heavy-ion collisions. At RHIC √s = 200 GeV many different ion species have been collided in A+A collisions such that one can perform a scan across the charge fraction Y_Q = Z/A where the proton number is Z, and the baryon number is A. We used the heavy-ion collision data from RHIC to extract information about the equation of state when Y_Q varies. We first used the hadron yield ratio of experimental data of U+U, Au+Au, and Cu+Cu to make predictions for Zr+Zr, Ru+Ru, and O+O, then we take both the experimental ratio and predicted ratios to perform thermal fits across Y_Q such that we can extract isentropes and other thermodynamic information, using the code ThermalFIST. We discuss updates to ThermalFIST to include it within the open-source MUSES calculation Engine. Then, we calculate a new constraint on the finite temperature equation of state at finite densities by using the relation between the isentropes and Y_Q. We also calculate the second derivative of the isentropes at fixed temperature with respect to isospin asymmetry and obtained a negative derivative which is consistent with expectations from neutron star mergers.