First flow harmonic of net baryon from directed diffusion of stopped baryons

Abstract

We propose a new ansatz for baryon deposition that incorporates salient features from the baryon junction picture. The deposited baryon is coupled to a tilted fireball and deployed to study the directed flow of identified hadrons in Au+Au collisions at $\sqrt{s_{NN}}=7.7-200$ GeV. We find a parameter space in the model where the resulting hydrodynamic evolution generates a suitable flow to describe the directed flow $v_1$ of identified hadrons including the observed double sign change between $\sqrt{s_{NN}}=7.7-39$ GeV of the rapidity slopes of the net proton and the net lambda $v_1$. Our model that includes stopping of baryons and their consequent diffusion within a relativistic hydrodynamic framework along with a crossover equation of state as obtained from lattice QCD calculations provides a noncritical baryonic baseline that is crucial in our ongoing searches for the QCD critical point and the initial strong electromagnetic field.