Directed flow of $\Lambda$ from heavy-ion collisions and hyperon puzzle of neutron stars

Abstract

We examine the $\Lambda$ potential from the chiral effective field theory ($\chi$EFT) via the $\Lambda$ directed flow from heavy-ion collisions. We implement the $\Lambda$ potential obtained from the $\chi$EFT in a vector potential version of relativistic quantum molecular dynamics. We find that the $\Lambda$ potentials obtained from the $\chi$EFT assuming weak momentum dependence reproduce the $\Lambda$ directed flow measured by the STAR collaboration in the Beam Energy Scan program. While the $\Lambda$ directed flow is not very sensitive to the density dependence of the potential, the directed flow at large rapidities is susceptible to the momentum dependence. Thus understanding the directed flow of hyperons in a wide range of beam energy and rapidity is helpful in understanding hyperon potentials in dense matter.