Format:Talk 

Title: Measurement of directed flow at the forward and backward pseudorapidity with the Event Plane Detector at STAR

Directed flow ($v_{1}$) describes the collective sideward motion of produced particles and nuclear fragments in heavy-ion collisions. The pseudorapidity ($\eta$) dependence of $v_{1}$ can provide unique constraints on the initial conditions and hydrodynamic evolution of the Quark Gluon Plasma (QGP). Directed flow in both spectator and participant regions is sensitive to early non-equilibrium dynamics and may provide insights into the baryon stopping mechanism. In 2018, the Event Plane Detector (EPD, $2.1 <|\eta|< 5.1$) was installed in STAR and used for the Beam Energy Scan phase-II (BES-II) data taking. The combination of EPD and high statistics BES-II data enables us to extend the $v_{1}$ measurement to the forward and backward $\eta$ regions, allowing us to test the phenomenon of limiting fragmentation. In this talk, I will present the measurement of $v_{1}$ over six units of $\eta$ in Au+Au collisions at $\sqrt{s_{NN}}=27$ and 19.6 GeV and compare the results with multiple physics models.