# Measurement of directed flow of $D^{0}$ and $\bar{D^{0}}$ mesons in 200 GeV Au+Au collisions at RHIC using the STAR detector

## TL;DR

This paper reports the first measurement of the directed flow of $D^0$ and $ar{D}^0$ mesons in 200 GeV Au+Au collisions at RHIC, providing insights into charm quark transport and early-time electromagnetic effects in heavy-ion collisions.

## Contribution

It presents the first experimental measurement of $D^0$ and $ar{D}^0$ directed flow at RHIC, testing predictions about charm quark dynamics and electromagnetic influences in the quark-gluon plasma.

## Key findings

- Measured directed flow of $D^0$ and $ar{D}^0$ mesons as a function of rapidity.
- Provides data to compare with theoretical models of charm quark transport.
- Offers insights into the early-time electromagnetic field effects on heavy quarks.

## Abstract

Charm quarks, owing to their large mass, are produced predominantly in the initial hard scatterings in heavy-ion collisions, and therefore can be a valuable tool for studying the early time dynamics of these collisions. The rapidity-odd directed flow at mid-rapidity in heavy-ion collisions originates from a tilt in the reaction plane of the thermalized medium caused by the asymmetry between the number of participants from projectile and target nuclei as a function of rapidity. Recently, it has been predicted that the slope of the directed flow at mid-rapidity for $D^0$ mesons, arising from the transport of charm quarks in the tilted medium, can be several times larger than that of light flavor hadrons. The magnitude of the slope is expected to be sensitive to the magnitude of the tilt and the charm quark drag coefficient in the medium. It has also been predicted that the transient electromagnetic field generated at early time can induce a much larger directed flow for heavy quarks than for light quarks. In these proceedings, we will report on the first measurement of the directed flow for the $D^0$ and $\bar{D}^0$ mesons as a function of rapidity in Au+Au collisions at $\sqrt{s_{_{\rm NN}}}$ = 200 GeV using high statistics data collected with the Heavy Flavor Tracker in 2014 and 2016 RHIC runs.