Open charm hadron measurement in p+p and Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV in STAR

TL;DR

This paper reports measurements of open charm hadrons in proton-proton and gold-gold collisions at 200 GeV, revealing charm production rates, scaling behaviors, and medium interactions in high-energy nuclear collisions.

Contribution

It provides new measurements of $D^0$ and $D^*$ production, charm cross sections, and insights into charm quark interactions with the quark-gluon plasma at RHIC.

Findings

Charm production scales with binary collisions, indicating initial hard scattering origin.

No suppression of $D^0$ $R_{AA}$ observed below 3 GeV/$c$, suggesting limited medium effects.

Discrepancies with blast-wave models imply early decoupling of charm from the medium.

Abstract

We present the measurements of $D^0$ and $D^*$ in p+p and $D^0$ in Au+Au collisions via hadronic decays $D^{0}\rightarrow K^{-}\pi^{+}$, $D^{*+}\rightarrow D^{0}\pi^{+}\rightarrow K^{-}\pi^{+}\pi^{+}$ in mid-rapidity $|y|<1$ at $\sqrt{s_{_{\rm NN}}}$ = 200 GeV, covering $p_T$ from 0.2 to 6 GeV/$c$ in p+p and 0.4 to 5 GeV/$c$ in Au+Au, respectively. The charm pair production cross section per nucleon-nucleon collision at mid rapidity is measured to be 202 $\pm$ 56 (stat.) $\pm$ 40 (sys.) $\pm$ 20 (norm.) $\mu$b in p+p and 186 $\pm$ 22 (stat.) $\pm$ 30 (sys.) $\pm$ 18 (norm.) $\mu$b in Au+Au minimum bias collisions. The number of binary collisions scaling of charm cross section indicates that charm is produced via initial hard scatterings. No suppression of $D^0$ $R_{AA}$ in Au+Au 0-80% minbias collisions is observed at $p_T$ below 3 GeV/$c$. Blast-wave predictions with light-quark hadron parameters are different from data, which may indicate that $D^0$ decouples earlier from the medium than the light-quark hadrons.