Muon spectra from charm semileptonic decay at $\sqrt{s_{_{NN}}} = 200$ GeV Au+Au Collisions at STAR

Chen Zhong

In relativistic heavy-ion collisions, charm quarks are believed to be produced at early stages via initial gluon fusion. Study of the $N_ {bin}$ scaling properties of the charm total cross-section can test whether the charm quarks as a probe are produced exclusively at the initial impact. However, it is difficult to reconstruct charmed hadrons and single electrons from charm semileptonic decays collisions with high precision at low $p_{T}$, where the yield accounts for a large fraction of the total cross section. The measurement of muons from charmed hadron semileptonic decay is not affected by background from photon conversions and $\pi0$ Dalitz decays that affects the equivalent electron measurement.

We present the first measurement of single muons spectra at low $p_{T}$ in Au+Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV at STAR. Muon are identified by measuring the energy loss in the Time Projection Chamber and velocity in the Time-of-Flight detector. Background muons from pion/kaon weak decays are subtracted using the distribution of the distance of closest approach to the collision vertex. These measurements significantly improve the determination of the charm total cross section over our previous measurements.