Abstract
We report the first measurement of the elliptic anisotropy () of the charm meson at midrapidity () in collisions at . The measurement was conducted by the STAR experiment at RHIC utilizing a new high-resolution silicon tracker. The measured in 0%–80% centrality collisions can be described by a viscous hydrodynamic calculation for a transverse momentum () of less than . The as a function of transverse kinetic energy (, where ) is consistent with that of light mesons in 10%–40% centrality collisions. These results suggest that charm quarks have achieved local thermal equilibrium with the medium created in such collisions. Several theoretical models, with the temperature-dependent, dimensionless charm spatial diffusion coefficient () in the range of , are able to simultaneously reproduce our result and our previously published results for the nuclear modification factor.
- Received 23 January 2017
DOI:https://doi.org/10.1103/PhysRevLett.118.212301
© 2017 American Physical Society