Toward a solution to the $R_{AA}$ and $v_2$ puzzle for heavy quarks

By S. Das, F. Scardina, S. Plumari, V. Greco. 2015

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The heavy quarks constitutes a unique probe of the quark-gluon plasma properties. Both at RHIC and LHC energies a puzzling relation between the nuclear modification factor $R_{AA}(p_T)$ and the elliptic flow $v_2(p_T)$ has been observed which challenged all the existing models, especially for D mesons. We discuss how the temperature dependence of the heavy quark drag coefficient is responsible for a large part of such a puzzle. In particular, we have considered four different models to evaluate the temperature dependence of drag and diffusion coefficients propagating through a quark gluon plasma (QGP). All the four different models are set to reproduce the same $R_{AA}(p_T)$ observed in experiments at RHIC and LHC energy. We point out that for the same $R_{AA}(p_T)$ one can generate 2-3 times more $v_2$ depending on the temperature dependence of the heavy quark drag coefficient. A non-decreasing drag coefficient as $ T \rightarrow\ T_c \,$ is a major ingredient for a simultaneous description of $R_{AA}(p_T)$ and $v_2(p_T)$.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/454e31f7d356be81a1ceeb233616f273625888ec