Extracting $\hat{q}$ from single inclusive data at RHIC and at the LHC   for different centralities: a new puzzle?
  We present here an extraction of the jet transport coefficient, $\hat{q}$, using RHIC and LHC single-inclusive high-$p_T$ data for different centralities. We fit a $K$-factor that determines the deviation of this coefficient from an ideal estimate, $K \equiv \hat{q}/(2\epsilon^{3/4})$, where $\epsilon$ is given by hydrodynamic simulations. As obtained already in previous studies, this $K$-factor is found to be larger at RHIC than at the LHC. However it is, unexpectedly, basically no-dependent on the centrality of the collision. Taken at face value this result, the $K$-factor would not depend on local properties of the QGP as temperature, but on global collision variables such as the center of mass energy. 
Carlota Andres, Nestor Amesto, Matthew Luzum, Carlos A. Salgado and   Pia Zurita
nucl-th hep-ph nucl-ex