# Quark Matter 2014 - XXIV International Conference on Ultrarelativistic Nucleus-Nucleus Collisions

19-24 May 2014
Europe/Zurich timezone

## The puzzling relation between the $R_{AA}$ and the $v_2$ for heavy mesons in a Boltzmann and in a Langevin approach

20 May 2014, 16:30
2h

### spectrum

Board: F-50
Poster Open Heavy Flavour and Quarkonia

### Speaker

francesco scardina (INFN Catania)

### Description

The heavy quarks constitutes a unique probe of the quark-gluon plasma properties. Both at RHIC and LHC energies it has been observed a puzzling correlation between the nuclear modification factor $R_{AA}$ and the elliptic flow $v_2$ that has challenged all the existing models, especially for D mesons, We discuss how the treatment of the charm quark dynamics according to a Boltzmann or a Langevin dynamics can be responsible for a large part of such a puzzle. In particular, we see that depending on the angular and temperature dependence of the scattering matrix the $v_2$ can be quite different. In particular, once one reproduces the $R_{AA}$ with both a Boltzmann and/or a Langevin approach the $v_2(p_T)$ that is build-up can be as different as a 50-80%. This together with a coalescence hadronization mechanism strongly quenches the puzzling $R_{AA}$ and $v_2$ observation. Differences between Boltzmann and Langevin dynamics can be traced back to the fact that especially for large screening mass (nearly isotropic scatterings) the transferred momentum is not small but comparable with the charm mass as well as to the average momentum of the bulk. On the other hand such differences disappear for bottom quarks which are predicted to be free of the ambiguities coming from the difference between a Boltzmann or a Langevin approach, and should more properly considered as heavy quarks as regards their transport in the QGP. Our study allows also to shed lights on the different predictions of several models currently compared with the first data at LHC on D mesons. Reference: 1) S. K. Das, F. Scardina, V. Greco, arXiv:1312.6857 [nucl-th] 2) H. Van Hees, M. Mannarelli, V. Greco and R. Rapp, Phys. Rev. Lett.100,192301 (2008) 3)V. Greco, C. M. Ko and R. Rapp, Phys. Lett. B 595,202 (2004)

### Primary authors

Vincenzo Greco (University of Catania) francesco scardina (INFN Catania)

### Co-authors

Salvatore Plumari (University of Catania (Italy)) Santosh Kumar Das (University of Catania, Italy)

### Presentation Materials

 poster_scardina_finale.pdf poster_scardina_finale.pptx