Prompt D0 Meson Nuclear Modification Factor and Azimuthal Anisotropy in Heavy Ion Collisions with CMS

Jian Sun, Purdue University


The primary goal of heavy ion physics is to study the properties of the Quark Gluon Plasma (QGP), a state of matter comprising deconfined quarks and gluons. Heavy quarks (charm and bottom) are effective probes to study the properties of the QGP produced in heavy ion collisions. Because of their large masses, heavy quarks are primarily produced via initial hard scatterings in heavy ion collisions. They are expected to interact with the QGP differently than light quarks and gluons. The comparison between the nuclear modification factors of heavy flavor and light hadrons can provide insights into the expected flavor dependence of parton energy loss. The azimuthal anisotropy of heavy flavor hadrons can help quantify the interaction strength between the heavy quarks and the QGP medium at low transverse momentum (p T), and provide unique information about the path length dependence of heavy quark energy loss at high pT. This dissertation presents the measurements of the prompt D 0 meson nuclear modification factor (RAA) and azimuthal anisotropy coefficients v2 and v3 in PbPb collisions with the CMS detector at the CERN LHC. The D0 meson production is found to be strongly suppressed in heavy ion collisions and the suppression has strong dependence on centrality and pT. The suppression of D0 mesons is consistent with that of light hadrons for pT > 5 GeV/c, while a hint of smaller supression is observed for pT < 5GeVc. The v3 values are found to be positive in the p T range of 1 to 40 GeV/c. The v3 is measured for the first time and positive values are observed for p T < 6 GeV/c. Compared to those of light hadrons, the D 0 meson v2 and v 3 coefficients are found to be smaller for pT < 6 GeV/c. Through the comparison with theoretical calculations, the v2 and v3 results at low pT suggest that the charm quarks take part in the collective motion of the medium. The R AA, v2, and v3 results provide new constraints on the models of the interactions between the charm quarks and the QGP medium, and the charm quark energy loss mechanisms.




Xie, Purdue University.

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