M. Nguyen

Jet Fragmentation in Vacuum and Medium with γ-hadron Correlations in PHENIX

Jet fragmentation in p+p and Au+Au collisions is studied via back-to-back correlations of direct photons and charged hadrons. The direct photon correlations are obtained by statical subtraction of the background from decay photons. Results on the nuclear modification to the associated charged hadron yields are reviewed. Further studies of jet fragmentation in p+p using isolated direct photons are also presented. A kT -smeared LO pQCD calculation is used to interpret the data. The sensitivity of the data to the underlying fragmentation function is tested and the results are found to be compatible with expectations of a sample dominated by quark jet fragmentation.

High-pt direct photon-hadron correlations using the PHENIX detector

Direct photons are a powerful probe to study the property of quark–gluon plasma (QGP) in high energy heavy-ion collisions. In non-central collisions, the anisotropy of the collision region produces the different pressure gradients and particle density that results in different anisotropy of particle emission, depending on the production processes of photons. Therefore, an azimuthal anisotropy parameter v2 is a powerful tool to explore the source of direct photons. We report on the latest direct photon analysis of the nuclear modification factor in and 62.4 GeV Au + Au collisions, and v2 at high pT in 200 GeV Au + Au collisions at RHIC-PHENIX (Run4). We also present the analysis status, using a larger statistics and better reaction plane information from a new detector available from RHIC Run7 data. (Less)