Two-particle correlations in pp and Pb-Pb collisions with ALICE

Abstract

The measurement of azimuthal correlations between two particles is a powerful tool to investigate the properties of strongly-interacting nuclear matter created in ultra-relativistic heavy-ion collisions. We present measurements of di-hadron correlations in azimuth angle and pseudorapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76 \tev$ and photon-hadron correlations in pp collisions at $\sqrt{s} = 7 \tev$ with the ALICE detector, respectively. In di-hadron correlations, the near-side jet shape in the short-range correlation region is quantitatively analyzed at $\ptt < 8 \gmom$, and the modification of jet-particle yield, $I_{\rm AA}$ and $I_{\rm CP}$, is measured at $8 < \ptt < 15 \gmom$. In photon-hadron correlations, isolated leading photon and associated hadrons in its opposite azimuthal direction correlations are used to estimate the jet fragmentation function via the imbalance parameter, $x_{\rm E} \equiv -\frac{\vec{p}_{\rm T}^{\gamma}\cdot\vec{p}_{\rm T}^{\rm h^{\pm}}}{|\vec{p}_{\rm T}^{\gamma}|^{2}}$.