Hard physics in STAR

The hot and dense matter created in high-energy nuclear collisions is believed to undergo a transition into a deconfined phase where partonic degrees of freedom determine the dynamics of the medium. High-p ⊥ partons, that are produced in the initial collisions between nucleons of the incoming nuclei, lose energy as they propagate through the medium. This effect, called jet-quenching, is observed in high-p ⊥ particle spectra, in azimuthal correlations with the reaction plane (elliptic flow) and jet-like two-particle correlations. STAR consists of tracking detectors and electromagnetic calorimetry with large and azimuthally symmetric acceptance and is exceptionally well suited for single particle detection and correlation studies at high p ⊥. In the last five years, it has collected a large dataset including Au+Au and Cu+Cu collisions at different energies and reference data from p+p and d+Au collisions. We present particle spectra and two-particle correlations at high-p ⊥ , and relate these measurements to the properties of the medium. c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.