Mainz 2012 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 44: Schwerionenkollisionen und QCD Phasen

HK 44.4: Talk

Thursday, March 22, 2012, 17:30–17:45, P 5

Anisotropy of Neutral Pion production in Pb-Pb collisions at √s_NN=2.76 TeV measured by ALICE — •Daniel Lohner — Physikalisches Institut, Universitaet Heidelberg

The ALICE PbPb research program focusses on the quark-gluon plasma, a state of matter in which quarks and gluons are no longer confined in hadrons. The in-medium energy loss of partons is referred to as jet quenching and can be observed in experiments as a suppression of the particle production (R_AA). Furthermore, the asymmetric shape of the reaction plane in non-central collisions leads to an azimuthal anisotropy of the particle production. The neutral pion dominantly decays into two photons. Those are measured via their conversion in the detector material using the ALICE Inner Tracking System and Time Projection Chamber or by the ALICE calorimeters, PHOS and EMCAL. The neutral pion yield is studied as a function of the emission angle with respect to the reaction plane. The anisotropy is measured by the second harmonic Fourier component v₂. At low transverse momentum, v₂ can be described by collective expansion of the medium (elliptic flow), at high transverse momentum v₂ provides insights into the path-length dependence of QCD energy loss.