Recent photon physics results from the ALICE experiment at the LHC
LPSC, Université Joseph Fourier Grenoble1, CNRS/IN2P3, Institut Polytechnique de Grenoble, 53 rue des Martyrs, Grenoble, France
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We present an overview of the photon analysis in pp and Pb-Pb collisions with data taken by the ALICE experiment at the LHC. The ALICE detectors reconstruct photons by using the two electromagnetic calorimeters (photon spectrometer, sampling calorimeter) and central tracking systems for photon converted e+e− pairs in the material of the inner ALICE layers. In Pb-Pb collisions the direct photon calculations underpredict the data below 4 GeV/c where it is expected to have a contribution from thermal radiations. The direct photon measurement also shows evidence for a non-zero elliptic flow for 1 < pT < 3 GeV/c. The nuclear modification factor of the π0 production at different collision centralities shows a clear pattern of strong suppression in a hot QCD medium with respect to pp collisions. Finally, parton fragmentation following hard collisions is investigated by correlating high momentum direct photons and charged hadrons with the goal of revealing new insights into medium effects in the QGP.
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