{
  "id": "1210.5958",
  "version": "v2",
  "published": "2012-10-22T16:26:46.000Z",
  "updated": "2012-10-23T09:50:23.000Z",
  "title": "Measurement of Direct Photons in pp and Pb-Pb Collisions with ALICE",
  "authors": [
    "Martin Wilde",
    "for the ALICE Collaboration"
  ],
  "categories": [
    "hep-ex",
    "nucl-ex"
  ],
  "abstract": "The measurement of the direct photon transverse momentum spectrum in Pb-Pb collisions at \\unit[$\\sqrt{s_{_{NN}}}=2.76]{TeV}$ with data taken by the ALICE experiment is presented. The measurement shows a clear direct-photon signal for 0-40% most central collisions below \\unit[4]{GeV/$\\mathrm{c}$} that can not be described by next-to-leading-order perturbative QCD (NLO pQCD) calculations. Above this value of $p_{\\mathrm{T}}$ the result is in agreement with pQCD predictions. The low $p_{\\mathrm{T}}$ signal is expected to have thermal photon contributions. The inverse slope parameter of an exponential fit is extracted as $T_{\\mathrm{LHC}}=\\unit[304\\pm 51^{\\mathrm{syst+stat}}]{MeV}$. For a baseline measurement the analysis is performed for proton-proton collisions at \\unit[$\\sqrt{s}=7]{TeV}$ and for peripheral (40-80%) Pb-Pb collisions. Both results show no low $p_\\mathrm{T}$ direct-photon signal and are in agreement with pQCD calculations.",
  "revisions": [
    {
      "version": "v2",
      "updated": "2012-10-23T09:50:23.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "pb-pb collisions",
      "measurement",
      "direct photon transverse momentum spectrum",
      "clear direct-photon signal",
      "inverse slope parameter"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1016/j.nuclphysa.2013.02.079",
      "journal": "Nuclear Physics A",
      "year": 2013,
      "month": "May",
      "volume": 904,
      "pages": 573
    },
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1192040,
      "adsabs": "2013NuPhA.904..573W"
    }
  }
}