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Direct photon production at low transverse momentum in proton-proton collisions at $\mathbf{\sqrt{s}=2.76}$ and 8 TeV

The ALICE collaboration
No Journal Information, 2018

Abstract (data abstract)
CERN-LHC. Measurements of inclusive and direct photon production at mid-rapidity in pp collisions at $\sqrt{s}=2.76$ and 8 TeV are presented by the ALICE experiment at the LHC. The results are reported in transverse momentum ranges of $0.4<p_{\rm T}<10$ GeV/c and $0.3<p_{\rm T}<16$ GeV/c, respectively. Photons are detected with the electromagnetic calorimeter (EMCal) and via reconstruction of $e^+e^-$ pairs from conversions in the ALICE detector material using the central tracking system. For the final measurement of the inclusive photon spectra the results are combined in the overlapping $p_{\rm T}$ interval of both methods. Direct photon spectra, or their upper limits at 90% C.L. are extracted using the direct photon excess ratio $R_\gamma$, which quantifies the ratio of inclusive photons over decay photons generated with a decay-photon simulation. An additional hybrid method, combining photons reconstructed from conversions with those identified in the EMCal, is used for the combination of the direct photon excess ratio $R_\gamma$, as well as the extraction of direct photon spectra or their upper limits. While no significant signal of direct photons is seen over the full $p_{\rm T}$ range, $R_\gamma$ for $p_{\rm T}>7$ GeV/c is at least one $\sigma$ above unity and consistent with expectations from next-to-leading order pQCD calculations.

  • Table 1

    Data from Fig. 4

    10.17182/hepdata.88395.v1/t1

    Double Ratio RGAMMA in inelastic pp collisions at center-of-mass energy 2.76 TeV. RGAMMA is the ratio of inclusive GAMMA to...

  • Table 2

    Data from Fig. 4

    10.17182/hepdata.88395.v1/t2

    Double Ratio RGAMMA in inelastic pp collisions at center-of-mass energy 8 TeV. RGAMMA is the ratio of inclusive GAMMA to...

  • Table 3

    Data from Fig. 5

    10.17182/hepdata.88395.v1/t3

    Invariant differential cross section of inclusive GAMMA produced in inelastic pp collisions at center-of-mass energy 2.76 TeV, the uncertainty of...

  • Table 4

    Data from Fig. 5

    10.17182/hepdata.88395.v1/t4

    Invariant differential cross section of inclusive GAMMA produced in inelastic pp collisions at center-of-mass energy 8 TeV, the uncertainty of...

  • Table 5

    Data from Fig. 5

    10.17182/hepdata.88395.v1/t5

    Invariant differential cross section of direct GAMMA produced in inelastic pp collisions at center-of-mass energy 2.76 TeV, the uncertainty of...

  • Table 6

    Data from Fig. 5

    10.17182/hepdata.88395.v1/t6

    Invariant differential cross section of direct GAMMA produced in inelastic pp collisions at center-of-mass energy 8 TeV, the uncertainty of...

  • Table 7

    Data from not in paper

    10.17182/hepdata.88395.v1/t7

    Invariant differential yield of inclusive GAMMA produced in inelastic pp collisions at center-of-mass energy 2.76 TeV. Values are given in...

  • Table 8

    Data from not in paper

    10.17182/hepdata.88395.v1/t8

    Invariant differential yield of inclusive GAMMA produced in inelastic pp collisions at center-of-mass energy 8 TeV. Values are given in...

  • Table 9

    Data from not in paper

    10.17182/hepdata.88395.v1/t9

    Invariant differential yield of direct GAMMA produced in inelastic pp collisions at center-of-mass energy 2.76 TeV. Values are given in...

  • Table 10

    Data from not in paper

    10.17182/hepdata.88395.v1/t10

    Invariant differential yield of direct GAMMA produced in inelastic pp collisions at center-of-mass energy 8 TeV. Values are given in...

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