Measurement of isolated-photon pair production in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

The ATLAS collaboration
JHEP 01 (2013) 086, 2013.

Abstract (data abstract)
CERN-LHC. Measurement of the production cross section of events with two isolated photons in the final state, in proton-proton collisions at sqrt(s) = 7 TeV, by the ATLAS experiment at the LHC. The full data set collected in 2011, corresponding to an integrated luminosity of 4.9 fb^-1, is used. The amount of background, from hadronic jets and isolated electrons, is estimated with data-driven techniques and subtracted. The total cross section, for two isolated photons with transverse energies above 25 GeV and 22 GeV respectively, in the acceptance of the electromagnetic calorimeter (|eta| < 1.37 and 1.52 < |eta| < 2.37) and with an angular separation Delta(R) > 0.4, is 44.0 +3.2,-4.2 pb. The differential cross sections as a function of the di-photon invariant mass, transverse momentum, azimuthal separation, and cosine of the polar angle of the largest transverse energy photon in the Collins-Soper di-photon rest frame are also measured. NOTE: The cross section values reported in the table should be multiplied by a factor of 1.0141 to take into account the updated value of the integrated luminosity for the ATLAS 2011 data taking period. A relative uncertainty of 3.5% should be subtracted (in quadrature) from the total uncertainty to take into account the reduced value of the integrated luminosity uncertainty (1.8%) compared to the preliminary one used in the publication (3.9%). See Eur.Phys.J. C73 (2013) 2518 for more details. UPDATE 22 April 2016: Two files have been attached to document publicly the non-perturbative corrections used in the publication to compare the measurement to parton-level calculations.

  • Table 1

    Data from Table 2


    Experimental cross-section values per bin in PB*GEV**-1 for M(2GAMMA).

  • Table 2

    Data from Table 3


    Experimental cross-section values per bin in PB*GEV**-1 for PT(2GAMMA).

  • Table 3

    Data from Table 4


    Experimental cross-section values per bin in PB*RAD**-1 for DELTA(PHI(2GAMMA)).

  • Table 4

    Data from Table 5


    Experimental cross-section values per bin in PB for COS(THETA*(2GAMMA)).

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