Abstract
A measurement of the differential cross section for the inclusive production of isolated prompt photons in proton-proton collisions at a centre-of-mass energy of 7 TeV is presented. The data sample corresponds to an integrated luminosity of 36 inverse picobarns recorded by the CMS detector at the LHC. The measurement covers the pseudorapidity range |eta|<2.5 and the transverse energy range 25 < ET < 400 GeV, corresponding to the kinematic region 0.007 < xT < 0.114. Photon candidates are identified with two complementary methods, one based on photon conversions in the silicon tracker and the other on isolated energy deposits in the electromagnetic calorimeter. The measured cross section is presented as a function of ET in four pseudorapidity regions. The next-to-leading-order perturbative QCD calculations are consistent with the measured cross section.
Highlights
Photon candidates are identified with two complementary methods, one based on photon conversions in the silicon tracker and the other on isolated energy deposits in the electromagnetic calorimeter
The measurement of isolated prompt photon production in proton-proton collisions provides a test of perturbative quantum chromodynamics [1,2,3,4]
At the Large Hadron Collider (LHC) [7], a significant increase of center-of-mass energy with respect to previous collider experiments [8,9,10,11,12,13] allows for the exploration of new kinematic regions in the hard scattering processes in hadron-hadron collisions
Summary
The measurement of isolated prompt photon production in proton-proton collisions provides a test of perturbative quantum chromodynamics (pQCD) [1,2,3,4]. Photons are produced in the decay of hadrons, mainly 0 and mesons, which can mimic prompt production This background contamination can be estimated from data using photon identification characteristics, such as electromagnetic shower profile, extra energy surrounding the photon candidate (called ‘‘isolation sum’’ in this article), or kinematic variables of converted photons. Both the CMS and ATLAS Collaborations have performed measurements of the differential cross section of isolated prompt photon production with data collected in 2010 [14,15,16].
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