Isolated photon cross section in p p̄ collisions at √s = 1.8 TeV (original) (raw)
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Physical Review Letters, 2013
We report on a measurement of the cross section for direct-photon production in association with a heavy quark using the full data set of √ s = 1.96 TeV proton-antiproton collisions corresponding to 9.1 fb −1 of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron. The measurements are performed as a function of the photon transverse momentum, covering photon transverse momentum between 30 and 300 GeV, photon rapidities |y γ | < 1.0, heavy-quark-jet transverse momentum p jet T > 20 GeV, and jet rapidities |y jet | < 1.5. The results are compared with several theoretical predictions. PACS numbers: 12.38.Qk, 13.85.Qk, 13.87.Ce The study of direct-photon (γ) production in association with a heavy quark Q (b or c) in hadronic collisions provides valuable information on the probability distributions of partons inside the initialstate hadrons. At photon transverse energies E γ T [1] smaller than 100 GeV, such events are produced predominantly by the Compton scattering process gQ → γQ, while at higher energies the dominant process is quark-antiquark annihilation with gluon (g) splitting to heavy quarks qq → γg → γQQ [2]. It is conventional to assume that the charm (c) and bottom (b) quarks in the proton arise only from gluon splitting. However, there are other models that allow the existence of intrinsic heavy quarks in the proton . A cross-section measurement of γ + Q + X (X can be any final-state particle) production provides information on the heavy-quark and gluon parton distribution functions (PDFs) and on the rate of final-state gluon splitting to heavy quarks.
Measurement of the isolated photon cross section in pp¯ collisions at s= 1.96 TeV
Physics Letters B, 2006
The cross section for the inclusive production of isolated photons has been measured in pp collisions at √ s = 1.96 TeV with the DØ detector at the Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV and have pseudorapidity |η| < 0.9. The cross section is compared with the results from two next-to-leading order perturbative QCD calculations. The theoretical predictions agree with the measurement within uncertainties.
Journal of High Energy Physics, 2012
The integrated and differential cross sections for the production of pairs of isolated photons is measured in proton-proton collisions at a centre-of-mass energy of 7 TeV with the CMS detector at the LHC. A data sample corresponding to an integrated luminosity of 36 inverse picobarns is analysed. A next-to-leading-order perturbative QCD calculation is compared to the measurements. A discrepancy is observed for regions of the phase space where the two photons have an azimuthal angle difference, Delta (phi), less than approximately 2.8.