Parton transverse momenta and direct photon production in hadronic collisions at high energies

Abstract

The invariant cross sections for direct photon production in hadron-hadron collisions are calculated for several initial energies (SPS, ISR, S$p\bar{p}$S, RHIC, Tevatron, LHC) including initial parton transverse momenta within the formalism of unintegrated parton distributions (UPDF). Different approaches from the literature are compared and discussed. A special emphasis is put on the Kimber-Martin-Ryskin (KMR) distributions and their extension into the soft region. Sum rules for UPDFs are formulated and discussed in detail. We find a violation of naive number sum rules for the KMR UPDFs. An interesting interplay of perturbative (large $k_t^2$) and nonperturbative (small $k_t^2$) regions of UPDFs in the production of both soft and hard photons is identified. The $k_t$-factorization approach with the KMR UPDFs is inconsistent with the collinear approach at large transverse momenta of photons. Kwieciński UPDFs provide very good description of all world data, especially at SPS and ISR energies. Off-shell effects are discussed and quantified. Predictions for the CERN LHC are given. Very forward/backward regions in rapidity at LHC energy are discussed and a possibility to test unintegrated gluon distributions (UGDF) is presented.

arXiv comment19 pages, 23 figures

References in corpus (21)

• Saturation in Diffractive Deep Inelastic Scattering
• Unintegrated parton distributions
• Manifestations of high density QCD in the first RHIC data
• A unified BFKL and GLAP description of $F_2$ data
• Dynamical Parton Distributions Revisited
• Parton intrinsic motion in inclusive particle production: unpolarized cross sections, single spin asymmetries and the Sivers effect
• Unintegrated parton distributions and prompt photon hadroproduction
• Measurement of the Isolated Photon Cross Section in p-pbar Collisions at sqrt{s}=1.96 TeV
• Towards a solution of the charmonium production controversy: k_t-factorization versus color octet mechanism
• Effects of Parton Intrinsic Transverse Momentum on Photon Production in Hard-Scattering Processes
• Comparison of the Isolated Direct Photon Cross Sections in $p\bar{p}$ Collisions at $\sqrt{s}=1.8$ TeV and $\sqrt{s}=0.63$ TeV
• Direct J/Psi hadroproduction in k_\perp-factorization and the color octet mechanism
• Prompt photon photoproduction at HERA in the k_T-factorization approach
• Mid-Rapidity Direct-Photon Production in p+p Collisions at sqrt(s) = 200 GeV
• Higgs boson production at hadron colliders in the k_T-factorization approach
• Unintegrated parton distributions of pions and nucleons from the CCFM equations in the single-loop approximation
• Gluon transverse momenta and charm quark-antiquark pair production in $p-\bar{p}$ collisions at Tevatron
• Measurement of direct photon production at Tevatron fixed target energies
• Heavy Quark Photoproduction in k_T Factorization Approach
• Charm quark-antiquark correlations in photon-proton scattering
• Unintegrated gluon distributions and Higgs boson production in proton-proton collisions

Cited by in corpus (12)

• Inclusive production of $J/\psi$ meson in proton-proton collisions at BNL RHIC
• Deep inelastic scattering and prompt photon production within the framework of quark Reggeization hypothesis
• Prompt photon hadroproduction at high energies in off-shell gluon-gluon fusion
• Photon-jet correlations in $pp$ and $p\bar{p}$ collisions
• Reconsideration of the inclusive prompt photon production at LHC with kt-factorization
• Associated production of prompt photons and heavy quarks in off-shell gluon-gluon fusion
• Dijet correlations at RHIC, leading-order $k_t$-factorization approach versus next-to-leading order collinear approach
• Enhancement of prompt photons in ultrarelativistic proton-proton collisions from nonlinear gluon evolution at small-$x$
• Prediction for unintegrated parton distributions
• The P-P(P) cross-section of isolated single-photon production in the $k_t$-factorization and different angular ordering unintegrated parton distributions frameworks
• Dijet and photon-jet correlations in proton-proton collisions at RHIC
• Single photon production in ppBar collision in the collinear and kt-factorisation framework and investigation of their differences