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

Journal Article · Mon Jan 01 04:00:00 EST 2007 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.75.014023· OSTI ID:20933237

Pietrycki, T; Szczurek, A ^[1]

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1. Institute of Nuclear Physics, PL-31-342 Cracow (Poland)

The invariant cross sections for direct photon production in hadron-hadron collisions are calculated for several initial energies (SPS, ISR, SppS, 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{sub t}{sup 2}) and nonperturbative (small k{sub t}{sup 2}) regions of UPDFs in the production of both soft and hard photons is identified. The k{sub t}-factorization approach with the KMR UPDFs is inconsistent with the collinear approach at large transverse momenta of photons. Kwiecinski UPDFs provide very good description of all world data, especially at super proton synchrotron (SPS) and intersecting storage rings (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.

• OSTI ID: 20933237
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 1 Vol. 75; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
BROOKHAVEN RHIC
CERN LHC
CERN SPS SYNCHROTRON
CROSS SECTIONS
FACTORIZATION
FERMILAB TEVATRON
GLUONS
HADRON-HADRON INTERACTIONS
HADRONIC PARTICLE DECAY
PARTICLE PRODUCTION
PARTICLE RAPIDITY
PHOTONS
PROTONS
SUM RULES
TRANSVERSE MOMENTUM