Investigating the high-energy QCD approaches for prompt-photon production at the LHC

Abstract

We investigate the rapidity and transverse momentum distributions of the prompt photon production at the CERN LHC energies considering the current perturbative QCD approaches for this scattering process. Namely, we compare the predictions from the usual NLO pQCD calculations to the the color dipole formalism, using distinct dipole cross sections. Special attention is paid to parton saturation models at high energies, which are expected to be important at the forward rapidities in pp collisions ( √ s = 14 TeV) at the LHC.

Prompt photon production in high-energy pA collisions at forward rapidity

“…However, Ref. [25] demonstrates that a large-x correction should be added to consistently describe the prompt photon phenomenology. Therefore, we have multiplied the GBW dipole cross section by a threshold factor (1 − x 2 ) n (with n = 7).…”

“…[24]; such an approach includes QCD gluon evolution via the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) equation. It should be noticed that, in the color transparency regime, the Hankel integrals can be analytically performed [25]. We will discuss this case in detail when the x T scaling is studied.…”

Study on the low mass Drell-Yan production at the CERN LHC within the dipole formalism

“…It has been shown before [25] that in central rapidities at RHIC and Tevatron, saturation effects do not play a significant role for the measured range of p T . This situation can be changed at the LHC even at midrapidities as the saturation scale is enhanced by a sizable factor.…”

Photon plus heavy-quark production in high-energy collisions within the target rest frame formalism

“…In next section we introduce the main formulae to compute the hadronic differential cross section. It is already known from previous studies [7] that the photon transverse momentum spectrum is a sensitive probe of color dipole scattering cross section. We investigate the consequence of using several implementations of dipole cross sections which are constrained from deep inelastic scattering data.…”

“…Their interaction with the medium is purely electromagnetic, which gives a baseline for the interpretation of jetquenching models. From the theoretical point of view, the prompt photon production is reasonably described in the next-to-leading order (NLO) perturbative QCD (pQCD) approach [1] and on the color dipole formalism [2][3][4][5][6][7] as well. Recently, the first measurements of inclusive photon production in association with heavy flavour jets have been reported by D0 Collaboration [8].…”