The color dipole picture for prompt photon production in pp and pPb collisions at the CERN-LHC

Abstract

A study on the prompt photon production within the QCD color dipole picture with emphasis in pp and p A collisions at the LHC energy regimes is performed. We present predictions for the differential cross section as a function of photon transverse momentum at different rapidity bins considering updated phenomenological color dipole models, which take into account the QCD gluon saturation physics. The results are directly compared to the recent experimental measurements provided by CMS and ATLAS Collaborations, showing a reasonable agreement in all rapidity bins with no free parameters. Special attention is given to the IPSAT model given its good description of the data in all rapidity bins from low-to highp T ranges. As a result, a freeparameter approach has succeeded in describing the LHC data for prompt photon production, while new predictions for the 13-TeV data is presented in view of new data to confirm such prospect.

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

“…These results are an extension of the previous investigations presented in Ref. [17], where the differential cross section in pp and pA collisions at the LHC energies has been analyzed. Moreover, we carefully examine the theoretical mechanism responsible for the observed x T scaling in pp and/or pA collisions.…”

“…The main uncertainty in the GS approach is the prescription for the nuclear saturation scale, Q 2 s,A , and in Ref. [17] we determined the uncertainty being ≈20%.…”

D0 meson production in high‐energy pp collisions based on dipole transverse momentum approach

“…It is important to stress that the color dipole approach is phenomenologically successful for small x physics or equivalent high‐energy process. In the literature, such formalism was employed to describe numerous observables in high‐energy phenomenology, for instance, one can cite the prompt photon production in pp (Sampaio dos Santos et al 2020a), pA (Sampaio dos Santos et al 2020b) and AA (Santos et al 2022b) collisions at the LHC. Moreover, for further results on the D ‐meson production in pp collisions see Sampaio dos Santos et al (2021), such results are an extension of this present study.…”

An Energy Independent Scaling of Transverse Momentum Spectra of Direct (Prompt) Photons from Two‐Body Processes in High‐Energy Proton–Proton Collisions

“…Before summary and conclusions, we would like to collect a few other physical approaches describing the spectra of direct (prompt) photons. For examples, i) QCD color dipole picture, [ 105,106 ] in which the low‐$$p_T$$ region is described by the parton saturation effects and pQCD evolution is reproduced accurately. The $$x_T$$ scaling can be also addressed in this formalism.…”