A new critical study of photon production in hadronic collisions

TL;DR

This paper reexamines prompt photon production in hadronic collisions using new PHENIX and D0 Run II data and compares them with NLO QCD predictions implemented in JETPHOX, focusing on direct versus fragmentation contributions and the role of photon isolation. It demonstrates that, with appropriate scale choices and isolation criteria, the NLO framework describes data over a wide energy range, challenging earlier tensions and supporting the fragmentation approach. The authors discuss theoretical ambiguities, the benefits of a Monte Carlo implementation for applying experimental cuts, and the impact of resummation in various kinematic regimes. Overall, the work reinforces confidence in perturbative QCD for prompt photon production and outlines avenues for further refinements and correlation studies.

Abstract

In the light of the new prompt photon data collected by PHENIX at RHIC and by D0 at the run II of the Tevatron, we revisit the world prompt photon data, both inclusive and isolated, in hadronic collisions, and compare them with the NLO QCD calculations implemented in the Monte Carlo programme JETPHOX.

Figures (10)

• Figure 1: The isolated D$\emptyset$ photon cross section in the central ($|\eta | < .9$) pseudorapidity region. The histogram is the NLO QCD prediction discussed in the text. The errors are the sum of the statistical and systematic errors. The scales are $\mu = p_T$.
• Figure 3: Ratio $\sigma^{th \, isol}/\sigma^{th \, incl}$ of the NLO isolated cross sections to the NLO inclusive prompt-photon cross sections at $\sqrt{s} = 200$ GeV. The scales used are $\mu= p_T/2$. PHENIX criterion: colored dots; standard criterion: black dots
• Figure 4: The PHENIX isolated prompt-photon cross section at $\sqrt{s} = 200$ GeV compared with NLO cross section predictions. Only the statistical errors on the data are shown. The scales used in the theoretical calculation are $\mu= p_T/2$.
• Figure 5: The ratio of PHENIX isolated photon data to NLO QCD using $\mu = p_{_T}/2$. The lower curve corresponds to the ratio $\hbox{NLO}(2 p_T)/\hbox{NLO}(p_T/2)$. Only the statistical errors on the data are shown.
• Figure 6: Ratios data/theory for collider and fixed target data with the scale $\mu = p_T/2$. For PHENIX and lower energy data the inclusive cross section is used while the isolated one is used for CDF and D$\emptyset$. Statistical erros only for PHENIX data.