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Next-to-next-to-leading-order soft-gluon corrections in direct photon production

Nikolaos Kidonakis, J. F. Owens

TL;DR

This paper extends soft-gluon resummation for direct photon production to NNLO accuracy by including additional subleading soft terms. It provides explicit NNLO soft and virtual corrections for the dominant partonic channels within the MSbar scheme and introduces a decomposition of the NLO coefficient c1 into mu-dependent and constant parts, plus new D0 and delta terms. Numerical results show these extra terms are small and mainly serve to further stabilize the scale dependence, with comparisons to UA-6 and E-706 data indicating modest shifts at low pT. Overall, the work demonstrates good perturbative convergence of the resummation approach and reinforces its reliability for constraining gluon distributions via direct photon production.

Abstract

Previous work on soft-gluon resummation for direct photon production is extended to include additional subleading logarithmic terms through O(alpha alpha_s^3) and some representative comparisons are made to experimental results from the E-706 and UA-6 Collaborations. The additional terms are small in magnitude, indicating good convergence properties to the level of accuracy calculated. The scale dependence remains much smaller than that of the next-to-leading-order calculation.

Next-to-next-to-leading-order soft-gluon corrections in direct photon production

TL;DR

This paper extends soft-gluon resummation for direct photon production to NNLO accuracy by including additional subleading soft terms. It provides explicit NNLO soft and virtual corrections for the dominant partonic channels within the MSbar scheme and introduces a decomposition of the NLO coefficient c1 into mu-dependent and constant parts, plus new D0 and delta terms. Numerical results show these extra terms are small and mainly serve to further stabilize the scale dependence, with comparisons to UA-6 and E-706 data indicating modest shifts at low pT. Overall, the work demonstrates good perturbative convergence of the resummation approach and reinforces its reliability for constraining gluon distributions via direct photon production.

Abstract

Previous work on soft-gluon resummation for direct photon production is extended to include additional subleading logarithmic terms through O(alpha alpha_s^3) and some representative comparisons are made to experimental results from the E-706 and UA-6 Collaborations. The additional terms are small in magnitude, indicating good convergence properties to the level of accuracy calculated. The scale dependence remains much smaller than that of the next-to-leading-order calculation.

Paper Structure

This paper contains 4 sections, 15 equations, 4 figures.

Table of Contents

  1. Introduction
  2. NNLO soft corrections
  3. Numerical results
  4. Conclusions

Figures (4)

  • Figure 1: NLO and NNLO results for direct photon production in hadronic collisions compared to $pp$ data from the UA-6 Collaboration UA6 at $\sqrt s = 24.3\ $ GeV.
  • Figure 2: NLO and NNLO results for direct photon production in hadronic collisions compared to $pp$ data for the rapidity distribution from the UA-6 Collaboration UA6 at $\sqrt s = 24.3\ $ GeV.
  • Figure 3: NLO and NNLO results for direct photon production in hadronic collisions compared to $p \overline p$ data from the UA-6 Collaboration UA6 at $\sqrt s = 24.3\ $ GeV.
  • Figure 4: NLO and NNLO results for direct photon production in hadronic collisions compared to data from the E-706 Collaboration E706 at p$_{lab} = 530\ $ GeV/c.