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The Process gamma* + p -> eta_c + X: A Test for the Perturbative QCD Odderon

J. Bartels, M. A. Braun, G. P. Vacca

TL;DR

This work computes the inclusive diffractive production of eta_c in gamma^* p collisions within perturbative QCD, testing the perturbative odderon via the triple Regge regime gamma(^*)+p -> eta_c + X. The amplitude is decomposed into a reggeizing piece (P) and a Pomeron–Odderon–Odderon (POO) transition, both evaluated in the large-N_c limit with an odderon solution of maximal intercept. The cross section is fixed by the gluon ladder coupling to the proton, determined from the proton structure function, and the odderon–proton coupling uncertainty is thereby mitigated. Numerical results show a sizable photoproduction rate around 60 pb and a substantial, energy-dependent enhancement from the POO contribution, indicating that inclusive diffractive eta_c production is a promising observable to test perturbative QCD odderon dynamics.

Abstract

The rates of inclusive photo- and electroproduction of the eta_c meson: gamma* + p -> eta_c + X are calculated in the triple Regge region, integrated over the diffractive mass X. For the Regge exchanges we use the hard Pomeron and Odderon, both being calculated in the framework of perturbative QCD. The integrated cross-section depends upon the coupling of the BFKL pomeron to two $C=-1$ odderons, and it is found to be of the order 60 pb for photoproduction and 1.5 pb at Q^2=25 GeV^2.

The Process gamma* + p -> eta_c + X: A Test for the Perturbative QCD Odderon

TL;DR

This work computes the inclusive diffractive production of eta_c in gamma^* p collisions within perturbative QCD, testing the perturbative odderon via the triple Regge regime gamma(^*)+p -> eta_c + X. The amplitude is decomposed into a reggeizing piece (P) and a Pomeron–Odderon–Odderon (POO) transition, both evaluated in the large-N_c limit with an odderon solution of maximal intercept. The cross section is fixed by the gluon ladder coupling to the proton, determined from the proton structure function, and the odderon–proton coupling uncertainty is thereby mitigated. Numerical results show a sizable photoproduction rate around 60 pb and a substantial, energy-dependent enhancement from the POO contribution, indicating that inclusive diffractive eta_c production is a promising observable to test perturbative QCD odderon dynamics.

Abstract

The rates of inclusive photo- and electroproduction of the eta_c meson: gamma* + p -> eta_c + X are calculated in the triple Regge region, integrated over the diffractive mass X. For the Regge exchanges we use the hard Pomeron and Odderon, both being calculated in the framework of perturbative QCD. The integrated cross-section depends upon the coupling of the BFKL pomeron to two odderons, and it is found to be of the order 60 pb for photoproduction and 1.5 pb at Q^2=25 GeV^2.

Paper Structure

This paper contains 8 sections, 75 equations, 7 figures.

Table of Contents

  1. Introduction
  2. The cross-section formula in perturbative QCD
  3. Contribution of the reggeizing piece $D_6^R$
  4. The POO vertex in leading order in $N_c$
  5. Part of the cross-section with a POO transition
  6. Numerical results
  7. Conclusions
  8. Acknowledgements

Figures (7)

  • Figure 1: Illustration of the process $\gamma^*+p \to \eta_c +X$. Diffractive cross section differential (a) and integrated (b) in the diffractive mass.
  • Figure 2: Illustration of the process $\gamma^*+p \to \eta_c +X$: the blob in the center of the figure denotes the transition vertex Pomeron $\to$ 2 odderons.
  • Figure 3: The second contribution to the same process as Fig.1: the Pomeron couples to the two odderons which consist of three noninteracting gluons.
  • Figure 4: The function $I(q/M)$ from eq.(\ref{['I8']}).
  • Figure 5: Differential cross-sections $d\sigma/dt$ from the reggeized pomeron exchange (P), POO transition (POO) and total at $Q^2=0$.
  • ...and 2 more figures