Elastic double diffractive production of axial-vector \chi_c(1^{++}) mesons and the Landau-Yang theorem

TL;DR

This paper investigates the exclusive production of axial-vector _c(1^{+}) mesons in proton-antiproton collisions, highlighting the non-applicability of the Landau-Yang theorem for off-shell gluons and providing differential cross section calculations.

Contribution

It introduces a derivation of the production amplitude within the k_t-factorisation approach considering off-shell gluons, and compares _c(1^{+}) and _c(0^{+}) production, including their measurable decay contributions.

Findings

The Landau-Yang theorem does not apply to off-shell gluons.

The _c(1^{+}) contribution to J/ + \u03b3 is smaller but measurable.

The ratio of _c(1^{+}) to _c(0^{+}) contributions is nearly independent of UGDF models.

Abstract

We discuss exclusive elastic double diffractive axial-vector \chi_c(1^{+}) meson production in proton-antiproton collisions at the Tevatron. The amplitude for the process is derived within the k_t-factorisation approach with unintegrated gluon distribution functions (UGDFs). We show that the famous Landau-Yang theorem is not applicable in the case of off-shell gluons. Differential cross sections for different UGDFs are calculated. We compare exclusive production of \chi_c(1^+) and \chi_c(0^+). The contribution of \chi_c(1^+) to the J/\Psi + \gamma channel is smaller than that of the \chi_c(0^+) decay, but not negligible and can be measured. The numerical value of the ratio of the both contributions is almost independent of UGDFs modeling.