Thermal width and gluo-dissociation of quarkonium in pNRQCD

TL;DR

This paper connects the effective field theory description of quarkonium thermal width with the phenomenological gluo-dissociation mechanism, improving cross section calculations by including final-state interactions.

Contribution

It provides a natural derivation of the gluo-dissociation factorization formula within pNRQCD and enhances the cross section by accounting for octet potential effects.

Findings

Effective field theory offers a natural derivation of gluo-dissociation.

Including octet potential modifies the dissociation cross section.

Final-state interactions significantly impact the quarkonium thermal width.

Abstract

The thermal width of heavy-quarkonium bound states in a quark-gluon plasma has been recently derived in an effective field theory approach. Two phenomena contribute to the width: the Landau damping phenomenon and the break-up of a colour-singlet bound state into a colour-octet heavy quark-antiquark pair by absorption of a thermal gluon. In the paper, we investigate the relation between the singlet-to-octet thermal break-up and the so-called gluo-dissociation, a mechanism for quarkonium dissociation widely used in phenomenological approaches. The gluo-dissociation thermal width is obtained by convoluting the gluon thermal distribution with the cross section of a gluon and a 1S quarkonium state to a colour octet quark-antiquark state in vacuum, a cross section that at leading order, but neglecting colour-octet effects, was computed long ago by Bhanot and Peskin. We will, first, show that the effective field theory framework provides a natural derivation of the gluo-dissociation factorization formula at leading order, which is, indeed, the singlet-to-octet thermal break-up expression. Second, the singlet-to-octet thermal break-up expression will allow us to improve the Bhanot--Peskin cross section by including the contribution of the octet potential, which amounts to include final-state interactions between the heavy quark and antiquark. Finally, we will quantify the effects due to final-state interactions on the gluo-dissociation cross section and on the quarkonium thermal width.