Ultrasoft Effects in Heavy-Quarkonium Physics

TL;DR

This paper investigates ultrasoft gluon effects in heavy-quarkonium systems within nonrelativistic QCD, providing analytical formulas for energy shifts and wave function modifications, with implications for top-antitop and Upsilon physics.

Contribution

It introduces a new class of radiative corrections at N3LO due to ultrasoft gluons and derives analytical expressions for their impact on quarkonium properties.

Findings

Analytical formulas for energy level shifts and wave function modifications.

Implications for top-antitop and Upsilon systems.

Limitations in modeling charmonium with Coulomb potential.

Abstract

In the framework of nonrelativistic QCD, we consider a new class of radiative corrections, which are generated at next-to-next-to-next-to-leading order through the chromoelectric dipole interaction of heavy quarkonium with ultrasoft virtual gluons. We provide analytical formulae from which the resulting shifts in the quarkonium energy levels and the wave functions at the origin may be calculated. We discuss the phenomenological implications for the top-antitop and Upsilon systems and point out some limitations of describing charmonium using a Coulomb potential.