Light quark mass dependence in heavy quarkonium physics

TL;DR

This paper investigates how light quark masses influence heavy quarkonium properties, emphasizing the importance of nonanalytic chiral extrapolations near open flavor thresholds for accurate lattice QCD predictions.

Contribution

It demonstrates that light quark mass dependence in heavy quarkonia can be significant and nontrivial, especially near open flavor thresholds, highlighting the need for proper chiral extrapolations in lattice studies.

Findings

Decay widths of hindered M1 transitions are sensitive to quark mass variations.

Results at 500 MeV pion mass can differ by a factor of two from physical mass.

Nonanalytic chiral effects are important near open flavor thresholds.

Abstract

The issue of chiral extrapolations in heavy quarkonium systems is discussed. We show that the light quark mass dependence of the properties of heavy quarkonia is not always suppressed. For quarkonia close to an open flavor threshold, even a nonanalytic chiral extrapolation is needed. Both these nontrivial facts are demonstrated to appear in the decay widths of the hindered M1 transitions between the first radially excited and ground state P-wave charmonia. The results at a pion mass of about 500 MeV could deviate from the value at the physical pion mass by a factor of two. Our findings show the necessity of performing chiral extrapolations for lattice simulations of heavy quarkonium systems.