Strong Isospin Breaking in Heavy-Meson Decay Constants: Employing Borelized QCD Sum Rules in Local-Duality Limit

TL;DR

This paper uses Borelized QCD sum rules in the local-duality limit to quantify isospin breaking effects on heavy-meson decay constants, finding a small but measurable difference due to up-down quark mass differences.

Contribution

It introduces a novel application of Borelized QCD sum rules in the local-duality limit to analyze isospin breaking in heavy-meson decay constants.

Findings

Neutral and charged heavy-meson decay constants differ by about 1 MeV.

Isospin breaking effects are primarily due to the non-zero mass gap between up and down quarks.

The method provides a precise estimate of isospin breaking in heavy-light mesons.

Abstract

Applying the QCD sum-rule machinery in the so-called local-duality shape to heavy-light mesons reveals that, as a consequence of the non-zero mass gap between up and down quarks, the leptonic decay constants of the neutral and charged versions of the $D,$ $D^\ast,$ $B$ and $B^\ast$ mesons differ by approximately 1 MeV.