Isospin symmetry breaking and the neutron-proton mass difference

TL;DR

This paper uses QCD sum rules with polynomial kernels to evaluate the strong contribution to the neutron-proton mass difference, highlighting the importance of the four quark condensate value in matching experimental results.

Contribution

It introduces a model-independent approach using polynomial kernels in QCD sum rules to estimate the neutron-proton mass difference.

Findings

The mass difference depends sensitively on the four quark condensate value.

Reproduces experimental mass difference for <(qq)^2> approximately twice <qq>^2.

Highlights the significance of condensate values in QCD sum rule calculations.

Abstract

QCD sum rules using polynomial kernels are used to evaluate the strong part of the proton-neutron mass difference DeltaM_np in a model independent fashion. The result for the mass difference turns out to depend sensitively on the value of the four quark condensate <(qq)^2> and reproduces the experimental value of DeltaM_np for <(qq)^2>~ 2<qq>^2.