Finite-Volume Corrections to Electromagnetic Masses for Larger-Than-Physical Electric Charges

Understand

The numerical value of the fine-structure constant generally leads to small isospin-breaking effects due to electromagnetism in QCD.

• This smallness complicates determining isospin breaking from lattice QCD computations that include electromagnetism.
• One solution to this problem consists of performing computations using larger-than-physical values of the electric charge, and subsequently extrapolating (or interpolating) to the physical value of the fine-structure constant.
• Motivated by recent lattice QCD + QED computations of electromagnetic masses employing this setup, we consider finite-volume effects arising from the use of larger-than-physical electric charges.