Electromagnetic corrections to the leptonic decay rates of charged pseudoscalar mesons: lattice results

Understand

Electromagnetic effects in the leptonic decay rates $\pi^+ \to \mu^+ \nu$ and $K^+ \to \mu^+ \nu$ are evaluated for the first time on the lattice.

• Following a method recently proposed in Ref.
• [1] the emission of virtual photons at leading order in the electromagnetic coupling is evaluated on the lattice and the infrared divergence computed for a point-like meson at finite lattice volume is subtracted.
• The physical decay rate is then obtained by adding the emission of real and virtual photons regularised with a photon mass.