Virtual and soft pair corrections to polarized muon decay spectrum

Abstract

Radiative corrections to the muon decay spectrum due to soft and virtual electronpositron pairs are calculated.

On spin asymmetry in muon and tau decays

“…The NNLO result for virtual and soft e + e − pair corrections to the spin asymmetry in muon decay was presented in Ref. 18 Numerical results for g 0 , g 1 , and g LLA 2 are presented in Table 1. For tau lepton decays we took into account only the electron-positron pair contribution since its impact is enhanced by the large logarithm ln(m 2 τ /m 2 e ) ∼ 16.3 (even squared for τ → 2eēν e ν τ ) while the logarithm with the muon mass is considerably smaller, ln(m 2 τ /m 2 µ ) ∼ 5.6.…”