New results in rare allowed muon and pion decays
Abstract
Simple dynamics, few available decay channels, and highly controlled radiative and loop corrections, make pion and muon decays a sensitive means of exploring details of the underlying symmetries. We review the current status of the rare decays: pi+ -> e+ nu, pi+ -> e+ nu gamma, pi+ -> pi0 e+ nu, and mu+ -> e+ nu nu-bar gamma. For the latter we report new preliminary values for the branching ratio B(E_gamma >10 MeV, theta_(e-gamma) > 30deg) = 4.365 (9)_stat (42)_syst x 10^{-3}, and the decay parameter eta-bar = 0.006 (17)_stat (18)_syst, both in excellent agreement with standard model predictions. We review recent measurements, particularly by the PIBETA and PEN experiments, and near-term prospects for improvement. These and other similar precise low energy studies complement modern collider results materially.
Keywords
Cite
@article{arxiv.1403.7416,
title = {New results in rare allowed muon and pion decays},
author = {D. Pocanic and E. Munyangabe and M. Bychkov and V. A. Baranov and W. Bertl and Yu. M. Bystritsky and E. Frlez and V. A. Kalinnikov and N. V. Khomutov and A. S. Korenchenko and S. M. Korenchenko and M. Korolija and T. Kozlowski and N. P. Kravchuk and N. A. Kuchinsky and M. C. Lehman and D. Mekterovic and D. Mzhavia and A. Palladino and P. Robmann and A. M. Rozhdestvensky and I. Supek and P. Truoel and Z. Tsamalaidze and A. van der Schaaf and B. Vandevender and E. P. Velicheva and V. P. Volnykh},
journal= {arXiv preprint arXiv:1403.7416},
year = {2015}
}
Comments
5 pages, 2 figures, talk presented at the 9th International Workshop on e+ e- Collisions "From phi to psi 2013", held in Rome, 9-12 Sept 2013