New Constraint on the Existence of theμ+→e+γDecay

Abstract

The analysis of a combined data set, totaling 3.6 × 10(14) stopped muons on target, in the search for the lepton flavor violating decay μ(+) → e(+)γ is presented. The data collected by the MEG experiment at the Paul Scherrer Institut show no excess of events compared to background expectations and yield a new upper limit on the branching ratio of this decay of 5.7 × 10(-13) (90% confidence level). This represents a four times more stringent limit than the previous world best limit set by MEG.

Lepton parameters in the see-saw model extended by one extra Higgs doublet

“…Therefore, the see-saw mechanism makes the generic prediction that neutrino masses should be much smaller than the quark or charged lepton masses, although the precise value cannot be predicted. Furthermore, and due to the high scale of lepton flavour violation, this framework predicts tiny rates for the rare lepton decays [10][11][12][13], in agreement with the stringent experimental bounds BR(µ → eγ) ≤ 5.7 × 10 −13 [14], BR(τ → µγ) ≤ 4.4 × 10 −8 [15], BR(τ → eγ) ≤ 3.3 × 10 −8 [15].…”

Impact of sterile neutrinos on nuclear-assisted cLFV processes

“…cLFV Process Present Bound Future Sensitivity µ → eγ 5.7 × 10 −13 [85] 6 × 10 −14 [86] τ → eγ Table 1. Current experimental bounds and future sensitivities for radiative and 3-body cLFV decays considered in our study.…”

Sterile neutrinos in leptonic and semileptonic decays

“…The radiative muon decay µ → eγ, searched for by the MEG experiment [29], provides the most stringent constraint. The rate induced by sterile neutrinos 2 should obey [9,10] 12) where…”