In:
The European Physical Journal C, Springer Science and Business Media LLC, Vol. 80, No. 9 ( 2020-09)
Abstract:
We present the first direct search for lepton flavour violating muon decay mediated by a new light particle X, $$\upmu ^+ \rightarrow \mathrm {e}^+\mathrm {X}, \mathrm {X} \rightarrow \upgamma \upgamma \ $$ μ + → e + X , X → γ γ . This search uses a dataset resulting from $$7.5\times 10^{14}$$ 7.5 × 10 14 stopped muons collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013. No significant excess is found in the mass region 20–45 MeV/c $$^2$$ 2 for lifetimes below 40 ps, and we set the most stringent branching ratio upper limits in the mass region of 20–40 MeV/c $$^2$$ 2 , down to $${\mathcal {O}}(10^{-11})$$ O ( 10 - 11 ) at 90% confidence level.
Type of Medium:
Online Resource
ISSN:
1434-6044
,
1434-6052
DOI:
10.1140/epjc/s10052-020-8364-1
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2020
detail.hit.zdb_id:
1397769-6
detail.hit.zdb_id:
1459069-4
Permalink