Final results of the MEG experiment

Mori, Toshinori (2016) Final results of the MEG experiment. Il nuovo cimento C, 39 (4). pp. 1-8. ISSN 1826-9885

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Transitions of charged leptons from one generation to another are basically prohibited in the Standard Model because of the mysteriously tiny neutrino masses, although such flavor-violating transitions have long been observed for quarks and neutrinos. Supersymmetric Grand Unified Theories (SUSY GUT), which unify quarks and leptons as well as their forces, predict that charged leptons should also make such transitions at small but experimentally observable rates. The MEG experiment was the first to have explored one of such transitions, μ+ → e+γ decays, down to the branching ratios predicted by SUSY GUT. Here we report the final results of the MEG experiment based on the full dataset collected from 2009 to 2013 at the Paul Scherrer Institut, corresponding to a total of 7.5×1014 stopped muons on target. No excess for μ+ → e+γ decays was found. Thus the most stringent upper bound was placed on the branching ratio, B(μ+ → e+γ) < 4.2 × 10−13 at 90% C.L., about 30 times tighter than previous experiments, and severely constrains SUSY GUT and other well-motivated theories. We are now preparing the upgraded experiment MEG II with the aim to achieve a sensitivity of 4 ×10−14 after three years of data taking. It is expected to start late in 2017.

Item Type: Article
Subjects: 500 Scienze naturali e Matematica > 530 Fisica
Depositing User: Marina Spanti
Date Deposited: 16 Nov 2020 20:18
Last Modified: 16 Nov 2020 20:18

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