MEG
The international collaboration MEG (Italy, Japan, Switzerland, USA, Russia) searches for the decay μ+ -> e+ γ at the Paul Scherrer Institut (Zurich). This decay, practically forbidden in the Standard Model of particle physics, is foreseen in many extensions of this model at an experimentally accessible level. The observation of μ+ -> e+ γ would be a clear signal of New Physics while stringents contraints on its Branching Ratio (BR) allow to set limits on the parameters space of new theoretical models or even to exclude some of them.
Since it is a very rare decay (if it exists) it is necessary to have an intense muon beam; at PSI the most intense continuous muon beam in the world is available, up to 108 muons per second. The MEG experiment is placed at the intensity frontier of New Physics searches, complementary to the energy frontier (LHC).
The MEG final result, based on the analysis of the data taken in 2009-2013 is: BR (μ+ -> e+ γ) < 4.2 x 10-13 @ 90% C.L. ( EPJC76,8,434, 2016). It is the world best limit on this decay. The MEG experiment has been upgraded and is in the commissioning phase; it is foreseen that the MEG-II detector will take physics data for 3 years since 2021 reaching a sensitivity one order of magnitude better than MEG, 5 x 10-14.
The last commissioning run in 2020 (Oct-Dec), with all detectors in, has just finished. The muon beam is stopped by a thin plastic target and the muon decays at rest: a photon and a positron are searched, emitted simultaneously, back to back, with an energy equal to half of the muon mass. The positron is reconstructed in a spectrometer (drift chamber in a magnetic field) and then its time is measured by scintillator detectors; the photon is detected using a liquid Xenon calorimeter.
Websites:
Thesis Opportunities:
For information regarding thesis opportunities, please contact: Cecilia Voena and/or visit our local website.
Local Coordinator
Cecilia Voena| Name | Surname | Role | Position |
|---|---|---|---|
| Rita | Antonietti | Associata | Laureanda Magistrale |
| Gianluca | Cavoto | Associato | Prof. Associato |
| Gianluigi | Chiarello | Associato | Assegnista |
| Manuel | Meucci | Associato | Dottorando |
| Silvia | Milana | Associata | Assegnista |
| Valerio | Pettinacci | Dipendente | Tecnologo |
| Francesco | Renga | Dipendente | Ricercatore |
| Cecilia | Voena | Dipendente | Ricercatrice |