Mu to E Gamma

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The Mu to E Gamma (MEG) is a particle physics experiment dedicated to measuring the decay of the muon into an electron and a photon, a decay mode which is heavily suppressed in the Standard Model by lepton flavour conservation, but enhanced in supersymmetry and grand unified theories.[1] It is located at the Paul Scherrer Institute and began taking data September 2008.

MEG use a continues muon beam (3 × 107/s) incident on a plastic target. The decay is reconstructed to look for a back-to-back positron and monochromatic photon (52.8 MeV). A liquid xenon scintillator with photomultiplier tubes measure the photon energy, and a drift chamber in a magnetic field detects the positrons.

In May 2016 the MEG experiment published the world's leading upper limit on the branching ratio of this decay:

at 90% confidence level, [2] based on data collected in 2009–2013. This improved the MEG limit from the prior MEGA experiment[3] by a factor of about 28.

The MEG collaboration presented upgrade plans for MEG-II at the Particles and Nuclei International Conference 2014, with an order more sensitivity and increased muon production to begin data taking in 2017.[4] More experiments are planned to explore rare muon transitions, such as Mu2e and Mu3e.

External links[edit]


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  2. ^ Baldini, A. M.; et al. (MEG collaboration) (May 2016). "Search for the Lepton Flavour Violating Decay μ+→e+γ with the Full Dataset of the MEG Experiment". arXiv:1605.05081Freely accessible. 
  3. ^ Brooks, M. L.; et al. (MEGA Collaboration) (23 August 1999). "New Limit for the Lepton-Family-Number Nonconserving Decay μ+→e+γ". Physical Review Letters. 83 (8): 1521. arXiv:hep-ex/9905013Freely accessible. Bibcode:1999PhRvL..83.1521B. doi:10.1103/PhysRevLett.83.1521. 
  4. ^ Renga, F (2014). "Latest results of MEG and status of MEG-II". arXiv:1410.4705Freely accessible [hep-ex].