Mu to E Gamma

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 PMTs measure the photon energy and a drift chamber in a magnetic field detects the positrons.

In March 2013 the MEG experiment published the world's leading upper limit on the branching ratio of this decay:

$\Beta ( \mu^+ \to e^+ \gamma) < 5.7 \times 10^{-13}$

at 90% confidence level,^[2] based on data collected in 2009–2011. This improved the MEG limit from data up to 2010. These replace prior limits from the MEGA experiment.^[3]

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 2016.^[4] More experiments are planned that will explore this process such as Mu2e.

External links

• MEG home page

References

1. http://cerncourier.com/cws/article/cern/29118
2. J. Adam et al. (MEG Collaboration) (2013). "New Constraint on the Existence of the mu+ -> e+ gamma Decay". Physical Review Letters 110 (20): 201801. arXiv:1303.0754. Bibcode:2013PhRvL.110t1801A. doi:10.1103/PhysRevLett.110.201801.
3. M. L. Brooks et al. (MEGA Collaboration) (23 August 1999). "New Limit for the Lepton-Family-Number Nonconserving Decay μ+→e+γ". PRL 83, 1521. arXiv:hep-ex/9905013. Bibcode:1999PhRvL..83.1521B. doi:10.1103/PhysRevLett.83.1521.
4. Francesco Renga [for the MEG Collaboration]. "Latest results of MEG and status of MEG-II". arXiv:1410.4705.