The MEG experiment is looking for the lepton flavour violating decay of the muon into an electron-photon pair with a sensibility of a few 10^-13.
The observation of charged lepton flavour violation would be the evidence for physics beyond the Standard Model.
The µ->e gamma process is forbidden by SM while many SUSY-GUT theories predict that it should occur with a branching ratio close to the present experimental upper limit, set by MEG at 5.7 10^-13 @ 90% CL (PRL May 2013). For this reason an upgrade of MEG is foreseen in the following years.
The signature of µ->e gamma is given by a positron and a photon flying back to back with energy equal to half of the muon mass. Dedicated detectors provide the reconstruction of the photons and positrons momentum, the former is provided by a Liquid Xenon scintillating detector and the latter by a set of drift chambers submerged into an inhomogeneous magnetic field.
In MEG II the positron tracking system will be deeply revised while minor action will be taken on the photon side and on beam and target.