The MEG detector for μ +→e+ γ decay search

Abstract

The MEG (Mu to Electron Gamma) experiment has been running at the Paul Scherrer Institut (PSI), Switzerland since 2008 to search for the decay μ + → e + γ by using one of the most intense continuous μ + beams in the world. This paper presents the MEG components: the positron spectrometer, including a thin target, a superconducting magnet, a set of drift chambers for measuring the muon decay vertex and the positron momentum, a timing counter for measuring the positron time, and a liquid xenon detector for measuring the photon energy, position and time. The trigger system, the read-out electronics and the data acquisition system are also presented in detail. The paper is completed with a description of the equipment and techniques developed for the calibration in time and energy and the simulation of the whole apparatus.

Search for the lepton flavour violating decay $$\mu ^+ \rightarrow \mathrm {e}^+ \gamma $$ μ + → e + γ with the full dataset of the MEG experiment

“…The MEG detector is briefly presented in the following, emphasising the aspects relevant to the analysis; a detailed description is available in [8]. Briefly, it consists of the μ + beam, a thin stopping target, a thin-walled, superconducting magnet, a drift chamber array (DCH), scintillating timing counters (TC), and a liquid xenon calorimeter (LXe detector).…”

Muon polarization in the MEG experiment: predictions and measurements

“…The muon decay products are an important background when searching for rare decays such as μ + → e + γ ; a precise knowledge of their distribution is therefore mandatory. We report on the determination of the residual muon polarization in the PSI π E5 [1] channel and MEG beam line [2] The MEG experiment at the Paul Scherrer Institute (PSI) [3] has been searching for the lepton flavour violating decay μ + → e + γ since 2008. Preliminary results were published in [4,5] and [6].…”

“…The analysis of the MEG full data sample is under way and will soon be published. A detailed description of the experiment can be found in [2]. A high intensity surface muon beam (∼3 × 10 7 µ + /s), from the π E5 channel and MEG beam line, is brought to rest in a 205 µm slanted plastic target, placed at the centre of the experimental set-up.…”

cLFV searches using DC muon beam at PSI

“…The positron contamination in the beam is efficiently removed by a Wien filter installed at the end of the beam line. Figure 2 shows the MEG detector setup [2]. The surface muon beam transported through the PiE5 beam line is stopped on a muon stopping target of 18-mg/cm 2 thick polyethylene located at the center of the magnet.…”