MEG II experiment status and prospect

TL;DR

The MEG II experiment aims to significantly improve the sensitivity in detecting the rare muon decay $oldsymbol{ ext{μ}^+ o e^+ ext{γ}}$, through upgraded detectors and higher muon beam intensity, to explore physics beyond the Standard Model.

Contribution

This paper reports on the status and upgrades of the MEG II experiment, enhancing detector performance and beam intensity to achieve unprecedented sensitivity in lepton flavor violation searches.

Findings

Successful upgrade of detectors and electronics.

Preliminary results from the pre-engineering run.

Prospects for the 2021 data-taking run.

Abstract

The MEG II experiment at Paul Scherrer Institute (PSI) in Switzerland aims to achieve a sensitivity of $6\times10^{-14}$ on the charged lepton flavor violating decay $\mu^+\to e^+\gamma$. The current upper limit on this decay is $4.2\times10^{-13}$ at 90% Confidence Level (CL), set by the first phase of MEG. This result was achieved using the PSI muon beam at a reduced intensity, $3\times10^7~\mu^+/$s, to keep the background at a manageable level. The upgraded detectors in MEG~II can cope with a higher intensity, thus the experiment is expected to run at a $7\times10^7~\mu^+/$s intensity. The new low mass, single volume, high granularity tracker, together with a new highly segmented timing counter, guarantees better resolutions for the positron detection. Moreover, the replacement of the old PhotoMultiplier Tubes (PMTs) with Multi-Pixel Photon Counters (MPPCs) in the inner face of the liquid xenon photon detector improved its performance. The details of the upgraded detectors and their present status will be discussed, together with the latest results from last year's pre-engineering run and the perspective for the 2021 run, the first with all the detectors and electronics installed.