from 27 February 2017 to 3 March 2017
Budker Institute of Nuclear Physics
Asia/Novosibirsk timezone
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Contribution Contributed Oral

Electronics, Trigger and Data Acquisition

Scintillating Fibre Detector for the Mu3e Experiment

Speakers

  • Mr. Simon CORRODI

Primary authors

Content

Mu3e is a dedicated experiment for the rare lepton flavour violating decay $mu^{+} rightarrow e^{+}e^{-}e^{+}$. Its ultimate goal is to find or exclude this process if it occurs more than once in $10^{16}$ muon decays. This constitutes four orders of magnitude improvement with respect to the predecessor. A thin multi-layer scintillating fibre detector consisting of $250~mu m$ thick fibres read out on both sides with silicon photomultiplier arrays provides an excellent time measurement with $sigma<500~$ps in order to reject combinatorial background at a muon stopping rate around $10^8~$muon/s, concurrently minimizing the material budget to $X/X_{0}<0.3%$. The design, performance and readout concept, including the dedicated readout chip MuTRiG, is presented.

Summary

The Mu3e experiment is a dedicated experiment for the rare lepton flavour violating decay $mu^{+} rightarrow e^{+}e^{-}e^{+}$. This decay can occur in the Standard Model (SM) via neutrino mixing but is heavily suppressed with a BR$~<10^{-54}$. However its BR may be strongly enhanced in many beyond SM models. Any observation would be a clear sign of new physics. The ultimate goal is to find or exclude this process if it occurs more than once in $10^{16}~$muon decays. This requires a muon stopping rate up to $10^9~$muon/s, which is not available today. Phase I of the experiment will exploit the best available low-energy muon source in the world at the Paul Scherrer Institute (PSI, Switzerland) which provides muon rates up to $10^8~$Hz. In order to suppress combinatorial background emerging at these rates an excellent time resolution beside a very good vertex and momentum resolution is required.

In the central area of the detector, where a low material budget is crucial in order to minimize momentum resolution degradation due to multiple Coulomb scattering, a very thin multi-layer scintillating fibre detector provides a time measurement of $sigma<500~$ps. This sub-detector is accompanied by scintillating tiles at the outer parts of the detector providing a time resolution of $sigma <100~$ps.

The thin, $<1~$mm, scintillating fibre detector consists of $sim30~$cm long and $250~mu m$ thick fibres, segmented into 12 ribbons. A total efficiency above $95%$ is required and the total material budget has to be below $X/X_{0}<0.3%$. The ribbons are read out on both sides by silicon photomultiplier arrays. Dedicated electronics, the MuTRiG chip, able to deal with a single channel signal rate up to $1~$MHz is being developed for the experiment. An FPGA based readout chain integrates the sub-detector into the experiments trigger-less TBit/s readout.