Mu3e

Mu3e is a particle physics experiment at the Paul Scherrer Institute, searching for decays of anti-muons (Mu) to an electron and two positrons (3e).[1][2] This decay is extremely unlikely in the Standard Model of particle physics, as it changes the lepton number. Several new theories, especially supersymmetric ones, predict a much more frequent decay. Searching for this decay allows a test of these theories, even if they cannot be tested directly in other experiments like at the LHC.

Mu3e is constructed at the Paul Scherrer Institute, as it provides the world's most intense muon beam. More than one billion decays per second can be analyzed. This rate is necessary to study more than 1016 muon decays in total. Important backgrounds are the decays and . To distinguish between signal and background, the detector has a spatial resolution better than 200 µm, a time resolution better than 100 ps and an energy resolution better than 0,5 MeV for the individual electrons. To minimize multiple scattering, the detector is built as light as possible. Semiconductor detectors[3] are used for the spatial and energy resolution, scintillator fibers provide a good timing resolution. The whole experiment is in a magnetic field of 1 Tesla to determine the energy of the particles based on their curvature radius.

First data is expected for 2017, the full rate of more than one billion muons per second is expected for 2019. The experiment is expected to either find the decay or to set an upper limit of 10−16 on the branching fraction, a factor 10,000 better than previous experiments.[4]

See also

References

  1. ↑ Schöning, A.; Bachman, S.; Narayan, R. "A Novel Experiment to Search for the Decay μ→ eee". doi:10.1016/j.phpro.2011.06.035.
  2. ↑ Blondel, A.; Bravar, A.; Pohl, M.; Bachmann, S.; Berger, N.; Kiehn, M.; Schöning, A.; Wiedner, D.; Windelband, B.; Eckert, P.; Schultz-Coulon, H. -C.; Shen, W.; Fischer, P.; Perić, I.; Hildebrandt, M.; Kettle, P. -R.; Papa, A.; Ritt, S.; Stoykov, A.; Dissertori, G.; Grab, C.; Wallny, R.; Gredig, R.; Robmann, P.; Straumann, U. (2013). "Research Proposal for an Experiment to Search for the Decay μ -> eee". arXiv:1301.6113 [physics.ins-det].
  3. ↑ Berger, Niklaus; Augustin, Heiko; Bachmann, Sebastian; Kiehn, Moritz; Perić, Ivan; Perrevoort, Ann-Kathrin; Philipp, Raphael; Schöning, André; Stumpf, Kevin; Wiedner, Dirk; Windelband, Bernd; Zimmermann, Marco (2013). "A Tracker for the Mu3e Experiment based on High-Voltage Monolithic Active Pixel Sensors". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 732 (2013): 61–65. arXiv:1309.7896. Bibcode:2013NIMPA.732...61B. doi:10.1016/j.nima.2013.05.035.
  4. ↑ SINDRUM-Kollaboration: Search for the Decay mu+ ---> e+ e+ e-
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