Probing the Weak Interaction with Muon Decay

by Art Olin (TRIUMF (CA))

Tuesday 4 Nov 2014, 12:30 → 13:30 US/Pacific

Mad River (SLAC)

The TRIUMF Weak Interaction Symmetry Test (TWIST) collaboration has completed a simultaneous measurement of the muon decay parameters ρ, δ, and P_μξ [1] through the analysis of the momentum and angle distributions of positrons from polarized positive muon decay. The final data consisted of 5.4x10⁸ fully analyzed muon decays and the results represent an improvement in precision of approximately one order of magnitude compared to prior experiments, testing the validity of the standard model in a system dominated by leptonic interactions. We have recently reported [2] a search in this data for μ⁺→e⁺ X⁰ where the X⁰ boson does not decay to charged particles or otherwise interact with conventional detectors. The large angular acceptance of the TWIST apparatus enables us to extend this search to the case where the decays may be strongly anisotropic.

I will discuss some of the interesting results and challenges faced by the decay parameter measurement, results of the X⁰ search, and other information that may be gleaned in the future from the TWIST data.

[1] Phys. Rev. Lett. 106, 041804 (2011); Phys Rev D84,032005(2011); Phys. Rev D85,092013(2012).

[2] http://arxiv.org/abs/1409.0638

pictures arthead.png MuonDecaySpectrum.png

Slides slac.pdf