Los Alamos Crystal Box Experiment: A Search for mu Yields e gamma , mu Yields e gamma gamma , and mu Yields eee

摘要

A search has been performed for the decays mu yields eee, mu yields e gamma , and mu yields e gamma gamma with a sensitivity in the branching ratios at the level of 10 exp -10 . The experiment used a surface muon beam at LAMPF with an average intensity of 300 kHz. A total of > 10 exp 11 muon decays was examined for the present result. The detector for the experiment is the Crystal Box, which consists of a cylindrical drift chamber surrounded by 396 NaI(Tl) crystals. A layer of scintillation counters in front of the crystals provided timing for electrons and a veto for photons. The energy resolution for electrons and photons is approx. 6% (FWHM). The position resolution of the drift chamber is 350 mu m leading to a vertex cut with a rejection of 10 exp 3 for mu implies eee. The timing resolution is approx. 400 ps from the scintillators and approx. 1 ns from the crystals. From these values, the eee and e gamma gamma limits are expected to be background free. (ERA citation 09:044992)