Search For The Decay Mu E Gamma PDF Download

An experimental search for the lepton-family number nonconserving decay, .mu. .-->. e.gamma gamma., has been conducted at the Clinton P. Anderson Meson Physics Facility (LAMPF) using the Crystal Box detector. The detector consists of a modular NaI(Tl) calorimeter, scintillator hodoscope, and a high-resolution, cylindrical drift chamber. It provides a large solid-angle for detecting three-body decays and has good resolutions in the time, position, and energy measurements to eliminate unwanted backgrounds. No evidence for .mu.+ .-->. e+.gamma gamma. is found, giving an upper limit for the branching ratio of GAMMA(.mu. .-->. e.gamma gamma.)/GAMMA(.mu. .-->. e nu anti nu) less than or equal to 7.2 x 10−11 (90% C.L.). This result is an improvement of more than two orders of magnitude in the existing limit. 109 refs., 39 figs.