Muon conversion experiments--current and future

Many extensions of the standard model predict muon to electron conversion in the process μ+Nucleus→e+Nucleus at ratios, R, of 10-14 to 10-17 muon captures. A long history of experiments which have improved upper limits on R, to the current value of <6.1x10-13 set by SINDRUM II, have been limited by muon statistics rather than background. A new experiment, MECO, has been proposed to search for muon to electron conversion at levels below 5x10-17. MECO takes advantage of a pulsed, high-flux muon beam produced when a proton beam at the Brookhaven AGS is incident on a target in a graded solenoidal field. The detector has 800 KeV momentum resolution and is designed to minimize the background from the beam and maximize efficiency for signal electrons. With 1011 stopped muons per second, R=10-16 would give 5 detected events in a year of running with less than 0.5 background events expected