Precision Muon Experiments

University Of Kentucky Research Foundation, Lexington KY

Investigators

Abstract

Precise experimental tests of fundamental particle properties are now a well-established way to search for new laws of nature beyond our current physical knowledge. The proposed research is for two experiments to make precise measurements of an elementary particle called the muon, which is similar to the electron but with larger mass. One experiment at tha Fermi National Accelerator Laboratory, called g-2, will measure the magnetic moment of the muon to an accuracy of better than a part-per-million, which will provide a test of the Standard Model of particle physics, the theory that explains the properties of the elementary particles making up most of the visible matter in the Universe. The other experiment, called MuSun, at the Paul Scherrer Institute (PSI) in Switzerland will measure the lifetime of an atom comprised of a muon and a deuteron (a nucleus made from one proton and one neutron). This experiment will further the knowledge of the reaction of thermonuclear hydrogen burning which powers the sun, as well as helping to understand neutrino interactions with matter. The muon g-2 experiment will measure the muon anomalous magnetic moment to 140 parts-per-billion, a four-fold improvement over the previous experiment at Brookhaven National Laboratory (BNL), known as E821. The measurement will address the longstanding 3 standard deviation discrepancy between the same measurement from E821 and the Standard Model prediction. It represents a key test of the Standard Model and has broad sensitivity to new particles and interactions beyond the Standard Model. The muon g-2 project has involved the relocation of the muon storage ring from Brookhaven National Laboratory to Fermilab as well as new detector, electronics and acquisition systems. The PI and his group are responsible for the 8 GByte/sec calorimeter readout, using multi-teraflop GPU-based data processing, and distributed event building for the data acquisition system. The MuSun experiment will measure the mu- d to n n neutrino doublet capture rate to an accuracy of 1.5%. The measurement addresses a longstanding discrepancy among earlier measurements of mu d capture. It will provide a five-fold improvement in our knowledge of the two-body weak axial currents that plays a role in pp thermonuclear fusion, cross sections for neutrino experiments, and ordinary and double beta-decay.