Stopping Muon Beams

Physics experiments often use low-energy beams of unstable particles that stop in a target in order to provide high sensitivity to rare processes with reduced backgrounds. However, the stopping rate in the target is limited by the dynamics of the production process and by multiple scattering and energy straggling in the material used to slow the particles. As a result, the event rates and sensitivity to rare processes are limited. This project will apply new six-dimensional beam cooling inventions, improved capture techniques, and new simulation tools to develop designs for low-energy beam lines to stop many muons in small volumes. It will develop the helical cooling channel (HCC) and the newer pion momentum spread reduction schemes for experiments such as mu2e as well as for others that require polarization. We will use G4beamline to improve the mu2e experimental sensitivity and to develop methods to understand and suppress rare background events. Commercial Applications and other Benefits as described by the awardee: The use of the HCC and other new ideas for stopping muon beams will provide a new level of sensitivity for experimental physics searches for rare processes such as the direct conversion of muons into electrons. Many applications of intense stopping muon beams, such as spin-resonance investigations and muon-catalyzed fusion, will also benefit greatly.