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 while reducing backgrounds. However, the stopping rate in the target is limited by the kinematics of the production process and by multiple scattering and energy straggling in the material used to slow the particles. In practice, this means that the event rates and sensitivity are limited. Enlarging the target is not an option because this would compromise performance and/or increase the cost of the detector. This project will demonstrate that beam cooling can be used to improve the stopping of muon beams. A six-dimensional beam cooling technique will be developed, and simulation tools will be used to develop designs that can stop many muons in a small volume. As an example, a stopping muon beam design, using a helical cooling channel (HCC), will be developed for a particular experiment to search for the direct conversion of muons to electrons. Commercial Applications and other Benefits as described by the awardee: The use of the HCC for stopping muon beams would provide a new level of sensitivity for experimental physics, allowing the development of muon colliders and neutrino factories. Many applications of intense stopping muon beams, such as spin-resonance investigations and muon-catalyzed fusion, also would benefit.