Holographic Synchrotron Radiation Emission Spectroscopy for Muon-to-Electron Conversion

Charged lepton flavor violation (CLFV) is predicted by many BSM theories. Upcoming experiments like Mu2e and COMET aim to tightly constrain the branching ratio of the conversion μ → e, an import bound on CLFV processes. This requires precise momentum reconstruction using low-mass tracking detectors. Yet performance is inherently limited by scattering in the detector materials. We hope to avoid this problem, using a novel no-mass detector based on radiation emitted from synchrotron radiation for reconstruction. Similar to cyclotron radiation emission spectroscopy (CRES) which uses radio signals from low-energy electrons, holographic synchrotron radiation emission spectroscopy (HSRES) uses optical photons from relativistic electrons. These photons emitted stochastically and projected onto the cylindrical inner surface of a solenoidal magnet. Photodetectors result in measurements of where the photons hit the cylindrical detector surface. We demonstrate how these hits are simulated, separated with high efficiency into tracks, and fitted with precise momentum resolution compared with current methods. This technique is also insensitive to most non-relativistic backgrounds and compatible alongside current trackers.