Speaker
Description
Three fundamental searches or measurements can be made with muonium (M), a hydrogenic $\mu^+ e^-$ bound state: the search for charged-lepton flavor violation via M-$\overline{\mathrm{M}}$ oscillations, the M atomic spectrum, and the gravitational acceleration ($\overline{g}$) of antimatter in Earth’s field. M-$\overline{\mathrm{M}}$ transitions are allowed, but highly suppressed, via virtual neutrino mixing, and would yield a striking experimental signature; their observation would signal new doubly charged-lepton-flavor-violating physics coupling to 2nd-generation elementary particles. The M atomic spectrum is a precision test of QED, free of hadronic and finite-size effects. $\overline{g}$ has yet to be directly measured; measuring it with muonium is the only way to test the gravitational coupling of 2nd-generation particles. An unexpected outcome could change our understanding of gravity, the universe, and the existence of a fifth force. The PIP-II linac will be capable of producing unprecedented muon beam intensities to support a world-class, variable energy muon user facility at Fermilab, which would be the only one located in the US. R&D towards this future can start in the MTA/ITA facility at the existing 400 MeV Linac, which may be competitive for this physics with PSI. Other low-energy-muon applications can also be studied, including muon spin rotation as applied to superconducting RF resonators for QIS.