Speaker
Description
The ability of the Mu2e experiment to probe direct Charged Lepton Flavor Violation (CLFV) $\mu^+$ and $\pi^+$ decay modes is estimated. These direct modes complement the Mu2e indirect search for $\mu^-\rightarrow e^-$ conversion accomplished using proposed detector validation runs. The $\mu^+$ validation run operates at 50% magnetic field and reduced beam intensity, to observe the $e^+$ spectrum from $\mu^+$ decay, at and below the Michel edge $E_e$ ≤ 53 MeV. The validation is used to correct systematic errors by mapping the theoretical Michel spectrum, known to Ο($\alpha^2$), to the observed spectrum. Simultaneously, searches for two-body CLFV $\mu^+\rightarrow e^+ + X$ decay, where $X$ is a light new physics particle can be undertaken. In two weeks of data-taking, Mu2e can achieve 90% C.L. branching ratio limits of $BR_{90}=10^{-7}$ in the mass range 20 ≤ mX ≤ 50 MeV, improving the current experimental limit by two orders of magnitude. In the mass range mX ≤ 20 MeV, if assuming systematic error corrections can be made, it is estimated, using two weeks of data collection, $BR_{90}(m_X=0)=3\times10^{-7}$, an order of magnitude improvement over the current best limit, for the case of V+A or an isotropic coupling. In addition, a two-week $\pi^+$ validation run measuring the $e^+$ in the decay $\pi^+\rightarrow e^+ + \nu$, at 76% magnetic field and introduction of a momentum degrader, allows searching for $\pi^+\rightarrow e^+ + N$ decay, where N is a spin 1/2 particle, in the mass region 20 ≤ $m_N$ ≤ 65 MeV. A branching ratio limit at 90% C.L. of $3\times10^{-8}$ can be achieved, an improvement of the current search sensitivity limit by an order of magnitude.
