Probing Mu E Gamma Gamma Contact Interactions With Mu -> E Conversion

Contact interactions of a muon, an electron and two photons can contribute to the decay mu -> e gamma gamma, but also to the conversion of a muon into an electron in the electric field of a nucleus. We calculate the mu -> e conversion rate, and show that for the coefficients of operators involving the combination FF proportional to vertical bar(E) over right arrow vertical bar(2) (as opposed to F (F) over tilde proportional to (E) over right arrow . (B) over right arrow), the current bound on mu -> e conversion is more sensitive than the bound on mu -> e gamma gamma