Improved limit on the branching ratio of μ−→ e+ conversion on titanium

Abstract

The SINDRUM II spectrometer at PSI is used in searches for μ→ e conversion in muonic atoms. Here we report on a search for the charge-changing μ −→ e + conversion on titanium. The measurements yielded the new upper limits Γ( μ −Ti → e +Ca GS )/ Γ( μ −Ti capture)<1.7×10 −12 (90% CL) for the ground state transition and Γ( μ −Ti → e +Ca GDR )/ Γ( μ −Ti capture)<3.6×10 −11 (90% CL) for a giant dipole resonance excitation with both a mean energy and a width of 20 MeV. These results improve on our previous best limits by a factor of 2.5.