D ec 2 00 1 USM - TH - 120 The ( μ − , μ + ) conversion in nuclei as a probe of new physics

A detailed study of the muonic analogue of neutrinoless double beta decay, (μ, μ+) conversion, has been carried out for the A=44 nuclear system. We studied several lepton number violating (LNV) mechanisms potentially triggering this process: exchange by light and heavy Majorana neutrinos as well as exchange by supersymmetric particles participating in R-parity violating interactions. The nuclear structure has been taken into account within the renormalized Quasiparticle Random Phase Approximation method. To our knowledge, this is the first realistic treatment of nuclear structure aspects of the (μ, μ+) conversion. We estimated the rate of this process utilizing the existing experimental constraints on the parameters of the underlying LNV On leave of absence from Department of Nuclear Physics, Comenius University, Mlynská dolina F1, SK–842 15 Bratislava, Slovakia On leave of absence from Join Institut for Nuclear Research, Dubna, Russia 1 interactions and conclude that the (μ, μ+) conversion is hardly detectable in the near future experiments.