Lepton flavor violation without supersymmetry

Abstract

We study the lepton flavor-violating (LFV) processes µ-->egamma, µ-->3e, and µ-->e conversion in nuclei in the left-right symmetric model without supersymmetry and perform the first complete computation of the LFV branching ratios B(µ-->f) to leading nontrivial order in the ratio of left- and right-handed symmetry-breaking scales. To this order, B(µ-->egamma) and B(µ-->e) are governed by the same combination of LFV violating couplings, and their ratio is naturally of order unity. We also find B(µ-->3e)/B(µ-->e)~100 under slightly stronger assumptions. Existing limits on the branching ratios already substantially constrain mass splittings and/or mixings in the heavy neutrino sector. When combined with future collider studies and precision electroweak measurements, improved limits on LFV processes will test the viability of low-scale, nonsupersymmetric LFV scenarios.

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