Lepton-flavor violation via right-handed neutrino Yukawa couplings in the supersymmetric standard model

Abstract

Various lepton-flavor violating (LFV) processes in the supersymmetric standard model with right-handed neutrino supermultiplets are investigated in detail. It is shown that large LFV rates are obtained when tan β is large. In the case where the mixing matrix in the lepton sector has a similar structure as the KobayashiMaskawa matrix and the third-generation Yukawa coupling is as large as that of the top quark, the branching ratios can be as large as Br(µ → eγ) ≃ 10 −11 and Br(τ → µγ) ≃ 10 −7 , which are within the reach of future experiments. If we assume a large mixing angle solution to the atmospheric neutrino problem, rate for the process τ → µγ becomes larger. We also discuss the difference between our case and the case of the minimal SU (5) grand unified theory.

Right-handed sector leptogenesis

“…[34]). With M δ below TeV, a branching ratio of the order of the experimental limit (Br(µ → eγ) < 1.2 · 10 −11 at 90% C.L.…”

Model-independent analysis of lepton flavour violating τ decays

“…In the above list we have only shown operators that have treelevel contributions to leptonic τ -decays; more operators, which are bi-linear in the lepton fields and contribute at the loop level, can be found e.g. in [8,10,18]. We also neglected dim=8 operators involving additional covariant derivatives.…”

“…1 At the electro-weak scale these lepton-flavour-violating interactions manifest themselves in higher dimensional operators which have to be compatible with the SU(2) L × U(1) Y gauge symmetry of the SM. The leading operators for processes involving charged leptons will be of dim=6 and dim=8, which we shall construct in the following (similar analyses within the context of supersymmetric extensions of the SM can be found, for instance, in [8,10]). …”

“…There are many models which predict LFV τ decays of the form τ → ℓℓ ′ ℓ ′′ with ℓ, ℓ ′ , ℓ ′′ = e, µ [6][7][8][9][10][11][12][13][14][15][16][17]. All these models will eventually match onto a set of local four-fermion operators or radiative operators, the latter mediating τ → ℓγ * with subsequent decay of the (virtual) photon into a charged lepton pair.…”

Search for R-parity Violation from J-PARC and LHC

“…It is realized by the fact that the scalar partner of charged leptons have a different flavor basis from that of charged leptons. In addition, R-parity is often imposed on this class of the theory [12,13]. With it, µ → eγ process has the largest branching ratio among the three cLFV processes.…”