Lepton flavor violation inτdecays

Abstract

We study the lepton flavor violation (LFV) in tau decays in the framework of the supersymmetric seesaw mechanism with nonholomorphic terms for the lepton sector at a large tan. In particular, we analyze two new decay modes ! 'f 0 980 and ! 'K K ÿ arising from the scalar boson exchanges contrast to ! ' 0 from the pseudoscalar ones. We find that the decay branching ratios of the two new modes could be not only as large as the current upper limits of O10 ÿ7 , but also larger than those of ! ' 0 . Experimental searches for the two modes are important for the LFV induced by the scalarmediated mechanism. In addition, we show that the decay branching ratios of ! ' ÿ are related to those of ! ' and ! 'f 0 980. In the standard model (SM), since the neutrinos are regarded as massless particles, the processes associated with lepton flavors are always conserved. Inspired by the discoveries of nonzero neutrino masses [1,2], it has been studied enormously how to generate the neutrino masses which are less than a few eV. By supplementing with singlet right-handed Majorana neutrinos with masses M R required to be around the scale of unified theory, it is found that the seesaw mechanism is one of the natural ways [3] to obtain the small neutrino masses. Accordingly, in non-SUSY models, it is easy to understand that the effects of the lepton flavor violation (LFV) are suppressed by 1=M R . However, in models with SUSY, due to the nondiagonal neutrino mass matrix, the flavor conservation in the slepton sector at the unified scale will be violated at the M R scale via renormalization [4 -6]. The flavor violating effects could propagate to the electroweak scale so that instead of 1=M R , the suppression of the LFV could be 1=M SUSY with M SUSY

Sensitivity to the Higgs sector of supersymmetric-seesaw models in the lepton flavor violatingτ→μf0(980)decay

“…f 0 ð980ÞÞ improves the estimate of [18] in several aspects. First, we demand compatibility with present data on light neutrino masses and mixings.…”

“…[9,13,21] and ! f 0 ð980Þ [18] over the ! channel is their potential sensitivity to the Higgs sector.…”

Model-independent analysis of lepton flavour violating τ decays

“…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.…”

Recent Progress in Tau Lepton Physics

“…However, there are many new physics scenarios that predict LFV could occur at the O(10 −8 ) level [17][18][19][20][21][22][23][24]. Any observation of LFV would be a clear signature of new physics.…”