Lepton-number-violating four-body tau lepton decays

Abstract

We study the four-body AE ! l AE l AE X Ç decays where l ¼ e or and X ¼ , K, , and K Ã mesons. These decay processes violate the total lepton number (jÁLj ¼ 2) and can be induced by the exchange of Majorana neutrinos. We consider a scenario where these decays are dominated by the exchange of only one heavy neutrino, which produces an enhancement of the decay amplitude via the resonant mechanism. Searches for these novel decay channels with branching fractions sensitivities of Oð10 À7 Þ can provide constraints on the parameter space of the Majorana neutrinos, which are stronger than the ones obtained from ÁL ¼ 2 decays of charged pseudoscalar mesons.

The Phenomenology of Right Handed Neutrinos

“…Sterile neutrinos may also be produced in the decay of tauons[154][155][156] 33. It has been suggested that, if MM is generated by spontaneous symmetry breaking below the electroweak scale, it may be possible to detect even lighter (keV) sterile neutrinos[166].…”

Study of $\tau^- \to\nu_{\tau} \pi^{-}\pi^{0}\ell^{+}\ell^{-}$ decays in the framework of Resonance Chiral Theory

“…Currently the branching ratios of these LFV decay modes have upper bounds of (10 −8 ) [7], while their SM predictions are unmeasurably small [8,9]. These decays (for ℓ = ) can also be misidentified as lepton number violating processes of the type − → − − + [10]. To avoid these decays polluting new physics searches, it will be most useful to include them in the Monte Carlo Generator TAUOLA [11].…”

Constraints on lepton number violating short-range interactions from |Δ L | = 2 processes

“…complementary test of the lepton number non-conservation [10]. Among all these possibilities, the low energy studies of rare processes in |∆L| = 2 decays of pseudoscalar mesons and τ -lepton have attracted a lot of attention [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], especially since these are accessible to different high-intensity frontier experiments. According to their final state topology, they can be classified as:…”

“…It is known that if the exchanged Majorana neutrino has a mass around ∼ 0.1 GeV to a few GeV, this might be produced on its mass shell and strongly enhance the |∆L| = 2 decays of pseudoscalar mesons and τ -lepton [22,[26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]. Although this GeV-scale sterile neutrino scenario is very interesting, it is worth exploring the possibility of other underlying short-range mechanism that could induce these LNV decays without involving Majorana neutrinos directly, just as it occurs in 0νββ decays.…”