Abstract
The lepton number violation (LNV) process can be induced by introducing a fourth generation heavy Majorana neutrino, which is coupled to the charged leptons of the Standard Model (SM). There have been many previous studies on the leptonic number violating decay processes with this mechanism. We follow the trend to study the process: D→Kllπ with the same-sign dilepton final states. We restrict ourselves to certain neutrino mass regions, in which the heavy neutrino could be on-shell and the dominant contribution to the branching fraction comes from the resonance enhanced effect. Applying the narrow width approximation (NWA), we found that the upper limit for the branching fractions for D0 → K−l+l+π− are generally at the order of 10−12 to 10−9, if we take the most stringent upper limit bound currently available in the literature for the mixing matrix elements. We also provide the constraints, which is competitive compared to the LNV B decays, on the mixing matrix element |VeN|2 based on the upper limit of D0 → K−e+e+π− estimated from the Monte-Carlo (MC) study at BESIII. Although the constraints are worse than the ones from (0νββ) decay in the literature, the future experiment at the charm factory may yield more stringent constraints.
Highlights
The discovery of neutrino oscillations [1,2,3] and observation of unexpected large θ13 [4] have convincingly shown that neutrinos have finite mass and that lepton flavor is violated in neutrino propagation
We restrict ourself to certain neutrino mass regions, in which the heavy neutrino could be on shell and the dominant contribution to the branching fraction comes from the resonance enhanced effect
We provide the constrains, which is competitive compared to the lepton number violation (LNV) B decays, on the mixing matrix element |VeN |2 based on the upper limit of D0 → K−e+e+π− estimated from Monte-Carlo study at BESIII
Summary
The discovery of neutrino oscillations [1,2,3] and observation of unexpected large θ13 [4] have convincingly shown that neutrinos have finite mass and that lepton flavor is violated in neutrino propagation. As we have mentioned above, the existence of Majorana mass term could induce the lepton number violation (LNV) by exchange of virtual Majorana neutrinos between two associated beta decays. The first double-beta decay was proposed as early as 1935 by Goepper-Mayer, it was until four years later Furry first calculated the (0νββ) decay based on the Majorana theory[25]. These early exploration gave an impetus to many years of experimental and theoretical research. Most of the studies of these LNV processes focus on the three-body and four-body ∆L = 2 decays of K, D and B mesons, as well as tau lepton decays.
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