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In a scenario with two almost mass degenerate heavy sterile Majorana neutrinos with a mass $sim 1$ GeV, we present the semileptonic decay widths of heavy charged pseudoscalars such as $B$ mesons, either lepton-number-violating ($B^{pm} to mu^{pm} e^{pm} pi^{mp}$), or lepton-number-conserving ($B^{pm} to mu^{pm} e^{mp} pi^{pm}$), mediated by such on-shell neutrinos. It had been explained in the literature that such decays may be eventually detected, and that they can present even detectable CP violation effects. In this work we point out that, in addition, such decays may present detectable effects of heavy neutrino oscillation, allowing us to extract the oscillation length and thus the heavy neutrino mass difference $Delta M_N$, as well as a CP-violating Majorana phase.
Distinguishing the Dirac and Majorana nature of neutrinos remains one of the most important tasks in neutrino physics. By assuming that the $tau^- to pi^- mu^- e^+ u$ (or $bar{ u}$) decay is resonantly enhanced by the exchange of an intermediate mas
Heavy neutrinos were sought in pion decays $pi^+ rightarrow mu^+ u$ by examining the observed muon energy spectrum for extra peaks in addition to the expected peak for a massless neutrino. No evidence for heavy neutrinos was observed. Upper limits w
A discovery of the rare decay $B^{+} rightarrow pi^{+} mu^{+} mu^{-}$ is presented. This decay is observed for the first time, with 5.2 $sigma$ significance. The observation is made using $pp$ collision data, corresponding to an integrated luminosity
A high statistics data sample of the $K^{+}tomu^{+} u_{mu}$ decay was accumulated by the OKA experiment in 2012. The missing mass analysis was performed to search for the decay channel $K^{+}tomu^{+} u_{H}$ with a hypothetic stable heavy neutrino in
In recent times, several discrepancies at the level of $(2-3)sigma$ have been observed in the decay processes mediated by flavour changing neutral current (FCNC) transitions $b to s ell^+ ell^-$, which may be considered as the smoking-gun signal of N