Related papers: An Improved upper limit on the decay K^+ -> pi^+ m…
The lepton number violating process can be induced by introducing a fourth generation heavy Majorana neutrino, which is coupled to the charged leptons of Standard Model. There have been many previous studies on the leptonic number violating…
A search for the $K^{+} \to \pi^{0}\pi^{0}\pi^{0}e^+\nu$ decay is performed by the OKA collaboration. The search is based on $3.65 \times 10^9 ~ K^+$ decays. No signal is observed. The upper limit set is $BR(K^{+} \to…
We have performed a search for the angular-momentum forbidden decay K+ -> pi+ gamma with the E787 detector at BNL. No events were observed in the pi+ kinematic region around 227 MeV/c. An upper limit on the branching ratio for the decay is…
The KTeV experiment at Fermilab has isolated a total of 132 events from the rare decay KL->e+e-mu+mu-, with an estimated background of 0.8 events. The branching ratio of this mode is determined to be 2.69 +/- 0.24 (stat) +/- 0.12 (syst) x…
Using a sample of 5.8X10E7 J/$\psi$ events, the Beijing Spectrometer experiment has searched for the decay J/$\psi \to e\mu$. Four candidates, consistent with the estimated background, are observed, and an upper limit on the branching…
The lepton family number violation $Z$ boson decay, $Z \to e^-e^-\mu^+\mu^+$ or $e^+e^+\mu^-\mu^-$, mediated by a dilepton, e.g. from an SU(15) theory, is calculated. The branching ratio of such exotic decay for allowed dilepton masses is…
Based on a sample of $ (10.087\pm 0.044)\times 10^{9} J/\psi$ events collected by the BESIII detector at the BEPCII collider, we perform the first search for the lepton number violating decay $\eta \to \pi^+\pi^+ e^-e^- + \text{c.c.}$ No…
We search for lepton flavor and lepton number violating tau decays into a lepton (ell = electron or muon) and two charged mesons (h,h' = pi^\pm or K^\pm), tau- -> ell-h+h'- and tau- -> ell+h-h'-, using 671 fb^{-1} of data collected with the…
A search for the decay mu -> e gamma, performed at PSI and based on data from the initial three months of operation of the MEG experiment, yields an upper limit on the branching ratio of BR(mu -> e gamma) < 2.8 x 10**-11 (90% C.L.). This…
We present a search for the lepton number violating decay $\Xi^-\rightarrow\Sigma^+e^-e^- +c.c.$ with $(10087\pm44)\times10^6$ $J/\psi$ events collected by the BESIII detector at the BEPCII collider. Employing a blind analysis strategy, no…
Preliminary values for the K+ -> pi+ mu+ mu- branching ratio and form factor are reported, based on 400 events, a factor of 2 more in total events and 100 times the present world sample of fully reconstructed events. The results are…
In the framework of the minimal ${SU}(3)_C\otimes {SU}(3)_L \otimes {U}(1)_N$ model, the lepton-flavour-violating decay $\pi^+ \ra \mu^- \nu_\mu e^+ e^+ $ is calculated without directly invoking lepton mixing. The branching ratio for this…
We have searched for the tau lepton flavor violating decays tau- -> l-K0s (l = e or mu), using a data sample of 281 fb^-1 collected with the Belle detector at the KEKB e+e- asymmetric-energy collider. No evidence for a signal was found in…
We have performed a search for the lepton-flavor-violating decay tau -> mu gamma using a data sample of 86.3fb^{-1} accumulated by the Belle detector at KEK. No evidence for a signal is seen, and we set an upper limit for the branching…
We have searched for decays of the tau lepton into seven or more charged particles, using data collected with the OPAL detector from 1990 to 1995 in e^+e^- collisions at sqrt(s) ~ M_Z. No candidate events were found and an upper limit on…
We report on a search for eleven lepton-number violating processes B+ -> X- l+ l'+ with X- = K-, pi-, rho-, K*- or D- and l+/l'+ = e+ or mu+, using a sample of 471+/-3 million BBbar events collected with the BaBar detector at the PEP-II…
Experiment 865 at the Brookhaven AGS obtained 410 K+ -> e+ nu e+e- and 2679 K+ -> mu+ nu e+e- events including 10% and 19% background. The branching ratios were measured to be (2.48+-0.14(stat.)+-0.14(syst.))x10^-8 (m_ee>150 MeV) and…
The NA48/2 experiment at CERN collected a large sample of charged kaon decays into final states with multiple charged particles in 2003--2004. A new upper limit on the rate of the lepton number violating decay $K^{\pm} \to \pi^{\mp}…
The NA48/2 experiment at CERN collected a large sample of charged kaon decays to final states with multiple charged particles in 2003--2004. A new upper limit on the rate of the lepton number violating decay…
A search for the lepton-flavour violating decays $B^+ \to K^+ {\mu}^{\pm} e^{\mp}$ is performed using a sample of proton-proton collision data, collected with the LHCb experiment at centre-of-mass energies of $7$ and $8~{\rm TeV}$ and…