Related papers: Magneto-$\nu$: Heavy neutral lepton search using $…

We present an improved search for neutrinoless double-beta ($0\nu\beta\beta$) decay of $^{136}$Xe in the KamLAND-Zen experiment. Owing to purification of the xenon-loaded liquid scintillator, we achieved a significant reduction of the…

Background of germanium and xenon detectors due to the elastic scattering of $^{8}B$ solar neutrinos on electrons have been calculated. The background is 4.6 \times $10^{-4}$ counts/(keV$\cdot t\cdot$y) that defines the sensitivity of…

Heavy nearly-sterile neutrinos are a common ingredient in extensions of the Standard Model which aim to explain neutrino masses, like for instance in Type I seesaw models, or one of its variants. If the scale of the new Heavy Neutral…

The bounds on parameters of the eV and higher scale sterile neutrinos from the $0\nu \beta \beta$ decay have been refined and updated. We present a simple and compact analytic expression for the bound in the $\Delta m^2_{41} - \sin^2…

Using a three neutrino framework we investigate bounds for the effective Majorana neutrino mass matrix. The mass measured in neutrinoless double beta decay is its (11) element. Lepton-number and -flavor violating processes sensitive to each…

The search for neutrinoless double beta decay has internationally been recognized as the most promising approach to determine the Majorana nature of neutrinos. This hypothesized decay would, if observed, violate lepton number in weak…

We search for the lepton flavor-violating "tau -> mu gamma" decay using 29.7 million tau pairs accumulated by the Belle experiment. The main background sources are found to be tau pairs with "tau -> mu nu nu" decay and radiative dimuon…

Composite-fermion models predict excited quarks and leptons with mass scales which can potentially be observed at high-energy colliders like the LHC; the most recent exclusion limits from the CMS and ATLAS Collaborations corner…

We present a search for lepton-flavor-violating tau decays into three leptons (electrons or muons) using 782 fb^-1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. No evidence for these decays is…

We investigate the possibility of producing neutrinoless double beta decay without having an electron neutrino with a mass in the vicinity of 1 eV. We do so by having a much lighter electron neutrino mix with a much heavier (m > 1 GeV)…

The NEMO 3 experiment searches for neutrinoless double beta decay and makes precision measurements of two-neutrino double beta decay in seven isotopes. The latest two-neutrino half-life results are presented, together with the limits on…

The observation of neutrinoless double-beta decay (0${\nu}{\beta}{\beta}$) would show that lepton number is violated, reveal that neutrinos are Majorana particles, and provide information on neutrino mass. A discovery-capable experiment…

$\Delta L =2$ lepton number violation (LNV) at the TeV scale could provide an alternative interpretation of positive signal(s) in future neutrinoless double beta $(0\nu\beta\beta)$ decay experiments. An interesting class of models from this…

We present a framework to combine data from the latest neutrinoless double-beta decay experiments for multiple isotopes and derive a limit on the effective neutrino mass using the experimental energy distributions. The combined limits on…

We analyze the sensitivity of next-generation tonne-scale neutrinoless double $\beta$-decay ($0\nu\beta\beta$) experiments and searches for same-sign di-electrons plus jets at the Large Hadron Collider to TeV scale lepton number violating…

A search for lepton flavour violating decays of a neutral non-standard-model Higgs boson in the $\mu\tau$ and e$\tau$ decay modes is presented. The search is based on proton-proton collisions at a center of mass energy $\sqrt{s} =$ 13 TeV…

Displaced vertex (DV) signatures at colliders offer a powerful probe of new long-lived particles beyond the Standard Model. Among the best-motivated candidates are heavy neutral leptons (HNLs) - heavier counterparts of Standard Model…

Experimental searches for lepton-flavor-violating coherent muon-to-electron conversion in the field of a nucleus, have been proposed to reach the unprecedented sensitivity of 10^(-16) - 10^(-18) per stopped muon. At that level, they probe…

A search is performed for lepton-number-violating $B^-\to D^{(*)+}\mu^-\mu^-$ decays, using data collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of…

We argue that the COMET experiment --- a dedicated experiment for the $\mu$-$e$ conversion search --- can be a powerful facility to search for heavy neutrinos in the mass range $1\,{\rm MeV} \lesssim M \lesssim 100\,{\rm MeV}$. The stopped…