Related papers: Magneto-$\nu$: Heavy neutral lepton search using $…
A search for narrow resonances decaying to an electron and a muon is presented. The e-mu mass spectrum is also investigated for non-resonant contributions from the production of quantum black holes (QBHs). The analysis is performed using…
The CUORE experiment, a ton-scale cryogenic bolometer array, recently began operation at the Laboratori Nazionali del Gran Sasso in Italy. The array represents a significant advancement in this technology, and in this work we apply it for…
We study the impact of light GeV-scale heavy neutral leptons (HNLs) on Big Bang nucleosynthesis (BBN) in the neutrino-extended Standard Model Effective Field Theory ($\nu$SMEFT). We show that, based on very general considerations, BBN…
We have searched for the leptonic and radiative leptonic B decays, B^+ -> mu^+ nu, B^+ -> e^+ nu gamma and B^+ -> mu^+ nu gamma. Using a 140 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric e^+ e^- collider, we…
We have searched for neutrinoless $\tau$ lepton decays into $\ell$ and $V^0$, where $\ell$ stands for an electron or muon, and $V^0$ for a vector meson ($\phi$, $\omega$, $K^{*0}$ or $\bar{K}^{*0}$), using 543 fb$^{-1}$ of data collected…
We review and revise phenomenology of the GeV-scale heavy neutral leptons (HNLs). We extend the previous analyses by including more channels of HNLs production and decay and provide with more refined treatment, including QCD corrections for…
In modern experiments on flavour physics it is possible to search for the decays of $B$ or $D$ mesons or $\tau$ leptons into final states with heavy neutrinos $N$ (a.k.a. heavy neutral leptons). I present a common study of theorists and…
Neutrinoless double beta decay ($0\nu\beta\beta$) is a yet unobserved nuclear process which would demonstrate Lepton Number violation, a clear evidence of beyond Standard Model physics. The process two neutrino double beta decay…
The precise reconstruction of the mass peak of long-lived heavy neutral leptons (HNLs) helps to improve the sensitivity for sterile neutrino searches in both fixed-target and collider environments (e.g., SHiP and the LHC). We present an…
Heavy neutral leptons (HNLs), depending on their mass and mixing, can be efficiently produced in meson decays from the target or absorber in short- to medium-baseline accelerator neutrino experiments, leaving detectable signals through…
The NEXT-100 detector will search for the neutrinoless double beta decay of $^{136}$Xe using an electroluminescent high-pressure xenon gas TPC filled with 100 kg of enriched Xe. An observation of this hypothetical process would establish a…
In some models beyond the Standard Model where lepton number violation by two units is forbidden (implying neutrinos cannot be Majorana fermions), violation by four units can still occur, allowing neutrinoless quadruple beta decay. The…
We propose new searches that exploit the unique signatures of decaying sterile neutrinos with masses below $M_W$ at the LHC, where they can be produced in rare decays of Standard Model gauge bosons. We show that for few-GeV-scale sterile…
We explore signals of lepton-number-violation in the charm physics sector. We study the four-body $|\Delta L|= 2$ decays of the $D^0$ meson, $D^0 \to P^- \pi^-\mu^+ \mu^+$ ($P = \pi, K$) as an alternative evidence of the Majorana nature of…
This Letter presents a search for a heavy neutral particle decaying into an opposite-sign different-flavor dilepton pair, $e^\pm \mu^\mp$, $e^\pm \tau^\mp$, or $\mu^\pm \tau^\mp$ using 20.3 fb$^{-1}$ of $pp$ collision data at $\sqrt{s} = 8$…
In the past few decades, numerous searches have been made for the neutrinoless double-beta decay (0$\nu\beta\beta$) process, aiming to establish whether neutrinos are their own antiparticles (Majorana neutrinos), but no 0$\nu\beta\beta$…
The analysis of a combined data set, totaling 3.6 \times 10^14 stopped muons on target, in the search for the lepton flavour violating decay mu^+ -> e^+ gamma is presented. The data collected by the MEG experiment at the Paul Scherrer…
A search for excited neutrinos is performed using the full $e^{-}p$ data sample collected by the H1 experiment at HERA at a centre-of-mass energy of 319 GeV, corresponding to a total luminosity of 184 pb$^{-1}$.The electroweak decays of…
The multi-ton-scale liquid xenon detectors, with an excellent energy resolution of a few keV, will be constructed to probe the dark-matter particles. In this paper, we show that precision measurements of the low-energy solar neutrinos via…
The NA62 experiment at CERN reports searches for $K^+\to\mu^+N$ and $K^+\to\mu^+\nu X$ decays, where $N$ and $X$ are massive invisible particles, using the 2016-2018 data set. The $N$ particle is assumed to be a heavy neutral lepton, and…