Related papers: $\Delta L \ge 4$ processes

The cross sections for the reaction $\gamma\gamma\rightarrow 4\ell$ in proton--proton collisions are calculated at the LHC energies. We show that the purely electroweak process $\gamma\gamma\rightarrow 4\ell$ can be studied at the LHC and…

We continue our endeavor to investigate lepton number violating (LNV) processes at low energy in the framework of effective field theory (EFT). In this work we study the LNV tau decays $\tau^+\rightarrow \ell^-P_i^{+}P_j^{+}$, where…

Neutron and nuclear beta decay correlation coefficients are linearly sensitive to the exotic scalar and tensor interactions that are not included in the Standard Model. The proposed experiment will measure simultaneously 11 neutron…

The first evidence of new strong interactions may be a sufficiently massive fourth family observed at the LHC. The fourth family masses, of the leptons in particular, are constrained by the electroweak precision data, and this leads to…

We investigate the lepton flavor violation decays of vector mesons in the scenario of the unparticle physics by considering the constraint from $\mu-e$ conversion. In unparticle physics, the predictions of LFV decays of vector mesons depend…

We present $\nu$DoBe, a Python tool for the computation of neutrinoless double beta decay ($0\nu\beta\beta$) rates in terms of lepton-number-violating operators in the Standard Model Effective Field Theory (SMEFT). The tool can be used for…

The conservation of lepton flavor is a prediction of the Standard Model and is still an excellent approximate symmetry despite our observation of neutrino oscillations. Lepton flavor violation by one or two units have been discussed for…

The LHC experiments have measured the branching fraction for $Z$ decays to four leptons (electrons or muons). We have combined these measurements with the result $\mathcal{B}(Z \to 4\ell) = (4.58 \pm 0.26) \times 10^{-6}$, allowing a…

Neutrinoless double-beta decay($0\nu\beta\beta$) decay is a hypothetical process that violates lepton number, and whose observation would unambiguously indicate that neutrinos are Majorana fermions. In the standard inverted-ordering…

The MEGA experiment, which searched for the muon- and electron-number violating decay \mu -> e + \gamma, is described. The spectrometer system, the calibrations, the data taking procedures, the data analysis, and the sensitivity of the…

Searches for rare processes such as mu --> e gamma put stringent limits on lepton flavour violation expected in many Beyond the Standard Model physics scenarios. This usually precludes the observation of flavour violation at high energy…

Neutrinoless double beta decay can significantly help to shed light on the issue of non-zero neutrino mass, as observation of this lepton number violating process would imply neutrinos are Majorana particles. However, the underlying…

"Ultra-low" Q value $\beta$ decays are referred to as such due to their low decay energies of less than $\sim$1 keV. Such a low energy decay is possible when the parent nucleus decays into an excited state in the daughter, with an energy…

The possible discovery of proton decay, neutron-antineutron oscillation, neutrinoless beta decay in low energy experiments, and exotic signals related to the violation of the baryon and lepton numbers at collider experiments will change our…

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…

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…

A sensitive search for the rare decays \Omega^- \to \Lambda \pi^- and \Xi^0 \to p \pi^- has been performed using data from the 1997 run of the HyperCP (Fermilab E871) experiment. Limits on other such processes do not exclude the possibility…

We derive the three-nucleon neutrinoless double beta decay potential in $\Delta$-full chiral effective field theory through next-to-next-to-next-to leading order in Weinberg's power counting. The matrix elements of the resulting operators…

In the upcoming LHC Run 2, at $\sqrt{s} \sim13$ TeV, it is suggested to seek unusually charged ($Q= -4/3$ and $+5/3$) quarks with mass $M_Q \sim 3$ TeV which carry lepton number ($L = +2$ and $-2$ respectively) and decay superweakly to a…

We study lepton-number-violating interactions at dimension seven in the Standard Model effective field theory that contribute to the meson decays $B \to K \nu \nu$ and $K \to \pi \nu \nu$. Such interactions could washout the baryon…