Related papers: Constraining new interactions with leptonic tau de…
After the first observations of W bosons in leptonic interactions, about 4000 WW candidate events per experiment have been collected at LEP2. This data allows the measurement of the WW production cross section at different centre-of-mass…
Recent experimental results on exclusive semi-tauonic B meson decays, B -> D(*) tau nu, showing sizable deviations from the standard model prediction, suggest a new physics in which the structure of the relevant weak charged interaction may…
The evaluation, systematic analysis and numerical study of the semileptonic $\tau$-lepton decays with two mesons in the final state has been made in the frame of the standard model extended by right handed neutrinos. In the analysis,…
We explore a Z' boson with family-nonuniversal couplings to charged leptons. The general effect of Z-Z' mixing, of both kinetic and mass types, is included in the analysis. Adopting a model-independent approach, we perform a comprehensive…
We examine in detail the semi-leptonic decay $\Lambda_b \to \Lambda_c \tau{\bar \nu}_{\tau}$, which may confirm previous hints, from the analogous $B$ decay, of a new physics beyond the standard model. First of all, starting from rather…
We present the first measurement of the Michel parameters $\bar{\eta}$ and $\xi\kappa$ in the radiative leptonic decay of the $\tau$ lepton using 703 f$\mathrm{b}^{-1}$ of data collected with the Belle detector at the KEKB $e^+e^-$…
We discuss how four-lepton decays of the Z-boson probe currently unconstrained flat directions in the parameter space of the Standard Model Effective Field Theory (SMEFT). We derive the constraints from these decays on four-lepton operators…
We derive model-independent constraints on Higgs mass and couplings from associated signals for higher masses, accessible at LEP2. This work is motivated by the fact that, in many extensions of the standard model, the Higgs boson can have…
We speculate about the possible interpretations of the recently observed excess in the $h \to \tau \mu$ decay. We derive a robust lower bound on the Higgs boson coupling strength to a tau and a muon, even in presence of the most general new…
The Michel parameter xi" has been determined from a measurement of the longitudinal polarization of positrons emitted in the decay of polarized and depolarized muons. The result, xi" = 0.981 +- 0.045stat +- 0.003syst, is consistent with the…
We discuss the case of simultaneous mixing of gauge bosons and mixing of fermions in a model independent way and for a variety of extra-fermion representations. In this context we analyze a class of lepton family violating processes, namely…
We revisit a class of Z' explanations of the anomalies found by the LHCb collaboration in $B$ decays, and show that the scenario is tightly constrained by a combination of constraints: (i) LHC searches for di-muon resonances, (ii)…
We derive model-independent constraints on four-fermion contact interaction-type dynamics from the published preliminary LEP2 experimental data on e^+e^- annihilation into \mu^+\mu^- and \tau^+\tau^- pairs, measured at different energies…
We show that the $m_W$ measurement is a direct probe of New Physics (NP) contributing to lepton and missing transverse momentum ($\ell+MET$), independently from indirect tests via the electroweak fit. Such NP modifies the kinematic…
It has been recently proposed that neutrino mass could originate from Yukawa interactions of leptons with new colored particles. This raises the interesting possibility of testing mass generation through copious production of those…
There are many models beyond the standard model predicting the existence of non-universal gauge bosons $Z^{\prime}$, which can give rise to very rich phenomena. We calculate the contributions of the non-universal gauge bosons $Z^{\prime}$,…
We review the physics of purely leptonic decays of $\pi^\pm$, $K^\pm$, $D^{\pm}$, $D_s^\pm$, and $B^\pm$ pseudoscalar mesons. The measured decay rates are related to the product of the relevant weak-interaction-based CKM matrix element of…
The Belle Collaboration has recently measured the complete set of angular coefficient functions for the exclusive decays $\bar B \to D^* (D \pi) \ell \bar \nu_\ell$, with $\ell=e,\,\mu$, in four bins of the parameter…
We obtain new bounds on effective ALP-neutrino interactions from their loop-level impact on the ALP couplings to electroweak gauge bosons $\gamma Z$, $ZZ$ and $W^+W^-$. Both types of interactions are connected via the chiral anomaly, which…
Observing charge-parity (CP) or time-reversal (T) violations in the leptonic sector will give useful information to elucidate the nature of neutrinos. CP-violating couplings in charged leptonic currents carry out the weak phases necessary…