Related papers: Evading the Grossman-Nir bound with $\Delta I=3/2$…
Photonic events with large missing energy have been observed in e+e- collisions at a centre-of-mass energy of 189GeV using the OPAL detector at LEP. Results are presented for event topologies consistent with a single photon or with an…
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…
Hyperon nonleptonic decays that change strangeness by two units, such as $\Xi\to N\pi$ and $\Omega^-\to nK^-,\Lambda\pi^-,\Sigma^{(*)}\pi$, are highly suppressed in the standard model. Only a few of them have been searched for to date,…
We stress the importance of precise measurements of rare decays $K^+\rightarrow\pi^+\nu\bar\nu$, $K_L\rightarrow\pi^0\nu\bar\nu$, $K_{L,S}\to\mu^+\mu^-$ and $K_{L,S}\to\pi^0\ell^+\ell^-$ for the search of new physics (NP). This includes…
The recent Belle II observation of $B \to K E_{\rm miss}$ challenges theoretical interpretations in terms of Standard Model neutrino final states. Instead, we consider new physics scenarios where up to two new light-invisible particles of…
The excellent experimental prospects to measure the invisible mass spectrum of the $K^+\to\pi^+\nu\bar\nu$ decay opens a new path to test generalised quark--neutrino interactions with flavour changing $s\to d$ transitions and as such to…
In this report we discuss the main theories to understand the origin of baryon and lepton number violation in physics beyond the Standard Model. We present the theoretical predictions for rare processes such as neutrinoless double beta…
The Faddeev AGS equations are solved for coupled-channels $\bar{K}NN-\pi\Sigma{N}$ system with quantum numbers $I=1/2$ and $S=0$. Using separable potentials for $\bar{K}N-\pi\Sigma$ interaction, we have calculated the transition probability…
Using the four-body Alt-Grassberger-Sandhas (AGS) equations for the \( K^{-}ppn \) system, we investigate the possible formation of a \( K^{-}pp \) quasi-bound state through the low-energy \( K^{-} + {}^{3}\mathrm{He} \) reaction. The…
Recently the Belle II Collaboration has reported a measurement of the $B^+\to K^+\nu\bar\nu$ rate that is higher than the standard-model expectation. Since the emitted neutrinos are unobserved, the excess could be due to the $B^+$ decaying…
We study an effective theory beyond the standard model (SM) where either of two additional gauge singlets, a Majorana fermion and a real scalar, constitutes all or some fraction of dark matter. In particular, we focus on the masses of the…
Rare kaon decays offer a powerful tool for investigating new physics in $s\to d$ transitions. Currently, many of the interesting decay modes are either measured with rather large uncertainties compared to their theoretical predictions or…
We analyse the present experimental evidence for a complex CKM matrix, even allowing for New Physics contributions to $\epsilon_{K}$, $a_{J/\Psi K_{S}}$%, $\Delta M_{B_{d}}$, $\Delta M_{B_{s}}$, and the $\Delta I=1/2$ piece of $% B\to \rho…
We discuss the consequences of the approximate conservation of the vector and axial currents for the hadronic matrix elements appearing in beta decay if non-standard interactions are present. In particular the isovector (pseudo)scalar…
We present a model independent analysis of new-physics contributions to the decays K^+ \to \pi^+ \nu \bar \nu and K_L \to \pi^0 \nu \bar \nu. We parameterize the effects of new physics in these decays by two parameters: r_K and \theta_K,…
Dedicated underground experiments searching for dark matter have little sensitivity to GeV and sub-GeV masses of dark matter particles. We show that the decay of B mesons to K(K^*) and missing energy in the final state can be an efficient…
Photonic events with large missing energy have been observed in e+e- collisions at centre-of-mass energies of 130, 136 and 183 GeV collected in 1997 using the OPAL detector at LEP. Results are presented for event topologies with a single…
We investigate the possibility of disentangling different new physics contributions to the rare meson decays $K\rightarrow\pi+\displaystyle{\not}E$ and $B\rightarrow K(K^*)+\displaystyle{\not}E$ through kinematic distributions in the…
Low energy $\pi^+$ emission in hypernuclear weak decays is studied in the soft pion limit. It is found that the $\pi^+$ decay amplitude is dominated by the $\Delta I=3/2$ part of nonmesonic weak decays according to the soft pion theorem.…
It has been commonly assumed that pseudoscalar contributions to the leptonic decay of charged mesons, like pions and kaons, is strongly constrained due to the helicity suppression present in the ratio $R_{l/l'} = \Gamma(P \rightarrow…