Related papers: Three Exceptions to the Grossman-Nir Bound
The ratio $\mathcal{B}(K_L\to\pi^0\nu\bar\nu)/\mathcal{B}(K^+\to\pi^+\nu\bar\nu)$ of the branching fractions of kaon decays $K_L\to\pi^0\nu\bar\nu$ and $K^+\to\pi^+\nu\bar\nu$ has a maximum of about 4.3 under the assumption that the…
Rare kaon decays with missing energy, $K\to\pi$+$E_{\rm miss}$, have received considerable attention because their rates can be calculated quite precisely within the standard model (SM), where the missing energy is carried away by an…
The Grossman-Nir bound concept is robust, but the common perception of $K_L \to \pi^0\nu\bar\nu < 1.4 \times 10^{-9}$ may be circumvented. Because of the blinding $K\pi2$(3) decay, $K^+$ decay experiments such as E787/E949 and the currently…
The KOTO experiment has reported an excess of $K_L\to\pi^0\nu\bar\nu$ events above the Standard Model prediction, in tension with the Grossman-Nir (GN) bound. The GN bound heavily constrains new physics interpretations of an excess in this…
We study constraints on new physics from the recent measurement of Br ($K^+ \to \pi^+ \nu \bar \nu)$ by the E787 and E949 Collaborations. In our analysis we consider two models of new physics: $(a)$ extra down type singlet quark model…
The KOTO experiment recently reported four candidate events in the signal region of $K_L\to \pi^0 \nu\bar\nu$ search, where the standard model only expects $0.10\pm 0.02$ events. If confirmed, this requires physics beyond the standard model…
We analyze rare kaon decays in models in which the dominant new effect is an enhanced $\bar s d Z$ vertex $Z_{ds}$. We point out that in spite of large theoretical uncertainties the CP-violating ratio $\epsilon^\prime/\epsilon$ provides at…
We study the branching ratios of rare K and B decays in models with minimal flavour violation, using the presently available information from the universal unitarity triangle analysis and from the measurements of Br(B -> X_s gamma), Br(B ->…
We present a general discussion of the unitarity triangle from $\epsilon_K$, $\Delta M_{d,s}$ and $K \to \pi\nu\overline{\nu}$ in models with minimal flavour violation (MFV), allowing for arbitrary signs of the generalized Inami--Lim…
We compute the contribution of the decays $K_L \rightarrow \pi^0 Q \bar Q$ and $K^+ \rightarrow \pi^+ Q \bar Q$, where $Q$ is a dark fermion of the dark sector, to the measured widths for the rare decays $K^+\rightarrow \pi^+ \nu \bar \nu$…
We study generic effects of new physics on the rare decay modes $K_L \to \pi^0 \nu \bar\nu$ and $K^+ \to \pi^+ \nu \bar\nu$. We discuss several cases: left-handed neutrino couplings; right handed neutrino couplings; neutrino lepton flavour…
We analyze rare kaon decays in models in which the dominant new effect is an enhanced sbar d Z vertex Z_{ds}. We point out that in spite of large theoretical uncertainties the CP-violating ratio epsilon'/epsilon provides at present the…
Recently, the KOTO experiment at J-PARC has observed three anomalous events in the flavor-changing rare decay $K_L \to \pi^0 \nu \bar\nu$, which indicates that the corresponding branching ratio is almost two orders of magnitude larger than…
We analyze the decay $K_L \to \pi^0 \nu \bar \nu$ in a model independent way. If lepton flavor is conserved the final state is (to a good approximation) purely CP even. In that case this decay mode goes mainly through CP violating…
We study the parity-violating pion-nucleon coupling $G_\pi$ in the framework of a realistic three flavor Skryme model. We find a sizeable enhancement of $G_\pi \simeq 0.8 ... 1.3 \cdot 10^{-7}$ compared to previous calculations in…
In this work, we explore a well motivated beyond the Standard Model scenario, namely, R-parity violating Supersymmetry, in the context of light neutrino masses and mixing. We assume that the R-parity is only broken by the lepton number…
Motivated by the new experimental information reported by the BNL--E787 Collaboration, we analyse the present impact and the future prospects opened by the measurement of $\br(K^+\to\pi^+\nu\bar\nu)$. Although still affected by a large…
The correlations between two qubits belonging to a three-qubit system can violate the Clauser-Horne-Shimony-Holt-Bell inequality beyond Cirel'son's bound [A. Cabello, Phys. Rev. Lett. 88, 060403 (2002)]. We experimentally demonstrate such a…
We have derived new upper limits on several products (two at a time) of lepton number violating $\lambda'$-type couplings from the consideration of $\Delta S = 2$ and $\Delta B = 2$ box graphs. Each box contains one scalar lepton and one…
A recent LHCb measurement of the ratio $R_{K^*}$ of $B\to K^*\mu\bar\mu$ to $B\to K^*e\bar e$ branching fractions has produced results in mild tension with the standard model (SM). This adds to the known anomalies also induced by the $b\to…