Related papers: Standard Model predictions for weak decays of $\et…

Rare meson decay experiments promise to measure branching ratios as small as $10^{-13}$. This presents an opportunity to discover the $\mu^+\mu^-$ bound state true muonium. We consider a set of possible channels, all with branching ratios…

Nowadays the field of searching for a new physics became a very interesting subject in a light meson decays due to a recent results from KTeV collaboration which found the 3.3\sigma\ disagreement between Standard Model theory and their…

We review the status of the Standard Model theory of neutron beta decay. Particular emphasis is put on the recent developments in the electroweak radiative corrections. Given that some existing approaches give slightly different results, we…

In the framework of the Standard Model (SM) a theoretical description of the neutron beta decay is given at the level of 10^{-5}. The neutron lifetime and correlation coefficients of the neutron beta decay for a polarized neutron, a…

The branching ratio of the electromagnetic rare decays $\eta\to\pi^0\gamma\gamma$ and $\eta^\prime\to (\pi^0,\eta)\gamma\gamma$ are analysed in terms of scalar and vector meson exchange contributions using the frameworks of the Linear Sigma…

In a sample of 19 million produced B mesons we have observed decays B -> eta K*, and improved our previous measurements of B -> eta' K. The branching fractions we measure for these decay modes are B(B+ -> eta K*+) = (27.3 +9.6 -8.2 (stat)…

We improve the current predictions of the standard model for neutron beta decay observables and compare them with the currently available ones. Next we study their implications in the possible detection of new physics. We discuss where the…

In this work, we calculate the branching ratios for the $\eta(\eta')\rightarrow\bar{\ell}\ell$ decays, where $\ell = e,\mu$. These processes have tiny rates in the standard model due to spin flip, loop, and electromagnetic suppression, for…

The three-body decay $B^0(B_s)\to \gamma\nu \bar{\nu}$ can occur via penguin and box diagrams in the standard model (SM). These channels are useful to determine the decay constants $f_B$ ($f_{B_s}$) and $B$ ($B_s$) meson wave function.…

The WASA-at-COSY experiment has collected $3\times10^{7}$ events with $\eta$-mesons produced via the reaction $pd\rightarrow{^{3}\textrm{He}}\eta$ at $\textrm{T} = 1.0 \textrm{GeV}$. Using this data set, we evaluate the branching ratios of…

The simplest little Higgs model predicts a light pseudoscalar boson $\eta$ and opens up some new decay modes for $Z$-boson, such as $Z \to \bar{f} f \eta$, $Z\to \eta\eta\eta$, $Z\to \eta\gamma$ and $Z\to \eta gg$. We examine these decay…

The rare decays $B_{s(d)} \to \mu^+\mu^-$ play a key role for the testing of the Standard Model. An overview of the most recent theoretical predictions of the corresponding branching ratios is given, emphasizing that the sizable decay width…

We have searched for the rare decay of the eta meson $\eta \to e^{+}e^{-}$ using the CLEO II detector. The $\eta$'s were produced in $e^{+}e^{-}$ collisions with 10 GeV center-of-mass energy at the Cornell Electron Storage Ring (CESR). We…

We study the rare decays of $B_{s} \to M_s\ell \bar{\ell}$ ($M_s=\eta, \eta',\phi$ and $\ell=\nu,e,\mu,\tau$) in the standard model. With the hadronic form factors evaluated in the light front and constituent quark models, we estimate the…

In a sample of 19 million produced B mesons, we have observed the decays B -> eta K* and improved our previous measurements of B -> eta'K. The branching fractions we measure for these decay modes are BR(B+ -> eta K*+) = (26.4 +9.6-8.2 +-…

Decays of both $\eta$ and $\eta^\prime$ provide very useful information in our understanding of low-energy QCD, and experimental signatures for these decays would be extremely helpful at BES-III. The rare decays of the $\eta$ and…

For purely leptonic decays of pseudoscalar mesons, the decay rates are related to the product of the relevant weak interaction-based CKM matrix element of the constituent quarks on the one hand, and the strong interaction parameter, the…

A method for the general analysis of the sensitivities of neutron beta-decay experiments to manifestations of possible deviations from the Standard model is proposed. In a consistent fashion, we take into account all known (radiative and…

Some semileptonic weak decays of vector mesons are considered in the framework of the most popular quark models. The predicted branching ratios are unfortunately too small to make a study of these decays realistic at meson factories under…

A search for rare lepton decays of the eta meson was performed using the WASA detector at CELSIUS. Two candidates for double Dalitz decay eta->e+e-e+e- events are reported with a background of 1.3+/-0.2 events. This allows to set an upper…