Related papers: Standard Model and New Physics contributions to $K…
The decay $K_L \to \gamma \nu \bar{\nu}$ is analyzed within the standard model. Short-distance contributions are found to dominate, yielding a branching ratio of $\sim 0.7 \times 10^{-11}$. We examine the possibility that non-standard model…
We analyze $K_L$ lepton pair decays of $K_L \to l^+\l^-\gamma$ and $K_L \to l^+l^-l'^+l'^-$ $(l, l'=e, \mu)$ within the framework of the light-front QCD approach (LFQA). With the $K_L \to \gamma^* \gamma^*$ form factors evaluated in a model…
The rare four-fold decay $B_s \to K^*(\to K\pi)\mu^+\mu^- $, governed by the flavor-changing neutral current transition $b \to d\mu^+\mu^-$, provides a sensitive probe for testing the Standard Model (SM) and investigating signatures of new…
We present a model-independent analysis of rare B decays, $B \to K^{(*)} \nu \nu$. The effect of possible new physics is written in terms of dimension-6 four-fermi interactions. The lepton number violating scalar- and tensor-type…
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…
We analyze the New Physics sensitivity of a recently proposed method to measure the CP-violating ${\cal B}(K_S\to\mu^+\mu^-)_{\ell=0}$ decay rate using $K_S - K_L$ interference. We present our findings both in a model-independent EFT…
Tests of lepton-universality as rate ratios in $b\to s \ell\ell$ transitions can be predicted very accurately in the Standard Model. The deficits with respect to expectations reported by the LHCb experiment in muon-to-electron ratios of the…
We discuss the amplitude of the $B\to l^+l^-l'\nu'$ decays and the differential decay rate $d^2\Gamma/dq^2dq'^2$, $q$ the momentum of the $l^+l^-$ pair emitted from the electromagnetic vertex and $q'$ the momentum of the $l'\nu'$ pair…
It is generally believed that the decay mode $B\to K^*\ell^+\ell^-$ is one of the best modes to search for physics beyond the standard model. The angular distribution enables the independent measurement of several observables as a function…
Recent measurements of the lepton flavor universality ratios $R^{\mu e}_{K}$ and $R^{\mu e}_{K^*}$ in $B\to \left(K, K^*\right)\mu^{+}\mu^{-}\left(e^+e^-\right)$ at LHCb align with the Standard Model predictions, necessitating search for…
We model-independently analyze the angular distributions of B -> K ll decays, l = e, mu, for low dilepton mass using QCD factorization. Besides the decay rate, we study the forward-backward asymmetry A_FB^l and a further observable, F_H^l,…
We study the $L\to l l' l' \nu_l \nu_L$ decays ($L=\tau,\mu$; $l,l'=\mu,e$) in the Standard Model (SM) and in the effective field theory (EFT) description of the weak charged current at low energy, both for polarized and unpolarized $L$,…
In this work we study the implication of the fourth generation standard model (SM4) to the single and double lepton polarization asymmetries in the $B\rightarrow K^{\ast}\ell^{+}\ell^{-}$, $(l=\mu,\tau)$ decay. To see the variation in the…
Many models for physics beyond the Standard Model predict lepton-flavour violating decays of charged leptons at a level which may become observable very soon. We investigate the decays of a Tau-lepton into three charged leptons (Tau ->…
The most recent measurements of the observables $R_{D^{(*)}}$ are in tension with the Standard Model offering hints of New Physics in $b\rightarrow c \ell \bar{\nu}_{\ell}$ transitions. Motivated by these results, in this work we present an…
Recently, the LHCb Collaboration provided updated measurements for the lepton flavour ratios $R_K$ and $R_{K^*}$. The currently observed values align with the predictions of the standard model. In light of these recent updates, our…
The $B\to K^*\mu\mu$ decay exhibits deviations with respect to Standard Model expectations and the measurement of the ratio $R_K$ hints at a violation of lepton-flavour universality in $B\to K\ell\ell$ transitions. Both effects can be…
We present an analysis of the rare exclusive $B$ decays $B\to K\nu\bar\nu$ and $B\to K^{*}\nu\bar\nu$ within the Standard Model (SM), in a model-independent manner, and in a number of new physics (NP) models. Combining new form factor…
We present first theoretical predictions for various observables related to the $\bar B_d \to \mu^+ \mu^- e^+ e^-$ decay within the framework of the Standard Model. Our study encompasses the branching ratios, differential distributions, and…
A complete experiment on decay $K_L \to l^+ l^-$ will not only consist of measurement of the decay rates but also lepton polarization etc. These additional observations will yield tests of CP invariance in these decays. In $K_L$ and $K_S$…