Related papers: Leptonic Operators for Cabbibo Angle Anomaly with …
We study the properties of Cabibbo-Kobayashi-Maskawa (CKM) favored semileptonic decays of mesons and baryons containing a heavy quark at the point of no recoil. We first use a diagrammatic analysis to rederive the result observed by earlier…
Semileptonic decays of charged and neutral $B$ mesons play a critical role in the determination of the magnitudes of the CKM-matrix elements $V_{cb}$ and $V_{ub}$, and in the test of the lepton universality which is a basic assumption of…
Very compelling deviations in the recently observed lepton nonuniversality observables $\big (R_{D^{(*)}}, R_{K^{(*)}}, R_{J/\psi} \big )$ of semileptonic $B$ meson decays from their Standard Model predictions hint towards the presence of…
Motivated by the prospects for an improved test of lepton universality in K -> l \nu decays by the NA62 experiment at CERN, we study predictions for the possible lepton non-universality in K -> l \nu decays in supersymmetric models.…
New physics effects in $B$ decays are routinely modeled through operators invariant under the strong and electromagnetic gauge symmetries. Assuming the scale for new physics is well above the electro-weak scale, we further require…
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…
We scrutinize the recently further strengthened hints for new physics in semileptonic $B$-meson decays, focusing on the 'clean' ratios of branching fractions $R_K$ and $R_{K^\ast}$ and examining to which pattern of new effects they point…
We consider scenarios with a heavy $Z^\prime$ gauge boson with flavour non-universal quark and lepton couplings with the goal to illustrate how the cancellation of gauge anomalies generated by the additional U(1)$^\prime$ gauge symmetry…
In recent times, several hints of lepton non-universality have been observed in semileptonic $B$ meson decays, both in the charged-current ($b \to c l \bar \nu_l$) and neutral-current ($b \to s ll $) transitions. Motivated by these…
We study the exclusive semileptonic $B$-meson decays $B\to K(\pi)\ell^+\ell^-$, $B\to K(\pi)\nu\bar\nu$, and $B\to\pi\tau\nu$, computing observables in the Standard model using the recent lattice-QCD results for the underlying form factors…
Recent LHCb results on $R_{K^*}$, the ratio of the branching fractions of $B \to K^* \mu^+ \mu^-$ to that of $B \to K^* e^+ e^-$, for the dilepton invariant mass bins $q^2 \equiv m_{\ell\ell}^2 = [0.045 - 1.1]$ GeV$^2$ and $[1.1 - 6]$…
There are two tensions related to the Cabibbo angle of the CKM matrix. First, the determinations of $V_{us}$ from $K_{\mu 2}$, $K_{\ell3}$, and $\tau$ decays disagree at the $3\sigma$ level. Second, using the average of these results in…
Physics from beyond the Standard Model, such as leptoquarks, can induce four fermion operators involving a quark, an anti-quark, a lepton and an anti-lepton. We update the (flavour dependent) constraints on the coefficients of such…
Two categories of four-fermion SMEFT operators are semileptonic (two quarks and two leptons) and hadronic (four quarks). At tree level, an operator of a given category contributes only to processes of the same category. However, when the…
I will give a brief overview of the Standard Model theory inputs needed for the precise determination of the Cabibbo-Kobayashi-Maskawa matrix element $V_{us}$ from semileptonic kaon decays, focusing on the long-distance electromagnetic…
We study the effect of non-universal $Z'$ boson on the rare leptonic decay modes of $B_s^*$ mesons, mediated by $b arrow sll$ quark transition. Rare B decays are sensitive to various new physics operators. As B mesons are composite…
We critically examine the potential to disentangle Standard Model (SM) and New Physics (NP) in $B \to K^* \mu^+\mu^-$ and $B\to K^* e^+ e^-$ decays, focusing on $(i)$ the LHCb anomaly, $(ii)$ the search for right-handed currents, and…
Motivated by the recent observation of lepton universality violation in the flavour changing charged current transitions $b \to c l \bar{\nu}_l$, we intend to scrutinize the lepton non-universality effects in rare semileptonic $B$ meson…
We probe the rare semileptonic decays $B_{(s)} \to K_2^*(1430)(f_2'(1525)) \ell^+\ell^-$ proceeding via $b\to s \ell \ell$ transition in the presence of a light $Z^{\prime}$ boson. We employ the presence of an additional vector type…
In various extensions of the Standard Model (SM) tree level non-leptonic decays of hadrons receive contributions from new heavy gauge bosons and scalars. Prominent examples are the right-handed W' bosons in left-right symmetric models and…