Related papers: Interpreting LHCb's $\Lambda_b\to \Lambda_c\tau\ba…
The collection of a few anomalies in semileptonic $B$-decays, especially in $b\rightarrow c \tau \bar{\nu}$, invites to speculate about the emergence of some striking new phenomena, perhaps interpretable in terms of a weakly broken $U(2)^n$…
The recent measurements on $R_D$, $R_{D^*}$ and $R_{J/\psi}$ by three pioneering experiments, BaBar, Belle and LHCb, indicate that the notion of lepton flavour universality is violated in the weak charged-current processes, mediated through…
The observable $\mathcal{R} ( D^{(*)} ) = \mathcal{B}\left( B^{0}\to D^{(*)-} \tau^{+} \nu_{\tau} \right) / \mathcal{B}\left( B^{0}\to D^{(*)-} \mu^{+} \nu_{\mu} \right)$ is a probe for Lepton Universality violation, so it is sensitive to…
We present a measurement of angular observables and a test of lepton flavor universality in the $B\to K^\ast \ell^+\ell^-$ decay, where $\ell$ is either $e$ or $\mu$. The analysis is performed on a data sample corresponding to an integrated…
Inspired by the recent hints of lepton flavor universality violation in $b\to s\ell\ell$ and $b\to c\ell\nu$ transitions, we study lepton flavor violating exclusive $\Lambda_b\to\Lambda\ell_1^+\ell_2^-$ ($\ell_1\neq \ell_2$) decay, which is…
The BaBar measurements of the ratios ${\cal R}(D^{(*)})=\frac{{\cal B}(B \to D^{(*)} \tau {\bar \nu}_\tau)}{{\cal B}(B \to D^{(*)} \mu {\bar \nu}_\mu)}$ deviate from the standard model expectation, while new results on the purely leptonic…
Motivated by renewed evidence for new physics in $b \to s\ell\ell$ transitions in the form of LHCb's new measurements of theoretically clean lepton-universality ratios and the purely leptonic $B_s\to\mu^+\mu^-$ decay, we quantify the…
A sizable excess with respect to the SM expectation has been reported recently by the BaBar collaboration in the decay rates B -> D(*) Tau Nu, normalized by the corresponding light lepton modes. A violation of lepton flavor universality as…
The anomalously large experimentally measured ratios of the semitauonic decay $B\rightarrow D^{(*)} +\tau+\nu$ and the corresponding semileptonic $B\rightarrow D^{*} +\l+\bar{\nu}_l$ disagree with the predictions of the standard E.W + QCD…
We comparatively analyze the flavor changing neutral current process of the $\Lambda_b \rightarrow \Lambda \ell^+ \ell^-$ in the standard model as well as topcolor-assisted technicolor model using the form factors calculated via light cone…
Being strictly forbidden in the standard model, experimental detection of the lepton flavor violating decays $B(\bar B)\to\tau^+\mu^-$ and $b(\bar b)\to X\tau^+\mu^-$ would constitute an unmistakable indication of new physics. We study…
We propose two different and complementary observables for singling out possible signals of physics beyond the standard model in the semi-leptonic decays $\Lambda_b \to \Lambda_c \ell{\bar \nu}_{\ell}$, both with the $\tau$ lepton and with…
In recent years, the LHCb collaboration has published results on the measurement of several observables associated to semileptonic $b \to s$ transitions. Interestingly, various deviations from their expected values in the Standard Model…
Recent measurements of exclusive $B^{-} \to \tau^{-}\,\nu$ and $B^0 \to \pi^{+}\,l^{-}\,\bar{\nu}_l$ decays via the $b \to u\,l\,\nu$ transition process differ from the standard model expectation and, if they persist in future $B$…
We study the inclusive charmless semileptonic decay of $\Lambda_b$, $\Lambda_b \to X_u l \nu_l$, in the framework of heavy quark expansion and find that the rate is substantially enhanced by spectator effect. We obtain $Br(b \to X_u l…
In this work, we investigate angular observables such as the longitudinal polarization of charged leptons, $\tau$-polarization, and forward-backward asymmetry in semileptonic $B_c$ decays. Additionally, we provide predictions for lepton…
Semileptonic $b \rightarrow s\ell \ell$ processes constitute a good probe for new physics phenomena: new particles contributing to the loops could affect branching fractions and angular distributions, and have different couplings to…
The ratios of branching fractions $\mathcal{R}(D^{*})\equiv\mathcal{B}(\bar{B}\to D^{*}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(\bar{B}\to D^{*}\mu^{-}\bar{\nu}_{\mu})$ and $\mathcal{R}(D^{0})\equiv\mathcal{B}(B^{-}\to…
The LHCb collaboration has very recently released a new study of $B^+ \to K^{+} \ell^+ \ell^-$ and $B \to K^{*0} \ell^+ \ell^-$ ($\ell = e,\mu$) decays, testing lepton universality with unprecedented accuracy using the whole Run 1 and 2…
We review the current status and implications of the anomalies (i.e. deviations from the Standard Model predictions) in semi-leptonic $B$ meson decays, both in the charged and in the neutral current. In $b\to s\ell^+\ell^-$ transitions…