Related papers: A new approach to semi-leptonic tags in $B$-meson …
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…
Decays of $B$ mesons with leptons in the final state offer an interesting laboratory to search for possible effects of physics from beyond the Standard Model. In view of puzzling patterns in experimental data, the violation of lepton…
Three recent measurements of leptonic and semileptonic decays of $B$ mesons are presented here. All results use the full Belle II Run 1 $e^+e^- \to \Upsilon(4S) \to B\bar{B}$ dataset of 365 fb$^{-1}$. We present one leptonic $B$ decay…
Semi-leptonic $B_s \to K \ell \nu$ and $B_s \to D_s \ell \nu$ decays provide an alternative $b$-decay channel to determine the CKM matrix elements $|V_{ub}|$ and $|V_{cb}|$ or to obtain $R$-ratios to investigate lepton flavor universality…
New particles $\phi$ in the MeV-GeV range produced at colliders and escaping detection can be searched for at operating $b-$ and $\tau-$factories such as Belle II. A typical search topology involves pair-produced $\tau$s (or mesons), one of…
We present a set of Lorentz invariant kinematic variables for reconstructing mass of semi-invisible decaying particles pair-produced at lepton colliders, $m_{\rm RC}^{\rm min}$, $m_{\rm RC}^{\rm max}$ and $m_{\rm LSP}^{\rm max}$, with…
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…
We examine in detail the semi-leptonic decay $\Lambda_b \to \Lambda_c \tau{\bar \nu}_{\tau}$, which may confirm previous hints, from the analogous $B$ decay, of a new physics beyond the standard model. First of all, starting from rather…
Recently, several hints of lepton non-universality have been observed in the semileptonic B meson decays in terms of both in the neutral current ($b\to s l \bar{l}$) and charged current ($b\to c l \bar{\nu_{l}}$) transitions. Motivated by…
$B_s \to \mu^+ \mu^- \gamma$, measured at high $q^2$ as a partially reconstructed decay, can probe the origin of the existing discrepancies in semi-leptonic $b \to s$ and $b \to c$ decays. We perform a complete study of this possibility. We…
We report a study of semileptonic B decays to P-wave D** mesons. Semileptonic decay to D*_2 meson is observed for the first time and its product branching ratio is measured to be Br(B+ -> anti-D*0_2 l+nu) x Br(anti-D*0_2 -> D- pi+) = 0.22…
We study the possibility of utilising the constrained mass variable, $M_{2Cons}$, in reconstructing the semi-invisible events originated from a resonant production at the LHC. While this proposal is effective for any similar antler type…
Data in $B$-meson decays indicate violations of lepton flavour universality, thereby raising the question about such phenomena in the charm sector. We perform a model-independent analysis of NP contributions in (semi)-leptonic decays of…
We present a new measurement of the purely leptonic decay B- -> tau- nu_tau-bar with a semileptonic B tagging method, using a data sample containing 657*10^6 BB-bar pairs collected with the Belle detector at the KEKB asymmetric e+e-…
Semileptonic flavor changing neutral current transitions with a pair of neutrinos in the final state are very accurately determined in the standard model (SM) and thus provide an accurate and sensitive probe for physics beyond the SM. Until…
The Belle II experiment at the SuperKEKB energy-asymmetric $e^+e^-$ collider is a substantial upgrade of the B factory facility at the Japanese KEK laboratory. The design luminosity of the machine is $8\times10^{35}\,…
Semileptonic $B_s \to K \ell \nu$ decays provide an alternative $b$-decay channel to determine the CKM matrix element $|V_{ub}|$, and to obtain a $R$-ratio to investigate lepton-flavor-universality violations. Results for the CKM matrix…
Semileptonic decays of $B$ mesons that proceed via $b\rightarrow u$ and $b\rightarrow c$ transitions, as well as rare leptonic $B$ decays, are fertile grounds for probing new physics beyond the Standard Model. The Belle II experiment…
We present a new measurement of the decay B- -> tau- nu_tau-bar with a semileptonic B tagging method, using a data sample containing 657*10^6 BB-bar pairs collected at the (4S) resonance with the Belle detector at the KEKB asymmetric e+e-…
We have tried to measure $|V_{ub}|$ using inclusive semileptonic decay measurements with three different methods. The full reconstruction tag is the one of the most feasible method to measure inclusive process. Semileptonic $B\to…