Taking into account the gluon condensate contributions, the form factors of the semileptonic $B_c^- \to D^{*0}\ellν$ transition with $l=τ, e$ are calculated in the framework of the three point QCD sum rules. The heavy quark effective theory limit of the form factors are also computed. The relevant total decay width as well as the branching ratio are evaluated and compared with the predictions of the other non-perturbative approaches.
(Contribution to Proceedings of the Seventh International Symposium On Heavy Flavor Physics, July 7-11, 1997, Santa Barbara.) Theoretical approaches to form factors of semileptonic decays are discussed in application to $B \ra D + l+\bar ν_l$ decay.
Exclusive semileptonic B decays are discussed. The emphasis is on using semileptonic decays to determine |V_{ub}| and |V_{cb}|. Recent progress in our understanding of B semileptonic decays to excited charmed mesons is also reviewed.
In the framework of the heavy quark effective theory, the leading order Isgur-Wise functions relevant to semileptonic decays of the orbitally $P$-wave excited $B_{s}$ meson states $B^{**}_{s}$, including the newly found narrow $B_{s1}(5830)$ and $B^{*}_{s2}(5840)$ states, into the ($D_{s1}(2536)$, $D^{*}_{s2}(2573)$) doublet are calculated from QCD sum rules. With these universal form factors, the decay rates and branching ratios are also estimated.
We present an analysis of semileptonic decays of orbitally, $P$-wave excited $B_{s}$ meson states $B^{**}_{s}$, including the newly found narrow $B_{s1}(5830)$ and $B^{*}_{s2}(5840)$ states, into low lying $D_{s}$ mesons ($D_{s}(1968)$, $D^{*}_{s}(2112)$, $D_{sJ}(2317)$, $D_{sJ}(2460)$) within the framework of heavy quark effective theory. The relevant universal form factors are estimated using QCD sum rules at the leading-order of the heavy quark expansion. The decay widths are predicted and the branching ratios are estimated.
I review recent developments in Heavy Quark Effective Theory (HQET) that lead to an almost model--independent determination of the $|\Vcb|$ element of the Cabibbo--Kobayashi--Maskawa matrix from exclusive semileptonic $B\ra D^{(*)}$ decays. In particular, I compare the theoretical uncertainties in the $B\ra D^*\ell\,\barν$ and the $B\ra D\,\ell\,\barν$ decay modes. I discuss the applications of QCD sum rules within HQET to semileptonic heavy meson decays and give predictions for the form factors measurable in $B\ra D^{(*)}\ell\,\barν$ decays.
We calculate the transition form factors that occur in heavy $Λ$-type baryon semileptonic decays as e.g. in $Λ_{b} \to Λ_{c}^{+} + l^{-} + \barν_{l} $. We use Bauer-Stech-Wirbel type infinite momentum frame wave functions for the heavy $Λ$-type baryons which we assume to consist of a heavy quark and a light spin-isospin zero diquark system. The form factors at $ q^{2} = 0 $ are calculated from the overlap integrals of the initial and final $Λ$-type baryon states. To leading order in the heavy mass scale the structure of the form factors agrees with the HQET predictions including the normalizat…
We study the semileptonic branching fraction of $B$-meson into higher resonance of charmed meson $D^{**}$ by using the Bjorken sum rule and the heavy quark effective theory(HQET). This sum rule and the current experiment of $B$-meson semileptonic decay into $D$ and $D^*$ predict that the branching ratio into $D^{**}lν_l$ is about 1.7\%. This predicted value is larger than the value obtained by the various theoretical hadron models based on the HQET.
We investigate the structure of the $D_{1}^0(2420[2430]) (J^P=1^+)$ mesons via analyzing the semileptonic $B_{c}\to D_{1}^0 lν$ transition in the frame work of the three--point QCD sum rules and the heavy quark effective theory. We consider the $D_{1}^0$ meson in three ways; the pure $|c\bar{u}\rangle$ state, a mixture of two $|^3P_1\rangle$ and $|^1P_1\rangle$ states with a mixing angle $θ$ and a combination of two mentioned states with mixing angle $θ=35.3^\circ$ in the heavy quark limit. Taking into account the gluon condensate contributions, the relevant form factors are obtained for the t…
We proposed a new formulation for heavy quark effective theory (HQET), whose Lagrangian is hermitian and has a manifest reparameterization invariance. As an application, we calculated the semileptonic and nonleptonic inclusive heavy hadron decay rates up to second order mass corrections and found that there are no kinetic energy correction terms.
We estimate the heavy quark effective theory parameter λ_1 from inclusive semileptonic B-meson decay spectrum. By using recent CLEO double lepton tagging data of B -> X e nu, which shows the lepton momentum as low as 0.6 GeV, we extracted λ_1 \sim -0.58 GeV^2. We also derived \barΛ\sim 0.46 GeV and |V_{cb}| = 0.041 \pm 0.002.
The exclusive semileptonic heavy baryon decay Λ_b\to p l\barνis investigated using light-cone sum rule method in both full QCD and HQET. The form factors describing the decay are calculated and used to predict the decay width and differential distribution. The total decay width obtained from full QCD is in agreement with the previous theoretical predictions while the HQET result are typically one order smaller. Both results are consistent with the experimental upper limit and can be compared to the refined experimental data in the future.
We discuss the recent developments in inclusive decays of hadrons containing a heavy quark. The subject is approached in a model independent way using an operator product expansion for the time-ordered product of weak currents. We discuss the extraction of the weak mixing angle $|V_{cb}|$ from inclusive semileptonic $B$ decays and the application of these techniques to the endpoint of the $e^-$ spectrum in $B\rightarrow X_ueν$. We also suggest that the comparison of inclusive semileptonic widths for $D_s$ and $D$ mesons will give an indication of the consistency of this approach in charm decay…
Within the HQET, the heavy to light vector meson transitions are systematically analyzed to the order of 1/m_Q. Besides the four universal functions at the leading order, there are twenty-two independent universal form factors at the order of 1/m_Q. Both the semileptonic decay B->ρwhich is relevant to the |V_{ub}| extraction, and the penguin induced decay B -> K^* which is important to new physics discovering, depend on these form factors. Phenomenological implications are discussed.
We review the role of the universal Isgur-Wise functions parameterizing the $B$ meson semileptonic matrix elements to charm states in the infinite heavy quark mass limit. We also discuss the determination of one of such form factors by QCD sum rules in the framework of the Heavy Quark Effective Theory.
The paper gives the polarization of the tau lepton in the semileptonic B decays with respect to the direction of the virtual W boson. The result is given including the nonperturbative HQET corrections.The perturbative QCD corrections are probably negligible as suggested by the existing results for the longitudinal polarization of the charged lepton (Jezabek and Urban, 1998).
We compute the leading order (in alpha_s) perturbative QCD and power (1/m_b^2) corrections to the hadronic invariant mass and hadron energy spectra in the decay B \to X_s \ell^+ \ell^- in standard model using the heavy quark expansion technique (HQET). Results for the first two hadronic moments < S_H^n> and <E_H^n>, n=1,2, are presented here working out their sensitivity on the HQET parameters lambda_1 and \barΛ. Data from the forthcoming B facilities can be used to measure the short-distance contribution in B \to X_s \ell^+ \ell^- and determine the HQET parameters from the moments <S_H^n>. Th…
I discuss recent progress in our understanding of exclusive rare and semileptonic decays. I show the impact of HQET when combined with the predictions in the Large Energy Limit of QCD, focusing first on applications to $B\to K^*\ell^+\ell^+$. I also discuss the constraints on semileptonic form-factors that appear in HQET/LEET with the use of radiative decay data, and update these to include the effects of next-to-leading order contributions in $B\to K^*γ$, as well as the latest data.
We developed the new parton model approach for exclusive semileptonic decays of $B$-meson to $D,~D^*$ by extending the inclusive parton model, and by combining with the results of the HQET, motivated by Drell-Yan process. Without the nearest pole dominance ansätze, we {\bf derived} the dependences of hadronic form factors on $q^2$. We also calculated numerically the slope of the Isgur-Wise function, which is consistent with the experimental results.
Perturbative and nonperturbative QCD corrections to semileptonic B decay rates are calculated and given in analytical and numerical forms. We present the analytic expression for the double distribution in hadronic mass and electron energy in B to X(u) e nu_e decays through one loop order of QCD. We then study the leading twist corrections to that quantity within the formalism of HQET and employ it in a proposed method of measuring V_ub with an accuracy of 10%. Our other point of interest is the polarisation of the tau lepton in B to X(c) tau nu_tau processes. Analytic formulae are given for th…
From the experimental branching ratios for $B^- --> ρ^0 l^-\barν_l$ and $D^+ --> {\overl K}^{*0}({\overl K}^0) e^+ ν_e$ one finds, in the Heavy Quark Limit of $HQET$, $ |V_{bu}|=(8.1\pm 1.7) x 10^{-3}$, larger but consistent with the actual quoted range $(2 - 7) x 10^{-3}$. In the same framework one predicts for $R(B --> K^*γ)=( 2 \pm 2 ) 10^{-2}$.
We investigate the form factors for exclusive semileptonic decays of $B$-meson to $D,~D^*$, based on the parton picture and helped by the results of the HQET. We obtain the numerical results for the slope of the Isgur-Wise function, which is consistent with the experimental results, and we extracte the dependences of hadronic form factors on $q^2$ by varying input heavy quark fragmentation function without the nearest pole dominance ansätze.
B decay sum rules relate exclusive B semileptonic decay matrix elements to forward B-meson matrix elements of operators in HQET. At leading order the operators that occur are the b-quark kinetic energy $λ_1$ and chromomagnetic energy $λ_2$. The latter is determined by the measured $B^*-B$ mass splitting. The derivation of these sum rules is reviewed and perturbative QCD corrections are discussed. A determination of $λ_1$ and the energy of the light degrees of freedom in a B-meson, $\barΛ$, from semileptonic B decay data is presented. Future prospects for improving these sum rules are discussed…
The form factors for the weak currents between B and light mesons are studied by relating them to the corresponding D form factors at q^2_{max} according to HQET, by evaluating them at q^2=0 by QCD sum rules, and by assuming a polar q^2 dependence. The results found are consistent with the information obtained from exclusive non-leptonic two-body decays and, with the only exception of A_1, with lattice calculations.
Using quasipotential approach, we have studied exclusive semileptonic decays of heavy mesons with the account of relativistic effects. Due to more complete relativistic description of the $s$ quark more precise expressions for semileptonic form factors are obtained. Various differential distributions in exclusive semileptonic decays of heavy mesons are calculated. It is argued that consistent account of relativistic effects and HQET motivated choice of the parameters of quark-antiquark potential allow to get reliable value for the ratio $A_2(0)/A_1(0)$ in the $D\to K^*lν_l$ decay as well as th…
Semileptonic B decays are described by the Isgur-Wise form factor to the leading order in 1/m; four new functions appear in the first order [Luke]. Values of these functions are crucial for the applicability of the whole approach to processes involving c quark. We obtain the sum rules for three subleading form factors from the QCD sum rules with finite masses by expanding to the first order in 1/m. The results respect the pattern of the first 1/m corrections established in HQET, and obey the Luke's theorem. The numerical estimates show that 1/m_c corrections are sizable but not catastrophic.
A simple relativistic model of heavy-quark-light-quark mesons is proposed. In an expansion in inverse powers of the heavy quark mass we find that all zeroth and first order heavy quark symmetry relations are satisfied. The main results are: - the difference between the meson mass and the heavy quark mass plays a significant role even at zeroth order; - the slope of the Isgur-Wise function at the zero recoil point is typically less than $-1$; - the first order correction to the pseudoscalar decay constant is large and negative; - the four universal functions describing the first order correctio…
We study the exclusive semileptonic decays B_s->D_{s0}^*\ell\barνand B_s->D_{s1}^*\ell\barν, where p-wave excited D_{s0}^* and D_{s1}^* states are identified with the newly observed D_{sJ}(2317) and D_{sJ}(2460) states. Within the framework of HQET the Isgur-Wise functions up to the subleading order of the heavy quark expansion are calculated by QCD sum rules. The decay rates and branching ratios are computed with the inclusion of the order of 1/m_Q corrections. We point out that the investigation of the B_s semileptonic decays to excited D_s mesons may provide some information about the natur…
We calculate the form factors for the semileptonic decays of the $B$ meson to $D$ and $D^*$ mesons in a Bethe-Salpeter model. We show that our model is consistent with the constraints of Heavy Quark Effective Theory (HQET) and we extract the matrix elements that represent the $1/m_Q$ corrections to the form factors in HQET. With available data, we obtain $V_{cb} $=$ (31.9 \pm 1.4)\times10^{-3}$.
Positive powers of the mass parameter in a physical quantity calculated with the help of heavy quark effective theory originate from a Wilson coefficient in the matching of QCD and HQET Green function. We show that this mass parameter enters the calculation as a well--defined running current mass. We further argue that the recently found ill--definition of the pole mass, which is the natural expansion parameter of HQET, does not affect a phenomenological analysis which uses truncated perturbative series. We reanalyse inclusive semileptonic decays of heavy mesons and obtain the $c$ quark mass $…
Motivated by the recent extraction of the helicity amplitudes for the D+ -> K*0bar mu+ nu decay, done by the FOCUS collaboration, we determine helicity amplitudes for the D+ -> K*0bar l nu, D+ -> rho0 l nu and Ds -> phi l nu semileptonic decays using the knowledge of the relevant form factors. The vector and axial form factors for D -> V l nu decays are parameterized by including contributions of charm meson resonances and using the HQET and SCET limits. In the case that the vector form factor receives contributions from two poles while axial form factors are dominated by a single pole for D+ …
Exclusive semileptonic decays B->D_1(2420)l\barνand B->D_2^*(2460)l\barνare studied at the subleading order of the heavy quark expansion. The subleading Isgur-Wise functions resulted from the kinetic energy and chromomagnetic corrections to the HQET Lagrangian are calculated by QCD sum rules in the framework of the heavy quark effective theory. The decay rates and branching ratios are computed with the inclusion of the order of 1/m_Q corrections. It is found that the 1/m_Q correction to the decay rate is not large for B->D^*_2 but is very large for B->D_1.
We examine the rates for the exclusive decays $B\to K^{(*)}\ell^+\ell^-$. We use the scaling predictions of the heavy quark effective theory to extract the necessary form factors from fits to various combinations of data. These data include the $D\to K^{(*)}\ellν$ semileptonic decays, as well as the nonleptonic decays $B\to K^{(*)}ψ^{(\prime)}$ and the rare decay $B\to K^*γ$. We use different parametrizations of form factors, and find that integrated decay rates are not very sensitive to the forms chosen. However, the decay spectra and the forward-backward asymmetry in $B\to K^*\ell^+\ell^-$ a…
In this paper we discuss the Standard Model and new physics sensitivity of the $Λ_b\toΛ^\ast(1520)(\to N\!\bar{K})\ell^+\ell^-$ decay at low-recoil, where $\ell^\pm$ are massive leptons and $N\!\bar{K}=\{pK^-, n\bar{K}^0 \}$. We provide a full angular distribution with a set of operators that includes the Standard Model operators and their chirality flipped counterparts, and new scalar and pseudo-scalar operators. The resulting angular distribution allows us to construct observables that we study in the Standard Model and in model-independent new physics scenarios. To reduce the hadronic effec…
Semileptonic decay and form factors of $Ω_b^- \rightarrow Ω_c^0\,e\,\bar{ν_e}$
Department of Physics, Government College, Daman-396210, U. T. of Dadra & Nagar Haveli and Daman & Diu（达曼政府学院物理系）；Veer Narmad South Gujarat University, Surat, India（印度苏拉特维尔·纳姆纳德南古吉拉特大学）
本文基于超子构成夸克模型研究底超子Ω_b^-到Ω_c^0 e ν_e的半轻子衰变，计算形式因子并分析衰变率，与不同理论方法结果对比。
Leading order (in $α_s$) perturbative QCD and power ($1/m_b^2)$ corrections to the hadronic invariant mass and hadron energy spectra in the decay $B \to X_s \ell^+ \ell^-$ are reviewed in the standard model using the heavy quark expansion technique (HQET). In particular, the first two hadronic moments $<S_H^n>$ and $<E_H^n>$, $n=1,2$, are presented working out their sensitivity on the HQET parameters $λ_1$ and $\barΛ$. Data from the forthcoming B facilities can be used to measure the short-distance contribution in $B \to X_s \ell^+ \ell^-$ and determine the HQET parameters from the moments $<S…
We compute the leading order (in $α_s$) perturbative QCD and power ($1/m_b^2)$ corrections to the hadronic invariant mass and hadron energy spectra in the decay $B \to X_s \ell^+ \ell^-$ in standard model. This is done both by using the heavy quark expansion technique (HQET) and a perturbative-QCD improved Fermi motion (FM) model which takes into account $B$-meson wave-function effects. The corrections in the hadron energy ($E_H$) spectrum are found to be small over a good part of this spectrum in both the methods. However, the expansion in $1/m_b$ in HQET fails near the lower kinematic end-po…
We examine the measured rates for the decays $D\to K^{(*)}\ellν$, $B\to K^{(*)}ψ^{(\prime)}$ and $B\to K^*γ$ in a number of scenarios, in the framework of the heavy quark effective theory. We attempt to find a scenario in which all of these decays are described by a single set of form factors. Once such a scenario is found, we make predictions for the rare decays $B\to K^{(*)}\ell^+\ell^-$. While we find that many scenarios can provide adequate descriptions of all the data, somewhat surprisingly, we observe that two popular choices of form factors, namely monopolar forms and exponential forms,…
In this article, we calculate the $B_c^* \to η_c$ form-factors with the three-point QCD sum rules, then study the semileptonic decays $B_c^* \to η_c \ell \barν_{\ell}$. The tiny decay widths may be observed experimentally in the future at the LHCb, while the $B_c^* \to η_c$ form-factors can be taken as basic input parameters in other phenomenological analysis.
We analyze the semileptonic $ B_{s} \rightarrow D_{s2}^{*}(2573)\ell\bar{ν}_{\ell}$ transition, where $\ell=τ,~μ$ or $e$, within the standard model. We apply the QCD sum rule approach to calculate the transition form factors entering the low energy Hamiltonian defining this channel. The fit functions of the form factors are used to estimate the total decay widths and branching fractions in all lepton channels. The orders of branching ratios indicate that this transition is accessible at LHCb in near future.
We calculate $B_{(s)}$, and $D_{(s)}$ to $K^*_0(1430)$ transition form factors, and study semileptonic decays of $B_{(s)}$ and $D_{(s)}\to K_0^*(1430) \bar{\ell}ν$ based on QCD sum rule. Measuring these semileptonic decays with high statistics will give valuable information on the nature of light scalar mesons.
Small changes in the masses of massive external scattering states should correspond to small changes in the non-perturbative parameterization of form factors in quantum field theory, as long as the relevant energy range is not near strong deformations. Here, the definition of ``small'' is investigated and applied to $SU(3)$ breaking in semileptonic $B_{(s)}\rightarrow D_{(s)}$ transitions. When unitarity and analyticity are imposed, the differences in the form factors for semileptonic $B\rightarrow D$ versus $B_s\rightarrow D_s$ decays are found to be within $\mathcal{O}(1\%)$ over the entire …
We calculate the hadronic tensor for inclusive semileptonic B decay to O(alpha_s). This allows O(alpha_s Lambda_{QCD}/mb) corrections to hadronic invariant mass observables to be directly evaluated with experimentally required cuts on phase space. Several moments of phenomenological interest are presented to O(alpha_s Lambda_{QCD}/mb) and O(Lambda_{QCD}^3/mb^3), allowing a consistent extraction of the HQET parameters up to O(Lambda_{QCD}^3/mb^3) and the b quark mass with theoretical error ~ 50 MeV. The hadronic invariant mass spectrum is examined with a general moment to obtain observables tha…
Using recent results for nonperturbative contributions to the $B$ and $D$ meson inclusive semileptonic widths, a model independent extraction of $\vbc$, $m_c$ and $m_b$ is made from the experimentally measured $B$ and $D$ lifetimes and semileptonic branching ratios. Constraining the parameters of the HQET at $\CO(1/m_Q^2)$ by the $D$ semileptonic width, $\vbc$ is found to lie in the range $.040<\vbc< 0.057$. The $c$ and $b$ quark masses are not well constrained due to uncertainty in the relevant scale of $α_s$. These results assume the validity of perturbative QCD at the low scales relevant to…
The form factors of semileptonic $B_{(s)}\to a_{1}(K_1)\, \ell^{+}\ell^{-}$, $ \ell=τ,μ,e$ transitions are investigated in the framework of the light-cone sum rules with $B$-meson distribution amplitudes, which play an important role in exclusive $B$ decays. The $B$-meson distribution amplitudes, $φ_{\pm}(ω)$ are a model-dependent form, so we consider four different parameterizations which can provide a reasonable description of $φ_{\pm}(ω)$ from QCD corrections. The branching fractions of these transitions are calculated. For a better analysis, a comparison of our results with the prediction …
In anticipation of abundant $B^*$ data samples at high-luminosity heavy-flavor experiments in the future, the tree-dominated semileptonic $\bar{B}^*_{u,d,s} \to P \ell^- \barν_\ell$ $(P=D\,,D_s\,,π\,,K)$ decays are studied within the Standard Model. After a detailed calculation of the helicity amplitudes, the theoretical predictions for branching fraction~(decay rate), lepton spin asymmetry, forward-backward asymmetry and ratio $R_D^{\ast(L)}$ are firstly presented. It is found that the CKM-favored $\bar{B}^* \to D \ell^- \barν_\ell$ decays have relatively large branching fractions of ${\cal O…
We calculate $D_s^+\to ϕ$ transition form factors $V$, $A_0$, $A_1$ and $A_2$, and study semileptonic decay of $D_s^+\to ϕ\bar{\ell}ν$ based on QCD sum rule method. We compare our results of the ratios of $V(0)/A_1(0)$, $A_2(0)/A_1(0)$, $Γ_L/Γ_T$, and the total decay branching ratio of $D_s^+\to ϕ\bar{\ell}ν$ with experimental data, and find that they are consistent.
We work out the semileptonic $Λ_b\rightarrow Λ\ell^+ \ell^-$ transition in standard as well as different supersymmetric models. In particular, considering the parametrization of the matrix elements entered the low energy effective Hamiltonian in terms of form factors in full QCD, we calculate the amplitude and differential decay rate responsible for this decay channel in supersymmetric models. We then use the form factors calculated via light cone QCD sum rules in full theory to analyze the differential branching ratio and lepton forward-backward asymmetry of this decay channel in different su…
Heavy-quark effective theory (HQET) is applied to lattice QCD with Wilson fermions at fixed lattice spacing a. This description is possible because heavy-quark symmetries are respected. It is desirable because the ultraviolet cutoff $1/a$ in current numerical work and the heavy-quark mass $m_Q$ are comparable. Effects of both short distances, a and $1/m_Q$, are captured fully into coefficient functions, which multiply the operators of the usual HQET. Standard tools of HQET are used to develop heavy-quark expansions of lattice observables and, thus, to propagate heavy-quark discretization error…
In this work, the transition form factors are calculated for the semileptonic $D_{(s)} \to A \ell^+ ν$ where $A=a_{1}, b_{1}, K_{1}(1270,1400)$, i.e., $D^{+} \to a^{0}_{1} (b^{0}_{1}, K^{0}_{1}) \ell^+ ν$, $D^{0} \to a^{-}_{1} (b^{-}_{1}) \ell^+ ν$, and $D^{+}_{s}\to K^{0}_{1} \ell^+ ν$ in the frame work of the light-cone QCD sum rules (LCSR) approach up to the twist-3 distribution amplitudes (DAs). Since the masses of these axial vector mesons are comparable to the charm quark mass, we keep out in our calculations all terms including ${m_{A}}/{m_c}$ in expansion of two--parton DAs. Branching …
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 interaction and constrain the new physics coupling parameter using the existing experimental measurements on $R_K$ and $R_{K^*}$ observables. To understand the sensitivity of the new physics coupling, we investigate the impact of this coupling on various physical observables such as differential branching ratio, the forward-backward asymmetry, the lepton polarizati…
Within the framework of covariant confined quark model, we compute the transition form factors of $D$ and $D_s$ mesons decaying to light scalar mesons $f_0(980)$ and $a_0(980)$. The transition form factors are then utilized to compute the semileptonic branching fractions. We study the channels namely, $D_{(s)}^+ \to f_0(980) \ell^+ ν_\ell$ and $D \to a_0(980) \ell^+ ν_\ell$ for $\ell = e$ and $μ$. For computation of semileptonic branching fractions, we consider the $a_0(980)$ meson to be the conventional quark-antiquark structure and the $f_0(980)$ meson as the admixture of $s\bar{s}$ and ligh…
We discuss rare meson decays $K^ + \to π^ - \ell ^ + \ell '^ + $ and $D^ + \to K^ - \ell ^ + \ell '^ +$ ($\ell, \ell'=e, μ$) in a supersymmetric extension of the Standard Model with R-parity violation. Estimates of the branching ratios for these decays are presented.
Motivated by the recent hints of lepton flavor universality violation observed in semileptonic $B$ decays, we analyze how to test flavor and helicity structures of the corresponding amplitudes in view of future data. We show that the general assumption that such non-standard effects are controlled by a $U(2)_q \times U(2)_\ell$ flavor symmetry, minimally broken as in the Standard Model Yukawa sector, leads to stringent predictions on leptonic and semileptonic $B$ decays. Future measurements of $R_{D^{(*)}}$, $R_{K^{(*)}}$, ${\mathcal B}(\bar B_{c,u}\to \ell \bar ν)$, ${\mathcal B}(\bar B \to π…
We present precise theoretical predictions for the absolute branching fractions of $Λ_c^+ \to Λ\ell^+ ν_\ell\,(\ell=e,μ)$ decays in the covariant confined quark model. This study is motivated by two recent and accurate measurements of the absolute branching fractions of $Λ_c^+ \to p K^- π^+$ and $Λ_c^+ \to Λe^+ ν_e$ by the Belle Collaboration at the KEKB and by the BESIII Collaboration at the BEPCII. Our predictions for the branching fractions are consistent with both experimental results. We also provide detailed numerical results for differential decay distributions and polarization observab…
