Semileptonic decay processes of $Ξ_c \to Ξ\ellν_\ell$ are studied by light-cone QCD sum rules in this paper. The six form factors of $Ξ_c \to Ξ$ semileptonic transition matrix elements are calculated by this method with the light-cone distribution amplitudes of $Ξ$ baryon up to twist six. With the six form factors, the absolute branching ratios of $Ξ_c^0 \to Ξ^- \ell^+ ν_\ell$ and $Ξ_c^+ \to Ξ^0 \ell^+ ν_\ell$ are calculated by the helicity amplitudes formalism of semileptonic differential decay widths. The ratios of absolute branching ratios of electron and muon final states processes give the proof of lepton flavor universality. Our results are in accordance with the recent experimental and theoretical reports.
In this work, we analyze the semileptonic decay processes of $Λ_b \to Λ_c$ in the light-cone sum rule approach. In order to calculate the form factors of the $Λ_b$ baryon transition matrix element, we use the light-cone distribution amplitudes of $Λ_b$ obtained from the QCD sum rule in the heavy quark effective field theory framework. With the calculation of the six form factors of the $Λ_b \to Λ_c$ transition matrix element, the differential decay widths of $Λ_b^0 \to Λ_c^+ \ell^- \overlineν_\ell (\ell = e, ~μ, ~τ)$ and their absolute branching fractions are obtained. Additionally, the ratio …
We calculate the form factors V, A_1, A_2 and A_0 appearing in the (D -> phi) transition in light cone QCD sum rule method. We compare our results on these form factors with the current experimental results and existing theoretical calculations.
We use distribution amplitudes of the light $Σ$ baryon and the most general form of the interpolating current for heavy $Σ_b$ baryon to investigate the semileptonic $Σ_b\rightarrow Σl^+l^-$ transition in light cone QCD sum rules. We calculate all twelve form factors responsible for this transition and use them to evaluate the branching ratio of the considered channel. The order of branching fraction shows that this channel can be detected at LHC.
Using the most general form of the interpolating current of the heavy spin 1/2, $Σ_{b}$ baryon and distribution amplitudes of the nucleon, the transition form factors of the semileptonic $Σ_{b}\to Nlν$ decay are calculated in the framework of light cone QCD sum rules. It is obtained that the form factors satisfy the heavy quark effective theory relations. The obtained results for the related form factors are used to estimate the decay rate of this transition.
B_c mesons are laboratories for probing heavy quark physics. Furthermore, they decay into charmonia and hence their decays can be used to analyze possible exotic charmonium. In this work, the semileptonic decays of B_c mesons into P wave charmonia are analysed using light cone QCD sum rules (LCSR). The distributions amplitudes for the charmonia are taken from a quark model computation. The obtained decay rates for the ground state and excited charmonia are compared with the results found in the literature.
BELLE has recently reported the measurement of the branching fraction of the semileptonic $B^{-}\toπ^{+}π^{-}\ell^{-}\barν_\ell$ decay, where $\ell$ represents an electron or a muon. With the new information on the $ππ$ invariant mass spectrum, we extract $|V_{ub}|=(3.31\pm 0.61)\times 10^{-3}$ in agreement with those from the other exclusive $B$ decays. In particular, we determine the non-resonant $B\toππ$ transition form factors, and predict the non-resonant branching fraction ${\cal B}(B^{-}\toπ^{+}π^{-}\ell^{-}\barν_\ell)=(3.5\pm 1.4^{+4.3}_{-2.4})\times 10^{-5}$, which is accessible to th…
The electromagnetic form factors of the Xi baryons and the semileptonic decay process Xi_c->Xi e^+nu_e are investigated in the frame work of the light-cone QCD sum rule method with Ioffe-type interpolating currents. Our estimates on the magnetic moments are $mu_{Xi^0}=-(1.75\pm0.21) mu_N and mu_{Xi^-}=-(1.01\pm0.11)mu_N. The decay width of the semileptonic process is expected to be Gamma(Ξ_c\to Ξe^+ν_e)=(6.17^{+2.24}_{-2.48})\times10^{-14}GeV. The results make sure that the adoption of this type interpolating current improve the calculations of the magnetic form factors and give more reliable …
We present a new calculation of the $D\toπ$ and $D \to K$ form factors from QCD light-cone sum rules. The $\overline{MS}$ scheme for the $c$-quark mass is used and the input parameters are updated. The results are $f^+_{Dπ}(0)= 0.67^{+0.10}_{-0.07}$, $f^+_{DK}(0)=0.75^{+0.11}_{-0.08}$ and $f^+_{Dπ}(0)/f^+_{DK}(0)=0.88 \pm 0.05$. Combining the calculated form factors with the latest CLEO data, we obtain $|V_{cd}|=0.225\pm 0.005 \pm 0.003 ^{+0.016}_{-0.012}$ and $|V_{cd}|/|V_{cs}|= 0.236\pm 0.006\pm 0.003\pm 0.013$ where the first and second errors are of experimental origin and the third error …
We study the four-body exclusive semileptonic baryonic $\bar B$ decays of $B^-\to p\bar p \ell^- \barν_{\ell}$ ($\ell=e,μ,τ$) in the standard model. We find that their decay branching ratios are about $(1.0, 1.0,0.5)\times 10^{-4}$, respectively. In particular, the electron mode is close to the corresponding CLEO's upper limit of $5.2\times 10^{-3}$, while all results are about one or two orders of magnitude larger than the previous estimated values for the inclusive modes of $\bar B\to {\bf B\bar B'}\ell \bar ν$. Clearly, both B-factories of Belle and BaBar should be able to observe these exc…
The semileptonic decays of heavy spin--1/2, $Ξ_{b(c)}$ and $Ξ'_{b(c)}$ baryons to the light spin-- 1/2, $Ξ$ and $Σ$ baryons are investigated in the framework of the light cone QCD sum rules. In particular, using the most general form of the interpolating currents for the heavy baryons as well as the distribution amplitudes of the $Ξ$ and $Σ$ baryons, we calculate all form factors entering the matrix elements of the corresponding effective Hamiltonians in full QCD. Having calculated the responsible form factors, we evaluate the decay rates and branching fractions of the related transitions.
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.
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 …
Form factors of the weak $Ξ_c \to Ξ(Λ)$ transitions are calculated within the light cone QCD sum rules. The pollutions coming from the contribution of the negative parity $Ξ_c^*$ baryon is eliminated by considering the combinations of sum rules corresponding to the different Lorentz structures. Having obtained the form factors, the branching ratios of the $Ξ_c \to Ξ(Λ) \ell ν$ decays are also calculated, and our predictions are compared with the results of other approaches as well as the measurements done by BELLE and ALICE Collaborations.
In the semileptonic decays of heavy mesons and baryons the lepton-mass dependence factors out in the quadratic $\cos^2θ$ coefficient of the differential $\cosθ$ distribution. We call the corresponding normalized coefficient the convexity parameter. This observation opens the path to a test of lepton universality in semileptonic heavy meson and baryon decays that is independent of form-factor effects. By projecting out the quadratic rate coefficient, dividing out the lepton-mass-dependent factor and restricting the phase space integration to the $τ$ lepton phase space, one can define optimized …
Semileptonic decays $D_{(s)} \to η^{(\prime)} \ell^+ ν_\ell$ from QCD Light-Cone Sum Rules
School of Physics and Electronics, Hunan University（湖南大学物理与电子学院）；School for Theoretical Physics, Hunan University（湖南大学理论物理学院）；Hunan Provincial Key Laboratory of High-Energy Scale Physics and Applications（湖南省高能标物理与应用重点实验室）
We present the study of the semileptonic decay Λ_c to Λ\ell^+νby using the light-cone sum rule approach. Distribution amplitudes (DAs) for the Λbaryon are discussed to the leading order conformal spin, and QCD sum rule estimate for the corresponding parameters is presented. The form factors describing the decay are calculated and used to predict the decay width and the decay asymmetry parameter α. With the inclusion of twist-3 contributions the calculated decay width Γ=(7.2+/-2.0)X10^{-14} GeV as well as asymmetry α=-(0.88+/-0.03) is found in good agreement with the experimental data, while th…
Based on the mechanism of neutral meson mixing, we predict the branching fraction of the semileptonic decay of $D_s^+\to π^0 \ell^+ ν_\ell$ ($\ell=e$, $μ$) using recently measured branching fraction of $D_s^+\to ηe^+ν_e$ by BESIII experiment . We also give a formula that can describe the neutral meson mixing of $π^0$, $η$, $η'$ and a pseudoscalar gluonium $G$ in a unified way. The predicted branching fraction of $D_s^+\toπ^0 e^+ν_e$ decay is $\mathcal{B}(D_s^+\toπ^0 e^+ν_e)=(2.65\pm 0.38)\times 10^{-5}$. It is important to search for the decay $D_s^+\to π^0 \ell^+ ν_\ell$ in experiment, in ord…
Semileptonic decays of the $Ξ_b$ baryon are studied in the framework of the relativistic quark-diquark model based on the quasipotential approach. The weak decay form factors are calculated with the comprehensive account of all relativistic effects without employing nonrelativistic and heavy quark expansions. On this basis differential and total decay rates as well as different asymmetry parameters are calculated for the heavy-to-heavy $Ξ_b\to Ξ_c\ellν_\ell$ and heavy-to-light $Ξ_b\to Λ\ellν_\ell$ semileptonic decays. Predictions for the ratios of such decays involving $τ$ lepton and muon are …
Using the relativistic Bethe-Salpeter method, the electron energy spectrum and the semileptonic decay widths of $B^0_s\to D^-_s \ell^+{ν_\ell}$ and $B^0_s\to D_s^{*-}\ell^+{ν_\ell}$ are calculated. We obtained large branching ratios, $Br(B_s\to D_seν_e)=(2.85\pm0.35)% $ and $Br (B_s\to D_s^*eν_e)=(7.09\pm0.88)%$, which can be easily detected in the future experiment.
We study the exclusive semileptonic rare $B_c^+ \to D^+ ν\barν$ decay in the framework of light-cone quark model. The transition form factors $f_{+}(q^2)$ and $f_{T}(q^2)$ are evaluated in the time-like region using the analytic continuation method in $q^{+} = 0$ frame. The analytic solutions of these form factors are compared with the results obtained from the double pole parametric form. The branching ratio for $B_c^+ \to D^+ ν\barν$ decay is calculated and compared with the other theoretical model predictions. The predicted results in this model can be tested at the LHCb experiments in near…
Form factors of $D$ decays into $J^{PC}=2^{++}$ tensor mesons are calculated in the light-cone sum rules approach up to twist-4 distribution amplitudes of the tensor meson. The masses of the tensor mesons are comparable to that of the charm quark mass $m_c$; therefore all terms including powers of $m_T/m_c$ are kept out in the expansion of the two-particle distribution amplitude $\langle T|\bar q_{1α}(x) \, q_{2δ}(0)|0\rangle$. Branching ratios of the semileptonic $D \to T\,μ\,\barν_μ$ decays and nonleptonic $D\to T~ P ~(P=K, π)$ decays are taken into consideration. A comparison is also made b…
We consider leptonic $B^-\to \ell^- \barν_\ell$ and semileptonic $\bar B \to π\ell^- \barν_\ell$, $\bar B \to ρ\ell^- \barν_\ell$ decays and present a strategy to determine short-distance coefficients of New-Physics operators and the CKM element $|V_{ub}|$. As the leptonic channels play a central role, we illustrate this method for (pseudo)-scalar operators which may lift the helicity suppression of the corresponding transition amplitudes arising in the Standard Model. Utilising a new result by the Belle collaboration for the branching ratio of $B^-\to μ^- \barν_μ$, we explore theoretically cl…
Recent LHCb measurements show small discrepancies with respect to the Standard Model (SM) predictions in selected angular distributions of the mode $B^0 \to K^{*0} μ^+ μ^-$. The possibility of explaining such tensions within theories beyond the SM crucially depends on the size of the deviations of the Wilson coefficients of the effective Hamiltonian for this mode, in comparison to their SM values. We analyse this issue in the framework of the Randall Sundrum model with custodial protection (RS$_c$); in our study we also consider the mode with $τ$ leptons in the final state. We discuss the smal…
In the $\rm SU(3)_F$ symmetry limit, using two- and three-particle distribution amplitudes of $B^{\pm}$-meson for $B_s$, the transition form factors of semileptonic $B_{s}\to K_{0}^*(1430)$ decays are calculated in the framework of the light-cone sum rules. The two-particle distribution amplitudes, $φ_{_{+}}(ω)$ and $φ_{_{-}}(ω)$ have the most important contribution in estimation of the form factors $f_{+}(q^2)$, $f_{-}(q^2)$ and $f_{T}(q^2)$. The knowledge of the behavior of $φ_{_+}(ω)$ is still rather limited. Therefore, we consider three different parametrizations for the shapes of $φ_{_+}(…
Inspired by the new measurements on $B^{-}\to η^{(\prime)}\ell \barν_{\ell}$ from the BaBar Collaboration, we examine the constraint on the flavor-singlet mechanism, proposed to understand the large branching ratios for $B\to η^{\prime} K$ decays. Based on the mechanism, we study the decays of $\bar B_{d,s}\to η^{(\prime)} \ell^{+} \ell^{-}$ and find that they are sensitive to the flavor-singlet effects. In particular, we show that the decay branching ratios of $\bar B_{d,s}\to η^{\prime} \ell^{+} \ell^{-}$ can be as large as $O(10^{-8})$ and $O(10^{-6})$, respectively.
Semileptonic $B$($B_s, B_c$) decays are investigated systematically in the light-cone QCD sum rules. Special emphasis is put on the LCSR calculation on weak form factors with an adequate chiral current correlator, which turns out to be particularly effective to control the pollution by higher twist components of spectator mesons. The result for each channel depends on the distribution amplitude of the the producing meson. The leading twist distribution amplitudes of the related heavy mesons and charmonium are worked out by a model approach in the reasonable way. A practical scenario is suggest…
We report on the Lattice determination of the semileptonic form factors by lattice QCD. Comparison with the light-cone QCD sum rules are made for $\Btopi, \Btorho$ semileptonic decays.
The form factors of the weak $Ξ_c\to Ξ(Λ)$ transitions are calculated in the framework of the relativistic quark model based on the quasipotential approach. All relativistic effects including transformations of the baryon wave functions from the rest to moving reference frame and contributions of the intermediate negative energy states are systematically taken into account. The explicit analytic expressions which reliably approximate the momentum transfer $q^2$ dependence of the form factors in the whole accessible kinematical range are given. The calculated form factors are applied for the ev…
We systematically revisit the baryonic four-body semileptonic decays of $B^- \to {\bf B}\bar{\bf B}'\ell^- \barν_{\ell}$ by the perturbative QCD counting rules with ${\bf B}$ representing octet baryons and $\ell=e,μ$. We study the transition form factors of $B^- \to {\bf B} \bar{\bf B}'$ in the limit of $(p_{\bf B}+p_{\bar{\bf B}'})^2 \to \infty $ with the three-body $\bar{B}\to {\bf B}\bar{\bf B}' M$ and $B^- \to p\bar{p} μ^- \barν_μ$ data along with $SU(3)_f$ flavor symmetry. We calculate the decay branching ratios and angular asymmetries as well as the differential decay branching fractions…
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.
The weak decay process of $Ω_c$ to $Ξ$ is calculated in the method of QCD light-cone sum rule. The decay width of $Ω_c^0 \to Ξ^- l^+ ν_l$ and its decay branching ratio are also calculated with the form factors from this work's calculation. To the twist-6 distribution amplitudes, the form factors $f_1=0.66\pm0.02, f_2=-0.76\pm0.03, g_1=0.06\pm0.01$ and $g_2=-0.44\pm0.01$ are given at zero recoil point. The result of the semileptonic decay width of $Ω_c^0 \to Ξ^-l^+ν_l$ is $Γ=(7.51\pm0.36)\times10^{-15}~{\rm{GeV}}$ , and the prediction of the decay branching ratio $Br(Ω_c^0\toΞ^-l^+ν_l)=(3.06\pm…
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.
The tree-level $b\rightarrow c{\ell}\barν_{\ell}$ based hadronic transitions have been on the focus of much attention since recording significant deviations of the experimental data, on the ratios of the branching fractions in $ τ$ and $ e-μ$ channels of the semileptonic $ B \rightarrow D $ transition, from the SM predictions by BaBar Collaboration in 2012. It can be of great importance to look whether similar discrepancies take place in the semileptonic baryonic $Λ_{b}\rightarrow Λ_{c}{\ell}\barν_{\ell}$ decay channel or not. In this accordance we estimate the decay width as well as the ratio…
In this work, we study the semileptonic decay modes $B_s^0\to π^+π^-\ell^+\ell^-$ and $D_s^+\to π^+π^-\ell^+ ν$ in the kinematics region where the $π^+π^-$ system has a invariant mass in the range $0.5$-$1.3$ GeV. These processes are valuable towards the determination of S-wave $π^+π^-$ light-cone distribution amplitudes whose normalizations are scalar form factors. We compare the results for scalar form factors predicted in unitarized chiral perturbation theory and extracted from the data on the $B_s\to J/ψπ^+π^-$. Then the $B_s\to π^+π^-$ and $D_s\to π^+π^-$ form factors are calculated in li…
Semileptonic sum rules in heavy-to-light charm decays
KEK Theory Center, IPNS, KEK（高能加速器研究机构理论中心）；Graduate Institute for Advanced Studies, SOKENDAI（综合研究大学院大学高等研究院）；Institute for Advanced Research (IAR), Nagoya University（名古屋大学先进研究院）；Kobayashi-Maskawa Institute (KMI) for the Origin of Particles and the Universe, Nagoya University（名古屋大学小林·益川粒子与宇宙起源研究所）；Department of Liberal Arts, Saitama Medical University（埼玉医科大学人文学部）；Department of Physics, Nagoya University（名古屋大学物理学系）；Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University（华中师范大学粒子物理研究所及夸克与轻子物理教育部重点实验室）
A field theoretic description for inclusive semileptonic B meson decays is formulated. We argue that large regions of the phase spaces for the decays are dominated by distances near the light cone. The light-cone dominance allows to incorporate nonperturbative QCD effects in a distribution function. A one-to-one correspondence with the heavy quark effective theory is developed, which can estimate the first two moments of the distribution function. These conditions are useful but not restrictive enough to specify the distribution function, which must still be determined from experiment. Several…
In terms of ${\cal P}_{c1,c2}={\cal P}_c(4380,4450)^+$ as the hidden charm pentaquark states to consist of $c\bar c uud$, we study the semileptonic $Λ_b\to ({\cal P}_{c1,c2}\to)J/ψp \ell^-\bar ν_\ell$ decays. In our discussion, while the main contribution to $Λ_b\to K^-J/ψp$ is from the non-perturbative process via the doubly charmful $b\to c\bar cs$ transition, we propose that the $Λ_b\to {\cal P}_{c1,c2}\to J/ψp$ transitions are partly contribute to the $Λ_b\to K^-({\cal P}_{c1,c2}\to)J/ψp$ decays, in which the required $c\bar c$ pair is formed by the sea quarks, intrinsic charm, or both. We…
We review a novel model-independent approach to the analysis of new-physics effects in the $s\to u\ell^-\barν$ transitions. We apply it to (semi)leptonic kaon decays and study their complementarity with pion and hyperon $β$ decays or with collider searches of new physics.
Semileptonic $Λ_b$ decays are investigated in the framework of the relativistic quark model based on the quasipotential approach and the quark-diquark picture of baryons. The decay form factors are expressed through the overlap integrals of the initial and final baryon wave functions. All calculations are done without employing nonrelativistic and heavy quark expansions. The momentum transfer dependence of the decay form factors is explicitly determined in the whole accessible kinematical range without any extrapolations or model assumptions. Both the heavy-to-heavy $Λ_b\toΛ_c\ellν_\ell$ and h…
We calculated the form factors of $B_{c}$ transitions into $η^{(')}$ meson and pseudoscalar Glueball, where the $B_{c}$ meson is a bound state of two different heavy flavors and is treated as a nonrelativistic state, while the mesons $η^{(')}$ and Glueball are treated as light-cone objects since their masses are smaller enough compared to the transition momentum scale. The mechanism of two gluon scattering into $η^{(')}$ dominated the form factors of $B_{c}$ decays into $η^{(')}$. We considered the $η-η'-$Glueball mixing effect, and then obtained their influences on the form factors. The form …
We extend our general framework for semileptonic decay, originally introduced in N. Penalva et al. [Phys. Rev. D100, 113007 (2019)], with the addition of new physics (NP) tensor terms. In this way, all the NP effective Hamiltonians that are considered in lepton flavour universality violation (LFUV) studies have now been included. Besides, we now also give general expressions that allow for complex Wilson coefficients. The scheme developed is totally general and it can be applied to any charged current semileptonic decay, involving any quark flavors or initial and final hadron states. We show t…
The tree level semileptonic $Λ_{b}\to plν$ and $Λ_{c}\to nlν$ transitions are investigated using the light cone QCD sum rules approach in full theory. The spin--1/2, $Λ_{Q}$ baryon with $Q=b$ or $c$, is considered by the most general form of its interpolating current. The time ordering product of the initial and transition currents is expanded in terms of the nucleon distribution amplitudes with different twists. Considering two sets of independent input parameters entering to the nucleon wave functions, namely, QCD sum rules and Lattice QCD parameters, the related form factors and their heavy…
We consider the form factors for the radiative semileptonic decays $\bar{B}(v) \rightarrow D^{(*)}(v') \ell {\bar ν}_\ell γ$ in the kinematic region where the photon momentum, $k$, is small enough that heavy quark symmetry (HQS) can be applied without the radiated photon changing the heavy quark velocity (i.e., $v^{(\prime)} \cdot k < m_{(b,c)}$). We find that HQS is remarkably powerful, leaving only four new undetermined form factors at leading order in $1/m_{(b,c)}$. In addition, one of them is fixed in terms of the leading order Isgur-Wise function in the kinematic region, $v^{(\prime)}\cdo…
We consider the Drell-Yan processes $pp \to \ell \ell^{(\prime)}$ and $pp\to \ell \barν$ at high-$p_T$ as probes of New Physics effects in semileptonic transitions. For this purpose, we describe the $2\to2$ scattering amplitudes in terms of general form-factors which we match to the SMEFT at $\mathcal{O}(1/Λ^{4})$ including corrections from dimension-$8$ operators and to tree-level mediators with $\mathcal{O}$(TeV) masses arising from ultraviolet models. By using the latest LHC run-II data from monolepton and dilepton production channels, we derive constraints on the SMEFT and on leptoquark mo…
Inclusive semileptonic decays of beauty baryons are studied using the heavy quark expansion to ${\cal O}(1/m_b^3)$, at leading order in $α_s$. The case of a polarized decaying baryon is examined, with reference to $Λ_b$. An extension of the Standard Model effective Hamiltonian inducing $b \to U \ell {\bar ν}_ \ell$ transitions ($U=u,\,c$ and $\ell=e,\,μ,\,τ$) is considered, which comprises the full set of D=6 semileptonic operators with left-handed neutrinos. The effects of the new operators in several observables are described.
We present a new calculation of the semileptonic tree-level and flavor-changing neutral current form factors describing $B$-meson transitions to tensor mesons $T=D_2^*,K_2^*,a_2,f_2$ ($J^{P}=2^{+}$). We employ the QCD Light-Cone Sum Rules approach with $B$-meson distribution amplitudes. We go beyond the leading-twist accuracy and provide analytically, for the first time, higher-twist corrections for the two-particle contributions up to twist four terms. We observe that the impact of higher twist terms to the sum rules is noticeable. We study the phenomenological implications of our results on …
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…
The following is an overview of the measurements of the CKM matrix elements V_cb and V_ub that are based on detailed studies of semileptonic B decays by the BABAR and Belle Collaborations and recent advances in QCD calculations. In addition, a new and improved measurement of the ratios R(D^(*))= BF(Bbar --> D^(*) tau^- nu_tau)/BF(Bbar -->D^(*) ell^- nu_ell) is presented. Here D^(*) refers to a D or a D^* meson and ell is either e or mu. The results, R(D) = 0.440 +/- 0.058 +/- 0.042 and R(D^*)= 0.332 +/- 0.024 +/- 0.018, exceed the Standard Model expectations by 2.0 s.d. and 2.7 s.d, respective…
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.
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.
