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 exclusive four-body modes.
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 th…
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…
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 …
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…
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 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…
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…
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…
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…
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）
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 …
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 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…
We apply the general formalism derived in N. Penalva et al. [Phys. Rev. D 101, 113004 (2020)] to the semileptonic decay of pseudoscalar mesons containing a $b$ quark. While present $B\to D^{(*)}$ data give the strongest evidence in favor of lepton flavor universality violation, the observables that are normally considered are not able to distinguish between different new physics (NP) scenarios. In the above reference we discussed the relevant role that the various contributions to the double differential decay widths $d^2Γ/(dωd\cosθ_\ell)$ and $d^2Γ/(dωdE_\ell)$ could play to this end. Here $ω…
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 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…
Leptonic and semileptonic decays in the charm sector have been well studied in recent years. With the largest data sample near $D\bar D$ threshold, precision measurements of leptonic and semileptonic decays of charm meson and baryon are perfromed at BESIII. Test for letpon flavor universality is also performed. Sensitivity for rare leptonic and semileptonic charm decays is significantly improved taking advantage of the huge statistics in LHCb and the $B$ factories.
Comparative analysis of the semileptonic $Λ_b \rightarrow Λ\ell^+ \ell^-$ transition in SM and different SUSY scenarios using form factors from full QCD
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 …
Semileptonic Decays of $Λ\to p \ell^{-} \barν_{\ell}$ in the Light-Front Dynamics
Chongqing University of Posts and Telecommunications（重庆邮电大学）；School of Fundamental Physics and Mathematical Sciences, Hangzhou Institute for Advanced Study, UCAS（杭州高等研究院基础物理与数学学院，UCAS）
利用光前夸克模型，在标准模型框架下研究 $\Lambda\to p \ell^{-} \bar\nu_{\ell}$ 的半轻衰变，通过处理非价贡献得到跃迁形状因子，计算的分支比与 BESIII 最新测量一致，表明非价贡献不可忽略。
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…
Radiative corrections to the three-body region of the Dalitz plot of baryon semileptonic decays with angular correlation between polarized emitted baryons and charged leptons: The initial-baryon rest frame case
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…
Semileptonic decays $Λ_c^+ \to Λ\ell^+ ν_\ell\,\,(\ell=e,μ)$ in the covariant quark model and comparison with the new absolute branching fraction measurements of Belle and BESIII
This article analyses the available inputs in $\btopilnu$ and $\btorholnu$ decays which include the measured values of differential rate in different $q^2$-bins (lepton invariant mass spectrum), lattice, and the newly available inputs on the relevant form-factors from the light-cone sum rules (LCSR) approach. We define different fit scenarios, and in each of these scenarios, we predict a few observables in the standard model (SM). For example, $R(M) =\frac{\mathcal{B}(B \to M\ell_iν_{\ell_i})}{\mathcal{B}(B\to M\ell_jν_{\ell_j})} $, $R^{\ell_i}_{\ell_j}(M) =\frac{\mathcal{B}(B\to \ell_iν_{\ell…
