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Hai-Bing Fu

Publications and source records attributed to Hai-Bing Fu.

At least 55 records · Page 3Linked to original sources
arXiv2023

Revisiting $D$-meson twist-2, 3 distribution amplitudes

Due to the significant difference between the experimental measurements and the theoretical predictions of standard model (SM) for the value of $\mathcal{R}(D)$ of the semileptonic decay $B\to D\ell\barν_{\ell}$, people speculate that it may be the evidence of new physics beyond the SM. Usually, the $D$-meson twist-2, 3 distribution amplitudes (DAs) $ϕ_{2;D}(x,μ)$, $ϕ_{3;D}^p(x,μ)$ and $ϕ_{3;D}^σ(x,μ)$ are the main error sources when using perturbative QCD factorization and light-cone QCD sum rules to study $B\to D\ell\barν_{\ell}$. Therefore, it is important to get more reasonable and accurate behaviors for those DAs. Motivated by our previous work [Phys. Rev. D 104, no.1, 016021 (2021)] on pionic leading-twist DA, we revisit $D$-meson twist-2, 3 DAs $ϕ_{2;D}(x,μ)$, $ϕ_{3;D}^p(x,μ)$ and $ϕ_{3;D}^σ(x,μ)$. New sum rules formulae for the $ξ$-moments of these three DAs are suggested to obtain more accurate values. The light-cone harmonic oscillator models for those DAs are improved, and whose model parameters are determined by fitting the values of $ξ$-moments with the least squares method.

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arXiv2023

New determination of $|V_{\rm cb}|$ using the three-loop QCD corrections for the $B\to D^{\ast}$ semi-leptonic decays

We present a new determination of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{\rm cb}|$ by using the three-loop perturbative QCD corrections for the $B\to D^{\ast}$ semi-leptonic decay. The decay width of $B\to D^{\ast}$ semi-leptonic decay can be factorized as perturbatively calculable short-distance part and the non-perturbative but universal long-distance part. We adopt the principle of maximum conformality (PMC) single-scale setting approach to deal with the perturbative series so as to achieve a precise fixed-order prediction for the short-distance parameter $η_{A}$. By applying the PMC, an overall effective $α_s$ value is achieved by recursively using the renormalization group equation, which inversely results in a precise scale-invariant pQCD series. Such scale-invariant series also provides a reliable basis for predicting the contributions from uncalculated perturbative terms. We then obtain $η_{A}=0.9225^{+0.0117}_{-0.0168}$, where the error is the squared average of those from $Δα_{s}(M_Z)=\pm0.0010$ and the uncertainties caused by the uncalculated higher-order perturbative terms. By using the data of $B\to D^{\ast}\ell\barν_{\ell}$, we finally obtain $|V_{\rm cb}|_{\rm PMC} =(40.60^{+0.53}_{-0.57})\times10^{-3}$, which is consistent with the PDG value within errors.

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arXiv2022

Searching for $a_0(980)$-meson parton distribution function

In this paper, we calculate the scalar $a_0(980)$-meson leading-twist wavefunction by using light-cone harmonic oscillator model (LCHO). In which the model parameters are determined by fitting the $ξ$-moments $\langleξ_{a_0}^n\rangle_ζ$ of its light-cone distribution amplitudes. Then, the $a_0(980)$-meson leading-twist light-cone distribution amplitudes with three different scales $ζ= (1.0, 2.0, 5.2)~{\rm GeV}$ are given. After constructing the relationship between $a_0(980)$-meson leading-twist parton distribution functions/valence quark distribution function and its LCHO wavefunction, we exhibit the $q^{a_0}(x,ζ)$ and $x q^{a_0}(x,ζ)$ with different scales. Furthermore, we also calculate the Mellin moments of the $a_0(980)$-meson's valence quark distribution function $\langle x^n q^{a_0}\rangle_ζ$ with $n = (1,2,3)$, i.e. $\langle x q^{a_0}\rangle_{ζ_5} = 0.026$, $\langle x^2 q^{a_0}\rangle_{ζ_5} = 0.017$ and $\langle x^3 q^{a_0}\rangle_{ζ_5} = 0.012$. Finally, the scale evolution for the ratio of the Mellin moments $x^n_{a_0}(ζ,ζ_k)$ are presented.

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arXiv2022

Investigation for $Z$-boson decay into $Ξ_{bc}$ and $Ξ_{bb}$ baryon with the NRQCD factorizations approach

The $Z$-boson decay provides good opportunities for the research on $Ξ_{bQ'}$ baryon due to large quantity of $Z$ events that can be collected at the high-energy colliders. We performed a completed investigation of the indirect production of the $Ξ_{bc}$ and $Ξ_{bb}$ baryon via $Z$-boson decay $Z\to Ξ_{bQ'}+\bar b +\bar Q'$ with $Q'= (c, b)$ quark according to NRQCD factorizations approach. After considering the contribution of the diquark states $\langle bc\rangle [^3S_1]_{\bar 3/6}$, $\langle bc\rangle [^1S_0]_{\bar 3/6}$, $\langle bb\rangle [^1S_0]_{6}$ and $\langle bb\rangle [^3S_1]_{\bar 3}$, the calculated branching ratio for $Z\toΞ_{bQ'}+X$ are ${\cal B}(Z\toΞ_{bc}+X) = 3.595\times 10^{-5}$ and ${\cal B}(Z\toΞ_{bc}+X) = 1.213\times 10^{-6}$. Moreover, the $Ξ_{bc}$ events produced are predicted to be of the $10^4(10^7)$ order at the LHC(CEPC), while the $Ξ_{bb}$ events produced are forecasted to be of the $10^3(10^6)$ order. Furthermore, we have estimated the production ratio ${\cal R}(Z_Q\toΞ^{+,0}_{bc})$ with four $Z$-boson decay channels. The ${\cal R}(Z_Q\toΞ^{+,0}_{bc})$ up to $10^{-6}$ for $Z\to c\bar c$ channel and $10^{-5}$ for $Z\to b\bar b$ channel, respectively. Finally, we present the differential decay widths of $Ξ_{bc}(Ξ_{bb})$ with respect to $s_{23}$ and $z$ distributions, and analysis the uncertainties.

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arXiv2022

Next-to-leading-order QCD correction to the exclusive double charmonium production via $Z$ decays

In this paper, we preformed a further research on the exclusive productions of double charmonium via $Z$-boson decay by using nonrelativistic QCD factorizations approach, where the single-photon fragmentation topologies of the QED diagrams, the interference terms between the QCD and full QED diagrams, the next-to-leading-order calculations of the interference terms are preformed. For the production of $J/ψ+J/ψ$ in $Z$-boson decay, the interference terms show a significantly phenomenological effect due to the addition of the newly calculated NLO QCD corrections. After adding together all contributions, the branching fraction $\mathcal{B}_{Z\to J/ψJ/ψ}$ still undershoots the CMS collaboration data obviously. In addition, we simultaneously complete the next-to-leading-order calculations for $Z\to J/ψ+η_c (χ_{cJ})$ with $J=(0,1,2)$. The calculated results show that the newly-calculated complete QED and cross terms will have obvious effective on the total decay widths.

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arXiv2022

Constraint of $ξ$-moments calculated with QCD sum rules on the pion distribution amplitude models

So far, the behavior of the pionic leading-twist distribution amplitude (DA) $ϕ_{2;π}(x,μ)$ $-$ which is universal physical quantity and enters the high-energy processes involving pion based on the factorization theorem $-$ has not been completely consistent. The form of $ϕ_{2;π}(x,μ)$ is usually described by phenomenological models and constrained by the experimental data of the exclusive processes containing pion or the moments calculated with the QCD sum rules and lattice QCD theory. Obviously, an appropriate model is very important for us to determine the exact behavior of $ϕ_{2;π}(x,μ)$. In this paper, by adopting the least squares method to fit the $ξ$-moments calculated with QCD sum rules based on the background field theory, we perform an analysis for several commonly used models of the pionic leading-twist DA in the literature, such as the truncation form of the Gegenbauer polynomial series, the light-cone harmonic oscillator model, the form from the Dyson-Schwinger equations, the model from the light-front holographic AdS/QCD and a simple power-law parametrization form.

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arXiv2022

$a_1(1260)$-meson longitudinal twist-2 distribution amplitude and the $D\to a_1(1260)\ell^+ν_\ell$ decay processes

In the paper, we investigate the moments $\langleξ_{2;a_1}^{\|;n}\rangle$ of the axial-vector $a_1(1260)$-meson distribution amplitude by using the QCD sum rules approach under the background field theory. By considering the vacuum condensates up to dimension-six and the perturbative part up to next-to-leading order QCD corrections, its first five moments at an initial scale $μ_0=1~{\rm GeV}$ are $\langleξ_{2;a_1}^{\|;2}\rangle|_{μ_0} = 0.223 \pm 0.029$, $\langleξ_{2;a_1}^{\|;4}\rangle|_{μ_0} = 0.098 \pm 0.008$, $\langleξ_{2;a_1}^{\|;6}\rangle|_{μ_0} = 0.056 \pm 0.006$, $\langleξ_{2;a_1}^{\|;8}\rangle|_{μ_0} = 0.039 \pm 0.004$ and $\langleξ_{2;a_1}^{\|;10}\rangle|_{μ_0} = 0.028 \pm 0.003$, respectively. We then construct a light-cone harmonic oscillator model for $a_1(1260)$-meson longitudinal twist-2 distribution amplitude $ϕ_{2;a_1}^{\|}(x,μ)$, whose model parameters are fitted by using the least squares method. As an application of $ϕ_{2;a_1}^{\|}(x,μ)$, we calculate the transition form factors (TFFs) of $D\to a_1(1260)$ in large and intermediate momentum transfers by using the QCD light-cone sum rules approach. At the largest recoil point ($q^2=0$), we obtain $ A(0) = 0.130_{ - 0.013}^{ + 0.015}$, $V_1(0) = 1.898_{-0.121}^{+0.128}$, $V_2(0) = 0.228_{-0.021}^{ + 0.020}$, and $V_0(0) = 0.217_{ - 0.025}^{ + 0.023}$. By applying the extrapolated TFFs to the semi-leptonic decay $D^{0(+)} \to a_1^{-(0)}(1260)\ell^+ν_\ell$, we obtain ${\cal B}(D^0\to a_1^-(1260) e^+ν_e) = (5.261_{-0.639}^{+0.745}) \times 10^{-5}$, ${\cal B}(D^+\to a_1^0(1260) e^+ν_e) = (6.673_{-0.811}^{+0.947}) \times 10^{-5}$, ${\cal B}(D^0\to a_1^-(1260) μ^+ ν_μ)=(4.732_{-0.590}^{+0.685}) \times 10^{-5}$, ${\cal B}(D^+ \to a_1^0(1260) μ^+ ν_μ)=(6.002_{-0.748}^{+0.796}) \times 10^{-5}$.

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arXiv2022

$B_c \to J/ψ$ helicity form factors and the $B_c^+ \to J/ψ+(P, V, \ell^+ ν_\ell)$ decays

In this paper, we calculate the $B_c\to J/ψ$ helicity form factors (HFFs) up to twist-4 accuracy by using the light-cone sum rules (LCSR) approach. After extrapolating those HFFs to the physically allowable $q^2$ region, we investigate the $B^+_c$-meson two-body decays and semi-leptonic decays $B_c^+ \to J/ψ+(P, V, \ell^+ ν_\ell)$ with $P/V$ stands for light pseudoscalar/vector meson, respectively. The branching fractions can be derived by using the CKM matrix element and the $B_c$ lifetime from the Particle Data Group, and we obtain ${\cal B}(B_c^+ \to J/ψπ^+)=(0.136^{+0.002}_{-0.002})\%$, ${\cal B}(B_c^+ \to J/ψK^+)=(0.010^{+0.000}_{-0.000})\%$, ${\cal B}(B_c^+ \to J/ψρ^+) =(0.768^{+0.029}_{-0.033})\%$, ${\cal B}(B_c^+ \to J/ψK^{\ast +})=(0.043^{+0.001}_{-0.001})\%$, ${\cal B}(B_c^+ \to J/ψμ^+ν_μ)=(2.802^{+0.526}_{-0.675})\%$ and ${\cal B}(B_c^+ \to J/ψτ^+ν_τ)=(0.559^{+0.131}_{-0.170})\%$. We then obtain ${\cal R}_{π^+/μ^+ν_μ} = 0.048^{+ 0.009}_{-0.012}$ and ${\cal R}_{K^+ / π^+} = 0.075^{+0.005}_{-0.005}$, which agree with the LHCb measured value within $1σ$-error. We also obtain ${\cal R}_{J/ψ}=0.199^{+ 0.060}_{-0.077}$, which like other theoretical predictions, is consistent with the LHCb measured value within $2σ$-error. Those imply that the HFFs under the LCSR approach are also applicable to the $B^+_c$ meson two-body decays and semi-leptonic decays $B_c^+ \to J/ψ+(P, V, \ell^+ ν_\ell)$, and the HFFs obtained by using LCSR in a new way implies that there may be new physics in the $B_c\to J/ψ\ell^+ ν_\ell$ semi-leptonic decays.

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arXiv2022

The ratio $\mathcal{R}(D_s)$ for $B_s \to D_s \ellν_\ell$ by using the QCD light-cone sum rules within the framework of heavy quark effective field theory

In the paper, we study the $B_s\to D_s$ transition form factors by using the light-cone sum rules within the framework of heavy quark effective field theory. We adopt a chiral current correlation function to do the calculation, the resultant transition form factors $f_+^{B_s\to D_s}(q^2)$ and $f_0^{B_s\to D_s}(q^2)$ are dominated by the contribution of $D_s$-meson leading-twist distribution amplitude, while the contributions from less certain $D_s$-meson twist-3 distribution amplitudes are greatly suppressed. At the largest recoil point, we obtain $f_{+,0}^{B_s \to D_s}(0)=0.533^{+0.112}_{-0.094}$. By further extrapolating the transition form factors into all the physically allowable $q^2$ region with the help of the $z$-series parametrization approach, we calculate the branching fractions $\mathcal{B}(B_s \to D_s \ell^\prime ν_{\ell^\prime})$ with $(\ell^\prime= e,μ)$ and $\mathcal{B}(B_s \to D_s τν_τ)$, which gives $\mathcal{R}(D_s)=0.334\pm 0.017$.

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arXiv2022

Investigating the ratio of CKM matrix elements $|V_{ub}|/|V_{cb}|$ from semileptonic decay $B_s^0\to K^-μ^+ν_μ$ and kaon twist-2 distribution amplitude

In this paper, we calculate the ratio of Cabibbo-Kobayashi-Maskawa matrix elements, $|V_{ub}|/|V_{cb}|$, based on the semileptonic decay $B_s^0\to K^-μ^+ν_μ$. Its key component, the $B_s\to K$ transition form factor $f^{B_s\to K}_+(q^2)$, is studied within the QCD light-cone sum rules approach by using a chiral correlator. The derived $f^{B_s\to K}_+(q^2)$ is dominated by the leading-twist part, and to improve its precision, we construct a new model for the kaon leading-twist distribution amplitude $ϕ_{2;K}(x,μ)$, whose parameters are fixed by using the least squares method with the help of the moments calculated by using the QCD sum rules within the background field theory. The first four moments at the initial scale $μ_0 = 1~{\rm GeV}$ are, $\langle ξ^1\rangle _{2;K} = -0.0438^{+0.0053}_{-0.0075}$, $\langle ξ^2\rangle _{2;K} = 0.262 \pm 0.010$, $\langle ξ^3\rangle _{2;K} = -0.0210^{+0.0024}_{-0.0035}$ and $\langle ξ^4\rangle _{2;K} = 0.132 \pm 0.006$, respectively. And their corresponding Gegenbauer moments are, $a^{2;K}_1 = -0.0731^{+0.0089}_{-0.0124}$, $a^{2;K}_2 = 0.182^{+0.029}_{-0.030}$, $a^{2;K}_3 = -0.0114^{+0.0008}_{-0.0016}$ and $a^{2;K}_4 = 0.041^{-0.003}_{+0.005}$, respectively. At the large recoil region, we obtain $f^{B_s\to K} _+ (0) = 0.270^{+0.022}_{-0.030}$. By extrapolating $f^{B_s\to K}_+(q^2)$ to all the physical allowable region, we obtain a $|V_{ub}|$-independent decay width for the semileptonic decay $B_s^0\to K^-μ^+ν_μ$, $5.626^{+1.271}_{-0.864} \times 10^{-12}\ {\rm GeV}$, which then leads to $|V_{ub}|/|V_{cb}| = 0.072\pm0.005$.

hep-ph↗
arXiv2021

$η^{(\prime)}$-meson twist-2 distribution amplitude within QCD sum rule approach and its application to the semi-leptonic decay $ D_s^+ \toη^{(\prime)}\ell^+ ν_\ell$

In this paper, we make a detailed discussion on the $η$ and $η'$-meson leading-twist light-cone distribution amplitude $ϕ_{2;η^{(\prime)}}(u,μ)$ by using QCD sum rules approach under the background field theory. Taking both the non-perturbative condensates up to dimension-six and NLO QCD corrections to the perturbative part, its first three moments $\langleξ^n_{2;η^{(\prime)}}\rangle|_{μ_0} $ with $n = (2,4,6)$ at initial scale $μ_0 = 1$ GeV can be determined. e.g. $\langleξ_{2;η}^2\rangle|_{μ_0} =0.231_{-0.013}^{+0.010}$, $\langleξ_{2;η}^4 \rangle|_{μ_0} =0.109_{-0.007}^{+0.007}$, and $\langleξ_{2;η}^6 \rangle|_{μ_0} =0.066_{-0.006}^{+0.006}$ for $η$-meson, $\langleξ_{2;η'}^2\rangle|_{μ_0} =0.211_{-0.017}^{+0.015}$, $\langleξ_{2;η'}^4 \rangle|_{μ_0} =0.093_{-0.009}^{+0.009}$, and $\langleξ_{2;η'}^6 \rangle|_{μ_0} =0.054_{-0.008}^{+0.008}$ for $η'$-meson. Next, we calculate $D_s\toη^{(\prime)}$ TFFs $f^{η^{(\prime)}}_+(q^2)$ within QCD light-cone sum rules approach up to NLO level. The values at large recoil region are $f^η_+(0) = 0.476_{-0.036}^{+0.040}$ and $f^{η'}_+(0) = 0.544_{-0.042}^{+0.046}$. After extrapolating TFFs to the allowable physical regions within the series expansion, we obtain the branching fractions of the semi-leptonic decay, i.e. $D_s^+\toη^{(\prime)}\ell^+ ν_\ell$, i.e. ${\cal B}(D_s^+\toη^{(\prime)} e^+ν_e)=2.346_{-0.331}^{+0.418}(0.792_{-0.118}^{+0.141})\times10^{-2}$ and ${\cal B}(D_s^+\toη^{(\prime)} μ^+ν_μ)=2.320_{-0.327}^{+0.413}(0.773_{-0.115}^{+0.138})\times10^{-2}$ for $\ell = (e, μ)$ channels respectively. And in addition to that, the mixing angle for $η-η'$ with $φ$ and ratio for the different decay channels ${\cal R}_{η'/η}^\ell$ are given, which show good agreement with the recent BESIII measurements.

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arXiv2021

An improved light-cone harmonic oscillator model for the pionic leading-twist distribution amplitude

In this paper, we study the pion leading-twist distribution amplitude $ϕ_{2;π}(x,μ)$ by improving the traditional light-cone harmonic oscillator model within the reconstruction of the function $φ_{2;π}(x)$. In order to constraining the model parameters, we calculate its moments $\langleξ^n\rangle_{2;π}|_μ$ in the framework of QCD background field theory sum rule (BFTSR) up to $10^{\rm th}$ order. Considering the fact that the sum rule of the $0^{\rm th}$ moment $\langleξ^0\rangle_{2;π}|_μ$ cannot be normalized, we suggest a more reasonable sum rule formula for $\langleξ^n\rangle_{2;π}|_μ$. Then, we obtain the values of $\langleξ^n\rangle_{2;π}|_{μ_0}$ with $n=(2,4,6,8,10)$ at the initial scale $μ_0 = 1~{\rm GeV}$. The first two moments are: $\langle ξ^2\rangle_{2;π}|_{μ_0} = 0.271 \pm 0.013$, $\langleξ^4\rangle_{2;π}|_{μ_0} = 0.138 \pm 0.010$; and the corresponding Gegenbauer moments are $a^{2;π}_2(μ_0) = 0.206 \pm 0.038$, $a^{2;π}_4(μ_0) = 0.047 \pm 0.011$, respectively. After fitting the moments $\langleξ^n\rangle_{2;π}|_μ$, we obtained the appropriate model parameters by using the least square method. The resultant behavior for twist-2 pion DA is more closely to the AdS/QCD and lattice result, but is narrower than that by Dyson-Schwinger equation. Furthermore, we calculate the pion-photon transition form factors (TFF) and $B\toπ$ TFF within light-cone sum rule approach, which are conform with experimental and theoretical results.

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arXiv2021

The $D_s$-meson leading-twist distribution amplitude within the QCD sum rules and its application to the $B_s \to D_s$ transition form factor

We make a detailed study on the $D_s$ meson leading-twist LCDA $ϕ_{2;D_s}$ by using the QCD sum rules within the framework of the background field theory. To improve the precision, its moments $\langle ξ^n\rangle _{2;D_s}$ are calculated up to dimension-six condensates. At the scale $μ= 2{\rm GeV}$, we obtain: $\langle ξ^1\rangle _{2;D_s}= -0.261^{+0.020}_{-0.020}$, $\langle ξ^2\rangle _{2;D_s} = 0.184^{+0.012}_{-0.012}$, $\langle ξ^3\rangle _{2;D_s} = -0.111 ^{+0.007}_{-0.012}$ and $\langle ξ^4\rangle _{2;D_s} = 0.075^{+0.005}_{-0.005}$. Using those moments, the $ϕ_{2;D_s}$ is then constructed by using the light-cone harmonic oscillator model. As an application, we calculate the transition form factor $f^{B_s\to D_s}_+(q^2)$ within the light-cone sum rules (LCSR) approach by using a right-handed chiral current, in which the terms involving $ϕ_{2;D_s}$ dominates the LCSR. It is noted that the extrapolated $f^{B_s\to D_s}_+(q^2)$ agrees with the Lattice QCD prediction. After extrapolating the transition form factor to the physically allowable $q^2$-region, we calculate the branching ratio and the CKM matrix element, which give $\mathcal{B}(\bar B_s^0 \to D_s^+ \ellν_\ell) = (2.03^{+0.35}_{-0.49}) \times 10^{-2}$ and $|V_{cb}|=(40.00_{-4.08}^{+4.93})\times 10^{-3}$.

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arXiv2021

Revisiting the production of $J/ψ+η_c$ via the $e^+e^-$ annihilation within the QCD light-cone sum rules

We make a detailed study on the typical production channel of double charmoniums, $e^+e^-\to J/ψ+η_c$, at the center-of-mass collision energy $\sqrt{s}=10.58$ GeV. The key component of the process is the form factor $F_{\rm VP}(q^2)$, which has been calculated within the QCD light-cone sum rules (LCSR). To improve the accuracy of the derived LCSR, we keep the $J/ψ$ light-cone distribution amplitude up to twist-4 accuracy. Total cross sections for $e^+e^-\to J/ψ+η_c$ at three typical factorization scales are $σ|_{μ_s} = 22.53^{+3.46}_{-3.49}~{\rm fb}$, $σ|_{μ_k} = 21.98^{+3.35}_{-3.38}~{\rm fb}$ and $σ|_{μ_0} = 21.74^{+3.29}_{-3.33}~{\rm fb}$, respectively. The factorization scale dependence is small, and those predictions are consistent with the BABAR and Belle measurements within errors.

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arXiv2020

Branching fractions and polarizations of $D\to V(ω,ρ, K^*) \ell ν_\ell$ within QCD LCSR

In this paper, we make a detailed study about the $D\to V$ helicity form factors (HFFs) within the framework of QCD light-cone sum rule (LCSR) up to twist-4 accuracy. After extrapolating the LCSR predictions of HFFs to the whole physical $q^2$-region, we get the longitudinal, transverse and total $|V_{cq}|$-independent decay widths of semileptonic decay $D\to V\ell^+ν_\ell$. Meanwhile, the branching fractions of these decays are also obtained by using the $D^0(D^+)$-meson lifetime, which agree well with the BES-III results within errors. As a further step, we also investigate the differential and mean predictions for charged lepton (vector meson) polarization in the final state $P_{\rm L,T}^\ell$ ($F_{\rm L,T}^\ell$), the forward-backward asymmetry ${\cal A}_{\rm FB}^\ell$, and the lepton-side convexity parameters ${\cal C}_{\rm F}^\ell$. Our predictions are consistent with Covariant Confining Quark Model results within the errors. Thus, we think the LCSR approach for HFFs is applicable for dealing with the $D$-meson semileptonic decays.

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arXiv2020

$D \to P(π,K)$ helicity form factors within light-cone sum rule approach

In this paper, the $D\to P(π, K)$ helicity form factors (HFFs) are studied by applying the QCD light-cone sum rule (LCSR) approach. The calculation accuracy is up to next-to-leading order (NLO) gluon radiation correction of twist-(2,3) distribution amplitude. The resultant HFFs at large recoil point are ${\cal P}_{t,0}^π(0) = 0.688^{+0.020}_{-0.024}$, ${\cal P}_{t,0}^K(0)=0.780^{+0.024}_{-0.029}$. In which, the contributions from three particles of the leading order (LO) are so small that can be safely neglected, and the maximal contribution of the NLO gluon radiation correction for ${\cal P}_{t,0}^{π,K}(0)$ is less than $3\%$. After extrapolating the LCSR predictions for these HFFs to whole $q^2$-region, we obtain the decay widths for semileptonic decay processes $D\to P\ellν_\ell$, which are consistent with BES-III collaboration predictions within errors. After considering the $D^{+}/D^{0}$-meson lifetime, we give the branching fractions of $D\to P\ellν_\ell$ with $\ell = e, μ$, our predictions also agree with BES-III collaboration within errors, especially for $D\to π\ellν_\ell$ decay process. Finally, we present the forward-backward asymmetry ${\cal A}_{\rm FB}^\ell(q^2)$ and lepton convexity parameter ${\cal C}_F^\ell(q^2)$, and further calculate the mean value of these two observations $\langle{\cal A}_{\rm FB}^\ell\rangle$ and $\langle{\cal C}_F^\ell\rangle$, which may provide a way to test those HFFs in future experiments.

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arXiv2020

The $D\to ρ$ semileptonic and radiative decays within the light-cone sum rules

The measured branching ratio of the $D$ meson semileptonic decay $D \to ρe^+ ν_e$, which is based on the $0.82~{\rm fb^{-1}}$ CLEO data taken at the peak of $ψ(3770)$ resonance, disagrees with the traditional SVZ sum rules analysis by about three times. In the paper, we show that this discrepancy can be eliminated by applying the QCD light-cone sum rules (LCSR) approach to calculate the $D\to ρ$ transition form factors $A_{1,2}(q^2)$ and $V(q^2)$. After extrapolating the LCSR predictions of these TFFs to whole $q^2$-region, we obtain $1/|V_{\rm cd}|^2 \times Γ(D \to ρe ν_e) =(55.45^{+13.34}_{-9.41})\times 10^{-15}~{\rm GeV}$. Using the CKM matrix element and the $D^0(D^+)$ lifetime from the Particle Data Group, we obtain ${\cal B} (D^0\to ρ^- e^+ ν_e) = (1.749^{+0.421}_{-0.297}\pm 0.006)\times 10^{-3}$ and ${\cal B} (D^+ \to ρ^0 e^+ ν_e) = (2.217^{+0.534}_{-0.376}\pm 0.015)\times 10^{-3}$, which agree with the CLEO measurements within errors. We also calculate the branching ratios of the two $D$ meson radiative processes and obtain ${\cal B}(D^0\to ρ^0 γ)= (1.744^{+0.598}_{-0.704})\times 10^{-5}$ and ${\cal B}(D^+ \to ρ^+ γ) = (5.034^{+0.939}_{-0.958})\times 10^{-5}$, which also agree with the Belle measurements within errors. Thus we think the LCSR approach is applicable for dealing with the $D$ meson decays.

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arXiv2019

The $B\to π\ellν_\ell$ semileptonic decay within the LCSR approach under heavy quark effective field theory

The heavy quark effective field theory (HQEFT) provides an effective way to deal with the heavy meson decays. In the paper, we adopt two different correlators to derive the light-cone sum rules of the $B \to π$ transition form factors (TFFs) within the framework of HQEFT. We label those two LCSR results as LCSR-${\cal U}$ and LCSR-${\cal R}$, which are for conventional correlator and right-handed correlator, respectively. We observe that the correlation parameter $|ρ_{\rm RU}|$ for the branching ratio ${\cal B}(B \to πl ν_{l})$ is $\sim 0.85$, implying the consistency of the LCSRs under different correlators. Moreover, we obtain $|V_{\rm ub}|_{{\rm LCSR}-{\cal U}}=(3.45^{+0.28}_{-0.20}\pm{0.13}_{\rm{exp}})\times10^{-3}$ and $|V_{\rm ub}|_{{\rm LCSR}-{\cal R}} =(3.38^{+0.22}_{-0.16} \pm{0.12}_{\rm{exp}})\times10^{-3}$. We then obtain $\mathcal{R}_π|_{{\rm LCSR}-{\cal U}}=0.68^{+0.10}_{-0.09}$ and $\mathcal{R}_π|_{{\rm LCSR}-{\cal R}}=0.65^{+0.13}_{-0.11}$, both of them agree with the Lattice QCD predictions. Thus the HQEFT provides a useful framework for studying the $B$ meson decays. Moreover, by using right-handed correlator, the twist-2 terms shall dominant the TFF $f^+(q^2)$, which approaches over $\sim97\%$ contribution in the whole $q^2$-region; and the large twist-3 uncertainty for the conventional correlator is greatly suppressed. One can thus adopt the LCSR-${\cal R}$ prediction to test the properties of the various models for the pion twist-2 distribution amplitudes.

hep-ph↗