Light Cone QCD Sum Rules Research Articles

Scalar form-factors fππ(Q2) and fKK(Q2) with light-cone QCD sum rules

In this paper, we calculate the scalar form-factors fππ(Q2) and fKK(Q2) in the framework of the light-cone QCD sum rules approach. The numerical value of fππ(Q2) changes quickly with the variation of Q2 near zero momentum transfer, while fKK(Q2) has a rather good behavior at small momentum transfer. The value fKK(0) = 2.21+0.35−0.19 GeV is compatible with the result from the leading order chiral perturbation theory. At large momentum transfer with Q2 > 6 GeV2, the form-factor fππ(Q2) takes up the asymptotic behavior approximately, while fKK(Q2) decreases more quickly than .

Analysis of the vertices DDV and D*DV with light-cone QCD sum rules

In this article, we study the vertices DDV and D*DV with the light-cone QCD sum rules. The strong coupling constants gDDV and fD*DV play an important role in understanding the final-state re-scattering effects in the hadronic B decays. They are related to the basic parameters β and λ respectively in the heavy quark effective Lagrangian; our numerical values are smaller than the existing estimations.

Structure of the axial-vector meson Ds1(2460) and the strong coupling constant with the light-cone QCD sum rules

In this paper, we take the point of view that the charmed axial-vector meson Ds1(2460) is the conventional meson and calculate the strong coupling constant in the framework of the light-cone QCD sum rules approach. The numerical values of strong coupling constants and are very large, and support the hadronic dressing mechanism. Just like the scalar mesons f0(980) and a0(980), the scalar meson Ds0(2317) and axial-vector meson Ds1(2460) may have small kernels of the typical meson size; the strong couplings to the hadronic channels (or the virtual mesons loops) may result in smaller masses than the conventional mesons in the constituent quark models, and enrich the pure states with other components.

Analysis of the verticesρNN,ρΣΣ, andρΞΞwith light-cone QCD sum rules

In this article, we calculate the strong coupling constants of the $\ensuremath{\rho}NN$, $\ensuremath{\rho}\ensuremath{\Sigma}\ensuremath{\Sigma}$, and $\ensuremath{\rho}\ensuremath{\Xi}\ensuremath{\Xi}$ in the framework of the light-cone QCD sum rules approach. The strong coupling constants of the meson-baryon-baryon are the fundamental parameters in the one-boson exchange model which describes the baryon-baryon interactions successfully. The numerical values are in agreement with the existing calculations in part. The electric and magnetic $F/(F+D)$ ratios deviate from the prediction of the vector meson dominance theory; the $SU(3)$ symmetry breaking effects are very large.

Analysis of the vector form factors f+ Kπ(Q2) and f- Kπ(Q2) with light-cone QCD sum rules

In this article, we calculate the vector form factors f+ Kπ(Q2) and f- Kπ(Q2) within the framework of the light-cone QCD sum rule approach. The numerical values of f+ Kπ(Q2) are compatible with existing theoretical calculations, and the central value of f+ Kπ(0) (f+ Kπ(0)=0.97) is in excellent agreement with the values from chiral perturbation theory and lattice QCD. The values of |f- Kπ(0)| are very large compared to the theoretical calculations and experimental data, and they cannot give any reliable prediction. At large momentum transfer with Q2 > 5 GeV2, the form factors f+ Kπ(Q2) and |f- Kπ(Q2)| can either show the asymptotic behavior of \(\frac{1}{Q^2}\) or decrease more quickly than \(\frac{1}{Q^2}\); more experimental data are needed to select the ideal sum rules.

Scalar form factor of the nucleon and nucleon-scalar meson coupling constant in QCD

Scalar form factor of the nucleon is calculated in the framework of light-cone QCD sum rules, using the most general form of the baryon current. Using the result on scalar form factor of the nucleon, the nucleon-scalar $\ensuremath{\sigma}$ and ${a}_{0}$ meson coupling constants are estimated. Our results on these couplings are in good agreement with the prediction of the external-field QCD sum rules method.

Analysis of the Σ–n form-factors with light-cone QCD sum rules

In this work, we study the four form-factors f1(Q2), f2(Q2), g1(Q2) and g2(Q2) of the Σ → n in the framework of the light-cone QCD sum rules approach up to twist-6 three valence quark light-cone distribution amplitudes. The f1(0) is the basic input parameter in extracting the CKM matrix element |Vus| from the hyperon decays. The four form-factors f1(Q2), f2(Q2), g1(Q2) and g2(Q2) at intermediate and large momentum transfers with Q2 > 3 GeV2 have significant contributions from the end-point (soft) terms. The numerical values of the four form-factors f1(0), f2(0), g1(0) and g2(0) are compatible with the experimental data and theoretical calculations (in magnitude), although the uncertainties are large.

Bc(B)→Dlν̃ FormFactors in Light-Cone Sum Rules and the D-Meson DistributionAmplitude

We calculate the weak form factors of the decays Bc(B)→Dlν̃by using the chiral current correlator within the framework of the QCDlight-cone sum rules (LCSRs). The expressions of the form factors onlydepend on the leading twist distribution amplitude (DA) of the Dmeson. Three models of the D-meson distribution amplitude areemployed. Our prediction, by using the D-meson distribution amplitudewith the exponential suppression at the end points, favours thethree-points sum rule (3PSR) approach with the Coulomb correctionsincluded, and is compatible with other approaches.

Meson-octet-baryon couplings using light cone QCD sum rules

The coupling constants of $K$ and $\ensuremath{\pi}$ mesons with the octet baryons are studied in light cone QCD sum rules taking into account $\mathrm{SU}(3{)}_{f}$ flavor symmetry breaking effects, but keeping the $\mathrm{SU}(2)$ isospin symmetry intact. It is shown that, in the $\mathrm{SU}(3{)}_{f}$ flavor symmetry breaking case, all of the couplings can be written in terms of four universal functions instead of $F$ and $D$ couplings which exist in the $\mathrm{SU}(3{)}_{f}$ symmetry case. A comparison of our results of kaon and pion-baryon couplings with existing theoretical and experimental results in the literature is performed.

Investigation of gf0ργ and ga0ργ coupling constants in light cone sum rules

We present a calculation of the coupling constant f0-->rho-gamma of and a0-->rho-gamma decays from the point of the light cone QCD sum rules. We estimate the coupling constants g_f0-rho-gamma and g_a0-rho-gamma which are an essential ingredient in the analysis of physical processes involving isoscalar f0(980) and isovector a0(980) mesons.

Form factor for B→Dlν˜ in the light-cone sum rules with chiral current correlator

Within the framework of QCD light-cone sum rules (LCSR), we calculate the form factor for B -> Dl (v) over tilde transitions with chiral current correlator. The resulting form factor depends on the distribution amplitude (DA) of the D-meson. We try to use three kinds of DA models of the D-meson. C In the velocity transfer region 1.14 Dl (v) over tilde, within the error. In the large recoil region 1.35 Dl (v) over tilde transitions. (c) 2006 Elsevier B.V. All rights reserved.

Analysis of the verticesD*DsK,Ds*DK,D0DsK, andDs0DKwith the light-cone QCD sum rules

In this article, we analyze the vertices ${D}^{*}{D}_{s}K$, ${D}_{s}^{*}DK$, ${D}_{0}{D}_{s}K$, and ${D}_{s0}DK$ within the framework of the light-cone QCD sum rules approach in an unified way. The strong coupling constants ${G}_{{D}^{*}{D}_{s}K}$ and ${G}_{{D}_{s}^{*}DK}$ are important parameters in evaluating the charmonium absorption cross sections in searching for the quark-gluon plasmas. Our numerical values of the ${G}_{{D}^{*}{D}_{s}K}$ and ${G}_{{D}_{s}^{*}DK}$ are compatible with the existing estimations although somewhat smaller; the $SU(4)$ symmetry breaking effects are very large, about 60%. For the charmed scalar mesons ${D}_{0}$ and ${D}_{s0}$, we take the point of view that they are the conventional $c\overline{u}$ and $c\overline{s}$ mesons, respectively, and calculate the strong coupling constants ${G}_{{D}_{0}{D}_{s}K}$ and ${G}_{{D}_{s0}DK}$ with the vector interpolating currents. The numerical values of the scalar-${D}_{s}K$ and scalar-$DK$ coupling constants ${G}_{{D}_{0}{D}_{s}K}$ and ${G}_{{D}_{s0}DK}$ are compatible with the existing estimations---the large values support the hadronic dressing mechanism. Furthermore, we study the dependence of the four strong coupling constants ${G}_{{D}^{*}{D}_{s}K}$, ${G}_{{D}_{s}^{*}DK}$, ${G}_{{D}_{0}{D}_{s}K}$, and ${G}_{{D}_{s0}DK}$ on the nonperturbative parameter ${a}_{4}$ of the twist-2 $K$ meson light-cone distribution amplitude.

FORM FACTORS OF ργ*→π0and γγ*→π0TRANSITIONS FROM THE FINITE-WIDTH LIGHT-CONE LOCAL QCD SUM RULES

Instead of the usual zero-width approximation, the finite-width approximation for the resonance, the ρ-ω mesons, is used to investigate the light-cone local QCD sum rules for the form factors of the transitions, ργ*→π0and γγ*→π0. To be more certain, a product of two weight functions is chosen in the method of the analytic continuation by duality to annihilate the uncertainty in the continuum region and the integrand in the integration range not covered by vector-meson dominance and where the theoretical expression may least be trusted. The resultant form factors in the cases for the zero- and finite-widths are almost the same, both agree well with the experimental measurements, and comparison with the results from the Laplacian transformed light-cone sum rules and etc. is discussed.

Investigation of gf0ργ and coupling constants in light cone sum rules

We present a calculation of the coupling constant f0-->rho-gamma of and a0-->rho-gamma decays from the point of the light cone QCD sum rules. We estimate the coupling constants g_f0-rho-gamma and g_a0-rho-gamma which are an essential ingredient in the analysis of physical processes involving isoscalar f0(980) and isovector a0(980) mesons.

COUPLING CONSTANT ga0ωγAS DERIVED FROM LIGHT-CONE QCD SUM RULES

We investigate the a0ωγ vertex and estimate the coupling constant ga0ωγin the framework of the light-cone QCD sum rules. We compare our result with the value of the coupling constant calculated in the QCD sum rules.

Structure of theDs0(2317)and the strong coupling constantgDs0DKwith the light-cone QCD sum rules

In this article, we take the point of view that the charmed scalar meson ${D}_{s0}(2317)$ is the conventional $c\overline{s}$ meson and calculate the strong coupling constant ${g}_{{D}_{s0}DK}$ within the framework of the light-cone QCD sum rules approach. The numerical values for the large scalar-$DK$ coupling constant ${g}_{{D}_{s0}DK}$ support the hadronic dressing mechanism. Just like the scalar mesons ${f}_{0}(980)$ and ${a}_{0}(980)$, the ${D}_{s0}(2317)$ may have small scalar $c\overline{s}$ kernel of the typical $c\overline{s}$ meson size. The strong coupling to the hadronic channels (or the virtual mesons loops) may result in smaller mass than the conventional scalar $c\overline{s}$ meson in the constituent quark models, and enrich the pure $c\overline{s}$ state with other components. The ${D}_{s0}(2317)$ may spend part (or most part) of its lifetime as virtual $DK$ state.

Scalar form factor of the proton with light-cone QCD sum rules

In this article, we calculate the scalar form-factor of the proton in the framework of the light-cone QCD sum rules approach with the three valence quark light-cone distribution amplitudes up to twist-6, and observe the scalar form-factor $\sigma(t=-Q^2)$ at intermediate and large momentum transfers $Q^2> 2GeV^2$ has significant contributions from the end-point (or soft) terms. The numerical values for the $\sigma(t=-Q^2)$ are compatible with the calculations from the chiral quark model and lattice QCD at the region $Q^2>2GeV^2$.

Tagging the pion quark structure in QCD

We combine the constraints on the pion quark structure available from perturbative QCD, nonperturbative QCD (nonlocal QCD sum rules and light-cone sum rules) with the analysis of current data on ${F}_{\ensuremath{\pi}\ensuremath{\gamma}{\ensuremath{\gamma}}^{*}}({Q}^{2})$, including recent high-precision lattice calculations of the second moment of the pion's distribution amplitude. We supplement these constraints with those extracted from the renormalon approach by means of the twist-four contributions to the pion distribution amplitude in order to further increase stability with respect to related theoretical uncertainties. We show which regions in the space of the first two nontrivial Gegenbauer coefficients ${a}_{2}$ and ${a}_{4}$ of all these constraints overlap, tagging this way the pion structure to the highest degree possible at present.

Strong decays ofDsJ(2317)andDsJ(2460)

With the identification of $({D}_{sJ}(2317),{D}_{sJ}(2460))$ as the $({0}^{+},{1}^{+})$ doublet in the heavy quark effective field theory, we derive the light-cone QCD sum rule for the coupling of an eta meson with ${D}_{sJ}(2317){D}_{s}$ and ${D}_{sJ}(2460){D}_{s}^{*}$. Through $\ensuremath{\eta}\ensuremath{-}{\ensuremath{\pi}}^{0}$ mixing we calculate their pionic decay widths, which are consistent with the experimental values (or upper limits). Combining the radiative decay widths derived by Colangelo, Fazio, and Ozpineci in the same framework, we conclude that the decay patterns of ${D}_{sJ}(2317,2460)$ strongly support their interpretation as ordinary $c\overline{s}$ mesons.

Symmetry relations for heavy-to-light meson form factors at large recoil

The description of large-recoil heavy-to-light meson form factors is reviewed in the framework of soft-collinear effective theory. At leading power in the heavy-quark expansion, three classes of approximate symmetry relations arise. The relations are compared to experimental data for D → K* and Ds → φ form factors, and to light-cone QCD sum rule predictions for B → π and B → ρ form factors. Implications for the extraction of |Vub| from semileptonic B → ρ decays are discussed.