Light Cone QCD Sum Rules Research Articles

Semileptonic Bc decays to P-wave charmonia in the light-cone QCDSR

Bc 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 Bc 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.

Gravitational transition form factors of N → ∆ via QCD light-cone sum rules

We present the first direct calculation on the gravitational form factors (GFFs) of the N → ∆ transition using an analytic method, the QCD light-cone sum rules. The matrix element of the quark part of the energy momentum tensor current sandwiched between the nucleon and ∆ states are parameterized in terms of five independent conserved and four independent non-conserved GFFs, for calculation of which we use the distribution amplitudes (DAs) of the on-shell nucleon expanded in terms of functions with different twists. We present the results for two sets of light-cone input parameters. The results indicate that the behavior of the form factors with respect to Q2 are described by multipole fit functions. Our results may be checked by other phenomenological models including the Lattice QCD as well as future related experiments.

Revisiting D-meson twist-2, 3 distribution amplitudes* *Supported in part by the National Natural Science Foundation of China (12265009, 12265010), the Project of Guizhou Provincial Department of Science and Technology (ZK[2021]024, ZK[2023]142), the Project of Guizhou Provincial Department of Education (KY[2021]030) and the Chongqing Graduate Research and Innovation Foundation (ydstd1912)

Owing to the significant difference between the experimental measurements and the theoretical predictions of the standard model (SM) for the value of of the semileptonic decay , researchers speculate that this decay may be evidence of new physics beyond the SM. Usually, the D-meson twist-2, 3 distribution amplitudes (DAs) , , and are the main error sources when perturbative QCD factorization and light-cone QCD sum rules are used to study . Therefore, it is important to obtain more reasonable and accurate behaviors for these 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 , , and . New sum rule formulae for the -moments of these three DAs are suggested for obtaining more accurate values. The light-cone harmonic oscillator models for the DAs are improved, and their parameters are determined by fitting the values of ξ -moments via the least squares method.

Axial-vector and pseudoscalar tetraquarks [ud][{overline{c}}{overline{s}}

Spectroscopic parameters and widths of the fully open-flavor axial-vector and pseudoscalar tetraquarks X_{textrm{AV}} and X_{textrm{PS}} with content [ud][{overline{c}}{overline{s}}] are calculated by means of the QCD sum rule methods. Masses and current couplings of X_{textrm{AV}} and X_{textrm{PS}} are found using two-point sum rule computations performed by taking into account various vacuum condensates up to dimension 10. The full width of the axial-vector state X_{textrm{AV}} is evaluated by including into analysis S-wave decay modes X_{textrm{AV}}rightarrow D^{*}(2010)^{-}K^{+}, {overline{D}}^{*}(2007)^{0}K^{0}, D^{-}K^{*}(892)^{+}, and {overline{D}}^{0}K^{*}(892)^{0}. In the case of X_{textrm{PS}}, we consider S-wave decay X_{textrm{PS}}rightarrow {overline{D}} _{0}^{*}(2300)^{0}K^{0}, and P-wave processes X_{textrm{PS}}rightarrow D^{-}K^{*}(892)^{+} and X_{textrm{PS}}rightarrow {overline{D}} ^{0}K^{*}(892)^{0}. To determine partial widths of these decay modes, we employ the QCD light-cone sum rule method and soft-meson approximation, which are necessary to estimate strong couplings at tetraquark–meson–meson vertices X_{textrm{AV}}D^{-}D^{*}(2010)^{-}K^{+} , etc. Our predictions for the mass m_{textrm{AV}}=(2800 pm 75)~text {MeV} and width Gamma _{textrm{AV}}=(58 pm 10)~text {MeV} of the tetraquark X_{ textrm{AV}}, as well as results m_{textrm{PS}}=(3000 pm 60)~text {MeV} and Gamma _{textrm{PS}}=(65 pm 12)~text {MeV} for the same parameters of X_{textrm{PS}} may be useful in future experimental studies of multiquark hadrons.

Branching fractions of B meson decays in Mesogenesis

Production of the matter-antimatter asymmetry in the B-Mesogenesis mechanism is directly related to the branching fraction of seemingly baryon number violating decays of B mesons into a light Standard Model baryon and missing energy. Achieving the observed baryon asymmetry requires that the branching fraction for such decays be greater than about 10−7–10−5. Experimental searches at B Factories and Hadron Colliders target specific decay modes. Therefore, computing the exclusive branching fraction for each decay is a critical step towards testing Mesogenesis. In this work we use QCD Light Cone Sum Rules to compute the form factors and branching fractions of the various possible channels contributing to the baryon asymmetry. Using the results, we comment on implications for current and future experimental searches.

Electromagnetic form factors of the Bc-like tetraquarks: Molecular and diquark-antidiquark pictures

In this study, we use the molecular and diquark-antidiquark tetraquark pictures to investigate magnetic and quadrupole moments of the Bc-like ground state tetraquarks with the QCD light-cone sum rules with quantum numbers JP=1+. In the numerical analysis, to obtain the magnetic and quadrupole moments of Bc-like tetraquark states molecular and diquark-antidiquark forms of interpolating currents, and photon distribution amplitudes have been used. The magnetic moments are acquired as μZucu¯b¯Mol=1.18−0.40+0.52μN, μZucu¯b¯Di=3.05−0.95+1.19μN, μZdcd¯b¯Mol=0.32−0.10+0.18μN, and μZdcd¯b¯Di=2.38−0.75+0.95μN. The hadrons' magnetic and quadrupole moments are another fundamental observable as their mass, which provides information on the underlying quark structure and dynamics. The results obtained in both pictures are quite different from each other. Any experimental measurement of the magnetic moments can provide an understanding of the internal structure of these states. We get nonzero but small values for the quadrupole moments of Bc-like tetraquark states showing non-spherical charge distributions. Hopefully, the examinations given in this study will be helpful to an experimental search of them, which will be an interesting research subject.

Investigation of magnetic moment of Pcs(4338) and Pcs(4459) pentaquark states

In this study, we discuss the magnetic moment of Pcs(4338) and Pcs(4459) hidden-charmed pentaquarks, which are closely related to their substructures. The magnetic moments of these states are calculated with the help of the QCD light-cone sum rules method with quantum numbers I(JP)=0(1/2−) and I(JP)=0(3/2−) for Pcs(4338) and Pcs(4459), respectively. Our predictions for the magnetic moment μPcs=0.34±0.12μN for the Pcs(4338) state, and μPcs=−1.67±0.58μN for the Pcs(4459) state. As a by-product, the magnetic moments of the isospin−1 partners of these states have also been obtained. The magnetic moments are obtained as μPcs=0.63±0.21μN and μPcs=−3.33±1.04μN for the isospin-1 partners of the Pcs(4338) and Pcs(4459) states, respectively. Our results regarding the magnetic moments of these color singlet-singlet type pentaquark states are compared with the results in the literature.

Semileptonic decay of Ξc→Ξℓ+νℓ from light-cone QCD sum rules

Semileptonic decay processes of $\Xi_c \to \Xi\ell\nu_\ell$ are studied by light-cone QCD sum rules in this paper. The six form factors of $\Xi_c \to \Xi$ semileptonic transition matrix elements are calculated by this method with the light-cone distribution amplitudes of $\Xi$ baryon up to twist six. With the six form factors, the absolute branching ratios of $\Xi_c^0 \to \Xi^- \ell^+ \nu_\ell$ and $\Xi_c^+ \to \Xi^0 \ell^+ \nu_\ell$ 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.

B-meson decay into a proton and dark antibaryon from QCD light-cone sum rules

The recently developed B-Mesogenesis scenario predicts decays of B mesons into a baryon and hypothetical dark antibaryon Ψ. We suggest a method to calculate the amplitude of the simplest exclusive decay mode B+→pΨ. Considering two models of B-Mesogenesis, we obtain the B→p hadronic matrix elements by applying QCD light-cone sum rules with the proton light-cone distribution amplitudes. We estimate the B+→pΨ decay width as a function of the mass and effective coupling of the dark antibaryon.

Λ b → Λ c form factors from QCD light-cone sum rules* *Supported in part by the National Natural Science Foundation of China (12175218, 11975112); Y.L.S also acknowledges the Natural Science Foundation of Shandong province with (ZR2020MA093); J.G is also supported by the National Natural Science Foundation of China (12147118)

In this study, we calculate the transition form factors of decaying into within the framework of light-cone sum rules with the distribution amplitudes (DAs) of the -baryon. In the hadronic representation of the correlation function, we isolate both the and states so that the form factors can be obtained without ambiguity. We investigate the P-type and A-type currents to interpolate light baryons for comparison because the interpolation current for the baryon state is not unique. We also employ three parametrization models for the DAs of in the numerical calculation. We present the numerical predictions for the form factors and branching fractions, averaged forward-backward asymmetry, averaged final hadron polarization, and averaged lepton polarization of the decays, as well as the ratio of the branching ratios . The predicted is consistent with LHCb data.

Rare radiative Ξb−→ Ξ−γ decay in the relativistic quark model

Recently, the LHCb collaboration put the upper limit on the [Formula: see text] decay branching ratio [Formula: see text]. The measured value is below the light-cone sum rule prediction. In this paper, the rare radiative decay of the [Formula: see text] baryon is studied in the framework of the relativistic quark model based on the quasipotential approach and QCD. The decay form factors are calculated with the comprehensive account of the relativistic effects. The obtained result for the branching ratio is found to be below the upper limit set by LHCb and is consistent with theoretical predictions based on the SU(3) flavor-symmetry, light-front quark model and light-cone QCD sum rules in full theory within theoretical uncertainties.

A_1(1260)-meson longitudinal twist-2 distribution amplitude and the Drightarrow a_1(1260)ell ^+nu _ell decay processes

In the paper, we investigate the moments langle xi _{2;a_1}^{Vert ;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 mu _0=1~{mathrm{GeV}} are langle xi _{2;a_1}^{Vert ;2}rangle |_{mu _0} = 0.223 pm 0.029, langle xi _{2;a_1}^{Vert ;4}rangle |_{mu _0} = 0.098 pm 0.008, langle xi _{2;a_1}^{Vert ;6}rangle |_{mu _0} = 0.056 pm 0.006, langle xi _{2;a_1}^{Vert ;8}rangle |_{mu _0} = 0.039 pm 0.004 and langle xi _{2;a_1}^{Vert ;10}rangle |_{mu _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 phi _{2;a_1}^{Vert }(x,mu ), whose model parameters are fitted by using the least squares method. As an application of phi _{2;a_1}^{Vert }(x,mu ), we calculate the transition form factors (TFFs) of Drightarrow 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(+)} rightarrow a_1^{-(0)}(1260)ell ^+nu _ell , we obtain {mathcal {B}}(D^0rightarrow a_1^-(1260) e^+nu _e) = (5.261_{-0.639}^{+0.745}) times 10^{-5}, {mathcal {B}}(D^+rightarrow a_1^0(1260) e^+nu _e) = (6.673_{-0.811}^{+0.947}) times 10^{-5}, {mathcal {B}}(D^0rightarrow a_1^-(1260) mu ^+ nu _mu )=(4.732_{-0.590}^{+0.685}) times 10^{-5}, {mathcal {B}}(D^+ rightarrow a_1^0(1260) mu ^+ nu _mu )=(6.002_{-0.748}^{+0.796}) times 10^{-5}.

B → D1(2420) and B → {mathrm{D}}_1^{prime } (2430) form factors from QCD light-cone sum rules

We perform the first calculation of form factors in the semileptonic decays B → D1(2420)ℓνℓ and B → {D}_1^{prime } (2430)ℓνℓ using QCD light-cone sum rules (LCSRs) with B-meson distribution amplitudes. In this calculation the c-quark mass is finite. Analytical expressions for two-particle contributions up to twist four are obtained. To disentangle the D1 and {D}_1^{prime } contributions in the LCSRs, we suggest a novel approach that introduces a combination of two interpolating currents for these charmed mesons. To fix all the parameters in the LCSRs, we use the two-point QCD sum rules for the decay constants of D1 and {D}_1^{prime } mesons augmented by a single experimental input, that is the B → D1(2420)ℓνℓ decay width. We provide numerical results for all B → D1 and B → {D}_1^{prime } form factors. As a byproduct, we also obtain the D1- and {D}_1^{prime } -meson decay constants and predict the lepton-flavour universality ratios R(D1) and R( {D}_1^{prime } ).

Magnetic moments of spin–1/2 triply heavy baryons: a study of light-cone QCD and quark–diquark model

In this study, the magnetic moments of the spin-1/2 triply-heavy baryons have been calculated using both light-cone QCD sum rules and Quark-diquark model. Theoretical investigations on magnetic moments of the triply-heavy baryons, are crucial as their results can help us better understand their internal structure and the dynamics of the QCD as the theory of the strong interaction. We compare the results extracted for the magnetic moment with the existing theoretical predictions. It is seen that the obtained magnetic moment values are quite compatible with the results in the literature.

Determination of the generalized parton distributions through the analysis of the world electron scattering data considering two-photon exchange corrections

We determine the valence generalized parton distributions (GPDs) $ H_v^q $ and $ E_v^q $ with their uncertainties at zero skewness by performing a $ \chi^2 $ analysis of the world electron scattering data considering two-photon exchange corrections. The data include a wide and updated range of the electric and magnetic form factors (FFs) of the proton and neutron. As a result, we find that there are no enough constraints on GPDs $ E_v^q $ from FFs data solely though $ H_v^q $ are well constrained. By including the new data of the charge and magnetic radius of the nucleon in the analysis, we show that they put new constraints on the final GPDs, especially on $ E_v^q $. Moreover, we calculate the gravitational FF $ M_2 $ and the total angular momentum $ J^q $ using the extracted GPDs and compare them with the FFs obtained from the light-cone QCD sum rules (LCSR) and Lattice QCD. We show that our results are interestingly in a good consistency with the pure theoretical predictions.

Magnetic moment of the $$\Xi _b(6227)$$ as a molecular pentaquark state

In this study, considering that the $\Xi_b (6227)$ state is in molecular structure, the magnetic moment of this state is extracted in the light-cone QCD sum rules. The numerical result is obtained as $\mu_{\Xi_b}= 0.12 \pm 0.03~\mu_N$. The magnetic moment of this state contains important information of its internal structure and shape deformations. Measurement of the magnetic moment of the $\Xi_b(6227)$ state in future experimental facilities can be very helpful in identification of the quantum numbers, as well as comprehension of the inner structure of this state.

Radiative Xi _{b}^{-}rightarrow Xi ^{-}gamma decay

Recently, the LHCb Collaboration performed first search for the rare radiative Xi _{b}^{-}rightarrow Xi ^{-}gamma decay and put an upper limit, mathcal{B}(Xi _{b}^{-}rightarrow Xi ^{-}gamma ) < 1.3 times 10^{-4}, on its branching ratio. The measurement agrees well with existing theory prediction using SU(3) flavor symmetry method, but shows a slight tension with the previous prediction from light-cone sum rules. Inspired by this, we investigate this decay as well as other radiative decays of Xi _b^{0(-)}(Xi ^{'-}_{b}) to Xi ^{0(-)} and Sigma ^{0(-)} baryons using the form factors calculated from light-cone QCD sum rules in full theory. we obtain mathcal{B}(Xi _{b}^{-}rightarrow Xi ^{-}gamma )=1.08^{+0.63}_{-0.49} times 10^{-5} , which lies below the upper limit set by LHCb and is consistent with flavor-symmetry driven prediction. Our predictions on other channels may be checked in experiment and by other phenomenological approaches.

Eta ^{(prime )}-meson twist-2 distribution amplitude within QCD sum rule approach and its application to the semi-leptonic decay D_s^+ rightarrow eta ^{(prime )}ell ^+ nu _ell

In this paper, we make a detailed discussion on the eta and eta ^prime -meson leading-twist light-cone distribution amplitude phi _{2;eta ^{(prime )}}(u,mu ) by using the QCD sum rules approach under the background field theory. Taking both the non-perturbative condensates up to dimension-six and the next-to-leading order (NLO) QCD corrections to the perturbative part, its first three moments langle xi ^n_{2;eta ^{(prime )}}rangle |_{mu _0} with n = (2, 4, 6) can be determined, where the initial scale mu _0 is set as the usual choice of 1 GeV. Numerically, we obtain langle xi _{2;eta }^2rangle |_{mu _0} =0.231_{-0.013}^{+0.010}, langle xi _{2;eta }^4 rangle |_{mu _0} =0.109_{ - 0.007}^{ + 0.007}, and langle xi _{2;eta }^6 rangle |_{mu _0} =0.066_{-0.006}^{+0.006} for eta -meson, langle xi _{2;eta '}^2rangle |_{mu _0} =0.211_{-0.017}^{+0.015}, langle xi _{2;eta '}^4 rangle |_{mu _0} =0.093_{ - 0.009}^{ + 0.009}, and langle xi _{2;eta '}^6 rangle |_{mu _0} =0.054_{-0.008}^{+0.008} for eta '-meson. Next, we calculate the D_srightarrow eta ^{(prime )} transition form factors (TFFs) f^{eta ^{(prime )}}_{+}(q^2) within QCD light-cone sum rules approach up to NLO level. The values at large recoil region are f^{eta }_+(0) = 0.476_{-0.036}^{+0.040} and f^{eta '}_+(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^+rightarrow eta ^{(prime )}ell ^+ nu _ell , i.e. {{mathcal {B}}}(D_s^+ rightarrow eta ^{(prime )} e^+nu _e)=2.346_{-0.331}^{+0.418}(0.792_{-0.118}^{+0.141})times 10^{-2} and {{mathcal {B}}}(D_s^+ rightarrow eta ^{(prime )} mu ^+nu _mu )=2.320_{-0.327}^{+0.413}(0.773_{-0.115}^{+0.138})times 10^{-2} for ell = (e, mu ) channels respectively. And in addition to that, the mixing angle for eta -eta ' with varphi and ratio for the different decay channels {{mathcal {R}}}_{eta '/eta }^ell are given, which show good agreement with the recent BESIII measurements.

Higher-twist corrections to the form factors from light-cone sum rules * *Supported in part by the National Natural Science Foundation of China (11675082, 11735010) and the Natural Science Foundation of Tianjin (19JCJQJC61100)

We calculate the transition form factors within the framework of the light-cone QCD sum rules (LCSR) with the D-meson light-cone distribution amplitudes (LCDAs). The next-to-leading power (NLP) corrections to the vacuum-to-D-meson correlation function are considered, and the NLP corrections from the high-twist D-meson LCDAs and the SU(3) breaking effect from a strange quark mass are investigated. Adopting the exponential model of the D-meson LCDAs, the SU(3) flavor symmetry breaking effects are predicted as and , respectively, confirming the results obtained from LCSR with pion LCDA. The numerical predictions of the form factors show that the contribution from two-particle higher-twist contributions is of great importance and the uncertainties are dominated by the inverse moment of . With the obtained form factors, the predicted Cabibbo-Kobayashi-Maskawa (CKM) matrix elements are and .

Strong and electromagnetic decays of the radially excited D_s and B_s mesons in light cone QCD sum rules

Recently, LHCb Collaboration announced the discovery of radial excitations of D_s and B_s mesons. In present work, we calculate the most promising strong and electromagnetic decay widths of radially excited D_s(2S) and B_s(2S) mesons within the light cone QCD sum rules method.