Satvir Kaur, Narinder Kumar, Jiangshan Lan, Chandan Mondal, Harleen Dahiya
In order to investigate the tomographical structure of light pseudoscalar mesons, particularly, pion and kaon, we study the valence quark distribution function (PDF) and the generalized parton distributions (GPDs) using light-cone quark model (LCQM).
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We discuss the hadroproduction of charmed mesons in the framework of the constituent cascade model taking into account the valence quark annihilation. It is shown that the small valence quark annihilation process dominates the leading particle production at large Feynman x and explains the recent experimental data on the asymmetry between D^0 and D^0 bar at 350 GeV/c.
A method for calculating the pion structure function directly in terms of light-cone wave functions is suggested. Taking twist-2 and twist-4 pion light-cone wave functions into account, it is shown that the QCD sum rule prediction is in agreement with quark distribution obtained from analysis of the Drell-Yan process. Twist-4 quark-gluon light-cone wave functions give a large positive contribution to the pion structure function for x_B<0.2. A new constraint on the twist-2 pion light-cone wave function is obtained. We argue that the leading twist pion wave function ϕ_π(u) \simeq 1 for u=0.3 wit…
We show that energetically favored meson-baryon fluctuations present in the light-cone wave function of a transversely polarized proton can account for the left-right asymmetries measured in inclusive meson production processes.
We study the influence of non-valence quark-pair contributions in weak transition form factors of heavy-light mesons. Form factors are first calculated for spacelike momentum transfers in a reference frame where such contributions are suppressed. Analytic continuation to the timelike region and a comparison with the direct decay calculation, done with pure valence degrees of freedom, provides an estimate of the role that quark-pair contributions may play. We use the point form of relativistic quantum mechanics, which is particularly useful when treating heavy-light systems.
A review of light-cone, covariant and gauge-invariant wave-functions of mesons is presented. They are basic non-perturbative objects needed for hard exclusive processes and for the method of light-cone QCD sum rules. The emphasis is on the vector mesons and a new (model-independent) way of computing the mass corrections of vector-meson wave functions is given.
In this paper leading twist light cone wave functions of 2S state charmonium mesons are studied and models of these functions are built.
The electromagnetic form factor of the eta meson is studied using the Light Cone QCD sum rules approach taking in to account higher twists contributions and SU(3) flavor symmetry breaking effects.
The pion cloud renormalises the light-cone wavefunction of the nucleon which is measured in hard, exclusive photon-nucleon reactions. We discuss the leading twist contributions to high-energy exclusive reactions taking into account both the pion cloud and perturbative QCD physics. The nucleon's electromagnetic form-factor at high $Q^2$ is proportional to the bare nucleon probability $Z$ and the cross-sections for hard (real at large angle or deeply virtual) Compton scattering are proportional to $Z^2$. Our present knowledge of the pion-nucleon system is consistent with $Z = 0.7 \pm 0.2$. If we…
It is shown that the D--meson, whose light quark is the initial-pion valence quark and whose charmed quark is produced in annihilation of valence quarks and has got a large enough momentum, is really a leading meson in reactions like $π^- p -> DX$. If such annihilation of valence quarks from initial hadrons is impossible there must be no distinct leading effect.
We present a study of light-cone distribution amplitudes of the light $1^1P_1$ mesons. The first few Gegenbauer moments of leading twist light-cone distribution amplitudes are calculated by using the QCD sum rule technique.
Using the recent results for the two-parton light-cone distribution amplitudes of the tensor meson, we calculate the form factors for the decays of $B_{u,d,s}$ into the light $J^{PC}=2^{++}$ tensor mesons via the vector/axial-vector/tensor current with the light-cone sum rules. We also obtain the $q^2$-dependence of the form factors.
The magnetic and quadrupole moments of the light-vector and axial-vector mesons are calculated in the light cone QCD sum rules. Our results for the static properties of these mesons are compared with the predictions of lattice QCD as well as other approaches existing in the literature.
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.
The magnetic moment $μ$ of the "rho" meson is studied in QCD light cone sum rules, and it is found that "mu = (2.3 pm 0.5)". A comparison of our result on the magnetic moment of the "rho" meson with the predictions of the other approaches, is presented.
To appear in the proceedings of The Phenomenology of Large N(c) QCD, Tempe, Arizona, 9-11 Jan 2002.
This paper is devoted to the study of leading twist light cone wave functions of J/Psi meson. The moments of these wave functions have been calculated within three approaches: potential models, nonrelativistic QCD and QCD sum rules. Using the results obtained within these approaches the models for the light cone wave functions of leading twist have been proposed. Similarly to the wave function of eta_c meson the leading twist light cone wave functions of J/Psi meson have very interesting properties at scales greater than m_c: improvement of the accuracy of the model, appearance of relativistic…
I present some recent applications of a light cone QCD-inspired model with the mass squared operator consisting of a harmonic oscillator potential as confinement in the meson spectra. The model gives an universal and satisfactory description of both singlet and triplet states of S-wave mesons. In the present work P-wave D_s mesons are also investigated. The mass of the recently found meson, D_s(2317) is reproduced fairly well by this simple model.
We describe a representation of the leading B-meson light-cone distribution amplitude in heavy-quark effective theory based on the eigenfunctions of its anomalous dimension kernel. In this representation (called the dual LCDA) different dual momenta no longer mix under renormalization. We discuss the perturbative and non-perturbative nature of different regions in this space.
The radiative transition form factors of the pseudoscalar mesons {$π$, $η$, $η'$} and the vector mesons {$ρ$, $ω$, $ϕ$} are restudied with $π$-$η$-$η'$ and $ρ$-$ω$-$ϕ$ in tri-meson-mixing pattern, which is described by tri-mixing matrices in the light-cone constituent quark model. The experimental transition decay widths are better reproduced with tri-meson-mixing than previous results in a two-mixing-angle scenario of only two-meson $η$-$η'$ mixing and $ω$-$ϕ$ mixing.
The $ρ$ meson gravitational form factors are studied based on a light-front constituent quark model which has been successfully employed to calculate its generalized parton distributions and some low-energy observables. The distributions of energy, spin, pressures, and shear forces inside the $ρ$ meson are explicitly given.
We discuss the B-meson light-cone wavefunction relevant for QCD factorization approach for exclusive B-meson decays. We derive the operator product expansion for the B-meson light-cone wavefunction, taking into account the local composite operators of dimension less than 6 and calculating the radiative corrections at order α_s for the corresponding Wilson coefficients. The result embodies peculiar UV and IR behaviors of the B-meson light-cone wavefunction, the Sudakov-type double logarithmic effects and the mixing of the multiparticle states with additional gluons inside the B meson. The forme…
The magnetic dipole moments of the light tensor mesons $f_2$, $a_2$ and strange $K_2^{\ast 0} (1430)$ tensor meson are calculated in the framework of the light cone QCD sum rules. It is observed that the values of the magnetic dipole moment for the charged tensor particles are considerably different from zero. These values are very close to zero for the light neutral $f_2$ and $a_2$ tensor mesons, while it has a small nonzero value for the neutral strange $K_2^{\ast 0} (1430)$ tensor meson.
Strong decay constants of the heavy tensor to heavy pseudoscalar (vector) and light pseudoscalar mesons are estimated within the light cone QCD sum rules. It is obtained that the values of these coupling constants are very strongly dependent on the choice of the Lorentz structure. Moreover, using these strong coupling constants the corresponding decay widths are calculated.
We present a systematic study of the B meson light-cone wavefunctions in QCD in the heavy-quark limit. We construct model-independent formulae for the light-cone wavefunctions in terms of independent dynamical degrees of freedom, which exactly satisfy the QCD equations of motion and constraints from heavy-quark symmetry. The results demonstrate novel behaviors of longitudinal as well as transverse momentum distribution in the B mesons.
The transition form factors of the radiative decays of the heavy tensor mesons to heavy pseudoscalar and heavy vector mesons are calculated in the framework of the light cone QCD sum rules method at the point $Q^2=0$. Using the obtained values of the transition form factors at the point $Q^2=0$ the corresponding decay widths are estimated. The results show that the radiative decays of the heavy--light tensor mesons can be measurable in the future planned experiments at LHCb.
New sum rules for $B\to π,K $ and $B\to ρ,K^*$ form factors are derived from the correlation functions expanded near the light-cone in terms of B-meson distribution amplitudes. The contributions of quark-antiquark and quark-antiquark-gluon components in the B meson are taken into account. Models for the B-meson three-particle distribution amplitudes are suggested, based on QCD sum rules in HQET. Employing the new light-cone sum rules we calculate the form factors at small momentum transfers, including $SU(3)_{fl}$ violation effects. The results agree with the predictions of the conventional li…
This paper is devoted to the study of leading twist light cone wave function of $η_c$ meson. The moments of this wave function have been calculated within three approaches: potential models, nonrelativistic QCD and QCD sum rules. Using the results obtained within these approaches the model for the light cone wave function of leading twist has been proposed. Being scale dependent light cone wave function has very interesting properties at scales $μ> m_c$: improvement of the accuracy of the model, appearance of relativistic tail and violation of nonrelativistic QCD velocity scaling rules. The la…
We investigate the electromagnetic form factors of the (rho) meson in light cone QCD sum rules. We find that the ratio of the magnetic and charge form factors is larger than two at all values of Q^2, (Q^2 >= 0.5 GeV^2). The values of the individual form factors at fixed values of Q^2 predicted by the light cone QCD sum rules are quite different compared to the results of other approaches. These results can be checked in future, when more precise data on (rho) meson form factors is available.
A recent renormalization group analysis of the effective light-cone Hamiltonian yields 5 flavor masses and 2 mass shifts as free parameters. These are determined in the present note and used to calculate the masses of all 30 physical mesons (The topped mesons have been omitted). The agreement between experiment and theoretical estimate is quite satisfactory over the whole dynamical range, from the lightest pseudo-scalar mesons like the pion up to the heaviest vector mesons like the upsilon. Evidence for an additive quark model is given and for how the concept of isospin is realized in a gauge …
We present a systematic study of the B meson light-cone distribution amplitudes which are relevant for the QCD factorization approach for the exclusive B meson decays. We construct representations for the quark-antiquark distribution amplitudes in terms of independent dynamical degrees of freedom, which exactly satisfy the QCD equations of motion and constraints from heavy-quark symmetry.
We present a study for two-quark light-cone distribution amplitudes for the $1^3D_2$ light tensor meson states with quantum number $J^{PC}=2^{--}$. Because of the G-parity, the chiral-even two-quark light-cone distribution amplitudes of this tensor meson are antisymmetric under the interchange of momentum fractions of the quark and antiquark in the SU(3) limit, while the chiral-odd ones are symmetric. The asymptotic leading-twist LCDAs with the strange quark mass correction are shown. We estimate the relevant parameters, the decay constants $f_T$ and $f_T^\perp$, and first Gegenbauer moment $a…
Transverse-momentum dependent (TMD) light-cone wave functions of a light meson are important ingredients in the TMD QCD factorization of exclusive processes. This factorization allows one conveniently resum Sudakov logarithms appearing in collinear factorization. The TMD light-cone wave functions are not simply related to the standard light-cone wave functions in collinear factorization by integrating them over the transverse momentum. We explore relations between TMD light-cone wave functions and those in the collinear factorization. Two factorized relations can be found. One is helpful for c…
The couplings of pions with lowest three doublets (0^-,1^-), (0^+,1^+) and (1^+,2^+) of heavy mesons are studied with ligh cone QCD sum rules in the leading order of heavy quark effective theory. The ambiguity due to the presence of two distinct 1^+ states are solved.
We give a complete re-analysis of the leading twist quark-antiquark light-cone distribution amplitudes of longitudinal and transverse $ρ$ mesons. We derive Wandzura-Wilczek type relations between different distributions and update the coefficients in their conformal expansion using QCD sum rules including next-to-leading order radiative corrections. We find that the distribution amplitudes of quarks inside longitudinally and transversely polarized $ρ$ mesons have a similar shape, which is in contradiction to previous analyses.
We investigate the radiative B_c -> rho^+ gamma and B_c -> K^{*+} gamma decays in the standard model. The transition form factors are calculated in the framework of the light cone QCD sum rules method. We estimate the branching ratios of the B_c -> rho^+ gamma and B_c -> K^{*+} gamma decays.
We introduce chiral-even and chiral-odd meson wave functions as vacuum-to-meson matrix elements of bilocal quark operators with well-defined (geometric) twist. Thereby, we achieve a Lorentz invariant classification of these distributions which differ from the conventional ones by explicitly taking into account the trace terms. The relations between conventional and new wave functions are given.
I discuss the renormalization-group equation governing the leading order light-cone distribution amplitude of the B-meson phi^B_+(omega,mu) and its exact analytic solution. The solution displays two features concerning the asymptotic behaviour of phi^B_+(omega,mu) for small and large values of omega. I comment on further applications and argue that the loss of normalizability is not a problem in practice.
We present the one-loop anomalous dimension matrices for the chiral-even twist-3 (nonsinglet) conformal operators, which govern the scale-dependence of the vector meson light-cone wave functions through the conformal expansion. It is clarified that the constraints from the charge-conjugation invariance and the chirality conservation allow only one independent anomalous dimension matrix for each conformal spin.
A complete set of asymptotic three particle light cone distribution amplitudes of twist 3 and 4 for a transversely polarized massive vector meson built out of massless current quarks is constructed. The method used is based on a modified conformal projectors technique which allows to handle kinematical corrections due to a finite hadron mass. Consequences of our finding for the ρ-meson hard diffractive electroproduction and γρπform factor are discussed. Our results may imply a breakdown of OPE for some exclusive processes beyond the leading twist level.
Valence quark distribution of rho meson using light-front quark model
本文在光前夸克模型框架下研究ρ介子的部分子结构，采用两类自旋波函数推导相关分布函数并完成能标演化，计算全套横动量依赖分布，验证正定性约束，明确张量极化的关键作用。
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 $B^+\to p Ψ$. Considering two models of $B$-Mesogenesis, we obtain the $B\to p$ hadronic matrix elements by applying QCD light-cone sum rules with the proton light-cone distribution amplitudes. We estimate the $B^+\to p Ψ$ decay width as a function of the mass and effective coupling of the dark antibaryon.
In this paper, we analyze the doubly heavy spin-3/2--spin-1/2 baryons and light meson vertices within the method of light-cone QCD sum rules. These vertices are parametrized in terms of one (three) coupling constant(s) for the pseudoscalar (vector) mesons. The said coupling constants are calculated for all possible transitions. The results presented here can serve to be useful information in experimental as well as theoretical studies of the properties of doubly heavy baryons.
We present a systematic study of twist-3 light-cone distribution amplitudes of vector mesons in QCD, which is based on conformal expansion. A complete set of distribution amplitudes is constructed for ρ, ω, K^* and ϕmesons, which satisfies all (exact) equations of motion and constraints from conformal expansion.
Using the general form of the baryon currents, we calculate the meson-baryon coupling constants and the F/D ratio within the framework of light cone QCD sum rules in the SU(3) flavor symmetry limit. The dependence of the results on the Dirac structure and on the free parameter (b) appearing in the general baryon current is considered. Comparison of our results on F/D ratio with the existing results is presented.
We calculate the strong coupling constants g_(P^(**)P^(*)π), where P^(**)(D^(**), B^(**)) is the 1^+ p-wave state, in the framework of the light cone QCD sum rules, and using these values of g_(P^(**)P^(*) pi, we compute the hadronic decay widths for D^(**) -> D^* pi and B^(**) -> B^* pi.
The color dipole gBFKL phenomenology of a diffraction cone for photo- and electroproduction $γ^{*}N \to VN$ of heavy vector mesons (charmonium & bottonium) at HERA and in fixed target experiments is presented. A substantial shrinkage of the diffraction cone from the CERN/FNAL to the HERA range of c.m.s. energy $W$ is predicted. The $Q^{2}$-controlled selectivity to the color dipole size (scanning phenomenon) is shown to lead to a decrease of the diffraction slope with $Q^{2}$ (which is supported by the available experimental data). An approximate flavor independence of the diffraction slope in…
The effective interaction between a quark and an anti-quark as obtained previously with by the method of iterated resolvents is replaced by the up-down-model and applied to flavor off-diagonal mesons including the positive pion. The only free parameters are the canonical ones, the coupling constant and the masses of the quarks.
In this article, we calculate the electromagnetic form-factor of the $π$ meson with the light-cone QCD sum rules. The numerical value $F_π^{p}(0) =0.999\pm 0.001$ is in excellent agreement with the experimental data (extrapolated to the limit of zero momentum transfer, or the normalization condition $F_π(0)=1$). For large momentum transfers, the values from the two sum rules are all comparable with the experimental data and theoretical estimations.
The formfactors of B_1 -> pi and D_1 -> pi transitions, where B_1(D_1) is the 1^+ P-wave -> Q gamma_νγ_5q meson state, are calculated in the framework of the light cone QCD. Furthermore these formfactors are compared with the pole dominance model prediction using the values of the strong coupling constants g_{B_1 B^* pi} and g_{D_1 D^* pi}, and a good agreement between these two different descriptions is observed.
An integro-differential equation governing the evolution of the leading-order B-meson light-cone distribution amplitude is derived. The anomalous dimension in this equation contains a logarithm of the renormalization scale, whose coefficient is identified with the cusp anomalous dimension of Wilson loops. The exact analytic solution of the evolution equation is obtained, from which the asymptotic behavior of the distribution amplitude is derived. These results can be used to resum Sudakov logarithms entering the hard-scattering kernels in QCD factorization theorems for exclusive B decays.
We present new models of the rho-meson leading-twist light-cone distribution amplitudes based on the QCD sum rule approach with nonlocal condensates. Their shapes differ noticeably from that known in the literature. The phenomenological consequences for physically important process B --> rho e nu are discussed in the framework of the light-cone sum rules. The results are compared with those found recently by P.Ball and V.M.Braun (1997).
We study the quark Wigner distributions of the pion meson which are the phase-space distributions containing the most general one-parton information.Using the pion wavefunctions deduced from a light-cone quark model, we calculate the Wigner distributions of the unpolarized, longitudinally polarized and transversely polarized quarks inside the pion meson via the Fock-state overlap representation, respectively.We present the numerical results of the transverse Wigner distributions in which the longitudinal momentum fraction is integrated out. The mixed Wigner distributions as functions of $b_y$ …
Mass renormalization group of heavy meson light-cone distribution amplitude in QCD
推导偏微分方程刻画QCD中重介子光锥分布振幅随重夸克质量的演化，揭示不同质量下介子内部结构联系，支持格点计算的外推。
The method for calculation of valence quark distributions at intermediate $x$ is presented. The imaginary part of the virtual photon forward scattering amplitude on the quark current with meson quantum number is considered. Initial and final virtualities $p^2_1$ and $p^2_2$ of the currents are assumed to be large, negative and different, $p^2_1 \not= p^2_2$. The operator product expansion (OPE) in $p^2_1, p^2_2$ up to dimension 6 operators is performed. Double dispersion representations in $p^2_1, p^2_2$ of the amplitude in terms of physical states contributions are used. Equalling them to tho…
We use a light cone harmonic oscillator model to study S wave meson spectra, namely the pseudoscalar and vector mesons. The model Hamiltonian is a mass squared operator consisting of a central potential (a harmonic oscillator potential) from which a hyperfine interaction is derived. The hyperfine interaction is responsible for the splitting in the pseudoscalar-vector spectra. With 4 parameters for the masses of up/down, strange, charm and bottom quarks, 2 for the harmonic oscillator potential and 1 for the hyperfine interaction, the model presents a reasonably good agreement with the data.
We investigate the energy behavior of the diffraction cone in the exclusive vector meson production in diffractive DIS within the k_t-factorization approach. In our calculations, we make full use of fits to the unintegrated gluon structure functions extracted recently from experimental data on F_2p. Confirming early predictions, we observe that shrinkage of the diffraction cone due to the slope of the Pomeron trajectory is significantly compensated by the anti-shrinkage behavior of the gamma -> V transition. In order to match recent ZEUS data on the energy behavior of the diffraction slope, al…
In this paper we calculate the weak form factors of the decays $B_c(B)\to Dl\tildeν$ by using the chiral current correlator within the framework of the QCD light-cone sum rules (LCSR). The expressions of the form factors only depend on the leading twist distribution amplitude (DA) of the $D$ meson. Three models of the $D$-meson distribution amplitude are employed and the calculated form factor $F_{B_c\to D}(0)$ is given. Our prediction, by using the $D$-meson distribution amplitude with the exponential suppression at the end points, is compatible with other approaches, and favors the three-poi…
We re-analyze the leading twist light-cone distributions for transversely polarized ρ-, ρ'- and b_1-mesons in the framework of QCD sum rules with nonlocal condensates. Using different kinds of sum rules to obtain reliable predictions, we estimate the 2-, 4-, 6- and 8-th moments for transversely polarized ρ- and ρ'-meson distributions and re-estimate tensor couplings f^T_{ρ,ρ',b_1}. We stress that the results of standard sum rules also support our estimation of the second moment of the transversely polarized ρ-meson distribution. New models for light-cone distributions of these mesons are const…
Valence quark distribution of light $ρ$ and heavy $J/ψ$ vector mesons in light-cone quark model
本文在光锥夸克模型中利用非极化GPD研究了ρ和J/ψ介子的价夸克结构，导出了形状因子、结构函数和PDFs，并通过DGLAP演化到5 GeV²，结果与其他模型和格点数据趋势一致。
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 …
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