We study the mass spectrum and decay constants of light and heavy mesons in a soft-wall holographic approach, using the correspondence of string theory in Anti-de Sitter space and conformal field theory in physical space-time.Comment: 17 pages, 6 figure
We describe the electroproduction of the N(1440) Roper resonance in soft-wall AdS/QCD. The Roper resonance is identified as the first radially excited state of the nucleon, where higher-Fock states in addition to the three-quark component are included. The main conclusion is that the leading 3q component plays the dominant role in the description of electroproduction properties of this resonance: form factors, helicity amplitudes and charge densities. The obtained results are in good agreement with the recent results of the CLAS Collaboration at JLab.Comment: 20 pages. arXiv admin note: text overlap with arXiv:1204.661
We discuss a holographic soft-wall model developed for the description of mesons and baryons with adjustable quantum numbers n, J, L, S. This approach is based on an action which describes hadrons with broken conformal invariance and which incorporates confinement through the presence of a background dilaton field. We show that in the case of the bound-state problem (hadronic mass spectrum) two versions of the model with a positive and negative dilaton profile are equivalent to each other by a special transformation of the bulk field. We also comment on recent works which discuss the dilaton sign in the context of soft-wall approaches.Comment: 21 pages, accepted for publication in Phys. Rev.
The nucleon helicity-independent generalized parton distributions (GPDs) of quarks are calculated in the zero skewness case, in the framework of the AdS/QCD model. The present approach is based on a matching procedure of sum rules relating the electromagnetic form factors to GPDs and AdS modes.
We present a detailed analysis of nucleon electromagnetic and axial form factors in a holographic soft-wall model. This approach is based on an action which describes hadrons with broken conformal invariance and incorporates confinement through the presence of a background dilaton field. For Nc = 3 we describe the nucleon structure in a superposition of a three valence quark state with high Fock states including an adjustable number of partons (quarks, antiquarks and gluons) via studying the dynamics of 5D fermion fields of different scaling dimension in anti-de Sitter (ADS) space. According to the gauge/gravity duality the 5D fermion fields of different scaling dimension correspond to the Fock state components with a specific number of partons. In the present application we restrict to the contribution of 3, 4 and 5 parton components in the nucleon Fock state. With a minimal number of free parameters (dilaton scale parameter, mixing parameters of partial contributions of Fock states, coupling constants in the effective Lagrangian) we achieve a reasonable agreement with data for the nucleon form factors.
We consider the light-front wave function for the valence quark state of mesons using the AdS/CFT correspondence, as has been suggested by Brodsky and Teramond. Two kinds of wave functions, obtained in different holographic Soft-Wall models, are discussed.Comment: 8 page
We present a high-quality description of the deuteron electromagnetic form factors in a soft-wall anti-de Sitter/quantum chromodynamics approach. We first propose an effective action describing the dynamics of the deuteron in the presence of an external vector field. Based on this action the deuteron electromagnetic form factors are calculated, displaying the correct 1=Q 10 power scaling for large Q 2 values. This finding is consistent with quark counting rules and the earlier observation that this result holds in confining gauge/gravity duals. The Q 2 dependence of the deuteron form factors is defined by a single and universal scale parameter κ, which is fixed from data.The experimental and theoretical study of the deuteron is one of the main focuses of hadronic physics during the last decades (for detailed reviews see e.g. Refs. [1][2][3][4]). Many theoretical approaches have been applied to the problem of the deuteron form factors: perturbative QCD, chiral effective and phenomenological approaches, potential and quark models (see e.g. Refs. ). For example, in potential models the nonrelativistic impulse approximation [7,8] was used. It leads to deuteron form factors factorized in terms of the isoscalar combinations of the nucleon form factors. These approaches are able to describe data up to 0.5 GeV 2 , but deviate from data for higher Q 2 and are not consistent with quark counting rules. To include relativistic effects, different types of relativistic nuclear models have been developed. One possibility is based on taking into account relativistic corrections in a v=c expansion of the nonrelativistic current (leading to so-called two-body interaction current diagrams) [9][10][11]. Such approaches are limited in their validity of the description of data up to 1-2 GeV 2 . There is a group of models based on relativistic Hamiltonian constraint dynamics, which uses certain phenomenological potentials (Argonne, Nijmegen, etc.) and three forms of quantization procedures (point, instant or front form) (see e.g. Refs. [12,13]). Field-theoretical methods formulated in terms of hadronic (mesons, nucleons, Δ-isobars) degrees of freedom are used in a wide range of approaches. These include models based on the solution of a quasipotential [14] or on Bethe-Salpeter [16] equations. These methods also include field theories quantized on the light cone [17,18], phenomenological Lagrangian approaches [19] and effective field theories treating the long-range dynamics explicitly while parametrizing the short-distance effects by contact interactions (for recent applications to deuteron form factors see e.g. Refs.[20]). Another class of approaches supposes to treat the deuteron in terms of fundamental degrees of freedom-quarks and gluons: nonrelativistic quark models [21,22] and perturbative QCD [6]. The analysis of Ref.[6] results in a prediction for the asymptotic large-momentum-transfer behavior of the deuteron form factors and the form of the deuteron distribution amplitude at short distances. Later on in Ref. [23] it was shown...
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