AdS/CFT and Light-Front QCD

Brodsky, Stanley J.; Téramond, Guy F. de

doi:10.1142/9789814293242_0008

Cited by 66 publications

(107 citation statements)

References 146 publications

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“…Nonzero quark masses are naturally incorporated into the AdS/LF predictions by including them explicitly in the LF kinetic energy i (k 2 ⊥i + m 2 i )/x i [27,118]. Given the nonpertubative LFWFs one can predict many interesting phenomenological quantities such as heavy quark decays, generalized parton distributions and parton structure functions.…”

Section: Discussionmentioning

confidence: 99%

“…Using (4) one can readily generalize the equations to allow for the kinetic energy of massive quarks [27]. In this case, however, the longitudinal mode X (x) does not decouple from the effective LF bound-state equations.…”

Section: The Physics Of Light Front Wavefunctionsmentioning

confidence: 99%

“…A linear confining potential U (ζ ) ∼ κ 2 ζ in the LF Dirac equation leads to linear Regge trajectories [27]. For fermionic modes the light-front matrix Hamiltonian eigenvalue equation D L F |ψ = M|ψ , H L F = D 2 L F , in a 2×2 spinor component representation is equivalent to the system of coupled linear equations…”

Section: Nucleons In Light-front Holographymentioning

confidence: 99%

“…To simplify the discussion we shall consider the spin-non flip proton form factors for the transition n, L → n L. Using the SU (6) spin-flavor symmetry we obtain the result [27] where we have factored out the plane wave dependence of the AdS fields…”

Section: Computing Nucleon Form Factors In Holographic Qcdmentioning

confidence: 99%

“…The orthonormality of the Laguerre polynomials in (26) implies that the nucleon form factor at Q 2 = 0 is one if n = n and zero otherwise. Using (27) in (25) we find…”

Section: Computing Nucleon Form Factors In Holographic Qcdmentioning

confidence: 99%

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Light-Front Holography, Light-Front Wavefunctions, and Novel QCD Phenomena

Brodsky

Téramond

2012

Few-Body Syst

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Light-front holography is one of the most remarkable features of the AdS/CFT correspondence. In spite of its present limitations, it provides important physical insights into the non-perturbative regime of QCD and its transition to the perturbative domain. This novel framework allows hadronic amplitudes in a higher dimensional anti-de Sitter (AdS) space to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The model leads to an effective confining light-front QCD Hamiltonian and a single-variable light-front Schrödinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate ζ which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound-state wavefunctions, and thus the fall-off as a function of the invariant mass of the constituents. The soft-wall holographic model modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics-a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryons. The model predicts a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number n. The hadron eigensolutions projected on the free Fock basis provides the complete set of valence and non-valence light-front Fock state wavefunctions n/H (x i , k ⊥i , λ i ) which describe the hadron's momentum and spin distributions needed to compute the direct measures of hadron structure at the quark and gluon level, such as elastic and transition form factors, distribution amplitudes, structure functions, generalized parton distributions and transverse momentum distributions. The effective confining potential also creates quark-antiquark pairs from the amplitude q → qqq. Thus in holographic QCD higher Fock states can have any number of extra qq pairs. We discuss the relevance of higher Fock-states for describing the detailed structure of space and time-like form factors. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms. A new perspective on quark and gluon condensates is also obtained.

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Section: Discussionmentioning

confidence: 99%

Section: The Physics Of Light Front Wavefunctionsmentioning

confidence: 99%

Section: Nucleons In Light-front Holographymentioning

confidence: 99%

Section: Computing Nucleon Form Factors In Holographic Qcdmentioning

confidence: 99%

“…The orthonormality of the Laguerre polynomials in (26) implies that the nucleon form factor at Q 2 = 0 is one if n = n and zero otherwise. Using (27) in (25) we find…”

Section: Computing Nucleon Form Factors In Holographic Qcdmentioning

confidence: 99%

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Light-Front Holography, Light-Front Wavefunctions, and Novel QCD Phenomena

Brodsky

Téramond

2012

Few-Body Syst

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Bacchetta¹,

Cotogno²,

Pasquini³

2017

Light Cone 2015

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We present a study of the pion structure in the context of the AdS/QCD soft-wall model. This approach provides the light-front wave function of the pion in terms of a set of parameters that we fit to available experimental information on the electromagnetic form factor and parton distribution of the pion. We discuss the corresponding predictions for the unpolarized transverse momentum dependent parton distribution of the pion. 1 Introduction AdS/QCD correspondence with soft-wall holographic models has been employed in a number of recent works to get new insights on hadronic physics [1-4]. Remarkably, light-front holographic QCD methods (see [5] and references therein for a complete review on the topic) have provided expressions for the light-front wave function (LFWF) of a meson valence Fock state [6,7]. This allows one to obtain direct information about many hadronic observables, which can be expressed in terms of overlaps of LFWFs. The outline of this work is as follows: In Sect. 2 we consider the expressions for the pion LFWF derived in [6,7]. We introduce the quark masses in a Lorentz invariant way and derive analytical expressions for the pion valence Parton Distribution Function (PDF) and electromagnetic Form Factor. We determine the free parameters of the LFWFs by fitting simultaneously the available experimental information on form factor and valence PDF. In Sect. 3, we discuss the corresponding predictions for the pion unpolarized valence Transverse Momentum Dependent parton distribution function (TMD). In the final section, we summarize the results. 2 The Pion LFWF The LFWFs in the soft-wall model of the AdS/QCD correspondence were originally derived in two different matching procedures [6,7].

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Light-front holographic ρ-meson distributions in the momentum space

Kaur

Mondal

Dahiya

2021

J. High Energ. Phys.

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We present the leading-twist quark transverse momentum-dependent parton distribution functions (TMDs) for the spin-1 target, such as the ρ-meson, in the light-front framework. Specifically, we predict the TMDs in the light-front holographic model and compare with the light-front quark model predictions. We obtain the TMDs using the overlap of the light-front wave functions. We evaluate the k⊥ moments upto second order and compare with the available theoretical predictions. Further, we analyze the leading-twist parton distribution functions (PDFs) of the ρ-meson in the light-front holographic model which are found to be in accord with the Nambu-Jona-Lasinio (NJL) model and the light-front quark model predictions. We further study the QCD evolution of the PDFs. The positivity bounds on the TMDs and the PDFs are also discussed. We also present the quark spin densities in the transverse momentum plane for different polarization configurations of the quark and the ρ-meson target.

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AdS/CFT and Light-Front QCD

Cited by 66 publications

References 146 publications

Light-Front Holography, Light-Front Wavefunctions, and Novel QCD Phenomena

Light-Front Holography, Light-Front Wavefunctions, and Novel QCD Phenomena

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Light-front holographic ρ-meson distributions in the momentum space

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