Hadron and Nuclear Physics on the Light Front

Abstract

The QCD light-front (LF) Hamiltonian equation H_{LF}|Ψ> = M^2 |Ψ> derived from quantization at fixed LF time τ= t+z/c provides a causal, frame-independent, method for computing hadron spectroscopy as well as dynamical observables such as structure functions, transverse momentum distributions, and distribution amplitudes. The LF formalism also leads to novel nuclear phenomena, such as "hidden color", "color transparency", "nuclear-bound quarkonium" and the shadowing and antishadowing of nuclear structure functions. For example, there are five distinct color-singlet Fock state representations of the six color-triplet quarks of the deuteron. The hidden color Fock states become manifest when the deuteron is probed when it has small transverse size, as in measurements of the deuteron form factor at large momentum transfer. The QCD Lagrangian with zero quark mass has no explicit mass scale. However, as shown by de Alfaro, Fubini, and Furlan (dAFF), a mass scale can appear in the equations of motion without affecting the conformal invariance of the Action. When one applies the dAFF procedure to the QCD LF Hamiltonian, it leads to a color confining potential κ^4 ζ^2 for mesons, where ζ^2 is the LF radial variable conjugate to the qbar-q invariant mass squared. The same result, including spin terms, is obtained using LF holography (AdS/QCD) -- the duality between LF dynamics and AdS_5 -- if one modifies the AdS_5 Action by the dilaton exp{+κ^2 z^2} in the fifth dimension z. If this procedure is generalized using superconformal algebra, the resulting LF eigensolutions provide unified Regge spectroscopy of mesons, baryons, and tetraquarks, including remarkable supersymmetric relations between the masses of mesons, baryons and tetraquarks with a universal Regge slope...

8 pages, 3 figures. Contribution to the proceedings of 13th International Conference on Nucleus-Nucleus Collisions (NN2018) in Omiya, Japan. Plenary talk given by S. J. Brodsky. arXiv admin note: text overlap with arXiv:1802.08552, arXiv:1709.01191, arXiv:1611.0719

References in corpus (14)

• The QCD Running Coupling
• Universality of Generalized Parton Distributions in Light-Front Holographic QCD
• Baryon Spectrum from Superconformal Quantum Mechanics and its Light-Front Holographic Embedding
• Determination of the effective strong coupling constant alpha_{s,g_1}(Q^2) from CLAS spin structure function data
• Superconformal Baryon-Meson Symmetry and Light-Front Holographic QCD
• Kinematical and Dynamical Aspects of Higher-Spin Bound-State Equations in Holographic QCD
• Experimental study of isovector spin sum rules
• Analysis of nucleon electromagnetic form factors from light-front holographic QCD : The spacelike region
• High precision determination of the $Q^2$-evolution of the Bjorken Sum
• Nuclear physics in soft-wall AdS/QCD: Deuteron electromagnetic form factors
• Meson/Baryon/Tetraquark Supersymmetry from Superconformal Algebra and Light-Front Holography
• Supersymmetry in the Double-Heavy Hadronic Spectrum
• Deuteron electromagnetic structure functions and polarization properties in soft-wall AdS/QCD
• The Light-Front Schrödinger Equation and Determination of the Perturbative QCD Scale from Color Confinement