Hadron Spectroscopy and Dynamics from Light-Front Holography and Superconformal Algebra

Journal Article · Thu May 24 00:00:00 EDT 2018 · Few-Body Systems

DOI:https://doi.org/10.1007/s00601-018-1409-4· OSTI ID:1443973

Brodsky, Stanley J. ^[1]

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1. Stanford Univ., Stanford, CA (United States). SLAC National Accelerator Lab

QCD is not supersymmetrical in the traditional sense – the QCD Lagrangian is based on quark and gluonic fields, not squarks nor gluinos. However, its hadronic eigensolutions conform to a representation of superconformal algebra, reflecting the underlying conformal symmetry of chiral QCD and its Pauli matrix representation. The eigensolutions of superconformal algebra provide a unified Regge spectroscopy of meson, baryon, and tetraquarks of the same parity and twist as equal-mass members of the same 4-plet representation with a universal Regge slope. The pion $$q\bar{q}$$ eigenstate has zero mass for m_q = 0. The superconformal relations also can be extended to heavy-light quark mesons and baryons. The combined approach of light-front holography and superconformal algebra also provides insight into the origin of the QCD mass scale and color confinement. A key observation is the remarkable dAFF principle which shows how a mass scale can appear in the Hamiltonian and the equations of motion while retaining the conformal symmetry of the action. When one applies the dAFF procedure to chiral QCD, a mass scale κ appears which determines universal Regge slopes, hadron masses in the absence of the Higgs coupling, and the mass parameter underlying the Gaussian functional form of the nonperturbative QCD running coupling: α_s(Q²) ∝ exp-Q²/4κ², in agreement with the effective charge determined from measurements of the Bjorken sum rule. The mass scale κ underlying hadron masses can be connected to the parameter Λ_{$$\overline{MS}$$} in the QCD running coupling by matching its predicted nonperturbative form to the perturbative QCD regime. The result is an effective coupling α_s(Q²) defined at all momenta. In conclusion, one also obtains empirically viable predictions for spacelike and timelike hadronic form factors, structure functions, distribution amplitudes, and transverse momentum distributions.

• Research Organization: SLAC National Accelerator Lab., Menlo Park, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC02-76SF00515
• OSTI ID: 1443973
• Report Number(s): SLAC-PUB-17201; TRN: US1900950
• Journal Information: Few-Body Systems, Vol. 59, Issue 5; Conference: NSTAR 2017, The 11th International Workshop on the Physics of Excited Nucleons, Univ. of South Carolina, Columbia, SC (United States), 20-23 Aug 2017; ISSN 0177-7963
• Publisher: Springer
• Country of Publication: United States
• Language: English