Light-front dynamics and AdS/QCD correspondence: The pion form factor in the space- and time-like regions

Stanley J. Brodsky and Guy F. de Téramond
Phys. Rev. D 77, 056007 – Published 17 March 2008

Abstract

The AdS/CFT correspondence between string theory in AdS space and conformal field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD which has scale invariance and dimensional counting at short distances and color confinement at large distances. The AdS/CFT correspondence also provides insights into the inherently nonperturbative aspects of QCD such as the orbital and radial spectra of hadrons and the form of hadronic wavefunctions. In particular, we show that there is an exact correspondence between the fifth-dimensional coordinate of anti–de Sitter (AdS) space z and a specific light-front impact variable ζ which measures the separation of the quark and gluonic constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and which allow the computation of decay constants, form factors and other exclusive scattering amplitudes. Relativistic light-front equations in ordinary space-time are found which reproduce the results obtained using the fifth-dimensional theory. As specific examples we compute the pion coupling constant fπ, the pion charge radius rπ2 and examine the propagation of the electromagnetic current in AdS space, which determines the space and timelike behavior of the pion form factor and the pole of the ρ meson.

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  • Received 13 October 2007

DOI:https://doi.org/10.1103/PhysRevD.77.056007

©2008 American Physical Society

Authors & Affiliations

Stanley J. Brodsky1 and Guy F. de Téramond1,2

  • 1Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309, USA
  • 2Universidad de Costa Rica, San José, Costa Rica

See Also

Light-front dynamics and AdS/QCD correspondence: Gravitational form factors of composite hadrons

Stanley J. Brodsky and Guy F. de Téramond
Phys. Rev. D 78, 025032 (2008)

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Vol. 77, Iss. 5 — 1 March 2008

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