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The Light-Cone Fock State Expansion and QCD Phenomenology

  • Stanley J. Brodsky
Conference paper
Part of the Centre de Physique des Houches book series (LHWINTER, volume 8)

Abstract

The concept of the “number of constituents” of a relativistic bound state, such as a hadron in quantum chromodynamics, is not only frame-dependent, but its value can fluctuate to an arbitrary number of quanta. Thus when a laser beam crosses a proton at fixed “light-cone” time τ = 3Dt + z/c = 3Dx 0 + x z , an interacting photon can encounter a state with any given number of quarks, anti-quarks, and gluons in flight (as long as n q - n = 3D3). The probability amplitude for each such n-particle state of on-mass shell quarks and gluons in a hadron is given by a light-cone Fock state wavefunction \({\Psi _{n/H}}({x_i}{\overrightarrow {,k} _{ \bot \iota }},\lambda )\) , where the constituents have longitudinal light-cone momentum fractions
$${x_i} = 3D\frac{{k_i^ + }}{{{p^ + }}} = 3D\frac{{{k^0} + k_i^x}}{{{p^0} + {p^z}}},\sum\limits_{i = 3D1}^n {{x_i} = 3D1} $$
(1)
relative transverse momentum
$${\overrightarrow k _{ \bot \iota }},\sum\limits_{i = 3D1}^n {{{\overrightarrow k }_{ \bot \iota }}} = 3D{\overrightarrow 0 _ \bot }$$
(2)
and helicities λ i . The ensemble {ψ n/H } of such hght-cone Fock wavefunctions is a key concept for hadronic physics, providing a conceptual basis for representing physical hadrons (and also nuclei) in terms of their fundamental quark and gluon degrees of freedom.[1]

Keywords

Transverse Momentum Invariant Mass Heavy Quarkonium Hadronic Amplitude Pion Distribution Amplitude 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • Stanley J. Brodsky
    • 1
  1. 1.Stanford Linear Accelerator CenterStanford UniversityStanfordUSA

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