New Approaches to QCD: Light-Front Holography and the Principle of Maximal Conformality

Who: Stanley J. Brodsky (SLAC & CP3-Origins)
When: Monday, October 3, 2011 at 14:15
Where: U142

Light‐front wavefunctions are the eigensolutions of the QCD Hamiltonian quantized at fixed light‐front time, describing the quark and gluon structure of hadrons at a fundamental level. Given the frame‐independent LFWFs, one can compute hadron form factors, “static” structure functions, distribution amplitudes, transverse momentum distributions, etc. from first principles. The Sivers, Boer‐Mulders, and Collins Transversity and single‐spin “dynamic” distributions can be computed from the frame‐independent LFWFs plus the lensing effects of initial and final state interactions.

“Light‐Front Holography” leads to a rigorous connection between hadronic amplitudes in a higher dimensional anti‐de Sitter (AdS) space and the LFWFs of of hadrons in 3+1 physical space‐time, thus providing a correspondence between theories in a modified AdS5 background and confining field theories in physical space‐time. The AdS/QCD model leads to 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.

The “Principle of Maximum Conformality” (PMC) fixes the renormalization scale of pQCD amplitudes at finite order, independent of the choice of renormalization scheme.

Finally, a method for computing the hadronization of quark and gluon jets at the amplitude level will be outlined.