Probing relativistic spin effects in the nucleon by means of Drell-Yan processes

Abstract

Significant differences between transverse and longitudinal polarized parton distributions are found at low energies within a light-front covariant quark model of the nucleon. These differences are due to relativistic spin effects introduced by the Melosh rotations and survive evolution to higher Q 2 scales. A specific observable related to double-spin asymmetries in lepton pair production in polarized hadron-hadron collisions is defined. The possibility of assessing the relevance of these relativistic spin effects in future experiments at RHIC and HERA-N is discussed.

Correlations in double parton distributions: perturbative and non-perturbative effects

“…The numerous applications to a large varieties of DIS observables like polarized [24] and unpolarized [26,27,28] structure functions, spin and angular momentum distributions [29,30], helicity-independent and dependent GPDs [31], demonstrate the reliability and flexibility of the approach.…”

“…The approach is particularly suitable for the description of Deep Inelastic Scattering (DIS) processes which find their natural environment in a LF-description. The numerous applications to a large varieties of DIS observables like polarized [24] and unpolarized [26][27][28] structure functions, spin and angular momentum distributions [29,30], helicity-independent and dependent GPDs [31][32][33], demonstrate the reliability and flexibility of the approach.…”

Transverse polarisation of quarks in hadrons

“…shown by Ma and Schmidt [262]. Taking g A /g V = 6 (Γ p −Γ n ) these authors find (the ranges are determined by the experimental and theoretical uncertainties) [263]. These authors use a three-quark wave function obtained by solving the Schrödinger equation with a hypercentral phenomenological potential (for details see [256]).…”

Hadronic Degrees of Freedom

“…A complete theoretical study of h 1 and g 1 has to account for both: the relativistic effects which distinguish h 1 from g 1 at the nonperturbative scale, and the pQCD evolution which differs for the two structure functions. A quantitative study of the relativistic effects in h 1 and g 1 due to the correlations of spin and parton motion in the hadronic systems has been recently completed 14 . It makes use of the light-front approach previously discussed and the interplay between motion and spin is made explicit through the Melosh rotations.…”

“…To this aim I discuss a constituent quark model approach based on a light-front realization of the Hamiltonian dynamics and recent applied for the calculation of both polarized and unpolarized parton distributions 13,14 . The parton distributions at the hadronic scale are assumed to be valence quarks and gluons, and their twist two component is determined by the quark momentum density.…”