Parton distribution amplitudes: Revealing correlations within the proton and Roper

Publication date: 10 August 2018Source: Physics Letters B, Volume 783Author(s): Cédric Mezrag, Jorge Segovia, Lei Chang, Craig D. RobertsAbstractConstrained by solutions of the continuum three-valence-body bound-state equations, we use perturbation theory integral representations (PTIRs) to develop algebraic Ansätze for the Faddeev wave functions of the proton and its first radial excitation, delivering therewith a quantum field theory calculation of the pointwise behaviour of their leading-twist parton distribution amplitudes (PDAs). The proton's PDA is a broad, concave function, with its maximum shifted relative to the peak in QCD's conformal limit expression for this PDA. The size and direction of this shift signal the presence of both scalar and pseudovector diquark correlations in the nucleon, with the scalar generating around 60% of the proton's normalisation. The radial-excitation is constituted similarly, and the pointwise form of its PDA, which is negative on a material domain, is the result of marked interferences between the contributions from both types of diquark; particularly, the locus of zeros that highlights its character as a radial excitation. These features originate with the emergent phenomenon of dynamical chiral-symmetry breaking in the Standard Model.

Source: Physics Letters B - July 12, 2018 Category: Physics Source Type: research