[Submitted on 24 Nov 2017]
Parton distribution amplitudes: revealing diquarks in the proton and Roper resonance
Cedric Mezrag🇮🇹 · Jorge Segovia🇪🇸 · Lei Chang🇨🇳 · Craig D. Roberts🇺🇸
We present the first quantum field theory calculation of the pointwise behaviour of the leading-twist parton distribution amplitudes (PDAs) of the proton and its lightest radial excitation. The proton's PDA is a broad, concave function, whose maximum is shifted relative to the peak in QCD's conformal limit expression for this PDA; an effect which signals 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 interference 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.
- Comments:
- 5 pages, 2 figures
- Subjects:
- Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
- arXiv:
- 1711.09101 [pdf]