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arXiv · 1711.09101

Parton distribution amplitudes: revealing diquarks in the proton and Roper resonance

Cedric Mezrag·Jorge Segovia·Lei Chang·Craig D. Roberts
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Abstract

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.

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Cedric Mezrag, Jorge Segovia, Lei Chang, Craig D. Roberts. 2017-11-24. Parton distribution amplitudes: revealing diquarks in the proton and Roper resonance. https://doi.org/10.1016/j.physletb.2018.06.062

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