Parton distributions of light quarks and antiquarks in the proton

Abstract

An algebraic Ansatz for the proton's Poincaré-covariant wave function, which includes both scalar and pseudovector diquark correlations, is used to calculate proton valence, sea, and glue distribution functions (DFs). Regarding contemporary data, a material pseudovector diquark component in the proton is necessary for an explanation of the neutron-proton structure function ratio; and a modest Pauli blocking effect in the gluon splitting function is sufficient to explain the proton's light-quark antimatter asymmetry. In comparison with pion DFs, the valence degrees-of-freedom in both proton and pion carry the same fraction of the host hadron's light-front momentum, but at a resolving scale typical of contemporary experiments, sea-quarks in the proton carry roughly 30% more momentum than their analogues in the pion and the proton glue fraction is 7% smaller. Understanding these differences may provide insights that explain distinctions between Nambu-Goldstone bosons and seemingly less complex hadrons.

Proton and pion distribution functions in counterpoint

“…( 11) becomes 0.110 (11), a value that is 20% larger than that determined in Ref. [46], which ignored quark mass effects in the evolution equations. On the other hand, we implemented mass-dependent evolution via Eq.…”

“…Against this backdrop, we exploit recent progress made using continuum Schwinger function methods (CSMs) [31,32,[43][44][45][46] in developing a unified set of predictions for all proton and pion DFs. Crucially, their common origin enables meaningful comparisons to be made between them.…”

“…Hadron scale and DF evolution. Using CSMs, the hadron scale, ζ H , is naturally identified with the resolving scale at which dressed valence degrees-of-freedom carry all measurable properties of the hadron, including its light-front momentum [31,32,[43][44][45][46], and ζ H is the same for both the proton and the pion. Defining the n th moment of a given DF as (H = p, π)…”

“…DFs at ζ = m J/ψ . Modern CSM analyses of hadron scale valence DFs for the pion and proton are detailed elsewhere [44,46] and the results therein are drawn in Fig. 2A.…”

“…When evolving singlet and glue DFs, we include a Pauli blocking factor in the gluon splitting function, as discussed elsewhere [46,Sec. 6]:…”