Pion and kaon valence-quark quasiparton distributions
Abstract
Algebraic Ansaetze for the Poincar\'e-covariant Bethe-Salpeter wave functions of the pion and kaon are used to calculate their light-front wave functions (LFWFs), parton distribution amplitudes (PDAs), quasi-PDAs (qPDAs), valence parton distribution functions (PDFs), and quasi-PDFs (qPDFs). The LFWFs are broad, concave functions; and the scale of flavour-symmetry violation in the kaon is roughly 15%, being set by the ratio of emergent masses in the s-and u-quark sectors. qPDAs computed with longitudinal momentum Pz =1.75\,GeV provide a semiquantitatively accurate representation of the objective PDA; but even with Pz=3\,GeV, they cannot provide information about this amplitude's endpoint behaviour. On the valence-quark domain, similar outcomes characterise qPDFs. In this connection, however, the ratio of kaon-to-pion u-quark qPDFs is found to provide a good approximation to the true PDF ratio on 0.3 x 0.8, suggesting that with existing resources computations of ratios of quasi-parton-distributions can yield results that support empirical comparison.