Spin content of constituent quarks and one-spin asymmetries in inclusive processes

Abstract

We consider mechanism for one-spin asymmetries observed in inclusive hadron production. The main role belongs to the orbital angular momentum of the quark-antiquark cloud in the internal structure of constituent quarks. We argue that the origin of the asymmetries in pion production is a result of retaining of this internal angular orbital momentum by the perturbative phase of QCD under transition from the non-perturbative phase. The non-perturbative hadron structure is based on the results of chiral quark models.

Hyperon polarization in the constituent quark model

“…the asymmetry associated with internal structure of this quark will be significant at p ⊥ > Λ χ ≃ 1 GeV/c where interactions at short distances give noticeable contribution. The behaviour of asymmetries in inclusive meson production was predicted [15] to have a corresponding p ⊥ -dependence, in particular, vanishing asymmetry at p ⊥ < Λ χ , its increase in the region of p ⊥ ≃ Λ χ , and p ⊥ -independent asymmetry at p ⊥ > Λ χ . Parameter Λ χ ≃ 1 GeV/c is determined by the scale of chiral symmetry spontaneous breaking.…”

“…The x-dependencies of the functions I sQ + (s, b, ξ) and I hQ + (s, b, ξ) are determined by the distribution of constituent quarks in hadrons and by the structure function of constituent quark respectively [15]:…”

“…In the recent papers [15] we considered a possible origin of asymmetry in the pion and ϕ-meson production under collision of a polarized proton beam with unpolarized proton target and argued that the orbital angular momentum of partons inside constituent quarks leads to significant asymmetries in meson production. In this paper we consider how the most characteristic features of hyperon and first of all Λ polarization can be accounted in such approach.…”

Single transverse-spin asymmetries in hadronic pion production

“…The twist-three analysis described here is in some sense a minimalist approach, depending on only light-cone variables, which we hope can serve as a benchmark for models which include models of both light-cone and transverse degrees of freedom. Other descriptions of single-spin asymmetries are based on multiquark interactions [23] and orbital motion [24]. Interesting comparisons of different approaches may be found in [25] and [26].…”

Flat transverse momentum dependence of the single-spin asymmetry in inclusive neutral pion production

“…As it often happens, this interpretation is not unique. Such a flat dependence can result from the finite size of a constituent quark and the presence of the orbital angular momentum of the current quarks residing inside the constituent one [13,14]. This mechanism is based on the similar ideas as the spin filtering one but is, in principle, different and has no predictive power for x F dependence of SSAs.…”