A lattice study of the spin structure of the Λ hyperon

Abstract

Abstract:The internal spin structure of the Λ is of special importance for the understanding of the spin structure of hadrons in general. The comparison between the nucleon and Λ allows for a test of the relevant flavour-symmetry breaking effects. Using nonperturbatively O(a) improved Wilson fermions in the quenched approximation we have calculated the first moments of the unpolarised, longitudinally polarised and transversity quark distribution functions in the Λ. The results indicate that flavour symmetry breaking has little effect on the internal spin structure, in accordance with model based expectations.

Baryons From the Lattice: Past, Present and Future

“…38 The fraction ∆q Λ of the spin carried by quarks of flavour q is given by the forward matrix element of the axial vector current, Λ(p ′ , s)|qγ µ γ 5 q|Λ(p, s) = 2 (p ′ − p) µ ∆q Λ , i.e. by the lowest moment of the helicity distribution.…”

Measurement of the longitudinal spin transfer to Λ and $\bar{\varLambda}$ hyperons in polarised muon DIS

“…This contribution varies from 100% for the SU(6) model to 60-70% in the BJ-model [3] or the lattice-QCD calculation [28]. It means that scattering off u-or d-quarks is important for the Λ(Λ) production but not for the spin transfer to Λ(Λ).…”

Structure of the nucleon in the unquenched quark model

“…Table 1 shows that the unquenched quark model gives rise to a negatively polarized sea of up and down quarks and a large positively polarized sea of strange quarks. Other theoretical studies, such as the chiral quark-soliton model [32], lattice QCD [33] and QCD sum rules [34], also give a negative polarization of the up and down quarks, Finally, the contribution of quark spins for the Λ is found to be larger than that for the proton, (∆Σ) Λ > (∆Σ) p , which is a result of SU (3) flavor breaking by the sea quarks.…”