Polarized and unpolarized nucleon structure functions from lattice QCD

Abstract

We describe a high statistics quenched lattice QCD calculation of the moments of the polarized deep-inelastic structure functions g 1 and g 2 of the proton and neutron.Speaker at the workshop

A lattice study of the spin structure of the Λ hyperon

“…These relations account for the operator renormalisation and different normalisations on the lattice and in the continuum [12,14]. The renormalisation constants Z v 2 , Z a 0 , Z a 1 , Z t 0 depend on the renormalisation scale µ of the continuum theory and the lattice cut-off 1/a or equivalently β.…”

“…The choice for Γ andΓ as well as t and the smearing parameters can be found in [12]. The quality of the data can be judged by how well pronounced a plateau is obtained for this ratio as function of τ .…”

“…(6) (the v 2b operator in the notation of [12]) is used in a spin-averaged matrix element, the other operators require a polarised baryon state to give a non-zero result. In these latter cases we choose the spin to point into the 2-direction.…”

Heavy quark distribution functions in heavy baryons

“…(6,8) corresponds to the fraction of the heavy baryon's light-cone momentum component, P + , carried by the heavy quark, Q. When it is in the range 0 ≤ α ≤ 1, Q(α) measures the probability to find the heavy quark with the "plus" momentum fraction α.…”

“…However, to determine the parton distribution functions at some low energy scale (the boundary condition for DGLAP), one needs to apply either lattice QCD [8] or nonperturbative effective models. In the heavy quark limit, the light degrees of freedom in a heavy baryon have good quantum numbers which can be used to classify heavy baryons.…”