Präpositionalattribute

asymmetry — a few remarks

“…In the language of the higher-twist expansion this means that the twist-4 contribution is rather large and negative. This phenomenolog-1 the traditional parton model do not posses this property ical observation is consistent with a recent QCD lattice result [ 15]. The substantial higher-twist effects strongly modify our present understanding of the applicability of the QCD-improved parton model.…”

Summary of the structure function working group at DIS'99

“…where the sum is over the contributions δ m of the sets. A status report on an effort to compute power corrections to structure functions numerically on the lattice was given by Schierholz [ 80]. When one contemplates computing (moments of) a structure function on the lattice, and extracts twist-4 power corrections from this, via…”

Higher-twist contributions to the Structure Functions coming from 4-fermion operators

“…One needs the renormalization factors of the operators on the lattice as well as in the continuum, in order to obtain physical continuum matrix elements from the Monte Carlo simulations. 3 For discussions of twist-4 operator bases and general higher-twist effects, see also [5,2,6]. 4 In principle also gauge-variant operators could appear in the mixing, but there are no such 4-fermion operators with dimension 6, and 2-fermion operators do not contribute.…”

“…The twist-4 contribution involves various operators 3 , but only 4-fermion operators can contribute to the I = 2 combination (2), and the only 4-fermion operator that appears in (1) at order g 2 is…”

“…When mixing with operators of leading twist is forbidden, one gets rid of renormalon ambiguities completely. When such a mixing occurs, a non-perturbative computation of the Wilson coefficients in the way proposed in[2,3] would avoid renormalon problems. That method will be a useful complement to the present one for an understanding of higher-twist effects.…”