Spin structure function g2(x, Q2) and twist-3 operators in QCD

Abstract

We investigate the spin structure function g 2 (x, Q 2 ) in the framework of the operator product expansion and the renormalization group. The twist-3 operators appearing in QCD are examined and their relations are studied. It is noted that operators proportional to equation of motion appear in the operator mixing through renormalization, which can be studied from the relevant Green's functions. We also note that the coefficient functions can be properly fixed after the choice of independent operators.

QCD corrections to the nucleon's spin structure function g2(x, Q2)

“…Furthermore, they included some contributions from the "one-particle-reducible"diagrams to take into account the circumstance that the partons can not be regarded as located on the mass shell [4]. This may cor-respond to the fact that even if the gauge invariant EOM operator is discarded, the gauge non-invariant EOM operators turn out to mix through the renormalization [6].…”

Gluon contribution to the structure function

“…On the theoretical side, a lot of effort was invested to understand the physical interpretation of twist-3 distributions (see e.g. [4,5,6] for the review of various aspects) and their scale dependence [7,8,9,10,11,12,13]. Conditions for the validity of the Burhardt-Cottingham (BC) sum rule [14] 1 0 dx g 2 (x) = 0 were discussed in detail [4,15,16,17] and the second moment 1 0 dx x 2 g 2 (x) was estimated using QCD sum rules [18] and on the lattice [19].…”

Spin structure functiong2(x,Q2)and twist-3 operators in large-Sasaki1 1998Phys. Rev. D7010View full textAdd to dashboardCite

“…The advantage of this choice of operator basis is that the coefficient functions take simple forms at the tree-level. In fact we have [17] …”

“…When eliminating R n F , we obtain a different set of coefficient functions. In other words, the (tree-level) coefficient functions are dependent upon the choice of the independent operators [17].…”

“…However, arbitrariness in the choice of the operator bases should not enter into physical quantities [17].…”