QCD evolutions of twist-3 chirality-odd operators

The chirally-odd twist-3 distribution ea(x)

Properties of the nucleon twist-3 distribution function e(x) are reviewed. It is emphasized that the QCD equations of motion imply the existence of a δ-function at x = 0 in e(x), which gives rise to the pion-nucleon sigma-term. According to the resulting “practical” DIS sum rules the first and the second moment of e(x) vanish, a situation analogue to that of the pure twist-3 distribution functi...

The chirally-odd twist-3 distribution e(x)

Properties of the nucleon twist-3 distribution function ea(x) are reviewed. It is emphasized that the QCD equations of motion imply the existence of a δ-function at x = 0 in ea(x), which gives rise to the pion-nucleon sigma-term. According to the resulting “practical” DIS sum rules the first and the second moment of ea(x) vanish, a situation analogue to that of the pure twist-3 distribution fun...

Q2 Evolution of Chiral-Odd Twist-3 Distributions hL(x,Q2) and e(x,Q2) in Large-Nc QCD.

Two-parton twist-3 factorization in perturbative QCD

Abstract We prove collinear factorization theorem for the process πγ∗ → π at the twist-3 level in the covariant gauge by means of the Ward identity, concentrating on the two-parton case. It is shown that soft divergences cancel and collinear divergences are grouped into the pseudo-scalar and pseudotensor two-parton twist-3 pion distribution amplitudes. The delicate summation of a complete set o...

QCD Evolutions in the small–x Region

The curvature of DIS structure functions like F p 2 (x,Q ), i.e., its second derivative with respect to the photon’s virtuality Q at fixed values of x, plays a decisive role in probing the range of validity of perturbative QCD evolutions of parton distributions in the small-x region. This has been observed recently [1, 2, 3, 4] and it was demonstrated that NLO(MS) evolutions imply a positive cu...