Polarized lepton-hadron scattering in asymptotically free gauge theories

Abstract:The singlet contribution to the g 1 (x, Q 2 ) structure function is calculated in the double-logarithmic approximation of perturbative QCD in the region x ≪ 1. Double logarithmic contributions of the type (α s ln 2 (1/x)) k which are not included in the GLAP evolution equations are shown to give a power-like rise at small-x which is much stronger than the extrapolation of the GLAP expressions. The dominant contribution is due to the gluons which, in contrast to the unpolarized case, mix with the fermions also in the region x ≪ 1. The two main reasons why the small-x behavior of the double logarithmic approximation is so much stronger than the usual GLAP evolution are: the larger kinematical region of integration (in particular, no ordering in transverse momentum) and the contributions from non-ladder diagrams.

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“…It agrees (as we have already mentioned before) with the singular part of [3,11]. The next-to-leading-order matrix has the form:…”

Section: Solution Of the Evolution Equationsupporting

confidence: 69%

Flavor singlet contribution to the structure functiong 1 at small-x

Bartels

Ermolaev

Ryskin

1996

Z. Phys. C - Particles and Fields

117

272

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“…The spin-dependent LO anomalous dimensions (splitting functions 1 ) have been originally calculated in [34,35] and are given by…”

Section: Discussionmentioning

confidence: 99%

Next-to-leading-order radiative parton model analysis of polarized deep inelastic lepton-nucleon scattering

et al. 1996

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A next-to-leading order QCD analysis of spin asymmetries and structure functions in polarized deep inelastic lepton nucleon scattering is presented within the framework of the radiative parton model. A consistent NLO formulation of the Q 2 -evolution of polarized parton distributions yields two sets of plausible NLO spin dependent parton distributions in the conventional MS factorization scheme. They respect the fundamental positivity constraints down to the low resolution scale Q 2 = µ 2 N LO = 0.34 GeV 2 . The Q 2 -dependence of the spin asymmetries A p,n,d 1 (x, Q 2 ) is similar to the leading-order (LO) one in the range 1 ≤ Q 2 ≤ 20 GeV 2 and is shown to be non-negligible for x-values relevant for the analysis of the present data and possibly forthcoming data at HERA.

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“…The associated evolution equations have the same form as Eq. 5, but with polarized splitting functions (2,23,24). Also, the spin-dependent gluon density ∆g, defined in analogy with Equation 8, appears.…”

Section: What We Have Learned From Polarized Dismentioning

confidence: 99%