Infrared contribution to the double-logarithmic small-x asymptotics of structure functions
Petersburg Nuclear Physics Institute, Russian Academy of Science, Gatchina, St.Petersburg district, 188350, Russia
Published online: 27 February 2005
The role playing by the “soft” (κ T < 1 GeV/c) region in the small-x behaviour ofg 1(x,Q 2) and the non-singlet structure functionf 1, NS(x, Q2) has been studied with the help of the effective QCD Lagrangian which takes into account the lightest degrees of freedom — the constituent quarks and the π-mesons (Goldstone bosons). It has been shown that the quark-quark interaction due to the pion exchange has a negative couplingg for the isovector component (I = 1 in thet-channel) off 1(x,Q 2) and isosinglet component ofg 1(x, Q2). Here the pion induced interaction changes mainly the normalization of the quark distribution (it decreasesf 1,NS I = 1 (x,Q 2) two times atx < 3·10−3) and changes slightly the effective exponents λ (ℕ1,NS ,g 1 ∼x −λ atx → 0). On the other hand due to a positive value of couplingg the value of λ increases by 15% for the isovector part ofg 1 (x,Q 2) and up to λ ≈ 0.5 (instead of λ ≈ 0.2 without the pion contribution) for the isoscalar non-singlet structure functionf 1,NS I = 0 (x,Q 2).
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