Low-x contribution to the Bjorken sum rule within double logarithmic ln²x approximation

2004/07/03 by D. Kotlorz, Dorota Kotlorz, Kotlorz, Dorota +2
Earth and Planetary Sciences · Physics and Astronomy · #FOS: Physical sciences #Geophysics and Gravity Measurements #High Energy Physics - Phenomenology (hep-ph) #hep-ph

paper · pdf · doi:10.48550/arxiv.hep-ph/0407040

17 pages, 3 figures

arxiv created 2004/07/03 · openalex publication_date 2004/07/03 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

The small-x contributions to the Bjorken sum rule within double logarithmic ln²x approximation for different input parametrisations g₁^NS(x,Q₀²) are presented. Analytical solutions of the evolution equations for full and truncated moments of the unintegrated structure function f^NS(x,Q²) are used. Theoretical predictions for ∫₀^0.003 g₁^NS(x,Q²=10) dx are compared with the SMC small-x data. Rough estimation of the slope λ, controlling the small-x behaviour of g₁^NS∼ x^-λ from the SMC data is performed. Double logarithmic terms ∼ (α_s ln²x)ⁿ become leading when x→ 0 and imply the singular behaviour of g₁^NS∼ x^-0.4. This seems to be confirmed by recent experimental SMC and HERMES data. Advantages of the unified ln²x+LO DGLAP approach and the crucial role of the running coupling α_s=α_s(Q²/z) at low-x are also discussed.

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