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arXiv · 2104.11765

Helicity Evolution at Small $x$: the Single-Logarithmic Contribution

Yuri V. Kovchegov·Andrey Tarasov·Yossathorn Tawabutr
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Abstract

We calculate single-logarithmic corrections to the small-$x$ flavor-singlet helicity evolution equations derived recently in the double-logarithmic approximation. The new single-logarithmic part of the evolution kernel sums up powers of $\alpha_s \ln(1/x)$, which are an important correction to the dominant powers of $\alpha_s \ln^2(1/x)$ summed up by the double-logarithmic kernel at small values of Bjorken $x$ and with $\alpha_s$ the strong coupling constant. The single-logarithmic terms arise separately from either the longitudinal or transverse momentum integrals. Consequently, the evolution equations we derive employing the light-cone perturbation theory simultaneously include the small-$x$ evolution kernel and the leading-order polarized DGLAP splitting functions. We further enhance the equations by calculating the running coupling corrections to the kernel.

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Yuri V. Kovchegov, Andrey Tarasov, Yossathorn Tawabutr. 2021-04-23. Helicity Evolution at Small $x$: the Single-Logarithmic Contribution. https://doi.org/10.1007/jhep03(2022)184

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