Abstract
We construct small-x evolution equations which can be used to calculate quark and anti-quark helicity TMDs and PDFs, along with the g 1 structure function. These evolution equations resum powers of α s ln2(1/x) in the polarization-dependent evolution along with the powers of α s ln(1/x) in the unpolarized evolution which includes saturation effects. The equations are written in an operator form in terms of polarization-dependent Wilson line-like operators. While the equations do not close in general, they become closed and self-contained systems of non-linear equations in the large-N c and large-N c & N f limits. As a cross-check, in the ladder approximation, our equations map onto the same ladder limit of the infrared evolution equations for the g 1 structure function derived previously by Bartels, Ermolaev and Ryskin [1].
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ArXiv ePrint: 1511.06737
An erratum to this article is available at http://dx.doi.org/10.1007/JHEP10(2016)148.
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Kovchegov, Y.V., Pitonyak, D. & Sievert, M.D. Helicity evolution at small x . J. High Energ. Phys. 2016, 72 (2016). https://doi.org/10.1007/JHEP01(2016)072
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DOI: https://doi.org/10.1007/JHEP01(2016)072