Small-$x$ asymptotics of the quark helicity distribution

Abstract

We construct a numerical solution of the small-$x$ evolution equations recently derived in \cite{Kovchegov:2015pbl} for the (anti)quark helicity TMDs and PDFs as well as the $g_1$ structure function. We focus on the case of large $N_c$ where one finds a closed set of equations. Employing the extracted intercept, we are able to predict directly from theory the behavior of the helicity PDFs at small $x$, which should have important phenomenological consequences. We also give an estimate of how much of the proton's spin may be at small $x$ and what impact this has on the so-called "spin crisis."

5 pages, 4 figures; minor changes, to appear in PRL

References in corpus (5)

• Extraction of Spin-Dependent Parton Densities and Their Uncertainties
• A first unbiased global determination of polarized PDFs and their uncertainties
• Evidence for polarization of gluons in the proton
• Helicity Evolution at Small $x$: Flavor Singlet and Non-Singlet Observables
• New analysis concerning the strange quark polarization puzzle

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