Speaker
Description
We expand upon small-$x$ helicity phenomenology by using the small-$x$ helicity evolution equations in a global analysis that now incorporates polarized proton-proton ($pp$) data in addition to the previously analyzed deep-inelastic scattering (DIS) and semi-inclusive DIS (SIDIS) data, all at $x < 0.1$. We specifically analyze the double longitudinal spin asymmetry in single-inclusive jet production, $A_{LL}^{\mathrm{jet}}$, at $x_{T,P}\approx \tfrac{p_T}{\sqrt{s}}e^{\pm y} < 0.1$. This analysis serves as a proof-of-principle to determine the effect $pp$ data has on our predictions for helicity PDFs (hPDFs) and the $g_1$ structure function at small-$x$; we utilize the pure-glue $gg \to g$ partonic channel for particle production in polarized $pp$ collisions in place of the jet production cross-section. We modify the large-$N_c\&N_f$ KPS-CTT evolution equations by setting $N_f = 0$ in order to replicate the large-$N_c$ (pure-glue) limit while retaining external quark flavors for the spinor field operators. We find that fitting to even a small number of $pp$ data points makes our spin-contributions, specifically the gluon hPDF $\Delta G$, significantly more positive. Additionally, the inclusion of gluon-sensitive observables reduces our small-$x$ uncertainties for the $g_1$ structure function and hPDFs.
