Small-x Helicity Phenomenology*

One of the key components to solving the proton spin problem is understanding the small-x asymptotics of the helicity parton distribution functions (hPDFs). Several years ago, novel, small-$x$ evolution equations were derived using the shock-wave/Wilson line formalism, designed for calculating the $x$-dependence of the quark and gluon hPDFs and the proton $g_1$ structure function. These equations can be used to predict the contribution to the spin of the proton coming from the helicities of the small-$x$ quarks and gluons. In this talk we will present the first-ever attempt to describe the world data on the $g_1$ structure function at small $x$ using the evolution equations derived the novel evolution equations within the JAM global analysis framework. Our results serve as a prediction for future measurements at the EIC and can be used to estimate the net amount of quark spin at small-$x$, ultimately bringing us one step closer to understanding the proton spin.