JAM small-$x$ helicity phenomenology

Abstract

We present the first-ever description the world data on the $g_1^{p,n}$ structure function at small Bjorken $x$ using evolution equations in $x$ derived from first principles QCD. This is a Monte-Carlo analysis within the JAM global framework that allows us to fit all existing polarized DIS data below $x<0.1$ as well as predict future measurements of small $x$ $g_1^{p,n}$ at the EIC. This is a necessary step in determining the quark helicity PDFs and, ultimately, the quark contribution to the proton spin.

arXiv comment9 pages, 4 figures, 1 logo, to appear in proceedings of DIS 2021. Version 2, fixed some errors and typos, included additional citations

References in corpus (20)

• Gauge-Invariant Decomposition of Nucleon Spin and Its Spin-Off
• Measurements of the Proton and Deuteron Spin Structure Functions g1 and g2
• Precise determination of the spin structure function ${\mathbf{g}}_1$ of the proton, deuteron and neutron
• Precision Determination of the Neutron Spin Structure Function g1n
• Evidence for polarization of gluons in the proton
• Measurement of the Neutron Spin Structure Function $g_1^n$ with a Polarized ^3He Target
• Deep Inelastic Scattering of Polarized Electrons by Polarized ${}^3$He and the Study of the Neutron Spin Structure
• Measurements of the $Q^2$-Dependence of the Proton and Neutron Spin Structure Functions g1p and g1n
• Measurement of the Deuteron Spin Structure Function g_1^d(x) for 1 (GeV/c)^2 < Q^2 < 40 (GeV/c)^2
• Flavor Singlet Contribution to the Structure Function $g_1$ at Small-x
• The Spin Structure Function $g_1^{\mathrm{p}}$ of the Proton and a Test of the Bjorken Sum Rule
• Simultaneous Monte Carlo analysis of parton densities and fragmentation functions
• Strange quark suppression from a simultaneous Monte Carlo analysis of parton distributions and fragmentation functions
• Helicity Evolution at Small $x$: Flavor Singlet and Non-Singlet Observables
• Small-$x$ Helicity Evolution: an Operator Treatment
• Monte Carlo sampling variant of the DSSV14 set of helicity parton densities
• Small-$x$ asymptotics of the quark helicity distribution
• Helicity-dependent generalization of the JIMWLK evolution
• Small-$x$ Asymptotics of the Quark Helicity Distribution: Analytic Results
• First analysis of world polarized DIS data with small-$x$ helicity evolution