Experimental studies at low $Q^2$ of the spin structure of the nucleon at Jefferson Lab

Abstract

We summarize the experimental program of Jefferson Lab that studies the nucleon spin structure at low $Q^2$. This program completes the precise experimental mapping of the nucleon spin structure functions $g_1(ν, Q^2)$ and $g_2(ν, Q^2)$ and their moments started at SLAC, CERN and DESY at high $Q^2$, and continued at Jefferson Lab at intermediate $Q^2$. The results presented cover the domain where Chiral Effective Field Theory ($χ$EFT) should describe the strong interaction. They provide a comprehensive set of benchmark measurements for $χ$EFT. The preliminary conclusion is that nucleon spin structure data are still challenging for $χ$EFT in spite of the notable improvements in these calculations.

7 pages, 2 figures. Contribution to the proceedings of the 9th International workshop on Chiral Dynamics (PoS CD18)