Speaker
Description
We will report on recently published experimental results on spin sum rules, and particularly on the generalized spin polarizabilities $\gamma_0^n(Q^2)$ and $\delta_{LT}^n(Q^2)$. The data were taken at Jefferson Lab in Hall A and B by experiments E97-110 and EG4, respectively. They covered the very low $Q^2$ domain, down to $Q^2 \sim 0.02$ GeV$^2$, where Chiral Effective Field Theory ($\chi$EFT) predictions should be valid. While some obervables agree with the state-of-the-art $\chi$EFT theoretical predictions, others are in tensions, including $\delta_{LT}^n(Q^2)$ for which $\chi$EFT prediction was expected to be robust. This suggests that $\chi$EFT does not yet consistently describe nucleon spin observables, even in the very low $Q^2$ domain covered by the experiments.
