Comment on "Measurement of the $Q^2$ Dependence of the Deuteron Spin Structure Function $g_1$ and its Moments at Low $Q^2$ with CLAS"

Abstract

We argue that the recently published CLAS results on the deuteron spin polarizability $\gamma_0$ [Adhikari {\it et al.}, Phys.\ Rev.\ Lett.\ {\bf 120}, 062501 (2018)], as well as their comparisons with chiral perturbation theory ($\chi$PT), are misleading. In reality, the deuteron polarizability is larger by 4 orders of magnitude, as demonstrated here by a novel calculation in pionless EFT. The CLAS paper, on the other hand, presents only a tiny correction to it, based on a partial evaluation of a sum rule for $\gamma_0$. The sum rule is assumed to have the same form as for the nucleon; we argue it does not. Moreover, their "test of $\chi$PT" tacitly involves assumptions which, as we demonstrate, may not be valid at the claimed accuracy.