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"

TL;DR

This paper critically examines recent CLAS results on deuteron spin polarizability, arguing that their interpretation and comparison with chiral perturbation theory are misleading due to fundamental misconceptions and invalid assumptions.

Contribution

The authors provide a novel pionless EFT calculation showing the deuteron polarizability is much larger than reported, challenging previous sum rule applications and interpretations.

Findings

Deuteron polarizability is larger by 4 orders of magnitude than CLAS claims.

The sum rule used by CLAS is not applicable to the deuteron.

Assumptions in the CLAS test of $ ext{chi}$PT may be invalid at claimed accuracy.

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.