Spin asymmetry A_1^d and the spin-dependent structure function g_1^d of the deuteron at low values of x and Q^2

TL;DR

This paper reports a highly precise measurement of the deuteron spin asymmetry A_1^d and the structure function g_1^d at low x and Q^2, finding results consistent with zero, which enhances understanding of nucleon spin structure.

Contribution

It provides the most precise measurements to date of A_1^d and g_1^d at low x and Q^2, with data collected by the COMPASS experiment, improving statistical accuracy over previous studies.

Findings

A_1^d and g_1^d are consistent with zero across the measured range.

Measurement precision is ten times better than previous data.

Results contribute to understanding of nucleon spin at low x.

Abstract

We present a precise measurement of the deuteron longitudinal spin asymmetry A_1^d and of the deuteron spin-dependent structure function g_1^d at Q^2 < 1 GeV^2 and 4*10^-5 < x < 2.5*10^-2 based on the data collected by the COMPASS experiment at CERN during the years 2002 and 2003. The statistical precision is tenfold better than that of the previous measurement in this region. The measured A_1^d and g_1^d are found to be consistent with zero in the whole range of x.