The Deuteron Spin-dependent Structure Function g1d and its First Moment

TL;DR

This paper reports precise measurements of the deuteron spin structure function g1d and its first moment, providing insights into the gluon spin contribution and QCD fits using data from the COMPASS experiment.

Contribution

It presents the first detailed measurement of g1d and its first moment, along with QCD fits that allow for both positive and negative gluon polarization solutions.

Findings

First moment of g1d measured accurately.

QCD fits suggest gluon polarization magnitude around 0.2-0.3.

Two viable solutions for gluon spin distribution, positive or negative.

Abstract

We present a measurement of the deuteron spin-dependent structure function g1d based on the data collected by the COMPASS experiment at CERN during the years 2002-2004. The data provide an accurate evaluation for Gamma_1^d, the first moment of g1d(x), and for the matrix element of the singlet axial current, a0. The results of QCD fits in the next to leading order (NLO) on all g1 deep inelastic scattering data are also presented. They provide two solutions with the gluon spin distribution function Delta G positive or negative, which describe the data equally well. In both cases, at Q^2 = 3 (GeV/c)^2 the first moment of Delta G is found to be of the order of 0.2 - 0.3 in absolute value.