Measurement of Inclusive Spin Structure Functions of the Deuteron

TL;DR

This study measures the spin structure functions of the deuteron at moderate momentum transfers, providing new data that enhances understanding of nucleon resonance contributions and the transition to deep inelastic scattering regimes.

Contribution

It presents new, high-precision measurements of the deuteron spin structure functions in the resonance region, extending previous data and analyzing the first moment's behavior across different Q^2 values.

Findings

Data agree with previous SLAC measurements where overlapping.

The first moment of g_1^d crosses zero between Q^2 of 0.5 and 0.8 (GeV/c)^2.

Rapid variation of the first moment indicates significant resonance effects.

Abstract

We report the results of a new measurement of spin structure functions of the deuteron in the region of moderate momentum transfer ($Q^2$ = 0.27 -- 1.3 (GeV/c)$^2$) and final hadronic state mass in the nucleon resonance region ($W$ = 1.08 -- 2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam at Jefferson Lab off a dynamically polarized cryogenic solid state target ($^{15}$ND$_3$) and detected the scattered electrons with the CEBAF Large Acceptance Spectrometer (CLAS). From our data, we extract the longitudinal double spin asymmetry $A_{||}$ and the spin structure function $g_1^d$. Our data are generally in reasonable agreement with existing data from SLAC where they overlap, and they represent a substantial improvement in statistical precision. We compare our results with expectations for resonance asymmetries and extrapolated deep inelastic scaling results. Finally, we evaluate the first moment of the structure function $g_1^d$ and study its approach to both the deep inelastic limit at large $Q^2$ and to the Gerasimov-Drell-Hearn sum rule at the real photon limit ($Q^2 \to 0$). We find that the first moment varies rapidly in the $Q^2$ range of our experiment and crosses zero at $Q^2$ between 0.5 and 0.8 (GeV/c)$^2$, indicating the importance of the $\Delta$ resonance at these momentum transfers.