Measurement of the Tensor Structure Function<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>b</mml:mi><mml:mn>1</mml:mn></mml:msub></mml:math>of the Deuteron

A. Airapetian, Н. Акопов, Z. Akopov, M. Amarian, V. V. Ammosov, A. Andrus, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian

Abstract

The Hermes experiment has investigated the tensor spin structure of the deuteron using the $27.6\text{ }\text{ }\mathrm{GeV}/c$ positron beam of DESY HERA. The use of a tensor-polarized deuteron gas target with only a negligible residual vector polarization enabled the first measurement of the tensor asymmetry ${A}_{zz}^{d}$ and the tensor structure function ${b}_{1}^{d}$ for average values of the Bjorken variable $0.01&lt;⟨x⟩&lt;0.45$ and of the negative of the squared four-momentum transfer $0.5\text{ }\text{ }{\mathrm{GeV}}^{2}&lt;⟨{Q}^{2}⟩&lt;5\text{ }\text{ }{\mathrm{GeV}}^{2}$. The quantities ${A}_{zz}^{d}$ and ${b}_{1}^{d}$ are found to be nonzero. The rise of ${b}_{1}^{d}$ for decreasing values of $x$ can be interpreted to originate from the same mechanism that leads to nuclear shadowing in unpolarized scattering.

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