CERN Accelerating science

Article
Title	Measurement of the longitudinal spin structure of the proton at COMPASS
Author(s)	Zemlyanichkina, Elena (Dubna, JINR)
Collaboration	on behalf of the COMPASS collaboration
Publication	2010
Number of pages	5
In:	PoS DIS2010 (2010) pp.254
In:	18th International Workshop on Deep-Inelastic Scattering and Related Subjects, Florence, Italy, 19 - 23 Apr 2010, pp.254
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN SPS ; COMPASS NA58
Abstract	Inclusive ($A_{1,p}$) and semi-inclusive ($A^{\pi +}_{1,p}$, $A^{\pi -}_{1,p}$, $A^{K+}_{1,p}$ and $A^{K-}_{1,p}$) double-spin asymmetries in deepinelastic muon-proton scattering have been measured at COMPASS (SPS CERN). The results have been obtained with data collected in 2007 for the longitudinal polarised NH$^{3}$ solid target and beam of positive muons with energy $E =$ 160 GeV. We improve the statistical precision of $g^{p}_{1} (x.Q^{2})$ by a factor of two in the low $x$ region. Proton asymmetries have been combined with published deuteron ones to extract the non-singlet spin-dependent structure function $g^{NS}_{1} (x,Q^{2})$. The first moment $\Gamma^{NS}_{1}$ confirms the validity of the Bjorken sum-rule. Our new semi-inclusive data were used to evaluate the $\Delta u$, $\Delta d$, $\Delta\bar{u}$, $\Delta\bar{d}$ and $\Delta s\equiv \Delta\bar{s}$ distributions.
Copyright/License	Publication: (License: CC-BY-NC-SA-3.0)

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