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An extensive experimental program to measure the spin structure of the nucleon has been conducted in Hall B at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) in the last decade. Using a longitudinally polarized beam scattering off longitudinally polarized NH3 and ND3 targets, inclusive Deep Inelastic Scattering (DIS), Semi‐Inclusive DIS (SIDIS) and DVCS experiments were carried out that make a significant contributions to the existing data. The inclusive double spin asymmetry A∥ was measured over a large range in Q2 and W, providing data of impressively high precision that give a better understanding of the structure of the nucleon in the DIS and the valence quarks regions. Using parameterizations A2 and F1 from world data, the virtual photon asymmetry A1 and the structure function g1 were extracted in a Q2 range from 0.05 to 5 GeV2 and a W range from 1.08 to 3.0 GeV. As a result of the extended kinematical range, first moments of structure functions were measured over a large range in Q2 and duality was tested. Furthermore, newly proposed experiments, using an upgraded accelerator at Jefferson Laboratory and an improved CLAS detector (CLAS12), are expected to increase the statistical precision of the current measurements and extend them to kinematic regions presently not accessible, such as high x. This will improve significantly our knowledge of the structure of the nucleon, including parton distribution functions, duality and higher twists contributions.


Copyright 2011 AIP Publishing

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This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in A. Biselli, "Spin physics with CLAS and CLAS12," AIP Conf. Proc. 1388, 53 (2011), proceedings of the conference Baryons 2010, Osaka, Japan, 7-11 December 2010.and may be found at

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AIP Conference Proceedings

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Biselli, A. (2011, October). Spin physics with CLAS and CLAS12. In AIP Conference Proceedings Vol. 1388, No. 1, pp. 53-59.