We present precision measurements of the target and beam-target spin asymmetries from neutral pion electroproduction in deep-inelastic scattering (DIS) using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. We scattered 6-GeV, longitudinally polarized electrons off longitudinally polarized protons in a cryogenic 14NH3 target, and extracted double and single target spin asymmetries for ep → e'π0X in multidimensional bins in four-momentum transfer (1.0 < Q2 < 3.2 GeV2), Bjorken-x (0.12 < x < 0.48), hadron energy fraction (0.4 < z < 0.7), transverse pion momentum (0 < PT < 1.0 GeV), and azimuthal angle фh between the lepton scattering and hadron production planes. We extracted asymmetries as a function of both x and PT, which provide access to transverse-momentum distributions of longitudinally polarized quarks. The double spin asymmetries depend weakly on PT. The sin2фh moments are zero within uncertainties, which is consistent with the expected suppression of the Collins fragmentation function. The observed sinфh moments suggest that quark gluon correlations are significant at large x.
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Funded by SCOAP3.
This work was supported in part by the U.S. Department of Energy and the National Science Foundation, the French Commissariat à l'Energie Atomique, the French Centre National de la Recherche Scientifique, the Italian Istituto Nazionale di Fisica Nucleare, the National Research Foundation of Korea, the United Kingdom's Science and Technology Facilities Council, and the Southeastern Universities Research Association (SURA), which operates the Thomas Jefferson National Accelerator Facility for the United States department of Energy under contract DE-AC05-06OR23177.
Supplementary material related to this article can be found on-line at https://doi.org/10.1016/j.physletb.2018.06.014.
Jawalkar, S.; Koirala, S.; Avakian, H.; Bosted, P.; Griffioen, K. A.; Keith, C.; Kuhn, S. E.; Adhikari, K. P.; Adhikari, S.; Adikaram, D.; Akbar, Z.; Amaryan, M. J.; Anefalos Pereira, S.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Biselli, A. S.; Boiarinov, S.; Briscoe, W. J.; Brock, J.; Brooks, W. K.; Bültmann, S.; Burkert, V. D.; Cao, Frank Thanh; Carlin, C.; Carman, D. S.; Celentano, A.; Charles, G.; and Gohn, Wesley P., "Semi-Inclusive π0 Target and Beam-Target Asymmetries from 6 GeV Electron Scattering with CLAS" (2018). Physics and Astronomy Faculty Publications. 654.