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Published on: July 19, 2019
Exploring the Three-Dimensional Momentum Distribution of Longitudinally Polarized Quarks in the Proton
Alessandro Bacchetta1,2, Alessia Bongallino3, Matteo Cerutti4,5
1Università di Pavia, Dipartimento di Fisica, via Bassi 6, I-27100 Pavia, Italy.
Abstract:
By analyzing experimental data on semi-inclusive deep inelastic scattering off longitudinally polarized targets, we extract the transverse momentum dependence of the quark helicity distribution, i.e., the difference between the three-dimensional motion of quarks with polarization parallel or antiparallel to the longitudinal polarization of the parent hadron. We perform the analysis at next-to-leading and next-to-next-to-leading perturbative accuracy. The quality of the fit is very good for both cases, reaching a χ^{2} per number of data points equal to 1.11 and 1.09, respectively. Although the limited number of data points leads to significant uncertainties, the data are consistent with an interpretation in which the helicity distribution is narrower in transverse momentum than the unpolarized distribution.
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