The g2p Experiment: A Measurement of the Proton's Spin Structure Functions

Abstract

The E08-027 (g2p) experiment measured the spin structure functions of the proton at Jefferson Laboratory in Newport News, Va. Longitudinally polarized electrons were scattered from a transversely and longitudinally polarized solid ammonia target in Hall A, with the polarized NH${}_3$ acting as an effective proton target. Focusing on small scattering angle events at the electron energies available at Jefferson Lab, the experiment covered a kinematic phase space of 0.02 GeV${}^2$ $<Q^2<$ 0.20 GeV${}^2$ in the proton's resonance region. The spin structure functions, $g_1^p(x,Q^2)$ and $g_2^p(x,Q^2)$ , are extracted from an inclusive polarized cross section measurement of the electron-proton interaction. Integrated moments of $g_1(x,Q^2)$ are calculated and compared to theoretical predictions made by Chiral Perturbation Theory. The $g_1(x,Q^2)$ results are in agreement with previous measurements, but include a significant increase in statistical precision. The spin structure function contributions to the hyperfine energy levels in the hydrogen atom are also investigated. The $g_2(x,Q^2)$ measured contribution to the hyperfine splitting is the first ever experimental determination of this quantity. The results of this thesis suggest a disagreement of over 100% with previously published model results.

arXiv commentPh.D. Thesis, University of New Hampshire. 2017

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Cited by in corpus (2)

• The proton structure in and out of muonic hydrogen
• Forward doubly-virtual Compton scattering off the nucleon in chiral perturbation theory: II. Spin polarizabilities and moments of polarized structure functions