Precision Measurement of the Neutron Twist-3 Matrix Element d super(n) sub(2) Probing Color Forces

• Published in: Physical review letters Vol. 113; no. 2
• Main Author: Posik, M
• Format: Journal Article
• Language: English
• Published: 11-07-2014
• Subjects: Asymmetry; Beams (radiation); Brackets; Color; Cross sections; Lattices; Mathematical analysis; Quantum chromodynamics
• ISSN: 0031-9007; 1079-7114

Double-spin asymmetries and absolute cross sections were measured at large Bjorken x (0.25 [< or =] x [< or =] 0.90), in both the deep-inelastic and resonance regions, by scattering longitudinally polarized electrons at beam energies of 4.7 and 5.9 GeV from a transversely and longitudinally polarized super(3)He target. In this dedicated experiment, the spin structure function g super(3He) sub(2) was determined with precision at large x, and the neutron twist-3 matrix element d super(n) sub(2)was measured at [left angle bracket]Q super(2)[right angle bracket] of 3.21 and 4.32 GeV super(2)/c super(2), with an absolute precision of about 10 super(-5). Our results are found to be in agreement with lattice QCD calculations and resolve the disagreement found with previous data at [left angle bracket]Q super(2)[right angle bracket] = 5 GeV super(2)/c super(2). Combining d super(n) sub(2)and a newly extracted twist-4 matrix element f super(n) sub(2) the average neutron color electric and magnetic forces were extracted and found to be of opposite sign and about 30 MeV in magnitude.