Precision Measurement of the Neutron $$d_{2}$$ : A Probe of the Color Force

Conference · Mon Oct 01 04:00:00 EDT 2012

OSTI ID:1993370

Posik, Matthew

The $$g_2$$ nucleon spin-dependent structure function measured in electron deep inelastic scattering contains information beyond the simple parton model description of the nucleon. It provides insight into quark-gluon correlations and a path to access the confining local color force a struck quark experiences just as it is hit by the virtual photon due to the remnant di-quark. The quantity $$d_2$$, a measure of this local color force, has its information encoded in an $x^2$ weighted integral of a linear combination of spin structure functions $$g_1$$ and $$g_2$$ and is dominated by the valence-quark region at large momentum fraction $$x$$. To date, theoretical calculations and experimental measurements of the neutron $$d_2$$ differ by about two standard deviations. As a result, JLab experiment E06-014, performed in Hall A, made a precision measurement of this quantity. Double spin asymmetries and absolute cross-sections were measured in both DIS and resonance regions by scattering longitudinally polarize electrons at beam energies of 4.74 and 5.89 GeV from a longitudinally and transversely polarized $^3$He target. Preliminary results for the absolute cross-sections and spin structure functions on $^3$He will be presented as well as preliminary results for $$d_2$$ on $^3$He.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1993370
• Report Number(s): JLAB-PHY-12-1715; DOE/OR/23177-6831
• Country of Publication: United States
• Language: English