Recent DIS Results from Jefferson Lab: A1n at High x and the Q2-dependence of g2n
In this talk, results were presented from two recently published Jefferson Lab experiments where longitudinally polarized electrons were scattered from a polarized {sup 3}He target in the inclusive reaction {sup 3}{rvec H}e({rvec e}, e{prime}) in the deep-inelastic region. Incident electrons with energies E = 3.5-5.7 GeV were scattered from polarized {sup 3}He nuclei whose spins could be oriented parallel or perpendicular to the incident electron momentum, in the scattering plane of the electron. The helicities of the incident electrons were flipped pseudo-randomly at a rate of 30 Hz to minimize helicity correlated systematic uncertainties. A feedback system was also used to keep the helicity-dependent beam charge asymmetry below 50 x 10{sup -6} for a typical run in the g{sub 2} measurement. Scattered electrons were detected in either one of two nearly identical spectrometers. The detector package included vertical drift chambers for particle tracking, two segmented scintillator trigger planes, and used a gas Cherenkov detector and lead-glass calorimeter for particle identification. Electron polarization was measured periodically using a Moeller polarimeter and monitored continuously using a Compton polarimeter. To study polarized neutrons, a target containing {sup 3}He nuclei was polarized using spin-exchange optical pumping. The {sup 3}He ground state is dominated by the S-state in which the two proton spins are anti-aligned and the spin of the nucleus is carried entirely by the neutron. To obtain neutron information, a correction based on the {sup 3}He wavefunction was applied to the measured {sup 3}He data. The {sup 3}He was contained in a sealed, two-chambered, aluminosilicate glass cell, along with a small quantity of N{sub 2} and Rb to aid in the polarization process. Polarized {sup 3}He is produced in the spherical upper chamber by first polarizing Rb atoms with optical pumping. These atoms can transfer their spin to the {sup 3}He nucleus during binary collisions. Incident electrons scatter from the polarized {sup 3}He in the cylindrical lower chamber which is 40 cm long with side walls of thickness {approx} 1.0 mm and end windows of thickness {approx} 130 {micro}m. The {sup 3}He density as seen by the beam is 2.9 x 10{sup 20}/cm{sup 3}. The average in-beam target polarization was P{sub t} = (40.0 {+-} 1.4)% as measured using both nuclear magnetic resonance and electron paramagnetic resonance.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Organization:
- USDOE - Office of Energy Research (ER)
- DOE Contract Number:
- AC05-84ER40150
- OSTI ID:
- 896998
- Report Number(s):
- JLAB-PHY-05-480; DOE/ER/40150-4189; TRN: US0700834
- Journal Information:
- AIP Conf.Proc., Vol. 842; Conference: Particles and Nuclei International Conference (PANIC 05), Santa Fe, New Mexico, 24-28 Oct 2005
- Country of Publication:
- United States
- Language:
- English
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