Quasielastic Asymmetry Research Articles

Updated results from the SAMPLE experiment

The SAMPLE collaboration has recently completed its measurements of the parity violating elastic electron scattering asymmetry from hydrogen and the quasielastic asymmetry from deuterium [1, 2, 3, 4, 5]. Neutral weak form factors of the nucleon, both vector and axial, can be extracted from these data and used to determine the strange quark contribution to electromagnetic form factors. The results of the original measurements at a Q 2 of 0.1 (GeV/c)2 [2, 3] have recently been reanalyzed [4], incorporating improvements in simulation and new background data, and combined with a new measurement of the quasielastic deuteron asymmetry at a Q 2 of 0.038 (GeV/c)2 [5]. Final results from this new analysis and data set will be presented.

Hadronic parity violation and inelastic electron-deuteron scattering

We compute contributions to the parity-violating (PV) inelastic electron-deuteron scattering asymmetry arising from hadronic PV. While hadronic PV effects can be relatively important in PV threshold electrodisintegration, we find that they are highly suppressed at quasielastic kinematics. The interpretation of the PV quasielastic asymmetry is, thus, largely unaffected by hadronic PV.

Precise measurement of the neutron magnetic form factor from quasielastic 3[formula omitted]e( [formula omitted], e′)

Polarized 3He targets have proven to be a useful tool for studying the electric and magnetic form factors of the neutron, and the spin structure of the neutron. The neutron magnetic form factor at low Q 2 was previously determined at MIT-Bates from the quasielastic 3 H e( e , e′) process. A new experiment is planned at TJNAF to systematically measure the inclusive 3He quasielastic transverse asymmetry, A T′, at Q 2 = 0.1−0.5 (GeV/c) 2 with high statistical and systematic accuracy. A 2% statistical uncertainty is aimed at all the proposed values of Q 2, and 3% systematic uncertainty for A T′ can be achieved for this experiment. The precise data will constrain theoretical calculations of 3He quasielastic asymmetry. Furthermore, the neutron magnetic form factor at Q 2 = 0.1−0.5 (Gev/c) 2 will be extracted from the measured asymmetries with an overall uncertainty of 2%. Precise measurements of G M n at low Q 2 will resolve the discrepancy among the existing data in the same Q 2 region.

He-vector3(e-vectore') quasielastic asymmetry.

Measurements of the spin-dependent asymmetry in scattering longitudinally polarized electrons from polarized He3 at quasielastic kinematics are reported. The measurements were made at two kinematics and spin angles, one sensitive to the helicity-dependent transverse-longitudinal interference response function, RTL′, and the other to the helicity-dependent transverse response function, RT′. For the experiment a metastability exchange optically pumped polarized He3 target was used; a general discussion of the technique used to polarized the He3, along with the details of the design and operation of the target system, are presented here. A comparison is made of the world’s data on the He→3(e→,e′) quasielastic asymmetry with several theoretical predictions, including calculations that use the plane wave impulse approximation and a fully spin-dependent spectral function. There is good agreement between data and theory at the current level of experimental precision.