(a New Proposal to Jefferson Lab 12 Gev -pac34) Measurement of the Semi-inclusive Π and K Electro-production in Dis Regime from Transversely Polarized He Target with the Sbs & Bb Spectrometers in Hall A
An experiment is proposed to measure the Single Spin Asymmetries of the Semi-Inclusive Deep Inelastic Scattering (SIDIS) process ~n(e, e′π±(K±)), using the large-solid-angle Super Bigbite Spectrometer (SBS), the BigBite Spectrometer, and a novel polarized He target that includes alkali-hybrid optical pumping and convection flow to achieve very high luminosity. Both spectrometer arms will utilize GEM-based tracking to accommodate the high rates. The abundant statistics will allow the determination of the Collins and Sivers functions for neutron roughly 10 times more accurate than obtained for proton at HERMES for a detailed grid of the kinematic variables x, p T , and z. Furthermore, by including data taking at two energies, an 8.8 and 11 GeV, we will have data at two values of Q for each bin in x. The azimuthal coverage of our experiment is excellent, and is facilitated by collecting data at a series of neutron polarization directions, always transverse to the beam direction. The SIDIS pions and kaons will be detected over a wide range of the hadron momenta above 2 GeV for the angle between the hadron production and the electron scattering planes up to ±60◦, and the angle between the hadron momenta and the virtual photon momenta up to 60◦. Between the large acceptances of the electron and hadron arms, an electron polarizednucleon luminosity on the level of 4 · 10 cm−2/s, and a target polarization of 65%, we will obtain in a two-month run about 100 times more statistics (after accounting for difference in polarization and dilutions) then was done by the HERMES experiment. The experiment has significant potential for the discovery of new effects in hadron physics.
Measurement of the Neutron Electric Form Factor GEN at High Q2
Experiment E02-0131 at Thomas Jefferson National Accelerator Facility (Jefferson Lab) will measure the neutron electric form factor GnE at the high four-momentum transfer values of Q^2 ~ 1.3, 2.4 and 3.4 (GeV/c)2 via a measurement of the cross section asymmetry A_T in the reaction 3He(e,e'n)pp. This measurement was approved for 32 days of running by Jefferson Lab PAC 212 in January 2002.
A simple nuclear-style mean field absorption/spin-orbit model for the Sivers function of the nucleon
I study the effect of scalar and spin-orbit absorption potentials, in the production of a nonzero Sivers-like asymmetry in hadron-hadron high energy collisions (Drell-Yan and single spin asymmetries). A basic model is built for the intrinsic state of a quark in the projectile hadron. S-wave and P-wave 2-component states are considered. Before the hard event, this quark is subject to absorbing scalar and spin-orbit local mean fields simulating interactions with a composite target. The relevant interaction terms are found to be the imaginary diagonal spin-orbit ones. Spin rotating terms, and scalar absorption, are not decisive. For $x$ $=$ 0 the found Sivers asymmetry vanishes, while at larger $x$ its qualitative dependence on $x$, $K_T$ follows the usual trends met in available models and parameterizations. Given the present-day knowledge of the considered phenomenological interactions, it is not possible to establish whether the related Sivers-like asymmetry is a leading twist one.