( A Proposal to Jefferson Lab 12 GeV - PAC 38 , Update to PR 12 - 09 - 018 , conditionally approved by PAC 34 and PAC 37 ) Target Single - Spin Asymmetries in Semi - Inclusive

An experiment is proposed to measure the Single Spin Asymmetries of the Semi-Inclusive Deep Inelastic Scattering (SIDIS) process �n(e, e�π±,0(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 figureof-merit. 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 the neutron roughly 10 times more accurately than obtained for the proton by the HERMES experiment, in a detailed grid of the kinematic variables x, pT , and z. Furthermore, by performing measurements at two energies, 8.8 and 11 GeV, we will have data at two values of Q for each x value. The azimuthal coverage of our experiment is chosen to optimize the figure of merit of the measured asymmetries for the proposed apparatus, 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 hadron momenta above 2 GeV, in a wide range of polar and azimuthal angles of the hadron momentum relative to the electron scattering plane and the momentum transfer. Between the large acceptances of the electron and hadron arms, an electron polarized-nucleon luminosity on the order 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 differences in polarization and dilutions) than the HERMES experiment. The experiment has significant potential for the discovery of new effects in hadronic physics.