Speaker
Description
At the Relativistic Heavy-Ion Collider (RHIC), the Polarized Hydrogen Gas Jet Target Polarimeter (HJET) is used to measure absolute transverse (vertical) polarization of the proton beams with low systematic uncertainties of about $\sigma^\text{syst}_P/P\le0.5\%$. HJET performance has been thoroughly studied in measurements of the ${pp}$ and ${pA}$ analyzing powers for a broad range of proton and ion beam energies (4--250 GeV/nucleon). Based on these results, HJET was suggested for proton beam polarimetry (with a required accuracy of 1\%) in the future Electron-Ion Collider (EIC). Here, the possibility of using HJET to measure the $^3$He ($h$) beam polarization at EIC will be considered. The experimentally determined ratio of the beam and target spin assymetries used to calculate the beam polarization must be adjusted by the ratio of the $p^{\uparrow}h$ and $h^{\uparrow}p$ analyzing powers, which rely on unknown proton-helion hadronic spin-flip amplitudes. Since these amplitudes are small, the existing theoretical accuracy of the relations between proton-helion and proton-proton (which have been measured by HJET) hadronic spin-flip amplitudes is sufficient to obtain the beam polarization with the required precision. Another potential source of systematic uncertainty in the $^3$He beam polarization measurement is the helion breakup in scattering. It has been demonstrated that while the breakup can cause corrections to the spin-flip interference terms of up to 4\%, the effect cancels out to a negligible value in the analyzing power ratio. Detailed explanations for the results obtained will be discussed.
