Polarization of a stored beam by spin-filtering

Abstract

The PAX Collaboration has successfully performed a spin-filtering experiment with protons at the COSY-ring. The measurement allowed the determination of the spin-dependent polarizing cross section, that compares well with the theoretical prediction from the nucleon-nucleon potential. The test confirms that spin-filtering can be adopted as a method to polarize a stored beam and that the present interpretation of the mechanism in terms of the proton-proton interaction is correct. The outcome of the experiment is of utmost importance in view of the possible application of the method to polarize a beam of stored antiprotons.<p>QC 20121212</p

The H and D Polarized Target for Spin–Filtering Measurements at COSY

“…The confirmation of the spinfiltering process and the extracted spin-dependent cross-section for the transverse case has been fulfilled in the 2011. 3 The upgrading of the COSY ring for this purpose involved many parts, requiring vacuum improvement along the whole ring, optics matching for low beam loss in the accelerator and at the PAX interaction point, and tuning and improved beam control, in order to avoid depolarization phenomena. The next steps are completing the full panorama of the spin-dependent crosssection, commissioning the longitudinal case, and showing sensible and useful polarization.…”

“…The next steps are completing the full panorama of the spin-dependent crosssection, commissioning the longitudinal case, and showing sensible and useful polarization. 3 The chance to have a polarized deuteron target, for the study of p (p)-d ↑ , will give more chances for the investigation of the process with polarized deuteron.…”

“…The spin-dependent cross-section studies and results, confirmed and clarified for the transverse case on proton, 3 together with the possibility of polarized deuteron gaseous target, have excited theoretical studies on p-d ↑ interaction predictions. A large discrepancy in cross-section are reported in Ref.…”

Polarization of a stored beam by spin filtering

“…4 allows us to determine dP dt = (4.8 ± 0.8) · 10 −7 s −1 . By making use of the measured polarization buildup and additional information like target polarization and density, and beam revolution frequency, the effective polarizing cross section has been derived [8]:σ meas 1 = −23.4 ± 3.9 (stat.) ± 1.9 (syst.)…”

“…where d t is the target areal density in atoms/cm 2 , f the particle revolution frequency [8].σ 1 accounts for the fact that only protons scattered at angles larger than the acceptance angle of the storage ring Θ acc contribute to the spin-filtering processσ 1 = σ 1 (Θ > Θ acc ). …”