NEPTUN-A spectrometer for measuring the Spin Analyzing Power in p-p elastic scattering at large P2⊥ at 400 GeV (and 3 TeV) at UNK

Abstract

We are constructing the NEPTUN-A spectrometer for measuring the Spin Analyzing Power in p-t-PT ~ p q-p at P~ = 2 to 10 (GeV/c) 2 at 400 GeV (or at 3 TeV) when the UNK accelerator in Protvino, Russia, becomes operational. The spectrometer consists of a 55 m long recoil arm with 3 horizontally bending magnets to guide the recoil protons onto a fixed 37 ~ line. Then two vertical dipole magnets bend the protons up by 12 ~ for momentum analysis. The momentum will be measured to an accuracy of 0.1 ~ using chambers. In order to accept a large solid angle, the spectrometex contains a strong-focusing pair of quadxupoles looking at the polarized proton jet target. The forward arm consists of scintillator hodoscopes for measurement of the forward vertical angle. Acceptances and event rates are calculated. The status of the spectrometer is reported.