Spin Effects in High-P(T)^2 p+p --> p+p at 800 to 900 GeV

Abstract

We propose to study the spin-orbit Analyzing Power, A, in p+p + p+p at large P{sub {perpendicular}}{sup 2}. We propose to run at Fermilab around Fall 1987 and scatter a high intensity unpolarized proton beam of 800 to 900 GeV from a Polarized Proton Target; we would measure the difference between the d{sigma}/dt when the target spin is up and when it is down. Our main goal is to see if the unexpected large values of A recently found at the 28 GeV AGS in proton-proton elastic scattering persist to Fermilab energies. The large A value of 24 {+-} 8% at P{sub {perpendicular}}{sup 2} = 6.5 (GeV/c){sup 2} was not only unexpected but also seems difficult to reconcile with the A = 0 prediction of conventional models of strong interactions, such as perturbative QCD. The validity of perturbative QCD is believed to improve with increasing energy and with increasing P{sub {perpendicular}}{sup 2}, and this proposed Fermilab experiment would increase the incident energy by about a factor of 30. The experiment would be done using a Polarized Proton Target (PPT) employing radiation-doped NH{sup 3} beads and a 'local' cooling power of about 130 mW at 1/2{sup o} K. Such a target could be used with a beam intensity of 3 to 6 10{sup 10} protons per second, which is 1.5 to 3.0 10{sup 12} protons per pulse with Fermilab's 50 sec rep rate. This high beam intensity would allow good measurements out to about P{sub {perpendicular}}{sup 2} = 10 (GeV/c){sup 2} where the p+p {yields} p+p cross section is quite small. We propose to run in an underground target station such as P-West, which is ideally suited for such a high-P{sub {perpendicular}}{sup 2} elastic scattering experiment. We would use a double-arm spectrometer consisting of magnets with considerable bending power and high resolution scintillation hodoscopes and wire chambers. The hodoscopes should operate successfully in the somewhat hostile environment caused by some 10{sup 12} protons per pulse. The resulting good resolution on both angle and momentum for both the forward and recoil protons should provide adequate discrimination against inelastic events and events from the non-hydrogen protons in the PPT. We would further improve the resolution by using a 2.5 mm diameter beam and 'rastering' it in a 15 mm x 10 mm (HxV) pattern across the PPT on each pulse. An additional improvement would come from 10{sup o} of vertical bending on the recoil arm. Using this large bend together with 2 mm resolution vertical wire chambers and the tiny rastered beam will give very good momentum resolution which should strongly discriminate against 'non-elastic' events. We would significantly increase the solid angle and further reduce the background by using a quadrupole pair on the recoil arm to make the diverging protons approximately parallel.