Spin Spin Interactions in High p-Transverse**2 Elastic p p Scattering

O'Fallon, J.R. ; Ratner, L.G. ; Schultz, P.F. ; et al.
Phys.Rev.Lett. 39 (1977) 733, 1977.
Inspire Record 5637 DOI 10.17182/hepdata.20968

We measured dσdt for p+p→p+p at 11.75 GeV/c using the zero-gradient synchrotron 70% polarized-proton beam and a 65% polarized-proton target. We obtained the spin-orbit asymmetry parameter A and the spin-spin correlation parameter Cm out to P⊥2=4.2 (GeV/c)2. We found that A drops smoothly towards zero, but that Cnn increases abruptly near P⊥2=3.6 (GeV/c)2, where the exp(−1.4P⊥2) component of elastic scattering becomes dominant. This suggests that large-P⊥2 "hard" elastic scattering may occur mostly when the two proton spins are parallel.

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Spin Dependence of High p-Transverse**2 Elastic p p Scattering

Crabb, D.G. ; Fernow, Richard C. ; Hansen, P.H. ; et al.
Phys.Rev.Lett. 41 (1978) 1257, 1978.
Inspire Record 7117 DOI 10.17182/hepdata.20867

We measured dσdt for p↑+p↑→p+p from P⊥2=4.50 to 5.09 (GeV/c)2 at 11.75 GeV/c. We used a 59%-polarized proton beam and a 71%-polarized proton target with both spins oriented perpendicular to the scattering plane. In these large-P⊥2 hard-scattering events, spin effects are very large and the ratio (dσdt)↑↑:(dσdt)↑↓ grows rapidly with increasing P⊥2, reaching a value of 4 at 90° (c.m.). Thus, hard elastic scattering, which is presumably due to the direct scattering of the protons' constituents, may only occur when the two incident protons' spins are parallel.

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THE ERRORS INCLUDE STATISTICAL AND SYSTEMATIC ERRORS ADDED IN QUADRATURE. THE PARALLEL/ANTIPARALLEL SPIN CROSS SECTION RATIO IS (1+CNN)/(1-CNN).