New Measurements of Polarization and Differential Cross Sections inK+pElastic Scattering in the 1.7-3-GeV/cRange

Abstract

We have measured the polarization parameter and differential cross sections in K + p elastic scattering from a polarized target from small \t I and small \u I at five momentum points: 1.7, 2.1, 2.4, 2.7, and 3.0 GeV/c. The polarized-proton target was butanol cooled at 0.5° by a 3 He-4 He refrigerator; a combination of multiwire proportional chambers and scintillation counters detected the scattered particles. The results for small \u\ are discussed in the context of pure Regge-pole models with exchange-degenerate A trajectories.Amplitudes for K + p elastic scattering construct ed from pure pole exchange in the u channel, with degenerate A and £ trajectories, yield predictions of zero polarization in the backward direction (small \u\) and a monotonic energy dependence of the 180° differential cross sections. 1 While published measurements indicate small backward polarizations, they are of limited statistical accuracy and do not extend above 2.1 GeV/c in incident beam momentum. 2 Previous measurements of the 180° cross sections, 3 as a function of beam momentum, have shown a deviation from the monotonic behavior predicted by such models. 4 This anomaly, occurring between 2 and 3 GeV/c laboratory momenta, might be due to unexplained structure in the amplitudes, possible systematic errors in previous experiments, 5 or a combination of the two. Our measurements were thus made in order to resolve these questions and to test the hypotheses of a pure pole-exchange Regge model.Since the forward-to-backward ratio of differential cross sections is large in K + p elastic scattering, we have also measured polarizations and angular distributions in the forward direction with significantly higher statistical accuracy than previously obtained. 2 The apparatus is shown in Fig.

Partial-wave analysis ofK+-nucleon scattering

“…Much of these data are available from compilations [30,31,32] but we try to give references to the original data as much as possible [33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53].…”

“…The T=1 data base used consists of 1880 data points including 1501 angular distribution points, 91 total cross section points, 265 polarization points and 23 reaction cross section points. Much of these data are available from compilations [30,31,32] but we try to give references to the original data as much as possible [33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53].…”