Precise measurement of the differential cross section for the π-p elastic scattering around 3 GeV/c

The differential cross section (DCS) for the π-p elastic scattering has been measured at four incident momenta between 2.85 and 3.48 GeV/c in a wide range of the CMS scattering angle 150 <= theta* <= 1600. The measurement has been made by detecting scattered pions in coincidence with recoil protons with a large aperture magnetic spectrometer placed in a forward direction and a track detector system at the other large angle side. Statistical accuracy is typically of a few to several %, and even in the worst case the accuracy is as good as 25%. The data show a sharp forward diffraction peak followed by a dip at t = -0.75 (GeV/c)2, a broad second peak, two clear dips at large angle region and a complicated structure in the largest /t/ region. The present experiment clarifies for the first time a detailed behavior of the dip-bump structure at large angles in quite a systematic and quantitative way. The data are compared with other experiments and also with a phase shift solution. The data are generally in accord with the others, but at large angles where the cross section decreases drastically and shows a complicated dip-bump structure, the agreement goes worse. The data are also compared with a constituent interchange model. It is found that the model can only reproduce the large angle behavior of the present data in a much narrower range than at higher energies. Furthermore, the author examined a possible existence of the so-called Ericson fluctuation using high-precision data around 2.5 GeV/c. The author found that there is no evidence for the Ericson fluctuation. (author)