DIFFERENTIAL CROSS SECTIONS FOR ELASTIC SCATTERING OF POSITIVE PI MESONS ON PROTONS IN THE ENERGY REGION 500 TO 1600 MeV

Abstract

Differential cross sections for the elastic scattering of positive pi mesons on protons were measured at the Berkeley Bevatron at laboratory kinetic energies of the pion between 500 and 1600 MeV.Fifty scintillation counters and a matrix coincidence system were used to ' detect the recoil proton and the pion, both before the latter reachid a liquid-hydrogen target and after scattering.Various corrections were applied to the data, and the results were fitted with a power series in the cosine of the scattering angle in the center-of-mass system.Total elastic cross sections were obtained by integrating under the fitted curves.The coefficients of the cosine series are shown plotted vs the laboratory kinetic energy of the pion.The most striking features of these curves are the large positive value of the coefficient of cos6 c/', and the large negative value of the coefficient of cos 4 e':', both of which peaked in the vicinity of the 1350-MeV peak in the total cross section.These results indicate that the most predominant state contributing to the scattering at the 1350 MeV peak has t:>tal angular momentum J = 7/2, considering that the coefficients for terms above cos 6 e':' are negligible at this energy.One possible explanation is that the 1350-MeV peak is the result of an F 7 ; 2 resonance lying on the same Regge-pole trajectory as the famous ( 3, 3) resonance near 195 MeV.' ' ' If 111\1111