Experimental Study of the Reaction pi exp - p Implies pi exp 0 pi exp 0 N at 2.01 GeV/C. Its Use in a Simultaneous Phase Shift Analysis of the pi pi Channels

摘要

We report results on pi exp + pi exp - implies pi exp 0 pi exp 0 total and differential cross sections from threshold to 1.1 GeV pi pi mass. These results have been obtained from a high-statistics experiment studying the reaction pi exp - p implies pi exp 0 pi exp 0 n at 2.01 GeV/c incident pi exp - momentum with the Chew-Low extrapolation method. The pi exp 0 's have been detected and their momenta analyzed in a large-gap cylindrical spark chamber placed in a magnetic field. The results show three salient features: 1) a large I = 0 production with sigma/sub tot/ ( pi exp + pi exp - implies pi exp 0 pi exp 0 ) approaching the S-wave unitary limit in the 550-750 MeV pi pi mass region, without any narrow structure; 2) a slow fall of sigma /sub tot/ ( pi exp + pi exp - implies pi exp 0 pi exp 0 ) in the region of 750-950 MeV pi pi mass. This feature is not predicted by the 'down' solution for the I = 0 S-wave pi pi phase shift which has been reported recently; 3) The presence of D wave effects above 850 MeV as indicated by our extrapolated angular distributions. We have used the preceding results in an energy independent phase shift analysis of the 4 measurable pi pi scattering channels. This analysis covers the energy range from threshold to 1200 MeV pi pi mass. A unique solution is obtained which gives information on the S sub 0 scattering length (a sub 0 = 0.50 + - 0.09) and on epsilon sub 0 (710MeV) and S sub 0 * (974 MeV) structures. (Atomindex citation 11:519970)