Search for backwards produced exotic meson resonances and study of particle spectra and mass distributions in the reaction. pi. /sup +/ + P. -->. n (forward) + X/sup + +/ at 8. 4 GeV/c. [Upper limits, G parity, 8. 4 GeV/c

Abstract

Results are reported from a hybrid experiment designed to search for backwards produced I = 2 exotic meson resonances by investigating the backward scattering reactions: ..pi../sup +/ + p ..-->.. in (forward) + ..pi../sup +/..pi../sup +/, ..pi../sup +/..pi../sup +/..pi../sup +/..pi../sup -/, ..pi../sup +/..pi../sup +/..pi../sup +/..pi../sup +/..pi../sup -/..pi../sup -/, and p anti p..pi../sup +/..pi../sup +/ at an incident pion momentum of 8.4 GeV/c. The SLAC 15'' rapid cycling bubble chamber, operating at 20 cycles per second, was triggered by detecting fast forward neutrons in an optical spark chamber and scintillation counter array downstream. Following two-component duality arguments, Jacob and Weyers and Rosner have suggested backward scattering processes as a favored mode for exotic meson resonance production. Upper limits of the order of one microbarn are reported for the production of narrow exotic meson resonances with masses less than or equal to 3 GeV and which could decay into even G-parity states: ..pi../sup +/..pi../sup +/, ..pi../sup +/..pi../sup +/..pi../sup +/..pi../sup -/, ..pi../sup +/..pi../sup +/..pi../sup +/..pi../sup +/..pi../sup -/..pi../sup -/, and p anti p..pi../sup +/..pi../sup +/. The mass resolution in the above channels varied from 5 to 30 MeV over the mass range for the most restrictive sample of events. The statistical significance of the data corresponds to 30 events per microbarn. Evidence for forward N* and rho/sup 0/ production are also reported. The main features of the data can be simulated by a Monte Carlo model which incorporates Lorentz-invariant phase space modified by exponential transverse momentum damping on each final state particle and, in addition, takes into account the geometrical constraints and trigger requirements of the experiment.