a Search for the E Meson in AN 11 Gev/c Negative Kaon-Proton Experiment.

An 11 GeV/c K('-)p experiment undertaken at the Large Aperture Solenoid Spectrometer facility at the Stanford Linear Accelerator Centre is described. A large number of events were taken (40 million) using a trigger that selected most of the non-elastic cross section. From this data sample a 10,400 event (KK(pi))('0(' ))data sample was selected which had a sensitivity of 35 and 31 events/(mu)b for the K('0)K('+)(pi)('-(' ))and K('0)K('-)(pi)('+) channels respectively. The selection was made by reconstruction of the K('0)(short)(--->)((pi)('+)(pi)('-)) decays and the identification of the charged kaons by the LASS particle identification system. Observation of the recoil baryon was not required experimentally; however a missing mass cut of 1 to 4 (GeV/c('2))('2) was made opposite the(' )KK(pi) system. No clear evidence was found in the KK(pi) mass spectrum for any narrow structure. Applying a (delta) cut to the(' )KK invariant mass did produce a broad bump at low mass (1.45 GeV/c('2)) in the(' )KK(pi) system. However using events generated by a Monte Carlo technique, this was shown to be in large part due to a kinematic enhancement. A channel separation analysis revealed that the(' )KK(pi) sample consisted of 3-body phase space and the two body decay mode K*K. No evidence is found for a (delta)(pi) decay mode. Events in the K*K channel forms a broad structure between 1.4 and 1.6 GeV/c('2). There was also a difference between the proportion of the K* charged and the K* neutral channels in this region. This is indicative of interference between resonances or a resonance and a non-resonant(' )KK(pi) background. A moments analysis revealed that at low mass the(' )KK(pi) system was consistent with a JP assignment of 1('+). Thus the analysis performed so far on this data sample provides no clear evidence for an E meson, nor does it exclude its existence. A partial wave analysis is suggested as the best method of understanding the mechanisms responsible for the production of the broad structure at low(' )KK(pi) mass in the K*K channel.