Search for exotic meson production at 13 GeV/c in the reaction pi-n → p/sub (forward)/X--

Recent developments in elementary particle theory suggest the possible existence of four-quark, or exotic, mesons. Such mesons can have quantum numbers not possible for normal mesons, which appear to be formed from only two quarks. This experiment, conducted at the Stanford Linear Accelerator Center, is designed to search for narrow, doubly charged mesons produced in the channel pi-n → p/sub (forward)/X--. A pion secondary beam, having a momentum of 13 GeV/c, is focused on a liquid deuterium target, located in the SLAC Two Meter Streamer Chamber. Forward proton events are detected by a spectrometer system consisting of a large-aperture magnet, two scintillation counter hodoscopes, twenty-four planes of wire spark chambers, and a threshold Cerenkov counter. This system has a good acceptance for a mass range of 1.5 to 3.5 GeV, and a range of (t-tmin) of up to 0.3 GeV. Results are examined in the missing mass and inclusive spectra. A strong feature of the data is the forward production of N* in all channels. The forward production of proton-antiproton systems, with a mass of 2.1 GeV, accounts for a third of all two-prong events, and is also seen in the three-prong data. Evidence for manifest (X--) exotics is not present in the missing mass or inclusive spectra. Final conclusions cannot be reached regarding fit states, because a systematic error in the beam momentum remains to be corrected. Resonant structure may be present in the antiproton-neutron system, produced against forward