a Study of the Reaction Pi-Minus Phosphorus - -> Nitrogen + Photons
A double arm spectrometer was used to study the reaction pi-minus P (--->) N + photons with beam energies of 5, 8.5, and 13 GeV. The experiment placed a sensitive upper limit on the production cross sections of mesons of narrow width decaying to two photons. No narrow resonances are seen within the mass region of 2.3-3.1 GeV, where an upper limit of 114 pico-barns, 90% confidence level, is placed on the production cross section times branching ratio. This limit conflicts with earlier observations of a state with a mass of 2.83 GeV produced in pion-nucleon collisions, a state that was suggested as the pseudoscalar bound state of a charmed quark and anti-quark, commonly called the eta-c. An upper limit of 2.1 nano-barns, 90% confidence level, is placed on the production cross section times branching ratio of narrow resonances near the mass of the E(1420) particle, where there is speculation that a resonance formed by the bound state of two gluons might exist.
- Pub Date:
- A SEARCH FOR THE ETA-C;
- Physics: Elementary Particles and High Energy