Six-prong events in [pi]{u207B}p interactions at 7.0 GeV/C

Abstract

We have studied 2250 events with 6 charged tracks in the final state from 7.0 GeV/c π⁻p film taken at the BNL 80-inch bubble chamber. The events were fitted to the final states

π⁻p → π⁻π⁻π⁻π⁺π⁺p 211 events (1) π⁻p → π⁻π⁻π⁻π⁺π⁺pπ⁰ 535 events (2) π⁻p → π⁻π⁻π⁻π⁺π⁺π⁺n 230 events (3)

We find the total six-prong cross section to be 2.40 ± 0.27 mb. The partial cross sections are: 0.22 ± 0.04 mb for reaction (1), 0.58 ± 0.09 mb for reaction (2), and 0.24 ± 0.05 mb for reaction (3).

Final state (1) shows significant ρ(760) and Δ⁺⁺(1238) production. In reaction (2) there is Δ⁺⁺(1238) production and a u bump at 1540 ± 20 MeV/c² with width 100 ± 40 MeV/c² in the pπ⁰ mass distribution (interpreted as N*(l520)). The π⁺π⁻π⁺π⁻ mass plot shows peaks at 1085 ± 20 MeV/c² and 1470 ± 20 MeV/c² with widths 70 ± 30 MeV/c² and 60 ± 25 MeV/c². These peaks appear less prominently in reaction (3).

The transverse momentum distributions are analyzed in terms of statistical model predictions. In particular the Hagedorn statistical thermodynamical model gives temperatures of 120 MeV for pions and 150 MeV for nucleons.

The influence of Bose-Einstein statistics as found by Goldhaber is observed in the angles between pion pairs.