Observation and analysis of the 1660 MeV 3π-resonance “A3” in 8 GeV/c π+p interactions

Abstract The production of the 1660 MeV 3 π -resonance called the A 3 is studied in 8 GeV/ c π + p interactions. Its mass and width are found to be (1660 ± 16) MeV and (115 ± 45) MeV, respectively. The cross section for π + p → p A 3 + → p( π + π + π − ) is found to be (46 ± 15) μb. The differential cross section has a slope of (5.5 ± 0.6) GeV −2 . The spin-parity values are found to be most probably in the series 0 − , 1 + , 2 − , 3 + …, while the isospin is one and the G -parity is odd. Branching ratios into (3 π ) and ( πf o are given for different spin-parity values, while the ( πϱ ) decay rate is found to be consistent with zero.