A study of the reaction π−p→ωπ−p at 18 GeV/c: the D and S decay amplitudes for b1(1235)→ωπ

Abstract The reaction π − p → ωπ − p , ω → π + π − π 0 has been studied at 18 GeV/ c . The ωπ − mass spectrum is found to be dominated by the b 1 (1235). Partial Wave Analysis (PWA) shows that b 1 production is dominated by natural parity exchange. The S -wave and D -wave amplitudes for b 1 (1235)→ ωπ have been determined, and it is found that the amplitude ratio, | D / S |=0.269±(0.009) stat ±(0.01) sys and the phase difference, φ ( D − S )=10.54°±(2.4°) stat ±(3.9°) sys .