A STUDY OF DI-PION RESONANCES PRODUCED AT LOW MOMENTUM TRANSFER IN NEGATIVE PION + P YIELDS NEGATIVE PION + POSITIVE PION + N AT 1.6 BEV/C.
Technical rept. no. 35,
PRINCETON UNIV N J ELEMENTARY PARTICLES LAB
Pagination or Media Count:
Spark chamber spectrometers were used to investigate the di-pion mass spectrum over the mass range 450 1000 MeV. The di-pions were produced in the reaction negative pion p yields negative pion positive pion n at an incident momentum of 1.6 BeVc. More than 600 events were obtained with a mass resolution of 4 MeV. The di-pion mass spectrum shows a strong contribution from the neutral RHO meson centered at approx. 740 MeV with a width on the order of 130 MeV. There is no evidence of any other structure in the spectrum. The data can be interpreted fairly well within the framework of the one pion exchange model OPE, but the distributions of the Treiman-Yang angle and the pion-neutron effective masses indicate the presence of non-OPE processes. The distributions could be explained by the formation of a recently reported I 12 pion-N state with a mass of 1.4 BeV. Comparisons with other measurements of the total cross section show a much larger resonant contribution to the data than expected from OPE this effect can be explained by a depolarization of approx. 35 of the rho meson due to rho-N final state absorption.