Search

The η → π 0 γγ rare decay was measured at the AGS with the Crystal Ball photon spectrometer and its relative branching ratio was extracted to be B 1 =(8.3±2.8±1.4)×10 −4 , based on the analysis of 3×10 7 detected η mesons. This leads to a lower partial width for this eta channel than past measurements and is in line with chiral perturbation theory calculations.

Precise new data for the reaction K−p→π0Λ are presented in the c.m. energy range 1565 to 1600 MeV. Our analysis of these data sheds new light on claims for the Σ(1580) 3 2 − resonance, which (if it exists with the specified quantum numbers) must be an exotic baryon because of its very low mass. Our results show no evidence for this state.

We report a helicity analysis of subthreshold rho production on 2H and 12C nuclei at low photoproduction energies and large |t|. The results are indicative of a large longitudinal rho polarization (l=1, m=0) and are consistent with a strong helicity-flip mechanism of rho production. The analysis is model-independent and supports the large mass shift reported from the earlier 3He experiments.

3 He(γ, pπ ± ) reactions are simultaneously measured for tagged photon energies of 380 ⩽ Eγ ⩽ 700 MeV. The yield ratio for the two channels, under the same kinematical and dynamical conditions, is found to be 0.90±0.07. Implications of this ratio in terms of the delta component in the ground state of 3He are examined. An alternate interpretation of this ratio as due to an admixture of isospin T = 1 2 and 3 2 transition amplitudes in a pure isovector interaction is also presented.

Angular correlations of the 12 C(π - , pp)X reaction cross sections were measured over a wide angular range at an incident pion kinetic energy of 165 MeV and the results were compared to published data. A broad peak was observed in the angular distribution of the differential cross section that deviates from the angular distribution expected from a three-body phase space calculation for the two detected protons. The observed angular correlation disagrees with correlations previously reported in the literature.

Angular distributions of the differential cross sections for the pionic fission 6 Li (π + , 3 He ) 3 He have been measured at pion energies of 60 and 80 MeV. The differential cross section is found to decrease monotonically with cos 2 θ ∗ and is compared with a theoretical prediction.