Search for Broad Resonances in ³He

Abstract

Recently experimental evidence has been presented for the existence of broad T = 1/2 resonances in the three-nucleon system. As a continuation of earlier studies the 6Li(p,α) reactions were investigated using 45.0 MeV incident protons. 3He and alpha-particle spectra were measured at extreme forward angles using a ΔE–E–VETO detector telescope in conjunction with an analog particle identifier. Excitation energies up to 30 MeV in 3He could be examined. The spectra do not show any structure that can be related to the resonances observed previously. However, the spectra exhibit evidence for quasi-free scattering of protons from the α cluster in 6Li. In a complementary study the 3He(p,2p) reactions were investigated at an incident energy of 45.0 MeV. Data were taken with coplanar, symmetric geometry at 10 pairs of angles between 25° and 60° and also with coplanar, asymmetric geometry at the following pairs of angles: θ1 = 40°; θ2 = 30°, 37.4°, 40°, 45°, 50°, 55°, 60°, and 70°. Pronounced kinematic bands due to the 3He(p,2p)d and 3He(p,2p)d* reactions were observed. A comparison of the continua of coincident proton–proton events with the predictions of four-body phase-space calculations shows good agreement. The four-body continua do not show any anomalies which can be interpreted as due to broad resonances in 3He.