No six-quark bound hadron, (other than the loosely bound deuteron) has been observed, despite several experimental searches. Some models of quark dynamics predict the existence of such a state, the doubly-strange six-quark H dibaryon (uuddss) being the most likely. The mass of the H would be between that of the deuteron and the 2m(sub (Lambda)) strong interaction decay threshold. In 1992, Experiment E888 at Brookhaven National Lab's Alternating Gradient Synchrotron collected data to search for this particle. The detector consisted of a two-arm spectrometer with drift chamber tracking and two magnets for momentum analysis, scintillator hodoscope triggering, Cerenkov particle identification, an electromagnetic calorimeter, and a muon hodoscope and rangefinder. The experiment searched for the decay (Lambda) (yields) p(pi)(sup -) from the weak decays of H (yields) (Lambda)n and H (yields) (Sigma)(sup 0)n (followed by (Sigma)(sup 0) (yields) (Lambda)(gamma)). This search was sensitive to weakly decaying H dibaryons with lifetimes from 6-230 us with production cross-sections greater than (approximately)2 (mu)b/steradian.
展开▼
