Can only flavor-nonsinglet H dibaryons be stable against strong decays?

Abstract

Using the QCD sum-rule approach, we show that the flavor-nonsinglet H dibaryon states with J{sup {pi}}=1{sup +}, J{sup {pi}}=0{sup +}, I=1 (27 plet) are nearly degenerate with the J{sup {pi}}=0{sup +}, I=0 singlet H{sub 0} dibaryon, which has been predicted to be stable against strong decay, but has not been observed. Our calculation, which does not require an instanton correction, suggests that the H{sub 0} is slightly heavier than these flavor-nonsinglet H{close_quote}s over a wide range of the parameter space. If the singlet H{sub 0} mass lies above the {Lambda}{Lambda} threshold (2231 MeV), then the strong interaction breakup to {Lambda}{Lambda} would produce a very broad resonance in the {Lambda}{Lambda} invariant mass spectrum which would be very difficult to observe. On the other hand, if these flavor-nonsinglet J=0 and 1 H dibaryons are also above the {Lambda}{Lambda} threshold, but below the {Xi}{sup 0}n breakup threshold (2254 MeV), then because the direct, strong interaction decay to the {Lambda}{Lambda} channel is forbidden, these flavor-nonsinglet states might be more amenable to experimental observation. The present results allow a possible reconciliation between the reported observation of {Lambda}{Lambda} hypernuclei, which argue against a stable H{sub 0}, and the possible existence of H dibaryons in general. {copyright}more » {ital 1997} {ital The American Physical Society}« less