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

Using the QCD sum rule approach, we show that the flavor-nonsinglet H dibaryon states with J = 1+, J = 0+, I=1 (27plet) are nearly degenerate with the J = 0+, I=0 singlet H0 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 H0 is slightly heavier than these flavor-nonsinglet Hs over a wide range of the parameter space. If the singlet H0 mass lies above the ΛΛ threshold (2231 MeV), then the strong interaction breakup to ΛΛ would produce a very broad resonance in the ΛΛ 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 ΛΛ threshold, but below the Ξ0n breakup threshold (2254 MeV), then because the direct, strong interaction decay to the ΛΛ 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 ΛΛ hypernuclei, which argue against a stable H0, and the possible existence of H dibaryons in general. PACS number(s): 12.40.Yx, 14.20.Pt e-mail address: [email protected] e-mail address: [email protected] e-mail address: [email protected] e-mail address: [email protected]