Search for an $H$-Dibaryon with a Mass near $2{m}_{\ensuremath{\Lambda}}$ in $\ensuremath{\Upsilon}(1S)$ and $\ensuremath{\Upsilon}(2S)$ Decays

Search for an $H$ -Dibaryon with a Mass near $2 m_{Λ}$ in $Υ (1 S)$ and $Υ (2 S)$ Decays

B. H. Kim et al. (Belle Collaboration)

Phys. Rev. Lett. 110, 222002 – Published 31 May 2013

Abstract

We report the results of a high-statistics search for $H$ dibaryon production in inclusive $Υ (1 S)$ and $Υ (2 S)$ decays. No indication of an $H$ dibaryon with a mass near the $M_{H} = 2 m_{Λ}$ threshold is seen in either the $H \to Λ p π^{-}$ or $Λ Λ$ decay channels and 90% confidence level branching-fraction upper limits are set that are between one and two orders of magnitude below the measured branching fractions for inclusive $Υ (1 S)$ and $Υ (2 S)$ decays to antideuterons. Since $Υ (1 S, 2 S)$ decays produce flavor- $S U (3)$ -symmetric final states, these results put stringent constraints on $H$ dibaryon properties. The results are based on analyses of 102 million $Υ (1 S)$ and 158 million $Υ (2 S)$ events collected with the Belle detector at the KEKB $e^{+} e^{-}$ collider.