Search for a dark baryon in the $\hat{I}{ž}^{-}\to \ddot{I}{€}^{-}+\mathrm{invisible}$ decay

Abstract

A search for a dark baryon is performed for the first time in the two-body decay $\hat{I}{ž}^{-}\to \ddot{I}{€}^{-}+\mathrm{invisible}$ using $(10.087\pm 0.044)\times 10^9$ $J/\ddot{I}ˆ$ events collected at a center-of-mass energy of $\sqrt{s}=3.097\,\mbox{GeV}$ with the BESIII detector at the BEPCII collider. No significant signal is observed, and the 90% (95%) confidence level upper limits on the branching fraction $B(\hat{I}{ž}^{-}\to \ddot{I}{€}^{-}+\mathrm{invisible})$ are determined to be $4.2\times 10^{-5}$ ($5.2\times 10^{-5}$), $6.9\times 10^{-5}$ ($8.4\times 10^{-5}$), $6.5\times 10^{-4}$ ($7.6\times 10^{-4}$), $1.1\times 10^{-4}$ ($1.3\times 10^{-4}$) and $4.5\times 10^{-5}$ ($5.5\times 10^{-5}$), under the dark baryon mass hypotheses of 1.07$\,\mbox{GeV}/c^2$, 1.10$\,\mbox{GeV}/c^2$, $m_{\hat{I}}›$ (1.116$\,\mbox{GeV}/c^2$), 1.13$\,\mbox{GeV}/c^2$, and 1.16$\,\mbox{GeV}/c^2$, respectively. The constraints obtained on the Wilson coefficients $C_{us,s}^L$ and $C_{us,s}^R$ are more stringent than the previous limits derived from the LHC searches for the colored mediators.

11 pages, 4 figures, 1 table