  A massless particle beyond the Standard Model is searched for in the two-body
decay $\Sigma^+\rightarrow p+{\rm invisible}$ using
$(1.0087\pm0.0044)\times10^{10}$ $J/\psi$ events collected at a center-of-mass
energy of $\sqrt{s}=3.097$ GeV with the BESIII detector at the BEPCII collider.
No significant signal is observed, and the upper limit on the branching
fraction $B(\Sigma^+\rightarrow p+{\rm invisible})$ is determined to be
$3.2\times10^{-5}$ at the 90% confidence level. This is the first search for a
flavor-changing neutral current process with missing energy in hyperon decays
which plays an important role in constraining new physics models.
