Decays of $\overline{\it \Lambda}_b^0$ baryons produced in dark matter annihilating into $b\overline b$ pairs could enhance the abundance of antihelium in cosmic rays. The LHCb collaboration provides the first experimental limits on related branching

fractions:

\begin{align*}

\mathcal B({\overline{\it \Lambda}_b^0\to{}^3{\rm He}\overline p\overline p})&<1.9\times10^{-9}\text{ at 90% CL,}\\

\mathcal B({\overline{\it \Lambda}_b^0\to{}^3{\rm He}\overline p\overline pX})&<1.6\times10^{-8}\text{ at 90% CL,}\\

\mathcal B({\overline{\it \Lambda}_b^0\to{}^3{\rm He}\overline pX})&<3.6\times10^{-8}\text{ at 90% CL,}

\end{align*}

where $X$ denotes one or several particles. The $\mathcal B({\overline{\it \Lambda}_b^0\to{}^3{\rm He}\overline p\overline pX})$ limit is extrapolated to the fully inclusive branching fraction $\mathcal B(\overline{\it \Lambda}_b^0\to{}^3{\rm He}X)$. The obtained result significantly restricts the aforementioned scenario for antihelium production.