BSM reach of rare charm decays, including the rising star ${\mathrm{\Lambda }}_c\to p{\mu }^{+}{\mu }^{-}$

We perform the first global fit of rare charm transitions using recent data on $D^0\to {\mu }^{+}{\mu }^{-}$, $D^{+}\to {\pi }^{+}{\mu }^{+}{\mu }^{-}$, ${\mathrm{\Lambda }}_c\to p{\mu }^{+}{\mu }^{-}$ and $D^0\to {\pi }^{+}{\pi }^{-}{\mu }^{+}{\mu }^{-}$ decays, including angular observables. We work out constraints on new physics in the framework of the weak effective field theory. While angular observables in $D^0\to {\pi }^{+}{\pi }^{-}{\mu }^{+}{\mu }^{-}$ decays provide sensitivities to different QCD models, future null tests in ${\mathrm{\Lambda }}_c\to p{\mu }^{+}{\mu }^{-}$ look more promising to extract limits because of less hadronic uncertainties. This marks ${\mathrm{\Lambda }}_c\to p{\mu }^{+}{\mu }^{-}$ as the rising star of rare charm decays.