BSM reach of rare charm decays, including the rising star $Λ_c\to pμ^+μ^-$

Abstract

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