Rare charm c → uν(ν)over-bar dineutrino null tests for e+e- machines

Rare vertical bar Delta c vertical bar = vertical bar Delta u vertical bar = 1 transitions into dineutrinos are strongly Glashow-Iliopoulos-Maiani-suppressed and constitute excellent null tests of the standard model. While branching ratios of D -> P nu(nu) over bar, D -> P+P- nu(nu) over bar P = pi, K, baryonic Lambda(+)(c) -> p nu(nu) over bar, and Xi(+)(c) -> Sigma(+)nu(nu) over bar and inclusive D -> X nu(nu) over bar decays are experimentally unconstrained, signals of new physics can be just around the corner. We provide model-independent upper limits on branching ratios reaching few x10(-5) in the most general case of arbitrary lepton flavor structure, similar to 10(-5) for scenarios with charged lepton conservation and few x10(-6) assuming lepton universality. We also give upper limits in Z' and leptoquark models. The presence of light right-handed neutrinos can affect these limits, a possibility that can occur for lepton number violation at a TeV, and that can be excluded with an improved bound on B(D-0 -> invisibles) at the level of similar to 10(-6), about two orders of magnitude better than the present one. Signatures of c -> u nu(nu) over bar modes contain missing energy and are suited for experimental searches at e(+)e(-)-facilities, such as BES III, Belle II and future e(+)e(-)-colliders, such as the FCC-ee running at the Z.