New opportunities for rare charm from Z → c\bar{c} decays
the Z pole, such as the FCC-ee or CEPC. In particular, we identify clean null-test observables in D0→π+π-νν¯ and in polarized Λ+c→pℓ+ℓ- decays with ℓ=e ,μ . Complementarity with the LHC and HL-LHC flavor [...] modes and charm production with significant polarization. We improve the theoretical description of D0→π+π-νν¯ decays and work out the phenomenology of polarization-induced null-test observables in Λ+c→pℓ+ℓ- …
