The photon polarization in radiative D decays, phenomenologically

We work out the phenomenology of untagged time-dependent analysis with radiative D 0 -decays into CP eigenstates, which allows to probe the photon polarization by means of the charm mesons’ finite width difference. We show that D 0 → ϕ γ or D 0 → K ¯ 0 ∗ γ decays, which are SM-dominated, or SM-like, respectively, together with U-spin allow to obtain chirality-predictions for radiative decay amplitudes. The order of magnitude of wrong-chirality contributions in the SM can be cross-checked with an up–down asymmetry in D 0 → K ¯ 1 0 ( → K ¯ π π ) γ . We explore the sensitivity to new physics in | Δ c | = | Δ u | = 1 dipole couplings in the decays D 0 → ρ 0 γ . We point out the possibility to test the SM with D s → K 1 + ( → K π π ) γ decays.