The photon polarization in radiative $D$ decays, phenomenologically

Abstract

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 $D^0\to \varphi \gamma$ or $D^0\to {\bar{K}}^{0\ast }\gamma$ 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 $D^0\to {\bar{K}}_1^0(\to \bar{K}\pi \pi )\gamma$. We explore the sensitivity to new physics in $|\Delta c|=|\Delta u|=1$ dipole couplings in the decays $D^0\to {\rho }^0\gamma$. We point out the possibility to test the SM with $D_s\to K_1^{+}(\to K\pi \pi )\gamma$ decays.

Comments: 15 pages plus references and appendices, 7 figures