Flavor & new physics opportunities with rare charm decays into leptons

Abstract

Updated standard model predictions for $D_{(s)}\to P{l}^{+}{l}^{-}$, $l=e,\mu$, $P=\pi ,K$ and inclusive decays are presented. Model-independent constraints on $|\Delta C|=|\Delta U|=1$ Wilson coefficients are worked out. New physics (NP) opportunities arise in semileptonic branching ratios for very large couplings only, however, are not excluded outside the resonance regions yet. The NP potential of resonance-assisted CP asymmetries and angular observables is worked out. Predictions are given for leptoquark models, and include lepton flavor violating and dineutrino decays. Whether NP can be seen depends on flavor patterns, and vice versa.

Comments: 19 pages plus references and appendices, 5 figures; v2: ${\eta }^{(\prime )}$ contribution fixed, references added, conclusion unchanged; v3: typos corrected and clarifications and references added, conclusions unchanged