Flavor & new physics opportunities with rare charm decays into leptons

TL;DR

This paper updates Standard Model predictions for rare charm decays into leptons, explores constraints on new physics via Wilson coefficients, and assesses potential signals of new physics in various decay observables and models.

Contribution

It provides the first comprehensive analysis of new physics opportunities in rare charm decays, including model-independent constraints and predictions for leptoquark models.

Findings

Large couplings could enhance semileptonic branching ratios outside resonance regions.

Resonance-assisted CP asymmetries and angular observables offer new physics sensitivity.

Predictions for leptoquark models include lepton flavor violation and dineutrino decays.

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.