Testing lepton flavour universality with (semi)-leptonic $$\varvec{D_{(s)}}$$ D(s) decays

• Main Authors: Robert Fleischer, Ruben Jaarsma, Gabriël Koole
• Format: Article
• Language: English
• Published: SpringerOpen 2020-02-01
• Series: European Physical Journal C: Particles and Fields
• Online Access: http://link.springer.com/article/10.1140/epjc/s10052-020-7702-7

Abstract Data in B-meson decays indicate violations of lepton flavour universality, thereby raising the question about such phenomena in the charm sector. We perform a model-independent analysis of NP contributions in (semi)-leptonic decays of $$D_{(s)}$$ D(s) mesons which originate from $$c \rightarrow d \bar{{\ell }} \nu _l$$ c→dℓ¯νl and $$c \rightarrow s \bar{{\ell }} \nu _{\ell }$$ c→sℓ¯νℓ charged-current interactions. Starting from the most general low-energy effective Hamiltonian containing four-fermion operators and the corresponding short-distance coefficients, we explore the impact of new (pseudo)-scalar, vector and tensor operators and constrain their effects through the interplay with current data. We pay special attention to the elements $$|V_{cd}|$$ |Vcd| and $$|V_{cs}|$$ |Vcs| of the Cabibbo–Kobayashi–Maskawa matrix and extract them from the $$D_{(s)}$$ D(s) decays in the presence of possible NP decay contributions, comparing them with determinations utilizing unitarity. We find a picture in agreement with the Standard Model within the current uncertainties. Using the results from our analysis, we make also predictions for leptonic $$D_{(s)}^+ \rightarrow e^+ \nu _e$$ D(s)+→e+νe modes which could be hugely enhanced with respect to their tiny Standard Model branching ratios. It will be interesting to apply our strategy at the future high-precision frontier.