# The new physics reach of null tests with $$D \rightarrow \pi \ell \ell$$ D→πℓℓ and $$D_s \rightarrow K \ell \ell$$ Ds→Kℓℓ decays

• Rigo Bause,
• Marcel Golz,
• Gudrun Hiller,
• Andrey Tayduganov

DOI
https://doi.org/10.1140/epjc/s10052-020-7621-7
Journal volume & issue
Vol. 80, no. 1
pp. 1 – 20

## Abstract

Abstract $$|\Delta c|=|\Delta u|=1$$ |Δc|=|Δu|=1 processes are unique probes of flavor physics in the up-sector within and beyond the Standard Model (SM). SM tests with rare semileptonic charm meson decays are based on an approximate CP–symmetry, a superior GIM–mechanism, angular distributions, lepton-universality and lepton flavor conservation. We analyze the complete set of null test observables in $$D \rightarrow \pi \ell \ell ^{(\prime )}$$ D→πℓℓ(′) and $$D_s \rightarrow K \ell \ell ^{(\prime )}$$ Ds→Kℓℓ(′) decays, $$\ell ^{(\prime )}=e, \mu$$ ℓ(′)=e,μ , and find large room for new physics safely above the SM contribution. We identify signatures of supersymmetry, leptoquarks and anomaly-free $$U(1)^\prime$$ U(1)′ –models with generation-dependent charges, for which we provide explicit examples. $$Z^\prime$$ Z′ –effects in $$c \rightarrow u \ell \ell ^{(\prime )}$$ c→uℓℓ(′) transitions can be sizable if both left-handed and right-handed couplings to quarks are present.