# 29th International Symposium on Lepton Photon Interactions at High Energies

5-10 August 2019
America/Toronto timezone

## Search for LFV and LNV decays of the $D^0$ meson and observation of $D^0\to K^-\pi^+e^+e^-$

8 Aug 2019, 09:00
12m
Parallel Session talk Collider -- Beyond Standard Model Searches

### Speakers

Fergus Wilson (Science and Technology Facilities Council STFC (GB)) Fergus Wilson (STFC - Science & Technology Facilities Council (GB))

### Summary

Decay modes with two oppositely charged leptons of different flavor correspond to lepton flavor violating (LFV) decays and are essentially forbidden in the Standard Model (SM) because they can occur only through lepton mixing. Decay modes with two leptons of the same charge are lepton-number violating (LNV) decays and are forbidden in the SM. Hence, decays of the form $D^0 \to hh'll’$ provide sensitive tools to investigate new mediators or couplings in physics beyond the SM. In this talk, we report on a search for decays of the type $D^0\to hh'll’$ (with $h,h'=K/\pi$ and $l,l’=e/\mu$) using data collected by the BABAR experiment at the PEP-II $e^+e^-$ collider at the SLAC National Accelerator Laboratory. Upper limits on the branching fractions are improved by up to two orders of magnitude. We also report the observation of the rare decay $D^0\to K^-\pi^+e^-e^+$. We measure $\mathcal{B}(D^0\to K^-\pi^+e^-e^+) = (4.0\pm0.5)\times 10^{-6}$ in the di-lepton mass range $0.675< m(e^+e^-) < 0.875$ GeV$/c^{2}$, where the production of the intermediate state $\rho \to e^+e^-$ dominates, and set upper limits for decays outside this interval where long-distance effects are not expected to be significant.

### Primary author

Fabio Anulli (Sapienza Universita e INFN, Roma I (IT))