# Observation of $D^0$ meson decays to $\pi^+\pi^-\mu^+\mu^-$ and $K^+K^-\mu^+\mu^-$ final states

Peter Clarke, Greig Cowan, Stephan Eisenhardt, Franz Muheim, Matthew Needham, Stephen Playfer, LHCb Collaboration

Research output: Contribution to journalArticlepeer-review

## Abstract

The first observation of the $D^0 \to \pi^+\pi^-\mu^+\mu^-$ and $D^0 \to K^+K^-\mu^+\mu^-$ decays is reported using a sample of proton-proton collisions collected by LHCb at a center-of-mass energy of 8$\,$TeV, and corresponding to 2$\,$fb$^{-1}$ of integrated luminosity. The corresponding branching fractions are measured using as normalization the decay $D^0 \to K^- \pi^+[\mu^+\mu^-]_{\rho^0/\omega}$, where the two muons are consistent with coming from the decay of a $\rho^0$ or $\omega$ meson. The results are $\mathcal{B}(D^0 \to \pi^+\pi^-\mu^+\mu^-)=(9.64\pm0.48\pm0.51\pm0.97)\times10^{-7}$ and $\mathcal{B}(D^0 \to K^+K^-\mu^+\mu^-)=( 1.54\pm0.27\pm0.09\pm0.16)\times10^{-7}$, where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalization branching fraction. The dependence of the branching fraction on the dimuon mass is also investigated.
Original language English Aaij:2017iyr 181805 Physical Review Letters 119 18 https://doi.org/10.1103/PhysRevLett.119.181805 Published - 31 Oct 2017

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