Model-independent search for CP violation in $D^0\to K^{-}{K}^{+}{\pi }^{-}{\pi }^{+}$ and $D^0\to {\pi }^{-}{\pi }^{+}{\pi }^{+}{\pi }^{-}$ decays

Abstract

A search for CP violation in the phase-space structures of $D^0$ and ${\overline{D}}^0$ decays to the final states $K^{-}{K}^{+}{\pi }^{-}{\pi }^{+}$ and ${\pi }^{-}{\pi }^{+}{\pi }^{+}{\pi }^{-}$ is presented. The search is carried out with a data set corresponding to an integrated luminosity of $1.0{\text{fb}}^{-1}$ collected in 2011 by the LHCb experiment in pp collisions at a centre-of-mass energy of $7\text{TeV}$. For the $K^{-}{K}^{+}{\pi }^{-}{\pi }^{+}$ final state, the four-body phase space is divided into 32 bins, each bin with approximately 1800 decays. The p-value under the hypothesis of no CP violation is 9.1%, and in no bin is a CP asymmetry greater than 6.5% observed. The phase space of the ${\pi }^{-}{\pi }^{+}{\pi }^{+}{\pi }^{-}$ final state is partitioned into 128 bins, each bin with approximately 2500 decays. The p-value under the hypothesis of no CP violation is 41%, and in no bin is a CP asymmetry greater than 5.5% observed. All results are consistent with the hypothesis of no CP violation at the current sensitivity.