Searches for CP violation in two-body charm decays

Abstract

The LHCb experiment recorded data corresponding to an integrated luminosity of 3.0 $f{b}^{-1}$ during its first run of data taking. These data yield the largest samples of charmed hadrons in the world and are used to search for CP violation in the $D^0$ system. Among the many measurements performed at LHCb, a measurement of the direct CP asymmetry in $D^0\to K_S^0{K}_S^0$ decays is presented and is found to be $A_{CP}(D^0\to K_S^0{K}_S^0)=(-2.9\pm 5.2\pm 2.2)\%,$ where the first uncertainty is statistical and the second systematic. This represents a significant improvement in precision over the previous measurement of this parameter. Measurements of the parameter $A^{\Gamma }$, defined as the CP asymmetry of the $D^0$ effective lifetime when decaying to a CP eigenstate, are also presented. Using semi-leptonic b-hadron decays to tag the flavour of the $D^0$ meson at production with the $K^{+}{K}^{-}$ and ${\pi }^{+}{\pi }^{-}$ final states yields $A^{\Gamma }(K^{+}{K}^{-})=(-0.134\pm 0.077_{-0.034}^{+0.026})\%,$ $A^{\Gamma }({\pi }^{+}{\pi }^{-})=(-0.092\pm 0.145_{-0.033}^{+0.025})\%.$ Thus no evidence of direct or indirect CP violation in the $D^0$ system is found, though it is tightly constrained.

Proceedings for The European Physical Society Conference on High Energy Physics, 22-29 July 2015, Vienna, Austria. On behalf of the LHCb collaboration

References in corpus (2)

• Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of summer 2016
• LHCb Detector Performance