Measurements of charm mixing and $CP$ violation using $D^0\to K^{\pm }\ddot{I}{€}^{\mp }$ decays

Abstract

Measurements of charm mixing and $CP$ violation parameters from the decay-time-dependent ratio of $D^0\to K^{+}\ddot{I}{€}^{-}$ to $D^0\to K^{-}\ddot{I}{€}^{+}$ decay rates and the charge-conjugate ratio are reported. The analysis uses $\overline{B}\to D^{\ast +}\hat{I}{¼}^{-}X$, and charge-conjugate decays, where $D^{\ast +}\to D^0\ddot{I}{€}^{+}$, and $D^0\to K^{\mp }\ddot{I}{€}^{\pm }$. The $pp$ collision data are recorded by the LHCb experiment at center-of-mass energies $\sqrt{s}$ = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb${}^{-1}$. The data are analyzed under three hypotheses: (i) mixing assuming $CP$ symmetry, (ii) mixing assuming no direct $CP$ violation in the Cabibbo-favored or doubly Cabibbo-suppressed decay amplitudes, and (iii) mixing allowing either direct $CP$ violation and/or $CP$ violation in the superpositions of flavor eigenstates defining the mass eigenstates. The data are also combined with those from a previous LHCb study of $D^0\to K\ddot{I}€$ decays from a disjoint set of $D^{\ast +}$ candidates produced directly in $pp$ collisions. In all cases, the data are consistent with the hypothesis of $CP$ symmetry.

All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-033.html. v3 fixes typographical errors in Tables II, V-X (cf. the errata)