Updated determination of $D^0$-$\overline{D}{}^0$ mixing and CP violation parameters with $D^0\to K^{+}\ddot{I}{€}^{-}$ decays

Abstract

We report measurements of charm-mixing parameters based on the decay-time-dependent ratio of $D^0\to K^{+}\ddot{I}{€}^{-}$ to $D^0\to K^{-}\ddot{I}{€}^{+}$ rates. The analysis uses a data sample of proton-proton collisions corresponding to an integrated luminosity of $5.0$ fb${}^{-1}$ recorded by the LHCb experiment from 2011 through 2016. Assuming charge-parity (CP) symmetry, the mixing parameters are determined to be $x^{\prime 2}=(3.9\pm 2.7)\times 10^{-5}$, $y^{\prime }=(5.28\pm 0.52)\times 10^{-3}$, and $R_D=(3.454\pm 0.031)\times 10^{-3}$. Without this assumption, the measurement is performed separately for $D^0$ and $\overline{D}{}^0$ mesons, yielding a direct CP-violating asymmetry $A_D=(-0.1\pm 9.1)\times 10^{-3}$, and magnitude of the ratio of mixing parameters $1.00<|q/p|<1.35$ at the $68.3\%$ confidence level. All results include statistical and systematic uncertainties and improve significantly upon previous single-measurement determinations. No evidence for CP violation in charm mixing is observed.

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-2017-046.html