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Abstract |
Measurements of charm mixing and $CP$ violation parameters
from the decay-time-dependent ratio of $ D^0 \to K^+ \pi^- $
to $ D^0 \to K^- \pi^+ $ decay rates and the charge-conjugate ratio
are reported.
The analysis uses
$\overline{B}\to D^{*+} \mu^- X$, and charge-conjugate decays, where $D^{*+}\to D^0\pi^+$, and
$D^0\to K^{\mp} \pi^{\pm}$. 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 $D^0\to K \pi$ decays
from a disjoint set of $ D^{*+} $ candidates produced directly in $pp$ collisions. In all cases, the data are consistent
with the hypothesis of $CP$ symmetry.
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