cern.ch

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

[to restricted-access page]

Abstract

We report measurements of charm-mixing parameters based on the decay-time-dependent ratio of $D^0\to K^+\pi^-$ to $D^0\to K^-\pi^+$ 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 $x'^2=(3.9 \pm 2.7) \times10^{-5}$, $y'=(5.28 \pm 0.52) \times 10^{-3}$, and $R_D=(3.454 \pm 0.031)\times10^{-3}$. Without this assumption, the measurement is performed separately for $D^0$ and $\overline{D}{}^0$ mesons, yielding a direct CP-violating asymmetry $A_D =(-0.1\pm9.1)\times10^{-3}$, 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.

Figures and captions

Distribution of $ M( D ^0 \pi_{\rm s} ^+)$ for selected (a) right-sign $ D ^0 \rightarrow K^-\pi^+$ and (b) wrong-sign $ D ^0 \rightarrow K^+\pi^-$ candidates.

Fig1a.pdf [31 KiB]
HiDef png [358 KiB]
Thumbnail [75 KiB]
*.C file
Fig1a.pdf
Fig1b.pdf [32 KiB]
HiDef png [437 KiB]
Thumbnail [96 KiB] *.C file
Fig1b.pdf

Efficiency-corrected ratios of WS-to-RS yields for (a) $ D ^{*+}$ decays, (b) $ D ^{*-}$ decays, and (c) their differences as functions of decay time in units of $ D ^0$ lifetime. Projections of fits allowing for (dashed line) no $ C\!P$ violation, (dotted line) no direct $ C\!P$ violation, and (solid line) direct and indirect $ C\!P$ violation are overlaid. The last two curves overlap. The abscissa of each data point corresponds to the average decay time over the bin. The error bars indicate the statistical uncertainties.

Fig2.pdf [14 KiB]
HiDef png [424 KiB]
Thumbnail [99 KiB]
*.C file
Fig2.pdf

Two-dimensional confidence regions in the $(x'^2,y')$ plane obtained (a) without any restriction on $ C\!P$ violation, (b) assuming no direct $ C\!P$ violation, and (c) assuming $ C\!P$ conservation. The dashed (solid) curves in (a) and (b) indicate the contours of the mixing parameters associated with $\overline{ D }{} {}^0$ ( $ D ^0$ ) decays. The best-fit value for $\overline{ D }{} {}^0$ ( $ D ^0$ ) decays is shown with an open (filled) point. The solid, dashed, and dotted curves in (c) indicate the contours of $ C\!P$ -averaged mixing parameters at 68.3%, 95.5%, and 99.7% confidence levels (CL), respectively, and the point indicates the best-fit value.

Fig3.pdf [18 KiB]
HiDef png [306 KiB]
Thumbnail [57 KiB]
*.C file
Fig3.pdf

Animated gif made out of all figures.

PAPER-2017-046.gif
Thumbnail
thumbnail_PAPER-2017-046.gif

Tables and captions

Results of fits for different $ C\!P$ -violation hypotheses. The first contribution to the uncertainties is statistical and the second systematic. Correlations include both statistical and systematic contributions.

Table_1.pdf [54 KiB]
HiDef png [130 KiB]
Thumbnail [21 KiB]
tex code
Table_1.pdf

Supplementary Material [file]

This ZIP file contains supplemetary material for the publication LHCb-PAPER-2017-046. The files are: Supplementary-LHCb-PAPER-2017-046.pdf : An overview of the extra figures *.pdf, *.png, *.eps, *.C : The figures in various formats

Fig10.pdf [15 KiB]
HiDef png [327 KiB]
Thumbnail [72 KiB]
*C file
Fig10.pdf
Fig4.pdf [34 KiB]
HiDef png [472 KiB]
Thumbnail [103 KiB]
*C file
Fig4.pdf
Fig5.pdf [17 KiB]
HiDef png [479 KiB]
Thumbnail [101 KiB]
*C file
Fig5.pdf
Fig6_11.pdf [10 KiB]
HiDef png [196 KiB]
Thumbnail [48 KiB]
*C file
Fig6_11.pdf
Fig6_12.pdf [10 KiB]
HiDef png [195 KiB]
Thumbnail [48 KiB]
*C file
Fig6_12.pdf
Fig6_15.pdf [10 KiB]
HiDef png [195 KiB]
Thumbnail [48 KiB]
*C file
Fig6_15.pdf
Fig6_16.pdf [10 KiB]
HiDef png [196 KiB]
Thumbnail [48 KiB]
*C file
Fig6_16.pdf
Fig7_11.pdf [12 KiB]
HiDef png [243 KiB]
Thumbnail [61 KiB]
*C file
Fig7_11.pdf
Fig7_12.pdf [12 KiB]
HiDef png [243 KiB]
Thumbnail [59 KiB]
*C file
Fig7_12.pdf
Fig7_15.pdf [12 KiB]
HiDef png [247 KiB]
Thumbnail [61 KiB]
*C file
Fig7_15.pdf
Fig7_16.pdf [12 KiB]
HiDef png [243 KiB]
Thumbnail [58 KiB]
*C file
Fig7_16.pdf
Fig8.pdf [14 KiB]
HiDef png [87 KiB]
Thumbnail [24 KiB]
*C file
Fig8.pdf
Fig9a.pdf [15 KiB]
HiDef png [312 KiB]
Thumbnail [75 KiB]
*C file
Fig9a.pdf
Fig9b.pdf [15 KiB]
HiDef png [374 KiB]
Thumbnail [89 KiB]
*C file
Fig9b.pdf
LHCb-P[..].pdf [372 KiB]
HiDef png [355 KiB]
Thumbnail [55 KiB]
*C file
LHCb-PAPER-2017-046-supplementary.pdf

Created on 17 December 2018.Citation count from INSPIRE on 18 December 2018.