Time-dependent $CP$ asymmetries in the decay rates of the singly Cabibbo-suppressed decays $D^0\rightarrow K^-K^+$ and $D^0\rightarrow \pi^-\pi^+$ are measured in $pp$ collision data corresponding to an integrated luminosity of 3.0 fb$^{-1}$ collected by the LHCb experiment. The $D^0$ mesons are produced in semileptonic $b$-hadron decays, where the charge of the accompanying muon is used to determine the initial state as $D^0$ or $\bar{D}^0$. The asymmetries in effective lifetimes between $D^0$ and $\bar{D}^0$ decays, which are sensitive to indirect $CP$ violation, are determined to be \begin{align*} A_{\Gamma}(K^-K^+) = (-0.134 \pm 0.077 \; {}^{+0.026}_{-0.034})\% A_{\Gamma}(\pi^-\pi^+) = (-0.092\pm 0.145 \; {}^{+0.025}_{-0.033})\% \end{align*} where the first uncertainties are statistical and the second systematic. This result is in agreement with previous measurements and with the hypothesis of no indirect $CP$ violation in $D^0$ decays.
Invariant mass distributions for (a) $ D ^0 \rightarrow K ^- K ^+ $ , (b) $ D ^0 \rightarrow \pi ^- \pi ^+ $ and (c) $ D ^0 \rightarrow K ^- \pi ^+ $ candidates. The results of the fits are overlaid. Underneath each plot the pull in each mass bin is shown, where the pull is defined as the difference between the data point and total fit, divided by the corresponding uncertainty. |
massal[..].pdf [21 KiB] HiDef png [237 KiB] Thumbnail [216 KiB] *.C file |
|
massal[..].pdf [21 KiB] HiDef png [241 KiB] Thumbnail [222 KiB] *.C file |
||
massal[..].pdf [21 KiB] HiDef png [205 KiB] Thumbnail [191 KiB] *.C file |
||
Raw $ C P$ asymmetry as function of $ D ^0$ decay time for (a) $ D ^0 \rightarrow K ^- K ^+ $ , (b) $ D ^0 \rightarrow \pi ^- \pi ^+ $ and (c) $ D ^0 \rightarrow K ^- \pi ^+ $ candidates. The results of the $\chi^2$ fits are shown as blue, solid lines with the $\pm1$ standard-deviation ($\sigma$) bands indicated by the dashed lines. The green, dashed lines indicate one $ D ^0$ lifetime ($\tau=410.1\rm fs $). Underneath each plot the pull in each time bin is shown. |
Agamma[..].pdf [28 KiB] HiDef png [217 KiB] Thumbnail [182 KiB] *.C file |
|
Agamma[..].pdf [28 KiB] HiDef png [227 KiB] Thumbnail [191 KiB] *.C file |
||
Agamma[..].pdf [27 KiB] HiDef png [183 KiB] Thumbnail [165 KiB] *.C file |
||
Mistag probability, before subtracting the contribution from wrong-sign (WS) decays, determined with $ D ^0 \rightarrow K ^- \pi ^+ $ candidates. The result of the fit to the data points with an exponential function is overlaid (solid, blue line). The red, dashed line indicates the expected mistag contribution from WS decays. |
momega[..].pdf [21 KiB] HiDef png [208 KiB] Thumbnail [161 KiB] *.C file |
|
Measured values of $ A_{\Gamma}$ for different magnet polarities and data-taking periods for (a) $ D ^0 \rightarrow K ^- K ^+ $ , (b) $ D ^0 \rightarrow \pi ^- \pi ^+ $ and (c) $ D ^0 \rightarrow K ^- \pi ^+ $ decays. The vertical line and error band indicate the average $ A_{\Gamma}$ obtained from the combined data set. The error bars indicate the statistical uncertainty only. |
polari[..].pdf [13 KiB] HiDef png [114 KiB] Thumbnail [101 KiB] *.C file |
|
polari[..].pdf [13 KiB] HiDef png [113 KiB] Thumbnail [100 KiB] *.C file |
||
polari[..].pdf [13 KiB] HiDef png [108 KiB] Thumbnail [97 KiB] *.C file |
||
Animated gif made out of all figures. |
PAPER-2014-069.gif Thumbnail |
Contributions to the systematic uncertainty of $ A_{\Gamma}( K ^- K ^+ )$ and $ A_{\Gamma}(\pi ^- \pi ^+ )$ . The constant and multiplicative scale uncertainties are given separately. |
Table_1.pdf [47 KiB] HiDef png [83 KiB] Thumbnail [36 KiB] tex code |
Supplementary material full pdf |
supple[..].pdf [118 KiB] |
|
This ZIP file contains supplemetary material for the publication LHCb-PAPER-2014-053. The files are: Supplementary.pdf : An overview of the extra figures *.pdf, *.png, *.eps, *.C : The figures in variuous formats |
Fig1-S.pdf [14 KiB] HiDef png [210 KiB] Thumbnail [191 KiB] *C file |
Created on 27 April 2024.