Abstract

A measurement of time-dependent CP violation in the decays of $B^0$ and $\overline{B}^0$ mesons to the final states $J/\psi(\to\mu^+\mu^-)K^0_S$, $\psi(2S)(\to\mu^+\mu^-)K^0_S$ and $J/\psi(\to e^+e^-)K^0_S$ with $K^0_S\to\pi^+\pi^-$ is presented. The data correspond to an integrated luminosity of 6 fb${}^{-1}$ collected at a center-of-mass energy of $\sqrt{s}=13$ TeV with the LHCb detector. The CP-violation parameters are measured to be \begin{align*} S_{\psi K^0_S} &= 0.717 \pm 0.013 (\text{stat}) \pm 0.008 (\text{syst}), \\ C_{\psi K^0_S} &= 0.008 \pm 0.012 (\text{stat}) \pm 0.003 (\text{syst}). \end{align*} This measurement of $S_{\psi K^0_S}$ represents the most precise single measurement of the CKM angle $\beta$ to date and is more precise than the current world average. In addition, measurements of the CP-violation parameters of the individual channels are reported and a combination with the LHCb Run 1 measurements is performed.

Figures and captions

Invariant-mass distribution of the selected candidates with an identified flavor at production of the three signal channels.	Fig1.pdf [52 KiB] HiDef png [436 KiB] Thumbnail [464 KiB] *.C file
Decay-time distribution of the signal with an identified flavor at production, where the background is statistically subtracted by means of the sPlot method. The projections of the time-dependent fit for the individual contributions of the three decay modes and for the total are superimposed.	Fig2.pdf [21 KiB] HiDef png [355 KiB] Thumbnail [385 KiB] *.C file
Time-dependent $ C P$ asymmetry from the maximum-likelihood estimator of the binned asymmetry with the fit result overlaid.	Fig3.pdf [16 KiB] HiDef png [220 KiB] Thumbnail [263 KiB] *.C file
Animated gif made out of all figures.	PAPER-2023-013.gif Thumbnail

Tables and captions

Flavor tagging efficiency and $\mathcal{D}^2$ factor for each decay channel.	Table_1.pdf [89 KiB] HiDef png [53 KiB] Thumbnail [25 KiB] tex code
Summary of systematic uncertainties on $S$ and $C$. Each contribution is a weighted average of the uncertainties of the individual fits, except for the fitter validation.	Table_2.pdf [55 KiB] HiDef png [87 KiB] Thumbnail [40 KiB] tex code

Supplementary Material [file]

Supplementary material full pdf	supple[..].pdf [605 KiB]
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Created on 27 April 2024.