Measurement of $CP$ asymmetry in $D^0 \to K^0_S K^0_S$ decays

Information

LHCb-PAPER-2020-047
CERN-EP-2021-058
arXiv:2105.01565 [PDF]

(Submitted on 04 May 2021)
Phys. Rev. D 104, L031102
Inspire 1861934

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Abstract

A measurement of the $CP$ asymmetry in $D^0 \to K^0_S K^0_S$ decays is reported, based on a data sample of proton-proton collisions collected by the LHCb experiment from 2015 to 2018, corresponding to an integrated luminosity of 6 fb$^{-1}$. The flavor of the $D^0$ candidate is determined using the charge of the $D^{*\pm}$ meson, from which the decay is required to originate. The $D^0 \to K^+ K^-$ decay is used as a calibration channel. The time-integrated $CP$ asymmetry for the $D^0 \to K^0_S K^0_S$ mode is measured to be: $$A^{CP}(D^0 \to K^0_S K^0_S) = (-3.1\pm 1.2\pm 0.4 \pm 0.2)\%, $$ where the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the $CP$ asymmetry of the calibration channel. This is the most precise determination of this quantity to date.

Figures and captions

Distributions and fit projections of the $\Delta m$ observable for representative candidate categories (2017--2018 data). See text for the definition of purities.	Fig_1a.pdf [30 KiB] HiDef png [202 KiB] Thumbnail [176 KiB] *.C file
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Distributions of weights (2017--2018 data) applied to signal candidates in the global fit to correct for detector, production, and physics of the calibration channel. Differences between Mag Up (left) and MagDown (right) are a consequence of different $ D ^0$ and $\overline{ D } {}^0$ acceptances, and of detector asymmetries. A small fraction of entries with large weights fall outside the range of the plot.	Fig_2a.pdf [15 KiB] HiDef png [324 KiB] Thumbnail [225 KiB] *.C file
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Animated gif made out of all figures.	PAPER-2020-047.gif Thumbnail

Tables and captions

Measurements of yields and $ {\mathcal{A}}^{ C P } ( D ^0 \rightarrow K ^0_{\mathrm{S}} K ^0_{\mathrm{S}} )$ in individual subsamples. For asymmetries, the first uncertainty is statistical and the second is systematic.

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Supplementary Material [file]

Supplementary material full pdf	Supple[..].pdf [1 MiB]
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