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Measurement of the CP-violating phase $\phi_s$ in $\bar{B}^{0}_{s}\to D_{s}^{+}D_{s}^{-}$ decays

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Abstract

We present a measurement of the $CP$-violating weak mixing phase $\phi_s$ using the decay $\bar{B}^{0}_{s}\to D_{s}^{+}D_{s}^{-}$ in a data sample corresponding to $3.0$ fb$^{-1}$ of integrated luminosity collected with the LHCb detector in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV. An analysis of the time evolution of the system, which does not constrain $|\lambda|=1$ to allow for the presence of $CP$ violation in decay, yields $\phi_s = 0.02 \pm 0.17$ (stat) $\pm 0.02$ (syst) rad, $|\lambda| = 0.91^{+0.18}_{-0.15}$ (stat) $\pm0.02$ (syst). This result is consistent with the Standard Model expectation.

Figures and captions

Invariant mass distributions of (a) $\overline{ B }{} {}^0_ s \rightarrow D ^+_ s D ^-_ s $ and (b) $ B ^0 \rightarrow D ^- D ^+_ s $ candidates. The points show the data; the individual fit components are indicated in the legend; the black curve shows the overall fit.

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Decay time acceptances in simulation and data: (a) the $ B ^0 \rightarrow D ^- D ^+_ s $ acceptance in data (green triangles) and simulation (blue squares), (b) the $\overline{ B }{} {}^0_ s \rightarrow D ^+_ s D ^-_ s $ acceptance in simulation (blue squares) and the $ B ^0 \rightarrow D ^- D ^+_ s $ acceptance corrected for $\overline{ B }{} {}^0_ s \rightarrow D ^+_ s D ^-_ s $ (red triangles). The correction is described in detail in the text.

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Distribution of the decay time for $\overline{ B }{} {}^0_ s \rightarrow D ^+_ s D ^-_ s $ signal decays with background subtracted using the sPlot method, along with the fit as described in the text. Discontinuities in the fit line shape are a result of the binned acceptance.

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Animated gif made out of all figures.

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Tables and captions

Summary of systematic uncertainties not already accounted for in the fit, where $\sigma$ denotes the statistical uncertainty.

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tex code
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Supplementary Material [file]

Supplementary material full pdf

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supplementary.pdf

This zip archive contains the supplementary figures and tables relating to LHCb-PAPER-2014-051, CERN-PH-EP-2014-223 "Measurement of the CP-violating phase phi_s in Bs->DsDs decays". The PDF file 'supplemental.pdf' shows all figures and tables with descriptions. The LaTeX file 'supplemental.tex' is the relevant source for supplemental.pdf. The figures are in four formats, - root '.C' macro, valid as of ROOT 5.99/05 (v5-99-05-lhcb@v5-99-05-lhcb, Jul 07 2014, 09:20:00 on linuxx8664gcc) - PDF and EPS vectors (reccommended) - png (not recommended) For further details or elaboration, contact conor.fitzpatrick@cern.ch

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Created on 05 November 2019.