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Effective lifetime measurements in the $B_{s}^{0} \rightarrow K^{+}K^{-}$, $B^{0} \rightarrow K^{+}\pi^{-}$ and $B_{s}^{0} \rightarrow \pi^{+}K^{-}$ decays

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Abstract

Measurements of the effective lifetimes in the $B_{s}^{0} \rightarrow K^{+}K^{-}$, $B^{0} \rightarrow K^{+}\pi^{-}$ and $B_{s}^{0} \rightarrow \pi^{+}K^{-}$ decays are presented using $1.0 \mathrm{fb^{-1}}$ of $pp$ collision data collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The analysis uses a data-driven approach to correct for the decay time acceptance. The measured effective lifetimes are $\tau_{B_{s}^{0} \rightarrow K^{+}K^{-}}$ = $1.407 \pm 0.016 \pm 0.007 \mathrm{ps}$, $\tau_{B^{0} \rightarrow K^{+}\pi^{-}}$ = $1.524 \pm 0.011 \pm 0.004 \mathrm{ps}$, $\tau_{B_{s}^{0} \rightarrow \pi^{+}K^{-}}$ = $1.60 \pm 0.06 \pm 0.01 \mathrm{ps}$. This is the most precise determination to date of the effective lifetime in the $B_{s}^{0} \rightarrow K^{+}K^{-}$ decay and provides constraints on contributions from physics beyond the Standard Model to the $B_{s}^{0}$ mixing phase and the width difference $\Delta\Gamma_{s}$.

Figures and captions

Fits to the (left) $K^{+}K^{-}$ and (right) $K^{+}\pi^{-}$ invariant mass spectrum, with the main contributory signal and background components displayed. The fit residuals are provided beneath each respective mass spectra.

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Fit to the reconstructed decay times of the (left) $ B ^0_ s \rightarrow K ^+ K ^- $ decay and simultaneous fit to the (right) $ B ^0 \rightarrow K ^+ \pi ^- $ and $ B ^0_ s \rightarrow \pi ^+ K ^- $ reconstructed decay times. The background distribution is the sum of all backgrounds displayed in Fig. 1. The fit residuals are provided beneath each respective decay time spectra.

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Animated gif made out of all figures.

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Tables and captions

Systematic uncertainties on the effective lifetimes. The uncertainties vary between the $ B ^0_ s \rightarrow K ^+ K ^- $ , $ B ^0 \rightarrow K ^+ \pi ^- $ and $ B ^0_ s \rightarrow \pi ^+ K ^- $ measurements due to the available sample size per decay mode.

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Table_1.pdf

Supplementary Material [file]

Supplementary material full pdf

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Created on 11 July 2020.