# Measurement of the effective $B_s^0 \to K^+ K^-$ lifetime

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## Abstract

A precise determination of the effective $B_s^0 \rightarrow K^+ K^-$ lifetime can be used to constrain contributions from physics beyond the Standard Model in the $B_s^0$ meson system. Conventional approaches select $B$ meson decay products that are significantly displaced from the $B$ meson production vertex. As a consequence, $B$ mesons with low decay times are suppressed, introducing a bias to the decay time spectrum which must be corrected. This analysis uses a technique that explicitly avoids a lifetime bias by using a neural network based trigger and event selection. Using 1.0 fb$^{-1}$ of data recorded by the LHCb experiment, the effective $B_s^0 \rightarrow K^+ K^-$ lifetime is measured as $1.455 \pm 0.046 \; \mathrm{(stat.)} \pm 0.006 \; \mathrm{(syst.)} \, \mathrm{ps}.$

## Figures and captions

 (a) Invariant mass spectrum for all selected $B ^0_ s \!\rightarrow K ^+ K ^-$ candidates. (b) Decay time distribution of $B ^0_ s \!\rightarrow K ^+ K ^-$ signal extracted using sWeights and the fitted exponential function. Fig1a.pdf [35 KiB] HiDef png [260 KiB] Thumbnail [82 KiB] *.C file Fig1b.pdf [18 KiB] HiDef png [154 KiB] Thumbnail [59 KiB] *.C file Combined efficiency of LHCb trigger, selection neural networks and particle identification requirements as a function of decay time for simulated $B ^0_ s \!\rightarrow K ^+ K ^-$ signal candidates. Fig2.pdf [19 KiB] HiDef png [157 KiB] Thumbnail [63 KiB] *.C file Animated gif made out of all figures. PAPER-2012-013.gif Thumbnail

## Tables and captions

 Contributions to the systematic uncertainty on the effective $B ^0_ s \!\rightarrow K ^+ K ^-$ lifetime measurement. The total uncertainty is calculated by adding the individual contributions in quadrature. Table_1.pdf [31 KiB] HiDef png [65 KiB] Thumbnail [10 KiB] tex code

Created on 16 February 2019.Citation count from INSPIRE on 16 February 2019.