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Measurement of the effective $B_s^0\rightarrow J/\psi K_{\mathrm S}^0$ lifetime

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Abstract

This paper reports the first measurement of the effective B_s^0 -> J/{\psi} K_S^0 lifetime and an updated measurement of its time-integrated branching fraction. Both measurements are performed with a data sample, corresponding to an integrated luminosity of 1.0 fb^{-1} of pp collisions, recorded by the LHCb experiment in 2011 at a centre-of-mass energy of 7 TeV. The results are: tau_J/{\psi}K_S^0 = 1.75 +/- 0.12 (stat) +/- 0.07 (syst) and BR(B_s^0 -> J/{\psi} K_S^0) = (1.97 +/- 0.23) X 10^{-5}. For the latter measurement, the uncertainty includes both statistical and systematic sources.

Figures and captions

Decay topologies contributing to the $B_{d(s)}$ $\rightarrow$ $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ {} $ K ^0_{\rm\scriptscriptstyle S}$ channel: (left) tree diagram and (right) penguin diagram.

 Bds2Jp[..].pdf [11 KiB]
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Bds2JpsiKs_Tree.pdf
Bds2Jp[..].pdf [13 KiB]
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Bds2JpsiKs_Penguin.pdf

Fitted $ B $ $\rightarrow$ $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ {} $ K ^0_{\rm\scriptscriptstyle S}$ candidate mass distributions and their associated residual uncertainties (pulls) for the (left) long and (right) downstream $ K ^0_{\rm\scriptscriptstyle S}$ samples, after applying the final requirement on the NN classifier outputs.

 Final_[..].pdf [27 KiB]
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Final_MassFit_LL.pdf
Final_[..].pdf [28 KiB]
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Final_MassFit_DD.pdf

Fitted $ B $ $\rightarrow$ $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ {} $ K ^0_{\rm\scriptscriptstyle S}$ candidate decay time distributions and their associated residual uncertainties (pulls) for the (left) long and (right) downstream $ K ^0_{\rm\scriptscriptstyle S}$ samples, after applying the final requirement on the NN classifier outputs.

 Final_[..].pdf [26 KiB]
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Final_decaytimeFit_LL.pdf
Final_[..].pdf [27 KiB]
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*.C file
Final_decaytimeFit_DD.pdf

Fitted $ B $ $\rightarrow$ $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ {} $ K ^0_{\rm\scriptscriptstyle S}$ candidate decay time distributions and their associated residual uncertainties (pulls) for the (left) long and (right) downstream $ K ^0_{\rm\scriptscriptstyle S}$ candidates in the $ B ^0_ s $ signal region $m_{ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} {} K ^0_{\rm\scriptscriptstyle S} }\in[5340,5390]\: {\mathrm{ Me V /}c^2} $, after applying the final requirement on the NN classifier outputs.

 Final_[..].pdf [22 KiB]
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Final_decaytimeFit_LL_BsOnly.pdf
Final_[..].pdf [23 KiB]
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Final_decaytimeFit_DD_BsOnly.pdf

Animated gif made out of all figures.

 PAPER-2013-015.gif
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thumbnail_PAPER-2013-015.gif

Tables and captions

Signal yields from the unbinned maximum likelihood fits to the $ B $ $\rightarrow$ $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ {} $ K ^0_{\rm\scriptscriptstyle S}$ candidate mass distributions. The uncertainties are statistical only. The yield ratio is calculated from the quantities highlighted in boldface, where the fitted $ B ^0$ yield is first multiplied by a factor of four.

 Table_1.pdf [118 KiB]
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tex code 		Table_1.pdf

Corrections and systematic uncertainties on the yield ratio.

 Table_2.pdf [45 KiB]
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tex code 		Table_2.pdf

Corrections and systematic uncertainties on the effective $ B ^0_ s $ $\rightarrow$ $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu}$ {} $ K ^0_{\rm\scriptscriptstyle S}$ lifetime.

 Table_3.pdf [33 KiB]
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tex code 		Table_3.pdf

Created on 27 April 2024.