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Observation of the $B_s^0 \rightarrow J/\psi \phi \phi$ decay

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Abstract

The $B_s^0 \rightarrow J/\psi \phi \phi$ decay is observed in $pp$ collision data corresponding to an integrated luminosity of 3 fb$^{-1}$ recorded by the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV. This is the first observation of this decay channel, with a statistical significance of 15 standard deviations. The mass of the $B_s^0$ meson is measured to be $5367.08 \pm 0.38 \pm 0.15$ MeV/c$^2$. The branching fraction ratio $\mathcal{B}(B_s^0 \rightarrow J/\psi \phi \phi)/\mathcal{B}(B_s^0 \rightarrow J/\psi \phi)$ is measured to be $0.0115 \pm 0.0012 ^{+0.0005}_{-0.0009}$. In both cases, the first uncertainty is statistical and the second is systematic. No evidence for non-resonant $B_s^0 \rightarrow J/\psi \phi K^+ K^-$ or $B_s^0 \rightarrow J/\psi K^+ K^- K^+ K^-$ decays is found.

Figures and captions

Invariant mass of reconstructed $ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi\phi$ candidates. The result of the fit to the distribution is also shown.

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(left) Invariant mass distribution of reconstructed $B^0_s \rightarrow J/\psi K^+ K^-$ candidates; (right) invariant mass distribution of the $K^+ K^-$ system, for those candidates which come from a $ B ^0_ s $ decay. For both distributions, the fit result is shown.

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Fig2b.eps [40 KiB]
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Invariant mass of the ($\phi,\phi$) ({left}) and ($J/\psi,\phi$) ({right}) pairs, in the $ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi\phi$ decay. In the $J/\psi \phi$ plot, for each candidate two values are calculated, one for each $\phi$ meson. The distribution of data and simulation (phase space) are shown. To compare the shape, the two distributions are normalised to the same area.

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Animated gif made out of all figures.

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Tables and captions

Summary of the relative systematic uncertainties (in percentage) on the branching fraction ratio measurement.

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Summary of the absolute systematic uncertainties (in $ {\mathrm{ Me V /}c^2}$ ) affecting the $ B ^0_ s $ mass determination from the $ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi\phi$ decay.

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Created on 27 April 2024.