# 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. Fig1.eps [25 KiB] HiDef png [216 KiB] Thumbnail [68 KiB] *.C file (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. Fig2a.eps [41 KiB] HiDef png [214 KiB] Thumbnail [66 KiB] *.C file Fig2b.eps [40 KiB] HiDef png [193 KiB] Thumbnail [60 KiB] *.C file 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. Fig3.eps [24 KiB] HiDef png [173 KiB] Thumbnail [65 KiB] *.C file Animated gif made out of all figures. PAPER-2015-033.gif Thumbnail

## Tables and captions

 Summary of the relative systematic uncertainties (in percentage) on the branching fraction ratio measurement. Table_1.pdf [53 KiB] HiDef png [91 KiB] Thumbnail [14 KiB] tex code 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. Table_2.pdf [16 KiB] HiDef png [78 KiB] Thumbnail [11 KiB] tex code

Created on 20 April 2019.Citation count from INSPIRE on 20 April 2019.