Determination of the Ratio of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>b</mml:mi></mml:math>-Quark Fragmentation Fractions<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>f</mml:mi></mml:mrow><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:msub><mml:mo stretchy="false">/</mml:mo><mml:msub><mml:mrow><mml:mi>f</mml:mi></mml:mrow><mml:mrow><mml:mi>d</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi><mml:mi>p</mml:mi></mml:math>Collisions at<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msqrt><mml:mi>s</mml:mi></mml:msqrt><mml:mo>=</mml:mo><mml:mn>7</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>TeV</mml:mi></mml:math>with the ATLAS Detector

With an integrated luminosity of $2.47\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ recorded by the ATLAS experiment at the LHC, the exclusive decays ${B}_{s}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\phi}$ and ${B}_{d}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}{K}^{*0}$ of $B$ mesons produced in $pp$ collisions at $\sqrt{s}=7\text{ }\text{ }\mathrm{TeV}$ are used to determine the ratio of fragmentation fractions ${f}_{s}/{f}_{d}$. From the observed ${B}_{s}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\phi}$ and ${B}_{d}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}{K}^{*0}$ yields, the quantity $({f}_{s}/{f}_{d})[\mathcal{B}({B}_{s}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\phi})/\mathcal{B}({B}_{d}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}{K}^{*0})]$ is measured to be $0.199\ifmmode\pm\else\textpm\fi{}0.004(\text{stat})\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0ex}{0ex}}0.008(\text{syst})$. Using a recent theory prediction for $[\mathcal{B}({B}_{s}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\phi})/\mathcal{B}({B}_{d}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}{K}^{*0})]$ yields $({f}_{s}/{f}_{d})=0.240\ifmmode\pm\else\textpm\fi{}0.004(\text{stat})\ifmmode\pm\else\textpm\fi{}0.010(\text{syst})\ifmmode\pm\else\textpm\fi{}0.017(\mathrm{th})$. This result is based on a new approach that provides a significant improvement of the world average.

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