A search for the decay $B^0_s\rightarrow J/\psi K^{*0}$ with $K^{*0} \rightarrow K^\pi^+$ is performed with 0.37 fb$^{1}$ of $pp$ collisions at $\sqrt{s}$ = 7 TeV collected by the LHCb experiment, finding a $\Bs \to J\psi K^\pi^+$ peak of $114 \pm 11$ signal events. The $K^\pi^+$ mass spectrum of the candidates in the $B^0_s$ peak is dominated by the $K^{*0}$ contribution. Subtracting the nonresonant $K^\pi^+$ component, the branching fraction of \BsJpsiKst is $(4.4_{0.4}^{+0.5} \pm 0.8) \times 10^{5}$, where the first uncertainty is statistical and the second systematic. A fit to the angular distribution of the decay products yields the \Kst polarization fractions $f_L = 0.50 \pm 0.08 \pm 0.02$ and $f_{} = 0.19^{+0.10}_{0.08} \pm 0.02$.
Tree and penguin decay topologies contributing to the decays $ B^0_s\rightarrow J/\psi \overline{ K }{} ^{*0} $ and $ B ^0_ s \rightarrow { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} \phi$. The dashed line indicates a colour singlet exchange. 
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Fit to the $K\pi$ mass spectrum for (a) $ B ^0 \rightarrow J/\psi K \pi$ events, and (b) $ B^0_s\rightarrow J/\psi K \pi$ events. The $ B^0_{(s)}\rightarrow J/\psi K \pi$ yields in each bin of $K\pi$ mass are determined from a fit to the $ { J \mskip 3mu/\mskip 2mu\psi \mskip 2mu} K \pi$ mass spectrum. The pink dasheddotted line represents the $ K ^{*0}$ , the red shortdashed line is the {Swave} and the black dotted line is the $K^{*}_2(1430)$. The black solid line is their sum. 
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Projections of the fit in $M_{J/\psi K\pi}$ and in the angular variables for the mass range indicated by the two dashed vertical lines in the mass plot. The red dashed, pink longdashed, and blue dotted lines represent the fitted contributions from $ B ^0 \rightarrow J/\psi K^{*0}$ , $ B^0_s\rightarrow J/\psi \overline{ K }{} ^{*0} $ and background. The black solid line is their sum. 
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Animated gif made out of all figures. 
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Summary of the measured $ B^0_s\rightarrow J/\psi \overline{ K }{} ^{*0} $ angular properties and their statistical and systematic uncertainties. 
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Angular parameters of $ B ^0 \rightarrow J/\psi K^{*0}$ needed to compute $ {\cal B}(B^0_s\rightarrow J/\psi \overline{ K }{} ^{*0} )$ . The systematic uncertainties from background modelling and the mass $\rm PDF$ are found to be negligible in this case. 
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Parameter values and errors for $\frac{ {\cal B}(B^0_s\rightarrow J/\psi \overline{ K }{} ^{*0} ) }{ {\cal B}( B ^0 \rightarrow J/\psi K^{*0}) }$. 
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Created on 15 February 2019.Citation count from INSPIRE on 15 February 2019.