# Measurement of the $B^0_s \rightarrow J/\psi \bar{K}^{*0}$ branching fraction and angular amplitudes

[to restricted-access page]

## Abstract

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 non-resonant $K^-\pi^+$ 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 $f_{||} = 0.19^{+0.10}_{-0.08} \pm 0.02$.

## Figures and captions

 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. Fig1a.pdf [10 KiB] HiDef png [48 KiB] Thumbnail [81 KiB] *.C file Fig1b.pdf [11 KiB] HiDef png [60 KiB] Thumbnail [98 KiB] *.C file 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 dashed-dotted line represents the $K ^{*0}$ , the red short-dashed line is the {S-wave} and the black dotted line is the $K^{*}_2(1430)$. The black solid line is their sum. Fig2a.pdf [22 KiB] HiDef png [219 KiB] Thumbnail [182 KiB] *.C file Fig2b.pdf [17 KiB] HiDef png [210 KiB] Thumbnail [176 KiB] *.C file 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 long-dashed, 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. Fig3a.pdf [24 KiB] HiDef png [239 KiB] Thumbnail [207 KiB] *.C file Fig3b.pdf [16 KiB] HiDef png [163 KiB] Thumbnail [136 KiB] *.C file Fig3c.pdf [16 KiB] HiDef png [155 KiB] Thumbnail [128 KiB] *.C file Fig3d.pdf [16 KiB] HiDef png [153 KiB] Thumbnail [125 KiB] *.C file Animated gif made out of all figures. PAPER-2012-014.gif Thumbnail

## Tables and captions

 Summary of the measured $B^0_s\rightarrow J/\psi \overline{ K }{} ^{*0}$ angular properties and their statistical and systematic uncertainties. Table_1.pdf [57 KiB] HiDef png [93 KiB] Thumbnail [44 KiB] tex code 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. Table_2.pdf [54 KiB] HiDef png [56 KiB] Thumbnail [26 KiB] tex code Parameter values and errors for $\frac{ {\cal B}(B^0_s\rightarrow J/\psi \overline{ K }{} ^{*0} ) }{ {\cal B}( B ^0 \rightarrow J/\psi K^{*0}) }$. Table_3.pdf [85 KiB] HiDef png [80 KiB] Thumbnail [39 KiB] tex code

Created on 17 August 2019.Citation count from INSPIRE on 23 August 2019.