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Observation of $B^0_s\rightarrow\chi_{c1}\phi$ decay and study of $B^0\rightarrow\chi_{c1,2}K^{*0}$ decays

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Abstract

The first observation of the decay $B^0_s\rightarrow\chi_{c1}\phi$ and a study of $B^0\rightarrow\chi_{c1,2}K^{*0}$ decays are presented. The analysis is performed using a dataset, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. The following ratios of branching fractions are measured: \begin{equation*} \begin{array}{lll} \dfrac{\cal{B}(B^0_s\rightarrow\chi_{c1}\phi)}{\cal{B}(B^0_s\rightarrow J/\psi\phi)} &=& (18.9 \pm1.8\,(stat)\pm1.3\,(syst)\pm0.8\,(\cal{B})) \times 10^{-2}, \nonumber \\ {} \dfrac{\cal{B}(B^0\rightarrow\chi_{c1}K^{*0})}{\cal{B}(B^0\rightarrow J/\psiK^{*0})} &=& (19.8 \pm1.1\,(stat)\pm1.2\,(syst)\pm0.9\,(\cal{B})) \times 10^{-2}, \nonumber \\ {} \dfrac{\cal{B}(B^0\rightarrow\chi_{c2}K^{*0})}{\cal{B}(B^0\rightarrow\chi_{c 1}K^{*0})} &=& (17.1 \pm5.0\,(stat)\pm1.7\,(syst)\pm1.1\,(\cal{B})) \times 10^{-2}, \nonumber \\ {} \end{array} \end{equation*} \noindent where the third uncertainty is due to the limited knowledge of the branching fractions of ${\chi_{c}\rightarrow J/\psi \gamma}$ modes.

Figures and captions

Leading-order tree level diagram for the $ B ^0 _{( s )}\rightarrow \chi _{ c } X $ decays.

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Invariant mass distributions for: (a) $ B ^0 \rightarrow \chi _{ c } K ^{*0} $ and (b) $ B ^0_ s \rightarrow \chi _{ c 1} \phi $ candidates with $\chi _{ c 1} $ mass constraint; (c) $ B ^0 \rightarrow \chi _{ c } K ^{*0} $ and (d) $ B ^0_ s \rightarrow \chi _{ c 1} \phi $ candidates with $\chi _{ c 2} $ mass constraint. The total fitted function (thick solid blue), signal for the $\chi _{ c 1} $ and $\chi _{ c 2} $ modes (thin green solid and dotted, respectively) and the combinatorial background (dashed blue) are shown.

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Background-subtracted invariant mass distributions for: (a) $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \gamma $ and (b) $ K ^+ \pi ^- $ final states from $ B ^0 \rightarrow \chi _{ c 1} K ^{*0} $ decays obtained with the $\chi _{ c 1}$ mass constraint applied to the $ B ^0 _{( s )}$ candidate invariant mass; (c) $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \gamma $ and (d) $ K ^+ \pi ^- $ final states from $ B ^0 \rightarrow \chi _{ c 2} K ^{*0} $ decays obtained with the $\chi _{ c 2}$ mass constraint applied to the $ B ^0 _{( s )}$ candidate invariant mass; (e) $ { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \gamma $ and (f) $ K ^+ K ^- $ final states from $ B ^0_ s \rightarrow \chi _{ c 1} \phi $ decays obtained with the $\chi _{ c 1}$ mass constraint applied to the $ B ^0 _{( s )}$ candidate invariant mass. The total fitted function (solid) and the non-resonant contribution (dotted) are shown.

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Invariant mass distributions for (a) $ B ^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^{*0} $ and (b) $ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi $. The total fitted function (thick solid blue), signal (thin solid green), the $ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^{*0} $ (green dotted) and the combinatorial background (dashed blue) are shown.

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Background-subtracted invariant mass distributions for (a) $ K ^+ \pi ^- $ combinations from $ B ^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} K ^{*0} $ decays and (b) $ K ^+ K ^- $ combination from $ B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \phi $ decays. The total fitted function (solid) and the non-resonant contribution (dotted) are shown.

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Animated gif made out of all figures.

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Tables and captions

Signal yields for the $ B $ decays.

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Total efficiencies for all decay modes. Uncertainties are statistical only and reflect the size of the simulation sample.

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Relative systematic uncertainties (in $\%$) on the ratio of branching fractions.

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Created on 09 December 2018.Citation count from INSPIRE on 09 December 2018.