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Amplitude analysis of $B^{0}_{s} \rightarrow K^{0}_{\textrm{S}} K^{\pm}\pi^{\mp}$ decays

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Abstract

The first untagged decay-time-integrated amplitude analysis of $B^{0}_{s} \rightarrow K^{0}_{\textrm{S}} K^{\pm}\pi^{\mp}$ decays is performed using a sample corresponding to $3.0 $fb$^{-1}$ of $pp$ collision data recorded with the LHCb detector during 2011 and 2012. The data are described with an amplitude model that contains contributions from the intermediate resonances $K^{*}(892)^{0,+}$, $K^*_2(1430)^{0,+}$ and $K^*_0(1430)^{0,+}$, and their charge conjugates. Measurements of the branching fractions of the decay modes $B^{0}_{s} \rightarrow K^{*}(892)^{\pm}K^{\mp}$ and $B^{0}_{s} \rightarrow K^{*}(892)^{0}\overline{ K}{}^{0}, \overline{ K}{}^{*}(892)^{0}K^{0}$ are in agreement with, and more precise than, previous results. The decays $B^{0}_{s} \rightarrow K^*_0(1430)^{\pm} K^{\mp}$ and $B^{0}_{s} \rightarrow K^{*}_{0}(1430)^{0}\overline{ K}{}^{0}, \overline{ K}{}^{*}_{0}(1430)^{0}K^{0}$ are observed for the first time, each with significance over 10 standard deviations.

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Feynman diagrams for (top left) external tree, (top right) internal penguin and (bottom left) electroweak penguin contributions for $ B ^0_ s \rightarrow K ^+ K ^{*-} ( K ^{*+} K ^- )$ decays; and (bottom right) internal penguin amplitude for the $ B ^0_ s \rightarrow K ^{*0} \overline{ K }{} {}^0 ( K ^0 \overline{ K }{} {}^{*0} )$ decay mode. The electroweak penguin diagram for the $ B ^0_ s \rightarrow K ^{*0} \overline{ K }{} {}^0 ( K ^0 \overline{ K }{} {}^{*0} )$ channel is not shown; neither are diagrams corresponding to annihilation amplitudes. In each case, the first set of final-state particles (black) leads to the $ K ^0_{\mathrm{ \scriptscriptstyle S}} K ^+ \pi ^- $ final state, while the second set (blue) leads to $ K ^0_{\mathrm{ \scriptscriptstyle S}} K ^- \pi ^+ $.

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Invariant-mass distribution of candidates in data for the (left) $ K ^0_{\mathrm{ \scriptscriptstyle S}} K ^+ \pi ^- $ and (right) $ K ^0_{\mathrm{ \scriptscriptstyle S}} K ^- \pi ^+ $ final states. Components are detailed in the legend.

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Background-subtracted and efficiency-corrected Dalitz plot distributions for (left) $ K ^0_{\mathrm{ \scriptscriptstyle S}} K ^+ \pi ^- $ and (right) $ K ^0_{\mathrm{ \scriptscriptstyle S}} K ^- \pi ^+ $ final states. Boxes with a cross indicate negative values.

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Invariant-mass distributions for (top) $m( K ^\pm \pi ^\mp )$, (middle) $m( K ^0_{\mathrm{ \scriptscriptstyle S}} \pi ^\mp )$ and (bottom) $m( K ^0_{\mathrm{ \scriptscriptstyle S}} K ^\pm )$, for (left) the $ K ^0_{\mathrm{ \scriptscriptstyle S}} K ^+ \pi ^- $ and (right) the $ K ^0_{\mathrm{ \scriptscriptstyle S}} K ^- \pi ^+ $ final states. The data are shown with black points, while the full fit result is shown as a blue solid line with individual signal and background components as detailed in the legend.

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Animated gif made out of all figures.

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Tables and captions

Yields obtained from the simultaneous fit to the invariant-mass distribution of $ B ^0_ s \rightarrow K ^0_{\mathrm{ \scriptscriptstyle S}} K ^\pm \pi ^\mp $ candidates in data for each fit category: signal, combinatorial background and cross-feed from misidentified $ B ^0_{( s )} \rightarrow K ^0_{\mathrm{ \scriptscriptstyle S}} h ^+ h ^{\prime-} $ decays. The uncertainties given on the yields in the full range are statistical only. Yields in the signal region $\pm2.5\sigma$ around the $ B ^0_ s $ peak are also given; the determination of uncertainties on these values is described in Sec. 7.

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Results of the fit with the baseline model to the $ K ^0_{\mathrm{ \scriptscriptstyle S}} K ^+ \pi ^- $ and $ K ^0_{\mathrm{ \scriptscriptstyle S}} K ^- \pi ^+ $ Dalitz plots. The fit fractions associated with each resonant component are given with statistical uncertainties only. The sums of fit fractions for both $ K ^0_{\mathrm{ \scriptscriptstyle S}} K ^+ \pi ^- $ and $ K ^0_{\mathrm{ \scriptscriptstyle S}} K ^- \pi ^+ $ final states are 102%, corresponding to low net interference effects.

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Systematic uncertainties on the fit fractions, quoted as absolute uncertainties in percent. The columns give the contributions from each of the different sources described in the text.

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Created on 11 July 2020.