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Study of $D^{(*)+}_{sJ}$ mesons decaying to $D^{*+} K^0_{\rm S}$ and $D^{*0} K^+$ final states

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Abstract

A search is performed for $D^{(*)+}_{sJ}$ mesons in the reactions $pp \to D^{*+} K^0_{\rm S} X$ and $pp \to D^{*0} K^+ X$ using data collected at centre-of-mass energies of 7 and 8 TeV with the LHCb detector. For the $D^{*+} K^0_{\rm S}$ final state, the decays $D^{*+} \to D^0 \pi^+$ with $D^0 \to K^- \pi^+$ and $D^0 \to K^- \pi^+ \pi^+ \pi^-$ are used. For $D^{*0} K^+$, the decay $D^{*0} \to D^0 \pi^0$ with $D^0 \to K^- \pi^+$ is used. A prominent $D_{s1}(2536)^+$ signal is observed in both $D^{*+} K^0_{\rm S}$ and $D^{*0} K^+$ final states. The resonances $D^*_{s1}(2700)^+$ and $D^*_{s3}(2860)^+$ are also observed, yielding information on their properties, including spin-parity assignments. The decay $D^*_{s2}(2573)^+ \to D^{*+} K^0_{\rm S}$ is observed for the first time, at a significance of 6.9 $\sigma$, and its branching fraction relative to the $D^*_{s2}(2573)^+ \to D^+ K^0_{\rm S}$ decay mode is measured.

Figures and captions

Distributions of $ D ^0 \pi ^+ $ invariant mass for (a) $ D ^0 \rightarrow K ^- \pi ^+ $ and (b) $ D ^0 \rightarrow K ^- \pi ^+ \pi ^+ \pi ^- $ . $\pi ^+ \pi ^- $ mass spectrum for (c) long and (d) downstream $ K ^0_{\mathrm{ \scriptscriptstyle S}}$ . The full (red) lines describe the fitting function. The dashed lines show the background contributions and the vertical dotted lines indicate the signal regions.

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Distribution of $\Delta m( D ^0 \pi ^0 )$ invariant mass. The full (red) line describes the fitting function. The dashed line shows the background contribution and the dotted vertical lines define the $D^{*0}$ signal region.

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Distribution of the $ D ^{*+} K ^0_{\mathrm{ \scriptscriptstyle S}} $ invariant mass for $ D ^0 \rightarrow K ^- \pi ^+ $ decay. The full (red) line describes the fitting function. The dashed line displays the fitted background and the dotted lines the $ D_{s1}(2536)^{+}$ , $ D^*_{s2}(2573)^{+}$ , $ D^*_{s1}(2700)^+$ , $ D_{sJ}^{*}(2860)^+$ and $ D_{sJ}(3040)^+$ contributions. The inset displays the $ D ^{*+} K ^0_{\mathrm{ \scriptscriptstyle S}} $ mass spectrum after subtracting the fitted background.

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Mass spectrum of $ D ^{*+} K ^0_{\mathrm{ \scriptscriptstyle S}} $ candidates for $ D ^0 \rightarrow K ^- \pi ^+ $ in (a) the NP sample, and (b) the UP sample. The full (red) lines describe the fitting function. The dashed lines show the fitted background and the dotted lines the $ D^*_{s2}(2573)^{+}$ , $ D^*_{s1}(2700)^+$ , $ D_{sJ}^{*}(2860)^+$ and $ D_{sJ}(3040)^+$ contributions. The insets display the $ D ^{*+} K ^0_{\mathrm{ \scriptscriptstyle S}} $ mass spectrum after subtracting the fitted background.

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Mass spectrum of (a) $ D ^{*+} K ^0_{\mathrm{ \scriptscriptstyle S}} $ candidates for $ D ^0 \rightarrow K ^- \pi ^+ \pi ^+ \pi ^- $ , and (b) $ D ^{*0} K ^+ $ candidates for the NP sample. The full (red) lines describe the fitting function. The dashed lines show the fitted background and the dotted lines the $ D^*_{s2}(2573)^{+}$ , $ D^*_{s1}(2700)^+$ , $ D_{sJ}^{*}(2860)^+$ and $ D_{sJ}(3040)^+$ contributions. The insets display the $ D ^{*+} K ^0_{\mathrm{ \scriptscriptstyle S}} $ and $ D ^{*0} K ^+ $ mass spectra after subtracting the fitted background.

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Distribution of the invariant mass of $ D ^+ K ^0_{\mathrm{ \scriptscriptstyle S}} $ candidates from Ref. [10]. The full (red) line is the result from the fit described in the text. The dashed line indicates the fitted background and the dotted line shows the fitted $ D^*_{s2}(2573)^{+}$ contribution.

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Mass spectra, in the $ D_{s1}(2536)^{+}$ mass region, for the NP sample of (a) $ D ^{*+} K ^0_{\mathrm{ \scriptscriptstyle S}} $ with $ D ^0 \rightarrow K ^- \pi ^+ $ , (b) $ D ^{*+} K ^0_{\mathrm{ \scriptscriptstyle S}} $ with $ D ^0 \rightarrow K ^- \pi ^+ \pi ^+ \pi ^- $ , and (c) $ D ^{*0} K ^+ $ final states. The full (red) lines describe the fitting function. The dashed lines show the fitted background and the dotted lines the $ D^*_{s2}(2573)^{+}$ contributions. The insets display the $ D ^* K$ mass spectra after subtracting the fitted background.

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Distributions of the measured signal yields for (a) $ D_{s1}(2536)^{+}$ and (b) $ D^*_{s2}(2573)^{+}$ as a function of the helicity angle $\cos\theta_{\rm H}$ . The distributions are fitted with UP (a) and NP (b) functions.

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Distributions of the measured signal yields for (a) $ D^*_{s1}(2700)^+$ , (b) $ D_{sJ}^{*}(2860)^+$ and (c) $ D_{sJ}(3040)^+$ as a function of the helicity angle $\cos\theta_{\rm H}$ . The distributions are fitted with NP (a,b) and UP (c) functions.

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Tables and captions

Results from the fits to the $ D ^{*+} K ^0_{\mathrm{ \scriptscriptstyle S}} $ and $ D ^{*0} K ^+ $ mass spectra. Resonances parameters are expressed in $\mathrm{ Me V}$ . When two uncertainties are presented, the first is statistical and the second systematic. The symbol ndf indicates the number of degrees of freedom.

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Contributions (in $\mathrm{ Me V}$ ) to the systematic uncertainties on the $ D^*_{s1}(2700)^+ $ and $ D_{sJ}^{*}(2860)^+ $ resonances parameters.

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Results from the fits to the $ D ^+ K ^0_{\mathrm{ \scriptscriptstyle S}} $ and $ D ^{*+} K ^0_{\mathrm{ \scriptscriptstyle S}} $ mass spectra for the evaluation of the $ D^*_{s2}(2573)^{+} \rightarrow D ^{*+} K ^0_{\mathrm{ \scriptscriptstyle S}} $ relative branching fraction.

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Measurements used to evaluate the $ D^*_{s2}(2573)^{+}$ relative branching fraction $\cal B ( D^*_{s2}(2573)^{+} \rightarrow D ^{*+} K ^0_{\mathrm{ \scriptscriptstyle S}} )/\cal B ( D^*_{s2}(2573)^{+} \rightarrow D ^+ K ^0_{\mathrm{ \scriptscriptstyle S}} )$.

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Relative systematic uncertainties in the evaluation of the ratio of branching fractions $\cal R$ .

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Values of $\chi^2/{\rm ndf}$ from the fits to the helicity angles distributions.

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Created on 19 October 2019.