Search for $XYZ$ states in $\mathrm{\Upsilon }(1S)$ inclusive decays

The branching fractions of the $\mathrm{\Upsilon }(1S)$ inclusive decays into final states with a $J/\psi$ or a $\psi (2S)$ are measured with improved precision to be $\mathcal{B}(\mathrm{\Upsilon }(1S)\to J/\psi +\text{anything})=(5.25\pm 0.13(\mathrm{stat})\pm 0.25(\mathrm{syst}))\times {10}^{-4}$ and $\mathcal{B}(\mathrm{\Upsilon }(1S)\to \psi (2S)+\text{anything})=(1.23\pm 0.17(\mathrm{stat})\pm 0.11(\mathrm{syst}))\times {10}^{-4}$. The first search for $\mathrm{\Upsilon }(1S)$ decays into $XYZ$ states that decay into a $J/\psi$ or a $\psi (2S)$ plus one or two charged tracks yields no significant signals for $XYZ$ states in any of the examined decay modes, and upper limits on their production rates in $\mathrm{\Upsilon }(1S)$ inclusive decays are determined.

Figure 1

Invariant mass distributions of the $J/\psi (\to {\ell }^{+}{\ell }^{-})$ (left column), $\psi (2S)(\to {\ell }^{+}{\ell }^{-})$ (middle column), and $\psi (2S)(\to {\pi }^{+}{\pi }^{-}J/\psi )$ (right column) candidates in the entire $x$ region (top row) and for $x$ bins of size 0.2 (remaining rows). The points with error bars are for the $\mathrm{\Upsilon }(1S)$ data sample; the shaded histograms are the continuum contributions scaled from the $\sqrt{s}=10.52\mathrm{GeV}$ data sample. The solid lines are the best fit with the total fitted background components represented by the dashed lines. The $J/\psi$ and $\psi (2S)$ signal regions used for the $XYZ$ searches are indicated by the arrows in the top-row plots.

Figure 2

Differential branching fractions for $\mathrm{\Upsilon }(1S)$ inclusive decays into the $J/\psi$ and $\psi (2S)$ versus the scaled momentum $x$ defined in the text. For each point, the error is the sum of the statistical and systematic errors.

Figure 3

The ${\pi }^{+}{\pi }^{-}J/\psi$ invariant mass distributions for the (a) lower- and (b) higher-mass regions; the (c) ${\pi }^{+}{\pi }^{-}\psi (2S)(\to {\ell }^{+}{\ell }^{-})$ and (d) ${\pi }^{+}{\pi }^{-}\psi (2S)(\to {\pi }^{+}{\pi }^{-}J/\psi )$ invariant mass distributions. The points with error bars are the $\mathrm{\Upsilon }(1S)$ events and the shaded histograms are the scaled continuum contributions determined from the data sample collected at $\sqrt{s}=10.52\mathrm{GeV}$. The solid lines are the best fits with the total background components represented by the dashed lines.

Figure 4

Invariant mass distributions of the (a) $K^{+}{K}^{-}J/\psi$, (b) $K^{+}{K}^{-}\psi (2S)(\to {\ell }^{+}{\ell }^{-})$, and (c) $K^{+}{K}^{-}\psi (2S)(\to {\pi }^{+}{\pi }^{-}J/\psi )$ candidates in $\mathrm{\Upsilon }(1S)$ inclusive decays. The points with error bars are the $\mathrm{\Upsilon }(1S)$ events and the slant-shaded histograms are the scaled continuum contributions with the data sample collected at $\sqrt{s}=10.52\mathrm{GeV}$ which overlie the normalized $\psi (2S)$ mass sideband backgrounds (the cross-shaded histograms) for the two $\psi (2S)$ decay modes. The solid line in panel (a) is the best fit with the fitted total background component represented as a dashed line.

Figure 5

Invariant mass distributions of the (a) $\varphi J/\psi$, (b) $\varphi \psi (2S)(\to {\ell }^{+}{\ell }^{-})$, and (c) $\varphi \psi (2S)(\to {\pi }^{+}{\pi }^{-}J/\psi )$ candidates in $\mathrm{\Upsilon }(1S)$ inclusive decays. The points with error bars are events observed at the $\mathrm{\Upsilon }(1S)$ peak, and the slant-shaded histograms are the scaled continuum contributions from the $\sqrt{s}=10.52\mathrm{GeV}$ continuum data sample which overlie the normalized $\psi (2S)$ mass sideband backgrounds (the cross-shaded histograms) for the two $\psi (2S)$ decay modes. The solid line in panel (a) is the best fit for the $\varphi J/\psi$ mass spectrum and the dashed line is the total fitted background.

Figure 6

Invariant mass distributions of the (a) ${\pi }^{\pm }J/\psi$, (b) ${\pi }^{\pm }\psi (2S)(\to {\ell }^{+}{\ell }^{-})$, and (c) ${\pi }^{\pm }\psi (2S)(\to {\pi }^{+}{\pi }^{-}J/\psi )$ candidates in $\mathrm{\Upsilon }(1S)$ inclusive decays. The points with error bars are the $\mathrm{\Upsilon }(1S)$ events and the shaded histograms are the scaled continuum contributions with the data sample collected at $\sqrt{s}=10.52\mathrm{GeV}$. The solid lines are the best fits with the fitted total background components represented by the dashed lines.

Figure 7

The (a) $K^{\pm }J/\psi$, (b) $K^{\pm }\psi (2S)(\to {\ell }^{+}{\ell }^{-})$, and (c) $K^{\pm }\psi (2S)(\to {\pi }^{+}{\pi }^{-}J/\psi )$ mass distributions for candidate events in the $\mathrm{\Upsilon }(1S)$ peak decay sample. The points with error bars are the $\mathrm{\Upsilon }(1S)$ events and the slant-shaded histograms are the scaled continuum contributions determined from the data collected at $\sqrt{s}=10.52\mathrm{GeV}$. The normalized $\psi (2S)$ mass-sideband events are shown as the cross-shaded histograms. The solid line in panel (a) is the best fit with the fitted total background component represented by the dashed line.