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

TL;DR

This paper measures the decay rates of the $5S$ state into final states with $J/ psi$ or $ 2S$ and searches for exotic $XYZ$ states, setting upper limits on their production in $5S$ decays.

Contribution

It provides improved measurements of $5S$ decay branching fractions and the first search for $XYZ$ states in $5S$ decays, establishing upper limits on their production.

Findings

Branching fraction for $5S o J/ psi +$ anything: (5.25 ± 0.13(stat) ± 0.25(syst))×10⁻⁴

Branching fraction for $5S o 2S +$ anything: (1.23 ± 0.17(stat) ± 0.11(syst))×10⁻⁴

No significant signals for $XYZ$ states in $5S$ decays, upper limits set.

Abstract

The branching fractions of the $\Upsilon(1S)$ inclusive decays into final states with a $J/\psi$ or a $\psi(2S)$ are measured with improved precision to be $\BR(\Upsilon(1S)\to J/\psi + {\rm anything})=(5.25\pm 0.13(\mathrm{stat.})\pm 0.25(\mathrm{syst.}))\times 10^{-4}$ and $\BR(\Upsilon(1S)\to \psi(2S) + {\rm anything})=(1.23\pm 0.17(\mathrm{stat.})\pm 0.11(\mathrm{syst.}))\times 10^{-4}$. The first search for $\Upsilon(1S)$ 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 $\Upsilon(1S)$ inclusive decays are determined.