$\Upsilon$ Dipion Transitions at Energies Near the $\Upsilon(4S)$

TL;DR

This study searches for dipion transitions between Upsilon resonances near the $S$ energy, setting upper limits on certain transitions and measuring cross-sections for others, enhancing understanding of bottomonium states.

Contribution

First measurement of upper limits on specific dipion transitions at the $S$ energy and cross-sections for radiative processes involving $S$ and $S$ resonances.

Findings

Upper limits on $S$ to $S$ and $S$ to $
S$ dipion transitions.

Measured cross-sections for $e^+e^- o S ext{ or }S$ with photon emission.

Observation of $S$ and $S$ to $
S$ transitions.

Abstract

Using a data sample collected with the CLEO II detector at CESR, we have searched for dipion transitions between pairs of $\Upsilon$ resonances at energies near the $\Upsilon(4S)$. We obtain upper limits $B(\Upsilon(4S)\to \Upsilon(2S)\pi^+\pi^-) < 3.9 \times 10^{-4}$ and $B(\Upsilon(4S)\to \Upsilon(1S)\pi^+\pi^-) < 1.2 \times 10^{-4}$. We also observe the transitions $\Upsilon(3S)\to \Upsilon(1S)$, $\Upsilon(3S)\to \Upsilon(2S)$, and $\Upsilon(2S)\to \Upsilon(1S)$, from which we measure the cross-sections for the radiative processes $e^+e^- \to \Upsilon(3S)\gamma$ and $e^+e^- \to \Upsilon(2S)\gamma$.