# Observation of a new structure near 10.75 GeV in the energy dependence of the $e^+e^-\to\Upsilon(nS)\pi^+\pi^-$ ($n=1,2,3$) cross sections

## TL;DR

This paper reports the discovery of a new resonance structure near 10.75 GeV in the energy dependence of certain bottomonium production cross sections, indicating a potential new state in the bottomonium spectrum.

## Contribution

The study provides the first observation of a new structure in the $e^+e^- oar{ ext{bottomonium}}$ cross sections with precise measurements of its mass and width, using data from the Belle detector.

## Key findings

- New structure observed at 10.75 GeV with 5.2 sigma significance.
- Measured mass of the new structure is approximately 10752.7 MeV/$c^2$.
- Width of the structure is approximately 35.5 MeV.

## Abstract

We report a new measurement of the $e^+e^-\to\Upsilon(nS)\pi^+\pi^-$ ($n=1,2,3$) cross sections at energies from 10.52 to 11.02 GeV using data collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We observe a new structure in the energy dependence of the cross sections; if described by a Breit-Wigner function its mass and width are found to be $M=(10752.7\pm5.9\,^{+0.7}_{-1.1})\,$MeV/$c^2$ and $\Gamma=(35.5^{+17.6}_{-11.3}\,^{+3.9}_{-3.3})\,$MeV, where the first error is statistical and the second is systematic. The global significance of the new structure including systematic uncertainty is 5.2 standard deviations. We also find evidence for the $e^+e^-\to\Upsilon(1S)\pi^+\pi^-$ process at the energy 10.52 GeV, which is below the $B\bar{B}$ threshold.