Study of $\Upsilon(10753)$ decays to $\pi^+ \pi^{\mathstrut -}\Upsilon(nS)$ final states at Belle II

Abstract We present an analysis of the process $e^{+}e^{-}\to\pi^{+}\pi^{-}\Upsilon(nS)$ (where $n$ = 1, 2, or 3) reconstructed in $19.6\rm$$\rm fb^{-1}$ of Belle II data during a special run of the SuperKEKB collider at four energy points near the peak of the $\Upsilon(10753)$ resonance. By analyzing the mass distribution of the $\pi^+\pi^-\Upsilon(nS)$ system and the Born cross sections of the $e^{+}e^{-}\to\pi^{+}\pi^{-}\Upsilon(nS)$ process, we report the first observation of $\Upsilon(10753)$ decays to the $\pi^{+}\pi^{-}\Upsilon(1S)$ and $\pi^{+}\pi^{-}\Upsilon(2S)$ final states, and find no evidence for decays to $\pi^{+}\pi^{-}\Upsilon(3S)$. Possible intermediate states in the $\pi^+\pi^-\Upsilon(1S,2S)$ transitions are also investigated, and no evidence for decays proceeding via the $\pi^\mp Z_b^\pm$ or $f_0(980)\Upsilon(nS)$ intermediate states is found. We measure Born cross sections for the $e^{+}e^{-}\to\pi^{+}\pi^{-}\Upsilon(nS)$ process that, combined with results from Belle, improve the precision of measurements of the $\Upsilon(10753)$ mass and width by nearly a factor of two to $(10756.3\pm2.7\pm0.6)$ MeV/$c^2$ and $(29.7\pm8.5\pm1.1)$ MeV, respectively. The relative ratios of the Born cross sections at the $\Upsilon(10753)$ resonance peak are also reported for the first time.
Tags
Working group Quarkonium
Principal authors @  Bryan Fulsom, Junhao Yin
Reference JHEP 07, 116 (2024), DOI: 10.1007/JHEP07(2024)116
Document BELLE2-PUB-PH-2023-009
Links arXiv:2401.12021, Inspire, JHEP
Bibtex 
@article{Belle-II:2024mjm,
    author = "Adachi, I. and others",
    collaboration = "Belle-II",
    title = "{Study of {\ensuremath{\Upsilon}}(10753) decays to {\ensuremath{\pi}}$^{+}${\ensuremath{\pi}}$^{−}${\ensuremath{\Upsilon}}(nS) final states at Belle II}",
    eprint = "2401.12021",
    archivePrefix = "arXiv",
    primaryClass = "hep-ex",
    doi = "10.1007/JHEP07(2024)116",
    journal = "JHEP",
    volume = "07",
    pages = "116",
    year = "2024"
}