Study of $Υ(10753)$ decays to $π^{+}π^{-}Υ(nS)$ final states at Belle II

Kavli Affiliate: T. Higuchi

| First 5 Authors: Belle II Collaboration, I. Adachi, L. Aggarwal, H. Ahmed, H. Aihara

| Summary:

We present an analysis of the process
$e^{+}e^{-}topi^{+}pi^{-}Upsilon(nS)$ (where $n$ = 1, 2, or 3)
reconstructed in $19.6rm$ $rm fb^{-1}$ 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
$e^{+}e^{-}topi^{+}pi^{-}Upsilon(nS)$ 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
$e^{+}e^{-}topi^{+}pi^{-}Upsilon(nS)$ 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 $(10756.3pm2.7pm0.6)$ MeV/$c^2$ and
$(29.7pm8.5pm1.1)$ MeV, respectively. The relative ratios of the Born cross
sections at the $Upsilon(10753)$ resonance peak are also reported for the
first time.

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