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

2024/01/22 by Belle II Collaboration, Adachi, I., Aggarwal, L. +393 · 1 citation
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex)

paper · doi:10.48550/arxiv.2401.12021

Abstract

We present an analysis of the process e⁺e^-→π⁺π^-Υ(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 Υ(10753) resonance. By analyzing the mass distribution of the π⁺π^-Υ(nS) system and the Born cross sections of the e⁺e^-→π⁺π^-Υ(nS) process, we report the first observation of Υ(10753) decays to the π⁺π^-Υ(1S) and π⁺π^-Υ(2S) final states, and find no evidence for decays to π⁺π^-Υ(3S). Possible intermediate states in the π⁺π^-Υ(1S,2S) transitions are also investigated, and no evidence for decays proceeding via the π^∓ Z_b^± or f₀(980)Υ(nS) intermediate states is found. We measure Born cross sections for the e⁺e^-→π⁺π^-Υ(nS) process that, combined with results from Belle, improve the precision of measurements of the Υ(10753) mass and width by nearly a factor of two to (10756.3±2.7±0.6) MeV/c² and (29.7±8.5±1.1) MeV, respectively. The relative ratios of the Born cross sections at the Υ(10753) resonance peak are also reported for the first time.

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