2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/184162$π^+π^-$ transitions of heavy quarkonia, especially the $ Υ(3S)\toΥ(1S)π^+π^-$ decay process, are revisited. In the framework of the Chiral Unitary Theory (ChUT), the $S$ wave $ππ$ final state interaction (FSI) is included. It is found that when an additional intermediate state with $J^P=1^+$ and I=1 is introduced, not only the $ ππ$ invariant mass spectrum and the $cosθ_π^*$ distribution in the $Υ(3S)\toΥ(1S)π^+π^-$ process can simultaneously be well-explained, but also a consistent description for other bottomonia $ π^+π^-$ transitions can be obtained. As a consequence, the mass and the width of the intermediate state are predicted. From the quark content analysis, this state should be a $b\bar bq\bar q$ state.17 pages, 8 figures; misprints correctedHigh Energy Physics - Phenomenologytext