Model for anomalous $\Upsilon'' \to \Upsilon \pi \pi$ transition with account of chiral phase shift in hadron bag of quarkonium

Abstract

We assume that a rather large bag of the $\Upsilon''(3S b\bar b)$ heavy quarkonium is in the phase of spontaneously broken chiral symmetry, in contrast to the $\Upsilon(1S b \bar b)$ hadron bag, having small size and being in the phase of exact chiral symmetry, so that the shift of the phases in the $\Upsilon'' \to \Upsilon \pi \pi$ transition is the additional source for the $\pi\pi$ pairs. This source causes an anomalous $\pi\pi$ invariant mass distribution, which is experimentally observed.