Puzzles in quarkonium hadronic transitions with two pion emission

TL;DR

This paper investigates unusual rates in quarkonium hadronic transitions involving two pions using QCD multipole expansion and a constituent quark model, explaining anomalies through hybrid states and molecular components.

Contribution

It introduces a calculation of hybrid intermediate states within an extended constituent quark model to explain anomalous transition rates.

Findings

Hybrid states near resonance masses explain some anomalies.

Molecular components in wave functions justify other anomalies.

Unexpected results highlight complex transition mechanisms.

Abstract

The anomalously large rates of some hadronic transitions from quarkonium are studied using QCD multipole expansion (QCDME) in the framework of a constituent quark model which has been successful in describing hadronic phenomenology. The hybrid intermediate states needed in the QCDME method are calculated in a natural extension of our constituent quark model based on the Quark Confining String (QCS) scheme. Some of the anomalies are explained due to the presence of an hybrid state with a mass near the mass of the decaying resonance whereas other are justified by the presence of molecular components in the wave function. Some unexpected results are pointed out.