Collectivity of the electromagnetic transitions in near-threshold resonances

TL;DR

This paper explores how coupling through decay channels causes near-threshold resonances to form collective states, affecting their electromagnetic decay properties, exemplified by B(EL) decays in 14C.

Contribution

It introduces a generic mechanism explaining collectivity in open quantum systems and extends the Ikeda diagram to include cluster correlations near decay thresholds.

Findings

Near-threshold states exhibit collective behavior due to channel coupling.

Electromagnetic decay patterns are influenced by this collectivity.

The mechanism is demonstrated with B(EL) decays in 14C.

Abstract

Mixing of the shell model (SM) eigenstates due to the coupling via the common decay channel leads in many cases to the formation of a collective eigenstate which carries many features of the nearby decay channel. This generic mechanism in open quantum systems explains the phenomenological Ikeda diagram and generalizes it for various clusters/correlations in the vicinity of the respective cluster decay thresholds. The near-threshold collectivization of the SM states may also influence their electromagnetic decays. We discuss this phenomenon on the example of B(EL) decays of near-threshold 2+ states in 14C.