A discussion on the anomalous threshold enhancement of – couplings and peak*

Abstract

Abstract The attractive interaction between and has to be strong enough if X(6900) is of the molecule type. We argue that since decays predominantly into a pair, the interactions between and may be significantly enhanced owing to the three point loop diagram. The enhancement originates from the anomalous threshold located at GeV , whose effect propagates into the s-channel partial wave amplitude in the vicinity of GeV. This effect may be helpful in the formation of the peak.