Sequential single pion production explaining the dibaryon "d*(2380)" peak* *R. M. acknowledges support from a CIDEGENT program with Ref. CIDEGENT/2019/015 and from the Spanish national grant PID2019-106080GB-C21. N. I. recieved partial support from JSPS Overseas Research Fellowships and the JSPS KAKENHI Grant Number (JP19K14709). This study was also partly supported by the Spanish Ministerio de Economia y Competitividad and European

Abstract

In this study, we investigate the two step sequential one pion production mechanism, that is, followed by the fusion reaction , to describe the reaction with in state . In this reaction, a narrow peak identified with a "" dibaryon has been previously observed. We discover that the second reaction step is driven by a triangle singularity that determines the position of the peak of the reaction and the high strength of the cross section. The combined cross section of these two mechanisms produces a narrow peak with a position, width, and strength, that are compatible with experimental observations within the applied approximations made. This novel interpretation of the peak accomplished without invoking a dibaryon explains why this peak has remained undetected in other reactions.