Sequential single pion production explaining the dibaryon d*(2380) peak

In this study, we investigate the two step sequential one pion production mechanism, that is, np(I=0)->pi(-)pp followed by the fusion reaction pp ->pi(+)d, to describe the np ->pi(+)pi(-)d reaction with in state I = 0 . In this reaction, a narrow peak identified with a d(2380) dibaryon has been previously observed. We discover that the second reaction step pp ->pi(+)d 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.

Automated summary

In this study, we investigate the mechanism of the np ->pi(+)pi(-)d reaction through the sequential steps of np(I=0)->pi(-)pp and pp ->pi(+)d. The narrow peak observed in this reaction, identified as a d(2380) dibaryon, is explained by a triangle singularity driving the second reaction step pp ->pi(+)d, determining the position and high strength of the peak. The combined cross section of these two mechanisms successfully reproduces the experimental observations of the peak under the applied approximations, providing a novel explanation for why it has not been detected in other reactions.