Theory Seminar - Raquel Molina

Speaker: Raquel Molina (University of Valencia)

Title: The observed dibaryon “d*(2380)” peak in n p -> pi- pi+ d

Abstract: We study the two step sequential one pion production mechanism, np(I = 0) -> pi- pp, followed by the fusion reaction pp -> pi+ d, in order to describe the np -> pi+ pi- d reaction with pi+ pi- in I = 0, where a narrow peak, so far identified with a “d*(2380)” dibaryon, has been observed. We find that the second step pp -> pi+ d is driven by a triangle singularity that determines the position of the peak of the reaction and the large strength of the cross section. The combined cross section of these two mechanisms produces a narrow peak with the position, width and strength compatible with the experimental observation within the approximations done. This novel interpretation of the peak without invoking a dibaryon explains why the peak is not observed in other reactions where it has been searched for.