We predict that triangle singularities of hadron spectroscopy are strongly
affected in heavy ion collisions. To do it we examine various effects of finite
temperature on the triangle loop yielding the singularity within the hadron
phase. Pion-containing triangles can be enhanced by exchanging them with the
medium, but in other cases, especially with heavy-quark hadrons, known thermal
effects over the particles mass and width can quickly reduce the singularity:
at temperatures of about 150 MeV, below the transition to a quark-gluon plasma,
even by two orders of magnitude. It appears that peaks seen in central heavy
ion collisions are more likely to be hadrons than rescattering effects unless
perhaps if a pion is involved in the triangle. The medium then acts as a
spectroscopic filter.Comment: 5 pages, 7 plot
