SEMINAR

Strangeness and causality constraint in heavy ion collision

Paolo Castorina

(Physics and Astronomy Depart., Uni. Catania, Italy)

Sala PA1, IST, Pavilhão de Matemática
Wednesday, April 2nd, 2014 at 04:00 PM

Abstract

The thermal multihadron production observed in different high energy collisions poses many basic problems: why do even elementary, e+ e-; and hadron-hadron, collisions show thermal behaviour? Why is there in such interactions a suppression of strange particle production? Why does the strangeness sup pression almost disappear in relativistic heavy ion collisions? Why in these collisions is the thermalization time less than ~ 0.5 fm/c? The recently proposed mechanism of thermal hadron production through Hawking-Unruh radiation can naturally answer the previous questions. Indeed, the interpretation of quark-antiquark pairs production, by the sequential string breaking, as tunneling through the event horizon of colour confinement leads to thermal behavior with a universal temperature, T ~ 170 Mev,related to the quark acceleration, a, by T = a/2?. The resulting temperature depends on the quark mass and then on the content of the produced hadrons, causing a deviation from full equilibrium and hence a suppression of strange particle production in elementary collisions. In nucleus-nucleus collisions, where the quark density is much bigger, one has to introduce an average temperature (acceleration) which dilutes the quark mass effect and the strangeness suppression almost disappears.