Published: 09 May 2017

A new appointment of the ALICE Journal Club, titled ‘Statistical hadronization and thermalization in high energy collisions’, will take place on Wednesday 17 May, from 3 to 5 pm.

Francesco Becattini, professor of Theoretical Physics at the University of Florence, Italy - and one of the major experts in this field - will give an overview of the main aspects and applications of the statistical hadronization model to elementary and relativistic heavy ion collisions. He will also discuss thermalization in the hot environment created in heavy-ion collisions.


Hadronization, the process of formation of hadrons out of quarks and gluons, is a fundamental process in all high-energy physics collisions. This process lies in the non-perturbative domain of QCD and thus it is not calculable from first principles. 

In heavy-ion collisions, hadronization occurs at the late stage of the expansion of a locally equilibrated medium (the QCD plasma) at the pseudo-critical transition temperature and it is thus believed to naturally generate hadrons from a locally thermally and chemically equilibrated source (hadronic black body). The model based on such assumptions, the Statistical Hadronization Model (SHM), provides indeed a very accurate prediction of particle abundances and spectra. However, the SHM is very successful in describing the relative particle abundances also in elementary collisions such as pp and even e+e-, where a locally equilibrated plasma is not expected and there is not enough time to achieve equilibration through post-hadronization collisions. This poses fundamental questions about the nature of the hadronization process as well as the thermalization mechanism in heavy-ion collisions. Why are particles "born in equilibrium", as supposed by Hagedorn?