Jet and flow for small system
Speaker: Urs Wiedemann (CERN)
Time: Jun. 8(Tuesday) 6:00am (San Fransisco), 9:00am (New York), 3:00pm (Frankfurt), 6:30pm(New Delhi), 9:00pm (Beijing), 10:00pm (Tokyo)
Abstract:
As a function of system size and center-of-mass energy, signatures of collectivity are known to arise smoothly and without any sharp threshold in ultra-relativistic proton-proton (pp), proton-nucleus and nucleus-nucleus collisions (AA). Yet, the physics concepts invoked in phenomenological descriptions of the smallest (pp) and the largest (central AA) hadronic collision systems are maximally different. Our baseline picture of pp collisions is a free-streaming but fragmenting partonic system in which final state interactions may be treated as perturbations. Our baseline picture of central heavy ion collisions is a perfect fluid, deviations of which are parametrized in terms of dissipative fluid dynamic properties. Given that the size of the smallest and the largest collision systems differ by only one order of magnitude, and given that the entire size-dependence is experimentally accessible, there are strong motivations for developing a phenomenological description that smoothly interpolates between almost free-streaming and almost perfect fluidity as a function of system size. In this talk, I discuss some of the resulting theoretical challenges and open experimental issues. I emphasize that such a phenomenological program can give access to some fundamental properties of hot QCD matter that escape a purely fluid-dynamic analysis of heavy ion data.
Chair: Jurgen Schukraft
ZOOM link: Please register here, the ZOOM link will be send in the comming Tuesday by group email. By attending this event you agree to the seminar and discussion being recorded and posted on the seminar web site.