New phases of QCD, the tricritical point, and RHIC as a ``nutcracker''

TL;DR

This paper discusses new phases of QCD including color superconductivity, the tricritical point's signatures, and RHIC collision flow, highlighting novel phenomena and potential experimental indicators.

Contribution

It introduces the concept of instanton-induced diquark formation, explores the tricritical point's fluctuations, and presents novel flow patterns like the 'nutcracker' in RHIC collisions.

Findings

Instanton effects can induce scalar diquarks and new QCD phases.

Sigma exchange fluctuations may help locate the tricritical point.

Lattice-inspired EOS leads to a 'nutcracker' shell formation in RHIC flow.

Abstract

Because too many interesting things are going on now, I have tried to squeeze three different subjects into one talk. The first is a brief summary of the color super-conductivity. During the last year we learned that instanton-induced forces can not only break chiral symmetry in the QCD vacuum, but also create correlated scalar diquarks and form new phases,some similar to the Higgs phase of the Standard model. The second issue I discuss is the remnant of the so called $tricritical$ point, which in QCD with physical masses is the endpoint of the first order transition. I will argue that exchange of sigmas (which are massless at this point even with quark masses included) create interesting event-by-event fluctuations, which can be used to locate it. Finally I describe first results on $flow$ calculations for non-central collisions at RHIC. It was found that it is extremely sensitive to Equation of State (EOS). Furthermore, the unusual ``nutcracker'' picture emerges for lattice-motivated EOS, which is formation of two $shells$ which are physically separated $before$ the freeze-out.