The Future of Quark Matter at RHIC

The matter discovered at RHIC has shown a number of very surprising properties. It is extremely dense and has an initial energy density well above that expected for the phase transition from ordinary hadronic matter into quark gluon plasma. [1–4] The dense matter is very opaque to colored particles, such as quarks or gluons, traversing it. This gives rise to the striking jet quenching observed at RHIC. [5,6]. Measurements of the elliptic flow of different hadrons indicate that the plasma at RHIC is a liquid with extremely low viscosity. [1–4] Furthermore, there is substantial evidence that hadron formation results from coalescence of constituent quarks from the collectively flowing medium. [7] It is natural to ask how this hot, dense partonic liquid transports particles, energy, momentum and charge. This means we should determine its diffusion constant, thermal conductivity, viscosity and (color)electric conductivity. Extracting such quantities quantitatively requires significant advances in both fundamental theory and phenomenology. Of course, these must be accompanied by extensive, high precision measurements. In this paper, we will discuss how increased luminosity at RHIC, along with upgraded detector capabilities, will probe how this new kind of plasma works. Upgrading the luminosity at RHIC is compelled by two kinds of questions. There are basic questions which for which we don’t yet have sufficient data. And there are entirely new questions, which arose from the initial discoveries at RHIC. Such new questions include: