Quark Matter 2009 Highlights

The 21st International Conference on Ultrarelativistic Nucleus-Nucleus Collisions, colloquially referred to as Quark Matter 2009, took place in Knoxville, Tennessee from March 30th to April 4th, 2009. (more…)


Over the past few months a new initiative, called Theory-Experiment Collaboration for Hot QCD Matter (TECHQM), has taken shape, which potentially will have great impact on how our community arrives at scientific conclusions on the nature and properties of hot and dense QCD matter created at the RHIC and LHC facilities. (more…)

The Virtue of Being Virtual

The photon that left your computer screen and just hit your retina now certainly was a ‘real’ photon. Right? Well, not so fast. Sketch the Feynman diagram for the process. The photon was emitted by an atom in the screen, and absorbed by an atom in your retina. The diagram is indistinguishable from that for a virtual process- it’s all a matter of scale. (more…)

What is “reco” scaling?

Over the past 1-2 years some confusion has entered the field as to what exactly constitutes the elliptic flow scaling law predicted by the parton recombination models. (more…)

Scaling and Non-Scaling of Elliptic Flow

The detailed dependence of the elliptic flow parameter v2 on the particle masses and transverse momentum has provided strong evidence for the applicability of hydrodynamics for describing the bulk motion of final-state particles at RHIC. (For a partial list of references, see the Hydro Primer elsewhere in this journal.) Equally intriguing have been various scaling patterns observed in the flow data: The separate curves v2(pT,m) for different mass particles are substantially more alike when studied versus “transvese kinetic energy” KET = mT -m. Plotting v2 as as a function of KET collapses the data into one curve for KET < 1 GeV, while showing two distinct branches for mesons and baryons for larger values of KET. These two branches collapse into one curve when both v2 and KET are divided by the quark content nq (2 for mesons, 3 for baryons). (more…)

The One That Started It All

The one that started it all was the first experimental paper from RHIC. (more…)