November 17, 2010
Alice!
Tonight, the ALICE collaboration released their first paper. This must be something of a record, as they just started observing Pb-Pb collisions on Nov. 7.
They’ve observed elliptic flow at center-of-mass-energy/nucleon-pair TeV. For those who were sceptical, the quark-gluon plasma is still a strongly-coupled liquid, with very low shear viscosity, at LHC energies — more than a order of magnitude larger than the GeV at RHIC.
As with the proton-proton experiments, they are currently operating at only half the design energy. But, unlike proton-proton, which beat the Tevatron by only a modest factor, the heavy-ion experiments are already probing energies an order-of-magnitude larger than those seen at RHIC.
Below is one of their plots (for , integrated over ). is the coefficient of in a Fourier series of the azimuthal dependence of the particle multiplicity produced in the collision; the larger , the stronger the elliptic flow.