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November 17, 2010


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 s NN=2.76\sqrt{s_{NN}}= 2.76 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 s NN=200\sqrt{s_{NN}}= 200 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 v 2v_2, integrated over p tp_t). v 2v_2 is the coefficient of cos(2ϕ)\cos(2\phi) in a Fourier series of the azimuthal dependence of the particle multiplicity produced in the collision; the larger v 2v_2, the stronger the elliptic flow.

Posted by distler at 11:31 PM | Permalink | Followups (13)