The 2011 PbPb run was the run for rare physics and pushing the boundaries of what can be measured and high precision. With an arsenal of dedicated triggers we showed a whole range of interesting new results at this years Quark Matter conference.
By looking at the top 0.01% of collisions which deposited the highest amount of energy in our detector we selected almost fully overlapping nuclear geometries. Measuring the fourier spectra of these collisions with the tight geometric control we provide some of the best constraints to the viscosity of the hot quark gluon plasma produced at the LHC.
By selecting jets and high momentum tracks right as the collisions occur in the machine, we have aquired and analyzed a dataset that paints a comprehensive picture of jet quenching and parton energy loss from many angles. We showed the azimuthal anisotropy of charged particles of momentum above 20 GeV/c up to 60 GeV/c which probes the path length dependence of energy loss in the quark gluon plasma. We showed a complete picture of particle suppresion in PbPb compared to proton proton collisions for both charged particles and jets, as well as bottom quarks through j/psi’s and tagged jets, which all show significant suppression. However bosons which don’t interact strongly with the medium have been measured to have no significant suppression compared to proton proton, in the isolated photon, and W and Z channels.
We have shown the direct energy loss of colored partons traversing the medium by precisely measuring the initial energy of the outgoing photon in gamma-jet events. In addition we have studied the detailed structure the constituents of jets both in momentum and angular redistributions compared to similar jets found in proton proton collisions. These measurements further probe in what ways the quark gluon plasma responds to high energy particles.