First Results from Pb+Pb Collisions at the LHC

Abstract

At the end of 2010, the CERN Large Hadron Collider started operation with heavy ion beams, colliding lead nuclei at a centre-of-mass energy of 2.76 TeV/nucleon and opening a new era in ultrarelativistic heavy ion physics at energies exceeding previous accelerators by more than an order of magnitude. This review summarizes the results from the first year of heavy ion physics at LHC obtained by the three experiments participating in the heavy ion program, ALICE, ATLAS, and CMS.

The shear channel spectral function in hot Yang-Mills theory

“…In this case, the result is expected to contain T -dependent terms of orders 1/ω 2 and 1/ω 4 [23], so a natural first step might be to generalize the OPE results of [18,20] to the presence of quarks. 2 …”

“…This work has been largely motivated by the experimental heavy ion programs taking place at RHIC and the LHC [1,2], which have highlighted the importance of not only understanding the bulk equilibrium properties of the produced matter but also its hydrodynamic behavior. One particularly prominent observation in this direction has been the discovery of the sizable effect that the small, yet finite value of the shear viscosity η has on the flow properties of the plasma [3,4].…”

“…As a preparation for this, the UV limit of the shear correlator was analyzed in terms of an Operator Product Expansion (OPE) in [20], leading to results compatible with known sum rules [21,22] as well as the arguments of [23]. Our hope is that the full NLO thermal spectral function will eventually find use in the extraction of the shear viscosity, 2) from lattice data. In addition, our results can immediately be used to evaluate the Euclidean imaginary time correlator, a quantity that has been addressed in several recent lattice and AdS/CFT calculations in both the shear and bulk channels (see e.g.…”

Non-linear response and event plane correlations

“…The Quark-Gluon Plasma (QGP), as observed in heavy-ion collisions at RHIC and the LHC, exhibits strong collective flow [1,2,3,4]. The observed flow pattern is characterized by long range correlations in the final state particle spectrum.…”

Quantitative extraction of the jet transport parameter from combined data at RHIC and LHC

“…Since then there have been a plethora of jet quenching phenomena in highenergy heavy-ion experiments, from suppression of single hadron spectra to suppression of back-to-back dihadron and gamma-hadron correlation at both RHIC and LHC. The most direct observation of jet quenching at LHC is through mono-jet events in ATLAS and CMS experiments at LHC [3]. We have come currently to a cross point at which we have to move the discussion about jet quenching from pure observation to using it as a tool to study properties of the dense medium in heavy-ion collisions.…”