Heavy ion physics at LHC

The nucleon-nucleon center of mass energy for collisions of the heaviest ions at the LHC (√sNN= 5.5 TeV) will exceed that available at RHIC by a factor of about 30, opening up a new physics domain. Some highlights of this new physics domain are presented here. Extrapolating from present results (from SPS and RHIC), all parameters relevant to the formation of Quark Gluon Plasma (QGP) will be more favorable: the energy density, the size and the lifetime of the system should all improve by a factor. The initial rapidity region will have a nearly vanishing baryon density, similar to the state of the early universe. It is explained how the high energy domain of the LHC allows abundant production of hard probes calculable in perturbative quantum chromodynamics, QCD. At the LHC, high momentum jets and the γ family, will be produced with high statistics for the first time in heavy ion collisions. A large set of observables covering hadronic, leptonic and as well photons will be measured at ALICE, a dedicated heavy ion experiment. Heavy ion part is also studied with CMS detector, which is well suited for heavy vector mesons and jet production, the most interesting probes of QGP. In the present talk, an overview of some of the important physics observables measured through various heavy ion experiments and how they test the properties of matter created at LHC will be given. (author)