Review of results using heavy ion collisions at CMS

Ultrarelativistic heavy ion collisions at the laboratory provide a unique chanceto study quantum chromodynamics (QCD) under extreme temperature (≈150 MeV) anddensity (≈1 GeV/ fm 3) conditions. Over the past decade, experimental resultsfrom LHC have shown further evidence for the formation of the quark-gluon plasma(QGP), a phase that is thought to permeate the early Universe and is formed inthe high-density neutron-star cores. Various QCD predictions that model thebehavior of the low-x gluon nuclear density, a poorly explored region, are alsotested. Since the photon flux per ion scales as the square of the emittingelectric charge Z 2 , cross sections of so far elusive photon-induced processesare extremely enhanced as compared to nucleon-nucleon collisions. Here, wereview recent progress on CMS measurements of particle production with largetransverse momentum or mass, photon-initiated processes, jet-induced mediumresponse, and heavy quark production. These high-precision data, along withnovel approaches, offer stringent constraints on initial state, QGP formationand transport parameters, and even parametrizations beyond the standard model.