Ultra-relativistic Heavy Ion Physics Research Articles

An overview of experimental results from ultra-relativistic heavy-ion collisions at the CERN LHC: Hard probes

The first collisions of lead nuclei, delivered by the CERN Large Hadron Collider (LHC) at the end of 2010, at a centre-of-mass energy per nucleon pair $\sqrt{s_{NN}}$ = 2.76 TeV, marked the beginning of a new era in ultra-relativistic heavy-ion physics. The study of the properties of the produced hot and dense strongly-interacting matter at these unprecedented energies is currently experimentally pursued by all four big LHC experiments, ALICE, ATLAS, CMS, and LHCb. The more than a factor 10 increase of collision energy at LHC, relative to the previously achieved maximal energy at other collider facilities, results in an increase of production rates of hard probes. This review presents selected experimental results focusing on observables probing hard processes in heavy-ion collisions delivered during the first three years of the LHC operation. It also presents the first results from Run 2 heavy-ion data at the highest energy, as well as from the studies of the reference pp and pPb systems, which are an integral part of the heavy-ion programme.

An overview of experimental results from ultra-relativistic heavy-ion collisions at the CERN LHC: Bulk properties and dynamical evolution

The first collisions of lead nuclei, delivered by the CERN Large Hadron Collider (LHC) at the end of 2010, at a centre-of-mass energy per nucleon pair $\sqrt{s_{NN}}$ = 2.76 TeV, marked the beginning of a new era in ultra-relativistic heavy-ion physics. Following the Run 1 period, LHC also successfully delivered PbPb collisions at the collision energy $\sqrt{s_{NN}}$ = 5.02 TeV at the end of 2015. The study of the properties of the produced hot and dense strongly-interacting matter at these unprecedented energies is experimentally pursued by all four big LHC experiments, ALICE, ATLAS, CMS, and LHCb. This review presents selected experimental results from heavy-ion collisions delivered during the first three years of the LHC operation focusing on the bulk matter properties and the dynamical evolution of the created system. It also presents the first results from Run 2 heavy-ion data at the highest energy, as well as from the studies of the reference pp and pPb systems, which are an integral part of the heavy-ion programme.

The CMS Collaboration

We outline the opportunities for ultra-relativistic heavy–ion physics which are offered by a next generation and multi-purpose fixed-target experiment exploiting the proton and ion LHC beams extracted by a bent crystal.

Ultra-relativistic heavy–ion physics with AFTER@LHC

We outline the opportunities for ultra-relativistic heavy-ion physics which are offered by a next generation and multi-purpose fixed-target experiment exploiting the proton and ion LHC beams extracted by a bent crystal.

Results from the first heavy ion run at the LHC

Early November 2010, the LHC collided for the first time heavy ions, Pb on Pb, at a centre-of-mass energy of 2.76 TeV/nucleon. This date marked both the end of almost 20 years of preparing for nuclear collisions at the LHC, as well as the start of a new era in ultra-relativistic heavy ion physics at energies exceeding previous machines by more than an order of magnitude. This contribution summarizes some of the early results from all three experiments participating in the LHC heavy ion program (ALICE, ATLAS, and CMS), which show that the high density matter created at the LHC, while much hotter and larger, still behaves like the very strongly interacting, almost perfect liquid discovered at RHIC. Some surprising and even puzzling results are seen in particle ratios, jet-quenching, and Quarkonia suppression observables. The overall experimental conditions at the LHC, together with its set of powerful and state-of-the-art detectors, should allow for precision measurements of quark-gluon-plasma parameters like viscosity and opacity.

First Results from Pb+Pb Collisions at the LHC

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

Ultra-relativistic heavy ion physics at RHIC and the LHC

Ultra-relativistic heavy ion physics at RHIC and the LHC

New developements in high precision, high particle density tracking with time projection chambers

Over the past few years, time projection chambers have become a major detector option for tracking and particle identification in ultrarelativistic heavy ion physics. This is particularly apparent in the forthcoming big experiments at the CERN SPS (NA49) and at the RHIC (STAR) and LHC (ALICE) colliders. For these difficult experimental environments (extremely high track densities, space charge and rate limitations, high requirements on space and double track resolution) the classic TPC concept has to be pushed to new limits. We will report on new developements in the context of the NA49 and ALICE experiments, especially concerning ultralight field cage structures, low density gas mixtures, improved space and double track resolution, alternative readout chamber concepts, and new electronics and information transmission schemes.

Ultra-relativistic heavy ion physics at the CERN SPS: Results from helios(NA34)

Transverse energy and multiplicity distribution are presented in different rapidity intervals together with the scaling behaviour of the dE T / dη and dη ch / dη distributions. Quantities derived from these distributions, the stopping power and energy density, are discussed. Recent results on the electromagnetic dissociations of 16O and 32S ions in emulsion are also presented: energy distributions of different topologies are given together with the integrated electromagnetic dissociation cross-section. The photo-nuclear cross section in several channels is derived.