Heavy Ions: Results from the Large Hadron Collider

TL;DR

The paper reports on the first heavy ion collision results from the LHC, showing that the created quark-gluon plasma is hotter, longer-lived, and larger than at previous energies, with new insights into quarkonia, heavy flavor suppression, and jet quenching.

Contribution

It provides the first experimental results from heavy ion collisions at the LHC, highlighting new properties of the quark-gluon plasma at unprecedented energies.

Findings

Higher temperature and longer lifetime of the fireball compared to lower energies.

Observation of quarkonia suppression and jet energy loss.

Larger size of the fireball at freeze-out.

Abstract

On November 8, 2010 the Large Hadron Collider (LHC) at CERN collided first stable beams of heavy ions (Pb on Pb) at center-of-mass energy of 2.76 TeV/nucleon. The LHC worked exceedingly well during its one month of operation with heavy ions, delivering about 10 microbarn-inverse of data, with peak luminosity reaching to $L_{0} = 2 \times 10^{25}{\rm cm}^{-2}{\rm s}^{-1}$ towards the end of the run. Three experiments, ALICE, ATLAS and CMS, recorded their first heavy ion data, which were analyzed in a record time. The results of the multiplicity, flow, fluctuations, and Bose-Einstein correlations indicate that the fireball formed in nuclear collisions at the LHC is hotter, lives longer, and expands to a larger size at freeze-out as compared to lower energies. We give an overview of these as well as new results on quarkonia and heavy flavour suppression, and jet energy loss.