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

## TL;DR

This paper reviews experimental results from ultra-relativistic lead-ion collisions at the CERN LHC, highlighting the increased production of hard probes at unprecedented energies and summarizing findings from the first three years of data collection.

## Contribution

It provides a comprehensive overview of experimental results on hard probes in heavy-ion collisions at the LHC, including new data from Run 2 at the highest energies.

## Key findings

- Increased production rates of hard probes at LHC energies.
- First results from Run 2 heavy-ion data at 2.76 TeV.
- Studies of reference pp and pPb systems.

## Abstract

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.