First LHCb results from pA and Pb-Pb collisions

TL;DR

This paper reports on LHCb's initial results from proton-nucleus and lead-lead collisions, highlighting measurements of heavy flavor production, nuclear effects, and the potential of fixed-target experiments to explore quark-gluon plasma physics.

Contribution

It presents the first LHCb results from pA and Pb-Pb collisions, including measurements of heavy flavor production and nuclear effects, and discusses the unique fixed-target program at LHCb.

Findings

Measurements of nuclear modification factors and quarkonium states.

Observation of collective effects in high-energy collisions.

Successful analysis of semi-central Pb-Pb collision data.

Abstract

In 2015, the LHCb collaboration endorsed the proposal to pursue an ambitious heavy-ion physics program. In 2013, LHCb has demonstrated its capabilities to operate successfully in p-Pb and Pb-p collisions, leading already to several important publications in the field. The measurements of the nuclear modification factor and forward-backward production of prompt and displaced J/$\psi$, $\psi$(2S) and $\Upsilon$(1S) states, as well as the production of prompt $D^{0}$ mesons, have allowed to extend the knowledge of Cold Nuclear Matter effects on open heavy flavours and quarkonium production. The measurement of Z-boson production, important to constrain nuclear PDFs, and the measurement of two-particle angular correlations, probing collective effects in the dense environment of high energy collisions, have also been performed. Furthermore, LHCb is the only experiment at the LHC that can be operated in fixed-target mode, owing to the injection of a small amount of gas inside the LHCb collision area. There have been several p-gas and Pb-gas data taking periods during Run 1 and beginning of Run 2. This fixed target programme is conducted at a center-of-mass energy of $\mathcal{O}$(100 GeV), and has great potential to bridge the gap of knowledge between SPS and RHIC in the domain of Quark Gluon Plasma physics. Finally, LHCb successfully participated to its first Pb-Pb data taking at the end of 2015. First studies show that up to semi-central Pb-Pb collisions can be successfully analysed to provide unique measurements in the forward region. In this proceeding, we will present a selection of LHCb results in pA collisions. We will also give some prospects for fixed target and Pb-Pb studies.