Quarkonium Physics at a Fixed-Target Experiment using the LHC Beams

TL;DR

This paper discusses the potential of a fixed-target experiment at the LHC using bent crystal extraction to significantly advance quarkonium physics, including production mechanisms, gluon PDFs, and spin asymmetries, with high luminosity and versatility.

Contribution

It proposes a novel fixed-target setup at the LHC that enables detailed quarkonium studies with unprecedented luminosity and kinematic coverage, opening new research avenues.

Findings

High quarkonium yields surpass RHIC and ALICE expectations.

Access to large negative-xF domain for the first time.

Versatile nuclear targets for studying nuclear matter and hot dense matter.

Abstract

We outline the many quarkonium-physics opportunities offered by a multi-purpose fixed-target experiment using the p and Pb LHC beams extracted by a bent crystal. This provides an integrated luminosity of 0.5 fb-1 per year on a typical 1cm-long target. Such an extraction mode does not alter the performance of the collider experiments at the LHC. With such a high luminosity, one can analyse quarkonium production in great details in pp, pd and pA collisions at sqrt(sNN)~115 GeV and at sqrt(sNN)~72 GeV in PbA collisions. In a typical pp (pA) run, the obtained quarkonium yields per unit of rapidity are 2-3 orders of magnitude larger than those expected at RHIC and about respectively 10 (70) times larger than for ALICE. In PbA, they are comparable. By instrumenting the target-rapidity region, the large negative-xF domain can be accessed for the first time, greatly extending previous measurements by Hera-B and E866. Such analyses should help resolving the quarkonium-production controversies and clear the way for gluon PDF extraction via quarkonium studies. The nuclear target-species versatility provides a unique opportunity to study nuclear matter and the features of the hot and dense matter formed in PbA collisions. A polarised proton target allows the study of transverse-spin asymmetries in J/psi and Upsilon production, providing access to the gluon and charm Sivers functions.