Experimental Aspects of Heavy Quarkonium Production at the LHC

TL;DR

The paper tackles the unresolved prompt production mechanism of J/psi and Upsilon(1S) at the LHC by employing a PYTHIA-based framework with NRQCD singlet and octet contributions and a cross-section regularisation scheme. It systematically investigates hadronic activity around the quarkonium through four shower scenarios, comparing differential cross sections and reconstruction efficiencies for J/psi and Upsilon(1S) in a CMS-like detector, and proposing observables such as z and local transverse-momentum densities to discriminate production models. While non-prompt backgrounds complicate J/psi analyses, Upsilon studies benefit from reduced backgrounds and higher reconstruction efficiency, enabling cleaner tests of associated radiation. The work highlights the importance of multi-observable approaches to resolve the quarkonium production puzzle at the LHC and outlines practical strategies for exploiting hadronic activity around quarkonia.

Abstract

More than 30 years after the discovery of the J/psi, its production mechanism is still poorly understood. With the LHC data it will be possible to study quarkonia up to very high transverse momenta and with high statistics. In this note we discuss experimental aspects of J/psi and Upsilon(1S) production at the LHC. In particular, we investigate the sensitivity of a general purpose LHC detector to observables, which are complementary to the cross section and polarisation measurement. These observables would be sensitive to the radiation produced in association with the quarkonium.

Figures (6)

• Figure 1: Left: $J/\psi$'s at the Tevatron. The old model (singlet only, normalised to fit CDF data, green line), the new model without reweighting (blue broken line), the new model with reweighting (red line), and the CDF data (black data points, from Ref. cdfxs_jpsi). Right: differential cross section at CMS-like detector for the four production cases separately.
• Figure 2: Differential cross section for non-prompt (black) and prompt (red) $J/\psi$'s.
• Figure 3: Left: expected $J/\psi$ reconstruction efficiency in general purpose LHC detector as function of $\rm P_{T}^{J/\psi}$. Right: the same but for $\Upsilon$'s. (see Sec. \ref{['upsrec']})
• Figure 4: Left: variable $z_{{J/\psi}}$ at reconstruction level. Right: variable $\frac{\rm d P_{T}^{around}(R)}{\rm d\Omega_R}$ at reconstruction level.
• Figure 5: Left: $\Upsilon$ production with singlet and octet in PYTHIA (red), together with CDF data (back dots). The latter are taken from Ref. cdfxs_ups. Right: Differential cross section at CMS-like detector for the four production cases separately.