Ensuring that toponium is glued, not nailed

TL;DR

This paper discusses the potential detection of toponium states at the LHC, comparing standard QCD binding with exotic short-range interactions, and explores how these differences affect observable cross sections and constraints on new physics.

Contribution

It provides a detailed analysis of how different binding mechanisms influence the line shape and cross section of toponium, offering insights into distinguishing standard QCD from new physics effects.

Findings

Distinct eta_t peak if binding energy exceeds 3 GeV

Exotic interactions increase cross section at similar binding energies

Constraints on new physics depend on measurement precision

Abstract

Hints of toponium might be incipient in LHC data, as given the vast numbers of t quarks produced, some survive on the exponential-decay tail long enough to fasten ttbar together. I here discuss a few differences between the standard Quantum Chromodynamics (QCD) binding (the ``glue'') and exotic short-range binding (the ``nail''). If the binding energy below threshold reaches the 3 GeV range the peak of the eta_t is distinct enough that a cross-section dip should be apparent in the line shape, should there only be one isolated resonance, but is filled by the excited QCD states adding about a pbarn to the cross section of ttbar production. Their effect for smaller binding energies is a tenuous increase in the cross section. A new-physics short-range interaction, on the other hand, yields a larger cross-section for equal binding energy (or hardly a visible bound state for similar cross section). This is due to its larger ttbar relative wavefunction at small distances. Finally, assuming that standard QCD plays out, I comment on what size of constraints on new-physics coefficients one can expect at given precision.