Ensuring that toponium is glued, not nailed

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 $t\overline{t}$ 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 $t\overline{t}$ 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 $t\overline{t}$ 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.