Abstract
Abstract Pair production of colored particles is in general accompanied by production of QCD bound states (onia) slightly below the pair-production threshold. Bound state annihilation leads to resonant signals, which in some cases are easier to see than the decays of the pair-produced constituents. In a previous paper (arXiv:1204.1119) we estimated the bound state signals, at leading order and in the Coulomb approximation, for particles with various spins, color representations and electric charges, and used 7 TeV ATLAS and CMS resonance searches to set rough limits. Here we update our results to include 8 and 13 TeV data. We find that the recently reported diphoton excesses near 750 GeV could indeed be due to a bound state of this kind. A narrow resonance of the correct size could be obtained for a color-triplet scalar with electric charge −4/3 and mass near 375GeV, if (as a recent lattice computation suggests) the wave function at the origin is somewhat larger than anticipated. Pair production of this particle could have evaded detection up to now. Other candidates may include a triplet scalar of charge 5/3, a triplet fermion of charge −4/3, and perhaps a sextet scalar of charge −2/3.
Highlights
The bound state annihilation signals are complementary to signals from pair production
We have updated our earlier work [3] and determined the current constraints on colored particles that follow from the non-observation of their near-threshold QCD resonances
Photon+jet, dijet and dilepton channels, using the latest ATLAS
Summary
It was shown in [14] that the diphoton resonance arising from stoponium of mass 750 GeV, computed at leading order using the potential approximation suggested in [33], is about 0.06 fb at 13 TeV. It was shown in [18] that the NLO corrections (and other small effects) increase the diphoton rate by 25%, leaving it a factor of 1.7 or so below the Coulomb approximation used in [3].
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