Phenomenology of fractionally charged particles: Two reps are better than one

We continue our study of fractionally charged particles (FCPs)—particles carrying electric charge a multiple of e/6. Discovering an FCP would inform us about both Standard Model physics (what the true gauge group and the one-form global symmetry are) and Beyond the Standard Model physics (ruling out many unified theories), which makes them a high-stakes target for collider searches. Here we find that with two FCPs there are vastly richer phenomenologies compared to the single-particle extensions we previously studied. Stringent constraints on colored FCPs can be dramatically weakened when decays are open; conversely the cross sections of the least visible species can be enlarged by up to ∼103, increasing their discovery potential enormously at the LHC and milliQan. Overall, these simple models motivate performing searches for FCPs produced along with jets or leptons, and highlight ‘free’ discovery potential in reanalyzing existing missing-energy datasets for low-quality tracks.