Long-lived colour triplet scalars from a split composite higgs model

Long-lived, colour-triplet scalars are a prediction of unnatural, or split, composite Higgs models where the spontaneous global-symmetry breaking scale f ≥ 10 TeV and an unbroken SU(5) symmetry is preserved. Since the triplet scalars are pseudo Nambu-Goldstone bosons, they are split from the much heavier composite-sector resonances and are the lightest exotic, coloured states. Due to discrete symmetries and the large suppression scale f, the triplet scalar is often metastable. We show that existing searches for collider-stable R-hadrons from Run-I at the LHC forbid triplet scalars below 845 GeV. In the future with 300 fb−¹ at 13 TeV, triplet scalar masses up to 1.4 TeV can be discovered, whereas for shorter lifetimes displaced-vertex searches provide a discovery reach of up to 1.8 TeV. Just like the role of long-lived gluinos in supersymmetry, long-lived color triplets will therefore provide a sign of unnaturalness in composite Higgs models.