Higgs Uncovering Light Scalar Remnants of High Scale Matter Unification

We consider the impact of colored scalars that can couple directly to matter fields on the recently measured h → γγ excess. Among all possible candidates only scalar states transforming as (8, 2, 1/2) and (6¯¯¯, 3, −1/3) under the Standard Model gauge group can individually accommodate the excess and remain in agreement with all available data. Current experimental constraints require such colored states to have an order one coupling to the Standard Model Higgs and a mass below 300 GeV. We use the best fit values to predict the correlated effect in h → Zγ and di-Higgs production. We furthermore discuss where and how these states appear in extensions of the Standard Model with primary focus on scenarios of matter unification. We revisit two simple SU(5) setups to show that these two full-fledged models not only accommodate a light color octet state but correlate its mass with observable partial proton decay lifetimes.