  Pair production of Higgs bosons at hadron colliders is an enticing channel to
search for new physics. New colored particles that couple strongly to the
Higgs, such as those most often called upon to address the hierarchy problem,
provide well motivated examples in which large enhancements of the di-Higgs
rate are possible, at least in principle. However, in such scenarios the
di-Higgs production rate is tightly correlated with the single Higgs production
rate and, since the latter is observed to be SM-like, one generally expects
that only modest enhancements in di-Higgs production are allowed by the LHC Run
1 data. We examine the contribution of top squarks (stops) in a simplified
supersymmetry model to di-Higgs production and find that this general
expectation is indeed borne out. In particular, the allowed deviations are
typically small, but there are tuned regions of parameter space where
expectations based on EFT arguments break down in which order 100% enhancements
to the di-Higgs production rate are possible and are simultaneously consistent
with the observed single Higgs production rates. These effects are potentially
observable with the high luminosity run of the LHC or at a future hadron
collider.
