New physics in resonant production of Higgs boson pairs

We advocate a search for an extended scalar sector at the LHC via $hh$ production, where $h$ is the 125 GeV Higgs boson. A resonance feature in the $hh$ invariant mass is a smoking gun of an $s$-channel heavy Higgs resonance, $H$. With one $h$ decaying to two photons and the other decaying to $b$-quarks, the resonant signal may be discoverable above the $hh$ continuum background for $M_H<$ 1 TeV. The product of the scalar and top Yukawa couplings can be measured to better than $10-20\%$ accuracy, and its sign can be inferred from the $hh$ lineshape via interference effects.