The breaking of the $SU(2)_L\times U(1)_Y$ symmetry: The 750 GeV   resonance at the LHC and perturbative unitarity
  If the di-photon excess at 750 GeV hinted by the 2015 data at the LHC is explained in terms of a scalar resonance participating in the breaking of the electro-weak symmetry, this resonance must be accompanied by other scalar states for perturbative unitarity in vector boson scattering to be preserved. The simplest set-up consistent with perturbative unitarity and with the data of the di-photon excess is the Georgi-Machacek model. 
Marco Fabbrichesi, Alfredo Urbano
hep-ph