Constraints on the Georgi-Machacek Model by Current LHC Data

In the Georgi-Machacek model with a custodial symmetry in the Higgs potential and vacuum alignment, the triplet vacuum expectation value is allowed to be of ${\cal O}(10)$ GeV, which leads to the possibility of significant modifications in the couplings of the SM-like Higgs bosons $h$ with other SM particles. In this talk given at the HPNP2015 conference held at Toyama University, we review constraints on the model based on the latest LHC data of the SM-like Higgs boson, like-sign $W$ boson events, and searches for additional neutral Higgs bosons. In particular, we concentrate on the parameter space for small mixing angle $\alpha$ between the two custodial singlets. It is pointed out that constraints from the non-SM custodial singlet are most constraining and those from the 5-plet are independent of $\alpha$. While currently there is no constraint from the 3-plet, we show that its $f \bar f$ and $\gamma\gamma$ channels through the gluon fusion production can be very promising for searches or constraining in the mass range between 160 GeV and 350 GeV because of its gauge-phobic property.