Searching for the heavy charged custodial fiveplet Higgs boson in the Georgi-Machacek model at the International Linear Collider

Abstract

The Georgi-Machacek (GM) model is one of many beyond Standard Model scenarios with an extended scalar sector that can group under the custodial $\mathrm{SU}(2{)}_{\mathrm{C}}$ symmetry into a fiveplet, a triplet, and two singlets. The heavy charged custodial fiveplet Higgs ${\mathrm{H}}_{5}^{\ifmmode\pm\else\textpm\fi{}}$ are typical particles in the GM model that couple to the electroweak gauge bosons, therefore providing a good testing ground for the detection of the ${\mathrm{H}}^{\ifmmode\pm\else\textpm\fi{}}{\mathrm{W}}^{\ensuremath{\mp}}\mathrm{Z}$ vertex. The neutral custodial fiveplet Higgs ${\mathrm{H}}_{5}^{0}$ in the GM model has the same mass with the ${\mathrm{H}}_{5}^{\ifmmode\pm\else\textpm\fi{}}$ and couples to both of the electroweak gauge bosons, ${\mathrm{W}}^{+}{\mathrm{W}}^{\ensuremath{-}}$ and ZZ. Here, we study the discovery prospects of the exotic scalar bosons ${\mathrm{H}}_{5}^{\ifmmode\pm\else\textpm\fi{}}$ and ${\mathrm{H}}_{5}^{0}$ at the International Linear Collider(ILC) via the vector boson associated production processes, and discuss two different decay modes for both the charged and neutral scalars. The discovery potential is discussed. Testing the mass degeneracy of charged and neutral scalar bosons in the GM model is also considered.