We study the extension of the minimal supersymmetric standard model by adding one singlet and one hypercharge zero $SU(2)$ triplet chiral superfield. The triplet sector gives an additional contribution to the scalar masses, and we find that the lightest $CP$-even Higgs boson can have a mass of 119–120 GeV at tree level, and radiative correction raises the value to 125 GeV. In this model no significant contributions from stop loops is needed to get the required Higgs mass that alleviates the fine-tuning problem of fixing the stop mass to a high precision at the grand unified theory scale. In addition, this model gives a neutralino dark matter of mass around 100 GeV that is a mixture of Higgsino and triplino with a dark matter density consistent with WMAP observations. The spin-independent scattering cross section with nucleons is ${10}^{-43}{\mathrm{cm}}^2$, which makes it consistent with the bounds from direct detection experiments like XENON100 and others.

• Received 4 May 2012

DOI:https://doi.org/10.1103/PhysRevD.86.075031