Speaker
Description
Summary
We show that the addition of a fourth generation with vector-like quarks to the minimal supersymmetric standard model (MSSM) can raise the predicted value of the physical Higgs mass by mixing with the top sector. The mixing requires a larger top quark Yukawa coupling (by up to $\sim 6 \%$) to produce the same top mass. Since loop corrections to $m_h$ go as $y_{top}^4$, this will in turn increase the predicted value of the physical Higgs mass, a point not previously emphasized in the literature. In the presence of mixing, for A-terms and soft masses around 900 GeV, the Landau pole for the top Yukawa can be pushed above the GUT scale while retaining perturbativity of the gauge couplings, generating a Higgs mass of 125 GeV and evading constraints from electroweak precision measurements (EWPM) and recent LHC searches. Soft terms can be as low as 600 GeV in parts of parameter space with a Landau pole at $\sim 10^{10}$ GeV. However, the Landau pole can still be pushed above the GUT scale if one sacrifices perturbativity at the unification scale by adding fields in a $\mathbf{5}$+$\mathbf{\bar{5}}$ representation. The model predicts new quarks and squarks with masses $\sim 800$ GeV. We briefly discuss potential paths for discovery or exclusion at the LHC.
