Abstract
The limitations of doublet-septet mixing models resulting from the deviations of electroweak oblique parameters and are studied. In the minimal model, the mixture of the septet and the scalar doublet in the standard model (SM) is driven by a non-Hermitian dimension-7 operator. For a smaller bare mass of the septet, puts a stringent constraint on the mixing angle between the -odd neutral parts of the SM Higgs doublet and . In general, increasing the mass of the scalar septet will enhance the deviation of from the SM, whereas it decreases the magnitude of for a larger bare mass within the range . We also examine two extended models from the ordinary doublet-septet mixture pattern. One of them is based on an inert doublet-septet mixing pattern, in which there is no vacuum expectation value for the neutral component of and stable dark matter could naturally exist. For a benchmark point with the inner doublet mass of and in this model, the mixing coefficient is found to be less than 1.8. The other extension is constructed by imposing a doubly charged scalar mixed with the doubly charged component of the septet. Apart from the contribution by the septet-doublet admixture, is suppressed by a factor of and has a significant constraint due to the vanishing vacuum polarization of at the momentum transfer .
- Received 23 December 2014
DOI:https://doi.org/10.1103/PhysRevD.91.073014
© 2015 American Physical Society