Speaker
Description
Electroweak precision observables are fundamental for testing the standard model (SM) or its extensions. The influences on observables from new physics within the electroweak sector will be expressed in terms of oblique parameters S, T, U. By performing the global fit with the CDF new W mass, we obtain $S=0.03 \pm 0.03$, $T=0.06 \pm 0.02$ and $U=0.16 \pm 0.03$ or $S=0.14 \pm 0.03$, $T=0.24 \pm 0.02$ with $U=0$, which strongly indicate the need of the new non-degenerate multiplets by extending SM. We discuss two different cases of simple extensions by a new hypercharge-one triplet scalar $\Delta$ or hyperchargeless real triplet scalar $\Sigma$. These triplets will firstly affect the oblique parameters and further observables so that we can directly choose the new triplet parameters to perform the global fit. For $Y=1$ case, we choose $m_H$, $\lambda_4$ and $v_\Delta$ as fit parameters and obtain $m_{H}=296.02 \pm 10.18$ GeV,
$\lambda_4=2.58 \pm 0.090$ and $v_\Delta=4.82 \pm 0.34$ GeV. For $Y=0$ case, the potential parameter $b_4$ gives the very stringent constraint so that we cannot find reasonable fit values. In the case of ignoring the $b_4$ constraint, we obtain $m_{H^+}=77.16 \pm 17.12$ GeV, $\Delta m=-14.27\pm4.22$ GeV and
$v_\Delta=3.20 \pm 0.30$ GeV. We conduct the specific phenomenological analysis, such as vacuum stability, perturbative unitarity, Higgs data and calculate the decay ratios of the new scalars. These can be further testified by future lepton colliders by pair production $H^{++}H^{--}$.
