| 日時: |
2008-12-17 14:00 - 15:00 |
| 場所: |
研究本館2階220室 |
| 会議名: |
Dynamical origin of heavy Higgs decoupling properties |
| 連絡先: |
菊池樹 |
| 講演者: |
Dr. Michio Hashimoto (University of Western Ontario) |
| アブストラクト: |
A dynamical origin of decoupling properties of heavy Higgs bosons is studied in the context of the two Higgs doublet model (THDM). We show that the subcritical dynamics of the Nambu-Jona-Lasinio (NJL) model may play an important role in the heavy Higgs decoupling properties. Needless to say, a model having such a nature is obviously viable. In general, the heavy Higgs decoupling limit is quoted as $M_{H,H^pm}^2=M_A^2+{cal O}(lambda_i v^2)$ with $M_A^2 gg {cal O}(lambda_i v^2)$, where $lambda_i$ represent several quartic couplings in the general Higgs potential. In the strongly interacting system, even if the above conditions are satisfied, there can potentially appear non-decoupling effects, for example, in the $T$-parameter, because $(M_H^2-M_A^2)/v^2, (M_{H^pm}^2-M_A^2)/v^2 sim lambda_i$ can be large. Thus, it is quite important whether or not the heavy Higgs masses are actually almost degenerate in such a model. We consider the top-Higgs system of the standard model (SM) with a positive Higgs mass squared $M_0^2 > 0$ plus a four-top-quark interaction, where the four-top-quark coupling constant $G_0$ is close to the critical coupling, but subcritical. We do not consider the UV completion and hence we treat the Higgs field $phi$ built in the model as an elementary scalar. The Yukawa coupling $y_0$ between $phi$ and $t$ generates an additional four-top-quark coupling $y_0^2/M_0^2$ in low-energy. When $G_0+y_0^2/M_0^2$ is supercritical, the top quark acquires the mass and simultaneously the Higgs field $phi$ develops the vacuum expectation value. The yukawa interaction $y_0$ also provides the Peccei-Quinn (PQ) $U(1)_{PQ}$ symmetry breaking term, which produces the mass of the CP odd Higgs boson. We also assume that $y_0$ is connected with the near-criticality of $G_0$. It then turns out that the resonances of the top quark are heavy and almost degenerate with a large top-yukawa coupling. We also find that the light CP even Higgs has SM-like couplings. If the masses of the heavy Higgs resonances are, say, less than ${cal O}(1 TeV)$, our model is directly testable at CERN Large Hadron Collider. |
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