Topcolor Dynamics and The Effective Gluon-Gluon-Higgs Operator

We discuss the production of the Higgs boson in topcolor models (TCMs) via the gluon fusion process. We consider the Higgs boson as a scalar bound state of t̄t. Nonstandard contributions of the top-yukawa coupling and effects of other heavy quarks, which are expected in realistic TCMs such as topcolor assisted technicolor models (TC2) and top-seesaw (TSS) models, are important for the gluon fusion process. However, there seems to be few analyses of the effects arising from the extension to QCD, such as the topcolor interaction. In order to estimate the contribution of colorons (Acol) to the effective gluon-gluon-Higgs (ggH-) operator, we derive a low-energy effective theory eliminating colorons by using the equation of motion for colorons. We then find that the coefficient Acol of the ggH-operator is proportional to mdyn/M, where M and mdyn denote the coloron mass and the dynamical mass, respectively. We also emphasize that the contribution of colorons is opposite to the top-loop contribution within our approach of the effective theory. We note that TCMs with one composite Higgs doublet predict very large dynamical masses mdyn(= 0.6 − 0.7 TeV) for M ∼ O(TeV). The contribution of colorons Acol thus becomes comparable to the top-loop effect Atop. The large dynamical mass can be realized in TSS models consistently with the experimental value of the top quark mass, while the dynamical mass itself is adjusted to be small in TC2. We find that the coloron contribution Acol can be sizable in a certain class of TSS models, numerically |Acol|/|Atop| = 0.2− 0.7 with the Higgs boson mass mH = 1 TeV for a parameter region being safe from the constraint of the T -parameter. We argue conservatively that the Higgs boson production for TSS models has to be studied in non-perturbative frameworks, because higher order loop corrections due to colorons may be also sizable. In TC2, we need not worry that the contribution of colorons smear out perturbative estimations for the gluon fusion process. Since the top-yukawa coupling in TC2 is larger than the standard value by factor 3 − 4, the Higgs production is considerably enhanced. We can observe signatures of the Higgs boson in TC2 with mH ∼ 200 GeV even at Tevatron Run II due to the enhancement of the top-yukawa coupling as well as at LHC. [email protected]