ar X iv : h ep - p h / 96 01 37 8 v 1 3 1 Ja n 19 96 New Physics Effects on Higgs Production at γγ Colliders ∗ †

We study heavy physics effects on the Higgs production in γγ fusion using the effective Lagrangian approach. We find that the effects coming from new physics may enhance the standard model predictions for the number of events expected in the final states b̄b, WW , and ZZ up to one order of magnitude, whereas the corresponding number of events for the final state t̄t may be enhanced up to two orders of magnitude. In the search of the nature and source of the electroweak symmetry breaking a decisive point will be the set in operation of the LHC and the next generation of linear ee collider (NLC). The NLC will permit us to use the old idea of Compton laser backscattering in order to reach a center of mass energy of √ s = 200− 500 GeV [1] in the γγ mode. In particular, the γγ colliders offer a great opportunity to study the dynamics of the elusive Higgs boson. If the standard model (SM) Higgs is detected through its dominant decay modes in ee or pp̄ collisions, then a γγ collider will allow a direct measurement of its partial decay width into two photons. The Hγγ interaction is an one-loop prediction of the SM and all Work supported by CONACyT. To appear in the Proceeding of the V Mexican Workshop of Particles and Fields, Puebla, México, October 1995. their extensions, in which all the contents of charged particles participates. Thus, a precise measurement of its decay width will permit us to discriminate between the SM and new physics predictions. In the present work we study possible effects of new physics on the Higgs boson production in γγ collisions within the context of the effective Lagrangian approach. The framework of effective Lagrangians, as a mean to parametrize physics beyond the SM in a model-independent manner, have been extensively discussed in the recent literature in both decoupling and nondecoupling cases [2]. In this work we consider the decoupling case [3], where the SM can be obtained as a low-energy limit of a weakly coupled renormalizable full theory. The heavy fields effects are parametrized by a series of high-dimensional nonrenormalizable operators, constructed out of the SM fields. These operators respect the SM symmetries [4], and because that, it is possible to establish the order of perturbative theory in which they may be generated in the full theory [5]. Since for mH◦ ≤ 400 GeV the total width of the Higgs boson is small in comparison with the energy of the photons beam, the number of H → X expected events may be written as: N = [