Some aspects of electroweak physics for a composite Higgs boson: application to the Z gauge boson decaying into two leptons and two pseudoscalar mesons

Abstract

I study phenomenological aspects of the SU(2)L x U(1) electroweak physics of a Higgs boson transforming like a quark-antiquark pair. A correspondence is established between its flavour content, the hierarchy of quark condensates, and the leptonic decay constants f of pseudoscalar mesons; the Higgs-mesons couplings coming from the symmetry-breaking scalar potential can then be expressed in terms of the f's, of the Cabibbo-Kobayashi-Maskawa mixing angles, and of the mass of the Higgs boson. Application is made to the decays of a Z boson into two leptons and two charged pseudoscalar mesons, more specially $e^+e^- B^+B^-, e^+e^- D_s^+D_s^-$ and $e^+e^- K^\pm π^\mp$; the last channel, involving new types of flavour changing neutral currents in the scalar sector, is characteristic of this approach. Unlike in the standard model for quarks, the detection of two outgoing charged $B$ mesons is hopeless, like, unfortunately, that of $K^\pm π^\mp$; the channel $D_s^+ D_s^-$ could have been missed in present experiments for a Higgs mass lower than $65 GeV$ because of insufficient statistics. For higher masses this Higgs becomes undetectable from such channels. This shows that too drastic conclusions should not be drawn from an eventual negative outcome from searches for the standard Higgs boson, that simple variants of it are more elusive, may have escaped detection, and could still escape in the near future.