Spinless bosons in electron-positron annihilation

Abstract

The contributions to the processes$e^ + e^ - \to \mu ^ + \mu ^ - ,q\bar q,\gamma \gamma ,e^ + e^ -$, mediated by scalar and/or pseudoscalar bosons are calculated. The constraints on their coupling constants and their masses are investigated as they arise from the radiative decayZ ⁰→⁺ e ⁻ γ and from the experimental data for the annihilation processes into lepton, photon and quark pairs. Data one ⁺ e ⁻→μ⁺ μ⁻, γγ ande ⁺ e ⁻ seriously reduce the domain of coupling constants to leptons and photons still allowed by the probable value of the width ofZ ⁰→e ⁺ e ⁻ γ. Experimentse ⁺ e ⁻→μ⁺ μ⁻, γγ,e ⁺ e ⁻ at 45 GeV c.m.s. energy with a sensitivity of 10% will decide about the existence of a heavy spinless boson with the presumed phenomenological couplings to leptons and photons. Assuming universality of the coupling to leptons and quarks a conservative bound on the contribution toR arising from spinless boson exchange is already in conflict with the presumed radiative width ofZ ⁰→e ⁺ e ⁻ γ.