Narrow Results

Ten three-body processes in e⁺e⁻ collisions for heavy particle productions such as Higgs, t-quark, W^± and Z⁰ are calculated by two independent computer codes for automatic calculation of Feynman amplitude. The results are in excellent agreement within statistical error of numerical integration (about 0.5%). This demonstrates that these systems are quite powerful for theoretical study for future e⁺e⁻, e^±γ and γγ colliders. Numerical values of cross sections are summarized in tables and a figure.

The relative center-of-mass energy spread ${\sigma }_W∕W$ at $e^{+}{e}^{-}$ colliders is $\mathcal{𝒪}(10^{-3})$, which is much larger than the widths of narrow resonances $J∕\psi$, $\psi (2S)$, $\mathrm{\Upsilon }(1S)$, $\mathrm{\Upsilon }(2S)$, $\mathrm{\Upsilon }(3S)$ mesons, tauonium and some others. Its reduction would significantly increase the resonance production rates and open up great opportunities in the search for new physics. In this paper, we propose a new monochromatization method for colliders with a large crossing angle (which can provide a high luminosity). The contribution of the beam energy spread to ${\sigma }_W$ is canceled by introducing an appropriate energy–angle correlation at the interaction point; ${\sigma }_W∕W\sim (0.5-1)\times 10^{-5}$ appears possible.

We report preliminary results on the measurement of the cross section of the process e⁺e^- → K⁺K^-π⁺π^- in the c.m. energy range from 1.5 GeV to 2 GeV. It is shown that the cross section is dominated by the contributions of several intermediate states K⁺K^-ρ, K*Kπ, ϕπ⁺π^- and K*K*.