Plasma-Wakefield Accelerator Group

Abstract:

Vector meson production is studied in the reaction γγ→K⁺K^-π⁺π^-. A clear Φ(1020) signal is seen in the K⁺K^- mass distribution and a K^*0 (890) signal is visible in the K^±π^∓ one. Both do not seem to be strongly correlated with quasi two body final states. Cross sections for the processes γγ→K⁺K^-π⁺π^-, γγ→Φπ⁺π^-, γγ→K⁺⁰K^±π^∓ and upper limits for the production of Φp, ΦΦ and K^*0 {Mathematical expression} are given as function of the invariant γγ mass. © 1986 Springer-Verlag.

Abstract:

The cross section for the process e⁺e^-→π⁰+ anything has been measured at an average center of mass energy of 34.6 GeV for π⁰ energies between 0.7 and 17 GeV. The angular distribution for π⁰ energies larger than 2 GeV is of the form dσ/dΩ∼1+Acos²θ, with A=1.2±0.5. The ratio of π⁰ to π^± production in the measured energy range is 2σ(π⁰)/(σ(π⁺)+σ(π^-))=1.13±0.18 The form of the differential cross sections agrees within the errors. The mean π⁰ multiplicity is 5.8±0.9. © 1986 Springer-Verlag.

Abstract:

We have studied the correlations between charged particles produced in e+e- annihilations into hadrons at c.m. energies between 29 and 37 GeV. We have analysed the correlations between the charged multiplicities of the jets and the two particle rapidity and charge correlations. No evidence for correlations between the multiplicities of the two jets is found. Two particle short range rapidity and charge correlations are observed, indicating that particles cluster in rapidity and that their charges compensate locally. An extensive study of these correlation effects by QCD Monte Carlo calculations was performed. Evidence for charge correlations due to Bose-Einstein statistics is also observed. © 1985 Springer-Verlag.

Abstract:

An analysis of the production of KS⁰KS⁰ and K^±Ks⁰π^∓ by two quasi-real photons is presented. The cross section for γγ→K⁰ {Mathematical expression}, which is given for the γγ invariant mass range from K {Mathematical expression} threshold to 2.5 GeV, is dominated by the f′(1525) resonance and an enhancement near the K {Mathematical expression} threshold. Upper limits on the product of the two-photon width times the branching ratio into K {Mathematical expression} pairs are given for Θ(1700), h(2030), and ξ(2220). For exclusive two-photon production of K^±Ks⁰π^∓ no significant signal was observed. Upper limits are given on the cross section of γγ→K⁺ {Mathematical expression}π^- or K^-K⁰π⁺ between 1.4 and 3.2 GeV and on the product of the γγ width times the branching ratio into the K {Mathematical expression}π final states for the ηc(2980) and the ι(1440), yielding Γ(γγ)→i(1440))·BR(i(1440)→K {Mathematical expression}π<2.2 keV at 95% C.L. © 1985 Springer-Verlag.

Abstract:

We have measured the cross sections for e+e- → e+e-, e+e- → μ+μ-, e+e- → γγ and e+e- → hadrons in an energy scan at center of mass energies between 39.79 and 46.72 GeV in 30 MeV steps. New spinless bosons, whose existence has been postulated as a possible means to explain the anomalously large radiative width of the Z0 found at the CERN SPS pp collider, are ruled out in the scan region. The data are used to set limits on the couplings to lepton, photon and quark pairs of bosons with masses above 46.72 GeV. © 1985.