U. Timm

Search for new heavy quarks in

Abstract The total e + e − annihilation onto hadron has been measured at CM energies between 33.00 and 36.72 GeV and between 38.66 and 46.78 GeV in steps of 20 and 30 MeV respectively. The average of the ratio R = σ ( e + e − → hadrons )/ σ is 〈 R 〉=3.85±0.12 and 〈 R 〉=4.04±0.10 for the two energy ranges. The systematic error on 〈 R 〉 is 0.31. Both values are consistent with the expectation for the known coloured quarks u, d, s, c and b. No evidence was found for the production of new quarks. If the largest fluctuation in R is interpreted as a narrow resonance, it corresponds to a product of the electronic width and the hadronic branching ratio Γ ee B had >2.9 keV at the 95% confidence level, well below the value expected for the toponium vector ground state with charge 2 3 e . The observed number of aplanar final states rules out the continuum production of a a new heavy flavour with pointlike cross section up to a CM energy of 45.4 GeV for a quarck charge of 1 3 e . and up to 46.6 GeV for 2 3 e at the 95% confidence level.

e^+e^-

Abstract An event from e+e− annihilation at √s = 43.450 GeV containing two topologically isolated energetic muons and two hadronic jets has been observed. The masses of the μ−μ, jet-jet and μ-jet combinations are all large. The expected number of such events from known processes is about 10−3.

collisions up to 46.78 GeV cm energy

Abstract Using the CELLO detector at PETRA a search has been made for excited leptons by studying e + e − interactions which yield l + l − γγ, l + l − γ and γγ final states, where l =e,μ or τ . Good agreement with QED is observed and new limits are set on e ∗ , μ ∗ , and τ ∗ production.

Observation of a multiparticle event with two isolated energetic muons in e+e- interactions

Abstract A search for single photons, produced in e + e − collisions together with particles interacting only weakly with matter, has been performed using the CELLO detector operating at the PETRA storage ring. From the absence of any signal, an upper limit is set at 15 (90% CL) on the number of light neutrino species, and lower limits on various supersymmetric particle masses are derived. For massless photinos, mass degenerate scalar partners of the left- and right-handed electrons are excluded below 37.7 GeV/ c 2 (90% CL).

EXCITED LEPTON SEARCH

Abstract A search has been performed for the production of charged Higgs bosons in e+ e− annihilation at center of mass energies up to 46.8 GeV. From the absence of both hadronic and leptonic decay signatures, we exclude them up to a mass of 19 GeV/c2 independent of the hadronic and leptonic branching ratios.

A search for single photons at petra

Abstract The e+e−→μ+μ− reaction has been studied at centre of mass energies ranging between 38.3 abd 46.8 GeV with the CELLO detector at PETRA. We present results on the cross section and the charge asymmetry for this channel. Combining all the data at the average energy 〈 s 〉=43 GeV we obtain Rμμ=〈σμμ/σ0〉=0.98±0.04±0.04, 〈Aμμ〉=(−14.1±3.7±1.0)%, where σ0 is the QED cross section and Aμμ is the charge asymmetry corrected for pure radiative effects. These results are in good agreement with the expected values of Rμμ=1.01 and Aμμ=−14.5% at that energy.

Search for production of charged Higgs particles

Mass limits are presented for various supersymmetric particles: scalar partners of electrons, muons, taus and quarks; photinos, winos and zinos. They were obtained from the analysis of an exposure of 48.6 pb−1 of the CELLO detector at the PETRAe+e− storage ring up to a center of mass energy of 46.8 GeV. Special attention has been given to the case where the photino is assumed to be the lightest supersymmetric particle, but other possibilities have also been considered.

A measurement of the Muon pair production in e+e− annihilation at 38.3⩽s⩽46.8GeV

Abstract We have studied the reactions e + e − → e + e − , e + e − → γγ , e + e − → μ + μ − , and e + e − → τ + τ − in the centre-of-mass (CM) energy range from 39.8 to 45.2 GeV using the CELLO detector at PETRA. Upper limits on the partial widths for new spin 0 bosons with masses both within and above the energy range covered are determined. No evidence for contributions of such new particles has been observed up to the highest PETRA energies in a model independent way. Under the assumptions of recently suggested models relating the existence of spin 0 bosons to the radiative width Γ τ of the Z 0 we exclude such bosons at the 95% confidence level for masses below the Z 0 -mass if Γ τ > 20 MeV.

Searches for supersymmetric particles with the CELLO detector at PETRA

Abstract The e+e−→μ+μ− reaction has been studied at centre of mass energies ranging between 38.3 abd 46.8 GeV with the CELLO detector at PETRA. We present results on the cross section and the charge asymmetry for this channel. Combining all the data at the average energy 〈 s 〉=43 GeV we obtain Rμμ=〈σμμ/σ0〉=0.98±0.04±0.04, 〈Aμμ〉=(−14.1±3.7±1.0)%, where σ0 is the QED cross section and Aμμ is the charge asymmetry corrected for pure radiative effects. These results are in good agreement with the expected values of Rμμ=1.01 and Aμμ=−14.5% at that energy.

Limits on spin 0 bosons in

Abstract The production of excited quarks has been looked for in e + e − interactions at PETRA at center of mass energies up to 46.8 GeV using the CELLO detector. The different final state topologies considered are four-jets, two-jets and two-photons, three-jets, two-jets and one-photon. No deviation from standard QCD predictions is observed, thus yielding limits on the coupling constants and the masses of these possible quark states.