P. Gabriel

τ Production and decay with the cello detector at petra

Abstract The reaction e + e − → τ + τ − has been studied at centre of mass energies between 14.0 and 46.8 GeV with the CELLO detector at the PETRA e + e − collider. We present results for the cross section σ τ and the charge asymmetry A τ . The results are in good agreement with the standard model. We have also measured the topological decay rates BR 1 , BR 3 and BR 5 for the inclusive decay of the τ lepton into one, three and five charge particles. The results confirm and improve earlier CELLO measurements at other energies. We find for the combined values at all energies BR 1 = (84.9 ± 0.4 ± 0.3)%, BR 3 = (15.0 ± 0.4 ± 0.3)% and BR 5 = (0.16 ± 0.13 ± 0.04)%.

a2(1320) andπ2(1670) formation in the reactionγγ→π+π−π0

The reactione+e−→e+e−π+π−π0 in the untagged mode has been measured with the CELLO detector at PETRA. The cross section is dominated by exclusivea2(1320) production, whose radiative width is determined to beΓγγ=1.00±0.07(stat.)±0.15(syst.)keV. An angular correlation analysis indicates pure helicity 2 with an upper limit on the helicity 0 contribution of 8.2% (at 95% c.l.). Excitation of the pseudotensor meson π20(1670) is observed for the first time in this reaction. The π2 radiative width and its dependence on interference effects are studied.

Inclusive strange particle production in e + e- annihilation

We present an analysis of strange particle production frome+e− annihilation into multihadronic final states. The experiment was performed with the CELLO detector at the PETRA storage ring at DESY, the data was taken at a centre of mass energy of 35 GeV with an integrated luminosity of 86 pb−1. The particlesKS0,K*± and Λ have been identified by their characteristic decays, and differential cross sections for their production have been obtained. From a comparison ofKS0 andK*± rates the Lund vector meson suppression parameterV/(V+P)S has been determined.

K s 0 Kπ production in tagged and untagged γγ interactions

AbstractWe have searched for resonance production in the reaction γγ→Ks0Kπ. No signal was found for theηc and an upper limit for the radiative with

Measurement of the reaction γγ → ϱ+ϱ− with the CELLO detector

\Gamma _{\gamma \gamma }^{\eta _c }

Exclusive τ decays with the CELLO detector at PETRA

keV (95% c.l.) is obtained. For the glueball candidate η(1440) (previouslyi) the upper limit

Global properties of pion production in the reaction γγ→3π+3π-

\Gamma _{\gamma \gamma }^{\eta (1440)} B(\eta (1440) \to K\bar K\pi )< 1.2keV(95\% c.l.)