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T: Teilchenphysik

T 206: Elektroschwache Wechselwirkung I

T 206.1: Vortrag

Montag, 18. März 2002, 16:15–16:30, HS 8

Study of Z Boson pair production with the OPAL detector at LEP — •Stefano Rosati¹, Michael Kobel¹, Markus Warsinsky¹, and Hartmut Rick² — ¹Physikalisches Institut der Universität Bonn — ²Department of Physics, University of California, Riverside

The e⁺e⁻ accelerator LEP has been operating, between 1997 and 2000, at center of mass energies above the production threshold for pairs of real Z bosons. The study of the process e⁺e⁻→ZZ represents an important test of the Standard Model. At tree level the process can occur only through the NC02 diagrams (e exchange), as vertices of three neutral gauge bosons (γZZ and ZZZ) are forbidden. New physics leading to anomalous γZZ and ZZZ couplings would modify the e⁺e⁻→ZZ cross section, the Z’s angular distribution, and their average polarisation. To fully exploit the kinematical information in each event, the method of Optimal Observables has been used for the measurement of the anomalous couplings. In this method, the full kinematic of the reconstructed event is combined in a single observable with optimal sensitivity.

The presentation describes the results of the analysis of the data taken at center of mass energies up to 209 GeV with the OPAL detector at LEP (in particular referring to the fully hadronic channel). The results of the event selections and cross section measurement are shown, together with limits on anomalous γZZ and ZZZ couplings.