First measurement of Z / gamma* production in Compton scattering of quasireal photons

We report the first observation of Z/gamma* production in Compton scattering of quasi-real photons. This is a subprocess of the reaction e+e- to e+e-Z/gamma*, where one of the final state electrons is undetected. Approximately 55 pb-1 of data collected in the year 1997 at an e+e- centre-of-mass energy of 183 GeV with the OPAL detector at LEP have been analysed. The Z/gamma* from Compton scattering has been detected in the hadronic decay channel. Within well defined kinematic bounds, we measure the product of cross-section and Z/gamma* branching ratio to hadrons to be (0.9+-0.3+-0.1) pb for events with a hadronic mass larger than 60 GeV, dominated by (e)eZ production. In the hadronic mass region between 5 GeV and 60 GeV, dominated by (e)egamma* production, this product is found to be (4.1+-1.6+-0.6) pb. Our results agree with the predictions of two Monte Carlo event generators, grc4f and PYTHIA.

Note:

18 pages, LaTeX, 5 eps figures included, submitted to Physics Letters B Report-no: CERN-EP/98-120

electron positron: colliding beams
photon electron: Compton scattering
Z0: electroproduction
Z0: hadronic decay
hadron: multiple production
analytic properties
angular distribution
OPAL
experimental results
CERN LEP Stor

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