"Search for New Particles in e^+e^- Collisions by the TOPAZ Detector"

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The TOPAZ detector has been operated since May 1987,and accumulated data at the center of mass energies from 52 to 60.8 GeV.For the off-line data analysis,we established a facility of processing the raw data at the high energy physics laboratory in Nagoya university,fully utilizing its dedicated mainframe computer system.KEKshared in 'pass-one' processing,while Nagoya shared in 'pass-two' processing in which the final calibration constants were used.As the result,we could get the final version of full DSTs for the physics analysis within a month after the data taking period.In looking for new particles and new phenomena,we carried out a search for top quark in the multi-hadron events,a search for heavy lepton,a measurement of forward-dackward asymmetry in the lepton pair production,and a search for supersymmetric (SUSY) particles.Top quark search was done by mesuring R-ratio and analysing event shape,and we found no positive evidence of top quark production upto <square root>s=55 GeV.However,the possibility of the production of charge-1/3 quark of the 4-th generation was not ruled out with the resent statistics. The result of a heavy lepton search was negative,and mass lower limit was set at 25.5 GeV/c^2. Forward-backward asymmetries of and pair production were consistent with the prediction of W-S standard model,and did not require the existance of the 2nd Z boson (Z').A search for pair produced SUSY particles was done.The candidate events were consistent with possible background processes like QED,and the lower mass limit for scaler ,scaler and scaler quark were renewed as 24.5 GeV/c^2,21.7 GeV/c^2 and 26.3 GeV/c^2,respectively.Along with these analyses,importance of making the TOPAZ detector be hermetic (to be sensitive to the single photon events) was realized if we were to be competitive with LEP-SLC in the field of the new particle search,and the upgrading project made progress.