A new measurement of the Z0 peak hadronic cross section σ0had using a high precision silicon-tungsten luminometer in Aleph

A new silicon-tungsten luminosity calorimeter (SICAL) was installed in the ALEPH experiment in 1992. Using this calorimeter, the absolute luminosity was measured with experimental systematic uncertainties of 0.15%. In two-month data taking period ALEPH recorded over 200000 hadronic decays of the Z0 boson. The peak hadronic cross section is determined from these data using MZ, Rl and γZ measured with 1990-1992 ALEPH data. The paper discusses the design of the SICAL, the analysis used to extract the absolute luminosity, and the results of the fit. 2 figs., 14 refs