Measurement of R and search for the top quark in e+e- annihilation between 39.8 and 45.2 GeV

e+e- annihilation into hadrons was studied at CM energies between 39.8 and 45.2 GeV and a search was made for new heavy quarks. No evidence was found for the existence of a narrow state excluding the possible existence of the lowest vector toponium state in this mass range. A search for continuum production of heavy quarks led to lower mass limits for new quarks of 22.0 GeV (esub(Q) = 2/3) and 21.0 GeV (esub(Q) = 1/3). Quarks are found to be pointlike, the corresponding mass parameter being larger than 288 GeV. A fit of the QCD and the electroweak contributions to R = sigmasub(tot)/sigmasub(μμ) yielded sin2thetasub(W) = 0.30sub(-0.07)sup(+0.23). (orig.)