Electroweak parameters of the z0 resonance and the standard model

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Measurement of B0 - anti-B0 mixing at the CERN S p anti-p S collider

We report on a new measurement of B0-BBAR0 mixing at the CERN SppBARS Collider. Mixing is measured in the non-isolated high mass dimuon sample using data from the 1988-1989 collider runs. The measured value of the mixing parameter, chi, is 0.145 +/- 0.035(stat.) +/- 0.014(syst.). The average of this measurement and that from our 1984-1985 data is chi = 0.148 +/- 0.029(stat.) +/- 0.017(syst.) assuming fully correlated systematic errors. Using the measurement of chi-d from ARGUS and CLEO, we obtain chi-s = 0.50 +/- 0.20, which gives a limit of chi-s > 0.17 (0.12) at 90% (95%) CL. Including the measurements of chi from the ALEPH and L3 experiments gives chi-s = 0.53 +/- 0.15, and a limit of chi-s > 0.27 (0.23) at 90% (95%) CL

First observation of the beauty baryon LAMBDA(b) in the decay channel LAMBDA(b) ---> J / psi LAMBDA at the CERN proton - anti-proton collider

We report on the first observation of the beauty baryon LAMBDA(b) in an exclusive decay channel at the CERN ppBAR collider. Using 4.7 pb-1 of muon data collected in the 1988/89 collider runs we reconstruct 16 +/- 5 LAMBDA(b)'s in the decay mode LAMBA(b) --> J/psi-LAMBDA above a background of 9 +/- 1 events, corresponding to a significance of about five standard deviations. We measure the LAMBDA(b) mass to be m(LAMBDA(b)) = 5640 +/- 50 +/- 30 MeV/c2. Using the beauty cross-section measured by UA1 we deduce for the product of the production fraction and branching ratio f(LAMBDA(b)) Br(LAMBDA(b) --> J/psi-LAMBDA) = (1.8 +/- 1.0) X 10(-3). Our sample contains a three-muon event in which the beauty particle opposite to the LAMBDA(b)BAR is tagged by the third muon. We also observe an indication of a signal in the decay channel B0 --> J/psi-K0* with a significance of three standard deviations

Events with large missing transverse energy at the CERN collider: III. Mass limits on supersymmetric particles

A sample of events with large missing transverse energy from 715 nb-1 of data from the UA1 experiment at the CERN proton-antiproton collider is used to search for evidence of supersymmetric particle production. Assuming that the photino is the lightest supersymmetric particle and that it is massless, we find a limit on the squark mass of mq>45 GeV/c2 at 90% CL, independently of the gluino mass. Similarly, we find a limit on the gluino mass of mg>53 GeV/c2 (at 90% CL) independently of the squark mass, provided that the gluino is not long-lived (i.e. provided that the squark is not too heavy, mq{less-than or approximate}1 TeV/c2). For equal squark and gluino masses we find a limit mq=mg>75 GeV/c2 at 90% CL. The effect of a non-zero photino mass on these limits is studied. © 1987

Measurement of the bottom quark production cross section in proton-antiproton collisions at ?s = 0.63 TeV

We summarize the results obtained in the UA1 experiment on the production of bottom quarks in proton-antiproton collisions at √s=0.63 TeV. Independent muon data samples are used to determine the bottom quark production cross section in different transverse momentum ranges from 6 to 30 GeV. A recent theoretical calculation to O(αs 3) of the inclusive bottom quark transverse momentum spectrum in hadronic collisions shows reasonable agreement with the data. We extrapolate the integral PT distribution to PT=0 and in rapidity to estimate the total cross section forthe production of bottom quark pairs. Assuming the shape in PT and rapidity given by the O(αs 3) calcultaion, we obtain σ(pp→bb+X) = 10.2 ±3.3 μb. © 1988