Measurements of the differential cross sections for e + e − →μ + μ − and e + e − →τ + τ − at values of s from 52 to 57 GeV are reported. The forward-backward asymmetries and the total cross sections for these reactions are found to be in agreement with predictions of the standard model of the electro-weak interactions. These measurements are used to extract values of the weak coupling constant g v e g v l and g A e g A l , where l = μ or τ .
Axis error includes +- 5/5 contribution (Included in the quoted errors for the total cross sections. The main contribution to SYS-ERR are the systematic uncertainty in the luminosity measurement and the uncertainty in the computer modeling of the various efficiencies and backgrounds).
Axis error includes +- 5/5 contribution (Included in the quoted errors for the total cross sections. The main contribution to SYS-ERR are the systematic uncertainty in the luminosity measurement and the uncertainty in the computer modeling of the various efficiencies and backgrounds).
No description provided.
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(α s 3 ) of the inclusive bottom quark transverse momentum spectrum in hadronic collisions shows reasonable agreement with the data. We extrapolate the integral P T distribution to P T =0 and in rapidity to estimate the total cross section forthe production of bottom quark pairs. Assuming the shape in P T and rapidity given by the O(α s 3 ) calcultaion, we obtain σ( p p→b b +X) = 10.2 ±3.3 μb .
No description provided.
A search for pair production of fourth-generation sequential leptons in e+e− annihilation at a center-of-mass energy s=56 GeV is reported. Event topologies corresponding to the cases where one particle decays leptonically while the other decays hadronically as well as those where both particles decay hadronically were explored. We set a 95%-confidence-level lower limit of 27.6 GeV/c2 for the mass of a fourth-generation lepton.
No description provided.
Cross sections for 180° inelastic electron scattering from deuterium were measured from breakup threshold to beyond the quasielastic peak for incident-beam energies of 0.843, 1.020, 1.189, and 1.281 GeV, corresponding to 0.75≤Q2≤2.57 (GeV/c)2. The data are in reasonable agreement with nonrelativistic models that include final-state interactions and meson-exchange currents. The scaling function F(y) for these data is generally in agreement with F(y) for forward-angle data at the same Q2. Values of GMn determined from the data are in good agreement with results from previous experiments.
Axis error includes +- 0.0/0.0 contribution (3.9 TO 12.0////).
Axis error includes +- 0.0/0.0 contribution (3.9 TO 12.0////).
Axis error includes +- 0.0/0.0 contribution (3.9 TO 12.0////).
We present a study of low mass dimuon events [ m ( μμ ) < 6 GeV/ c 2 ] from the UA1 experiment at the CERN p p collider. Contributions from semileptonic decays of heavy flavour particles, Drell-Yan type processes, J/ψ decays and leptonic decays of light mesons are extracted, and cross sections for high p T beauty and Drell-Yan production are derived. A limit for the branching fraction for the exotic decay B 0 →μ + μ − is also obtained. The cross section for section for low mass, high p T Drell-Yan prod uction is compared to the measured direct photon cross section using QED and QCD derived relationship. This relationship is used to infer a measurement of the single photon cross section at lower values of transverse momentum, where photons cannot be unambigously identified.
GLOBAL SYTEMATIC ERROR OF 30PCT HAS TO BE ADDED.
Two-jet mass distributions have been measured as a function of centre-of-mass scattering angle for high-mass jet pairs produced in proton-antiproton collisions at the CERN collider operating at a centre-of-mass energy of 630 GeV. The agreement between QCD expectations and the experimental measurements has been used to place limits on the production cross section of an object X decaying into two jets. In particular we consider the existence of a massive colour octet of vector gauge bosons (axigluons). We exclude axigluons with a width Λ A < 0.4 m A and a mass m A in the range 150 < m A < 310 GeV/ c 2 (95% CL).
No description provided.
Isolated photons, produced directly by a scattering process, have been observed in the UA1 experiment at the CERN p p collider at centre-of-mass energies √=546 GeV and √=630 GeV . Single and double photon differential cross sections have been determined and found to be consistent with the expectations of QCD.
No description provided.
No description provided.
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The production of transverse energy clusters in minimum bias proton-antiproton collisions at the CERN SPS Collider is studied with the UA1 detector over a new range of centre of mass energies (√ s = 0.2−0.9 TeV). This study is intended to investigate how low in transverse momentum perturbative QCD is able to describe the dynamics of hadron collisions. We observe that clusters with transverse energy in excess of a few GeV exhibit properties in agreement with QCD expectations for parton scattering, supporting their interpretation in terms of jet production. We find that the jet-event rate represents a sizeable fraction of the inelastic rate and is increasing with √ s over the measured energy range.
No description provided.
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A search has also been made for a fourth generation, charge 1/3 quark (b'). Assuming that theb' mass is smaller than that of the top quark and that it can-not be produced inW decays, the mass limits, using the above procedures, are respectivelymb'>32 GeV/c2 andmb'>44 GeV/c2, both at 95% confidence level.
We present a study of heavy flavour (charm and beauty) production using data collected with the UA1 detector at the CERN Proton-Antiproton collider at a centre-of-mass energy of 630 GeV for an integrated luminosity of 556 nb−1. This follows our earlier study ofb\(\bar b\) andc\(\bar c\) production in dimuon events and the evidence for mixing betweenB0 and\(\bar B^0 \) states. Properties of an inclusive sample of events containing a muon withpT>6 GeV/c are compared with QCD predictions for heavy flavour production, using the ISAJET Monte Carlo program. The predicted largepT muon yield from heavy flavour production and decay agrees with the data to within 30%. For events with a muon ofpT>10 GeV/c and at least one jet withET>10 GeV, we measure the ratio charm/(charm+beauty) to be (24±8±9)%. We also show that the correlations observed between the two heavy quark jets expected by flavour conservation are consistent with the mixture of lowest and higher order QCD processes. We study in detail the topological and kinematic properties of a subsample of events containing a highpT muon and one or more jets. The good agreement of the theoretical predictions with our data in a region dominated by the production of charm and beauty shows that one of the main background sources to a new heavy quark signature is well understood.
No description provided.
Numerical values supplied by K.Wacker. Muon spectrum with at least one jet with PT > 12 GeV/c.
No description provided.
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