Search

Matrix elements to be used in second order Monte Carlo generators for e e annihilation have been derived from the O(α) calculations by Ellis, Ross and Terrrano and by Kramer and Lampe. They were incorporated into the JETSET 6.3 Lund String Monte Carlo program. The recombination scheme dependence of the O(α) jet cross sections are studied in detail on the parton level (ERT) and on the hadron level (ERT and KL). [ABSTRACT FROM AUTHOR]

The cross sections for 2-, 3- and 4-jet production have been determined with the JADE detector, sited on the e e-storage ring PETRA. Data at $$\sqrt s = 14$$ , 22, 35 and 44 GeV were compared to two O(α) QCD calculations. A first analysis was performed with uncorrected data using the O(α) 3-jet matrix element calculation of Ellis, Ross and Terrano and the Lund String Monte Carlo program. In a second analysis the calculation of Kramer and Lampe was compared to corrected data. Both approaches gave a poor description of the data when the square of the momentum transfer Q= s was used as the scale of the running coupling constant. The description improved when the renormalization scale was adjusted to the process studied. The data ware used to fix the best renormalization scale. [ABSTRACT FROM AUTHOR]

Using the JADE detector at PETRA, a search for hadronic events with isolated leptons in e e annihilation was performed. No evidence was found for the production of leptoquarks or color octet leptons and mass limits were obtained. Three hadronic events, each of them with two isolated muons, were detected and found to be in agreement with predictions of the α QED process $$e^ + e^ - \to q\bar q\mu ^ + \mu ^ - $$ . At the highest PETRA energies, $$46.30 Gev \leqq \sqrt s \leqq 46.78$$ , five events with low thrust, T<0.8, and a muon at a large angle with respect to the thrust axis, |cos δ|<0.7, were observed. The number of such events expected from an extrapolation of control data at lower energies is 0.56±0.18. No satisfactory explanation for the excess in terms of background could be found. A corresponding excess of electron events was not seen. [ABSTRACT FROM AUTHOR]

Muon inclusive multihadronic final states in e e annihilation at $$\langle \sqrt s \rangle $$ =34.6 GeV, collected by the JADE detector at PETRA, have been analysed in terms of the semi-muonic branching ratios and fragmentation functions of heavy quarks. Defining the fragmentation variable, ζ, as $$z = \frac{{\left( {E + p_\parallel } \right)_{hadron} }}{{\left( {E + p} \right)_{quark} }}$$ we find < z>=(77±3±5)% and < z>=(86±4±5)%. The corresponding semi-muonic branching ratios are measured to be BR( c→μ v X)=7.8±1.5±2)% and BR ( b→μ v X)=(11.7±1.6±1.5)%. Defining ζ as $$x_E = \frac{{E_{hadron} }}{{E_{beam} }}$$ we observe an expected softening effect in the fragmentation due mainly to gluon emission, but find that this definition leads to semi-muonic branching ratiomeasurements which are strongly affected by uncertainties in the fragmentation process and the WCD calculation. [ABSTRACT FROM AUTHOR]

Hadronic jet production by e e-annihilation has been studied in the energy range of 14.0-46.7 GeV. The data have been analysed in terms of a cluster algorithm and other topological quantities. The results are compared with 2 order QCD calculations which incorporate models for the fragmentation of quarks and gluons into hadrons. At the higher energies we observe more spherical and 4-jet like events than predicted by these calculations. We cannot achieve a simultaneous description of the observed 3- and 4-jet production by adjusting the strong coupling constant α or the fragmentation parameters of the 2 order QCD models. The observed excess of spherical events can partially be explained by the production of multi-parton events expected from higher order QCD contributions. Consequences of the presented results for the value of α, determined in previous analyses, are discussed. QCD parton shower models, including soft gluon interference, are able to describe the observed number of spherical events. [ABSTRACT FROM AUTHOR]

A study of radiative τ pair production, e e→ττγ and e e→ττγγ, is presented. The observed events agree with QED predictions of order α and α. Excited τ′s have been searched for and lower limits on single and pair production are obtained. For QED-like coupling the τ mass is limited to values greater than 40 GeV (95% CL). A search for unstable charged scalars ( S) decaying into τ, e.g. charged Higgs, technipions or the supersymmetric partners of τ′s, yields no evidence for such particles. Assuming a branching fraction of B( S→τν)=1, S masses up to 18.7 GeV are excluded with 95% CL. [ABSTRACT FROM AUTHOR]

We have determined the lifetime of B-hadrons produced in e e annihilation into multihadronic final states, by measuring the impact parameter of the track with respect to the centre of the interaction region. Two different analyses of the data were performed and gave compatible results. The lifetime is τ=1.8±0.4 ps. [ABSTRACT FROM AUTHOR]

Lepton pair production by two-photon processes has been studied using the JADE detector at PETRA. The study probed QED to α in the highest Q region. Both electrons and positrons were tagged by the endcap or barrel shower counters. The observed events consist of two produced leptons as well as two tagged electrons. These events show good agreement with QED to order α. [ABSTRACT FROM AUTHOR]

An analysis of the three leptonic reactions e e→ e e, μ μ and τ τ over a wide range of energy, $$12< \sqrt s< 46.78 GeV$$ is presented. The data were obtained with the JADE detector at the e e storage ring PETRA. They are compared to predictions of electroweak theories, in particular the standard model. For the total cross-sections of all three reactions and for the differential cross-section of Bhabha scattering no deviation from QED is found over the entire energy range. The differential cross-sections of μ and τ pairs at high energies show the angular asymmetry predicted by electroweak interference. The axial-vector and vector weak coupling constant, sin θ and M are determined and compared to other measurements. Finally, limits on deviations from the standard model are given. [ABSTRACT FROM AUTHOR]

A search has been made for the chargino, the supersymmetric partner of the W (or the partner of the charged Higgs bosons), in e e annihilation at PETRA using the JADE detector. The chargino decay modes investigated are $$l\tilde v, l\bar v\tilde \gamma , q_1 \bar q_2 \tilde \gamma$$ and $$q_1 \bar q_2 \tilde g$$ (with subsequent gluino decay $$\tilde g \to q\bar q\tilde \gamma$$ ). No evidence for such events has been observed. The 95% C.L. lower limit for the chargino mass is typically 22.5 GeV, depending only slightly on the masses of other supersymmetric particles. If the chargino is stable, the lower mass limit is 21.1 GeV (95% C.L.). [ABSTRACT FROM AUTHOR]