91̽»¨

Abstract:

The rate Z → bbÌ„bbÌ„ was measured using about 2×10⁶ hadronic decays collected by the DELPHI experiment in 1994 and 1995. Events were forced into 3-jets with ymin > 0.06 and a b-tag was required for every jet. The rate was measured to be: R4b = BR(Z → bbÌ„bbÌ„)/BR(Z → hadrons), = (6.0 ± 1.9(stst.)) ± 1.4(Syst.)) × 10^-4 where the invariant mass of every bbÌ„ system is above twice the b quark mass. Using the value of R4b the probability of secondary production of a bbÌ„ pair from a gluon per hadronic Z decay, gbb, was extracted and found to be: gbb = (3.3 ± 1.0(stat) ± 0.8(syst.)) × 10^-3. © 1999 Published by Elsevier Science B.V. All rights reserved.

Abstract:

Data collected with the DELPHI detector from 1993 to 1995 combined with previous DELPHI results for data from 1991 and 1992 yield the branching fractions B(τ → evv̄) = (17.877 ± 0.109stat ± 0.110sys)% and B(τ → μvv̄) = (17.325 ± 0.095stat ± 0.077sys)%.

Abstract:

Measurements of the trilinear gauge boson couplings WWγ and WWZ are presented from data taken by DELPHI in 1997 at an energy of 183 GeV. From a study of the reactions e+ e- →W+W-, e+e- → Wev and e+ e-→ vvy, values are obtained for Δg1Z and Δκγ, the differences of the WWZ charge coupling and of the WWγ dipole couplings from their Standard Model values, and for λγ, the WWγ quadrupole coupling. The observations are consistent with the predictions of the Standard Model. © 1999 Elsevier Science B.V. All rights reserved.

Abstract:

Multiplicity fluctuations in rings around the jet axis and in off-axis cones have been measured by the DELPHI collaboration in e+ e- annihilations into hadrons at LEP energies. The measurements are compared with analytical perturbative QCD calculations for the corresponding multiparton system, using the concept of Local Parton Hadron Duality. Some qualitative features are confirmed by the data but substantial quantitative deviations are observed. © 1999 Published by Elsevier Science B.V. All rights reserved.

Abstract:

A search for pair produced charged Higgs bosons has been performed in the high energy data collected by DELPHI at LEP with √s = 161, 172 and 183 GeV. The analysis uses the τντν, cs̄τν and cs̄c̄s final states and a combination of event shape variables, di-jet masses and jet flavour tagging for the separation of a possible signal from the dominant W+W- and QCD backgrounds. The number of selected events has been found to be compatible with the expected background. The lower excluded value of the H± mass obtained by varying the H±→ hadrons decay branching ratio has been found to be 56.3 GeV/c2. © 1999 Published by Elsevier Science B.V. All rights reserved.