Search for the t and b' quarks in hadronic decays of the Z0 boson

We present a search for the third generation up type quark t and a possible fourth down type quark b' in hadronic Z0 decays observed in DELPHI at the LEP collider. For any scenario with a decay through the charged current or into a charged Higgs with a mass at least 6 GeV/c2 below the t and 3 GeVc2 below the b' mass, we set a lower limit for the t quark mass at 44.0 GeV/c2 and for the b' mass at 44.5 GeV/c2. For specific scenarios the mass limits are slightly higher, e.g. for charged current decays the limits are 44.5 and 45.0 GeV/c2 respectively, where all limits are given at a 95% confidence level. © 1990.

Evidence for B$^{0}_{s}$ meson production in Z$^0$ decays

Seven unambiguous events out of a sample of 270 000 Z0 decays, contain in tile same jet a D(s) meson and a muon at large transverse momentum relative to the et axis. These events are direct evidence for B(s)0 meson production in hadronic Z0 decays. The production rate of these events, relative to all hadronic Z0 decays is ( 18 +/- 8) x 10(-5) this number including the relevant branching fractions of the B(s)0 and D(s). The value of the B(s)0 meson lifetime relative to the average B meson lifetime is measured to be 0.8 +/- 0.4.

A Measurement of the Bbbar Forward-backward Asymmetry Using the Semileptonic Decay Into Muons

Search for the sgoldstino at √s = 189 to 202 GeV.

A search for the supersymmetric partner of the goldstino, the sgoldstino S, at LEP2 is presented. The production Sgamma followed by S decay into two gluons or into two photons was studied at 189 - 202 GeV LEP centre-of-mass energies. No evidence for the S production was found and limits on the S mass corresponding to different theory parameters are given.

Search for pair production of neutral Higgs bosons in Z$^0$ decays

The pair production of the lightest scalar Higgs boson, h, and a pseudoscalar Higgs boson, A, was searched for in a data sample containing 10 000 hadronic Z0 decays. The search involved both leptonic and purely hadronic decay channels of each Higgs boson. No signal was found, and limits on the Higgs boson masses, in the framework of the minimal supersymmetric extension of the standard model, ar reported up to 35 GeV/c2 at 95% CL, for both tan β > 1 and tan β < 1, where tan β is the ratio of the vacuum expectation values of the two Higgs doublets.

Determination of |Vub|/|Vcb| with DELPHI at LEP

The ratio of the CKM quark-mixing matrix elements |Vub|/|Vcb| has been measured using B hadron semileptonic decays. The analysis uses the reconstructed mass M_X of the secondary hadronic system produced in association with an identified lepton. Since B -&gt; X_u lepton anti-nu transitions are characterised by hadronic masses below those of the D mesons produced in B -&gt; X_c lepton anti-nu transitions, events with a reconstructed value of M_X significantly below the D mass are selected. Further signal enrichments are obtained using the topology of reconstructed decays and hadron identification. A fit to the numbers of decays in the b -&gt; u enriched and depleted samples with M_X above and…

Measurements of the trilinear gauge boson couplings WWV (V = $\gamma$ Z) in e$^+$e$^-$ collisions at 183 GeV

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 − → Weν and e + e − → ννγ , values are obtained for Δg 1 Z and Δκ γ , the differences of the WWZ charge coupling and of the WWγ dipole couplings from their Standard Model values, and for λ γ , the WWγ quadrupole coupling. The observations are consistent with the predictions of the Standard Model. (Elsevier)