Guy Wilkinson

Abstract:

The first measurement of like-sign charged kaon correlations in hadronic decays of the Z0 is presented, based on data collected by the DELPHI detector. The charged kaons are identified by means of ring imaging Cherenkov detectors. A significant enhancement at small values of the four-momentum difference is observed in the ratio of like-sign to unlike-sign KK pairs and in the ratio of like-sign pairs to a simulated reference sample. An update of the measurement of K0sK0s interference is also presented. An enhancement is found in the production of pairs of K0s of similar momenta, as compared with a simulated reference sample. The measured Bose-Einstein correlation parameters λ and r are similar for charged and neutral kaon pairs. The value of the Bose-Einstein correlation strength λ is consistent with unity.

Abstract:

The measurement of the average lifetime of B hadrons using inclusively reconstructed secondary vertices has been updated using both an improved processing of previous data and additional statistics from new data. This has reduced the statistical and systematic uncertainties and gives τB = 1.582 ± 0.011 (stat.) ± 0.027 (syst.) ps. Combining this result with the previous result based on charged particle impact parameter distributions yields τB = 1.575 ± 0.010 (stat.) ± 0.026 (syst.) ps.

Abstract:

A search for fully reconstructed Λ0b beauty baryons is performed using about 3 million Ζ decays collected with the DELPHI detector at LEP. The analysis relies on the combined use of the accurate tracking and of the hadron identification capabilities of DELPHI. A total of four events has been found, three in the Λ+cπ- channel and one in the Λ+ca-1 channel over a small background. The Λ0b beauty baryon mass is measured to be (5668 ± 16 (stat.) ± 8 (syst.)) MeV/c2.

Abstract:

From the data collected by DELPHI at LEP in autumn 1995, the multiplicity of charged particles at a hadronic energy of 130 GeV has been measured to be 〈nch〉 = 23.84 ± 0.51 (stat) ± 0.52(syst). When compared to lower energy data, the value measured is consistent with the evolution predicted by QCD with corrections at next-to-leading order, for a value αs(130 GeV) = 0.105 ± 0.003(stat) ± 0.008(syst).

Abstract:

The tau lepton lifetime has been measured using three different methods with the DELPHI detector. Two measurements of one-prong decays are combined, accounting for correlations, giving a result ofττ = 291.8 ± 3.3 (stat.) ± 2.0(sys.) fs while the decay length distribution of three-prong decays gives the result ττ = 286.7 ± 4.9 (stat.) ± 3.3 (sys.) fs. Combining the results presented here with previous DELPHI measurements, we get ττ = 291.4 ± 3.0 fs and find that the ratio of the coupling constant for tau decay relative to that for muon decay is 0.990 ± 0.009, compatible with lepton universality.