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Abstract:

During the last 1995 data acquisition period at LEP, the DELPHI experiment collected an integrated luminosity of 5.9 pb-1 at centre-of-mass energies of 130 GeV and 136 GeV. Radiative leptonic events (e, μ, τ) with high energy photons were studied and compared to Standard Model predictions. The data were used to search for charged excited leptons decaying through an electromagnetic transition. No significant signal was found. From the search for pair produced excited leptons, the limits me* > 62.5 GeV/c2, mμ* > 62.6 GeV/c2 and mτ* > 62.2 GeV/c2 at 95% confidence level were established. For single excited lepton production, upper limits on the ratio λ/mℓ* of the coupling of the excited charged lepton to its mass were derived.

Abstract:

The inclusive production of the f′2(1525) in hadronic Z⁰ decays has been studied in data collected by the DELPHI detector at LEP. The Ring Imaging Cherenkov detectors were important tools in the identification of the decay f′2(1525) → K⁺K^-. The average number of f′2(1525) produced per hadronic Z decay, 〈f′2〉 = 0.020 ± 0.005 (stat) ± 0.006 (syst), and the momentum distribution of the f′2(1525) have both been measured. The mass and width of the f′2(1525) are found to be 〈M ´Ú′2〉 = 1535 ± 5 (stat) ± 4 (syst) MeV/c², 〈Γ f′2〉 = 60 ± 20 (stat) ± 19 (syst) MeV/c².

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⁺cÏ€^- 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.