[en] A summary is given of the LEP measurements on the production and masses of B hadrons. It covers the production of B hadrons, evidence for for Ξ_b⁺ production and limits on B_c⁺ production. Further, the precise measurements of the B_s⁰ and Λ_b masses are discussed. The LEP results for B* mass and properties are summarized. Finally, the latest evidence is shown for B** production, and the results for the B** and B_s** masses are presented. (orig.)

[en] In the last decade, the LEP experiments played a central role in the study of B hadrons (hadrons containing a b quark). New B hadrons have been observed (B⁰_s, Λ_B, Ξ_b and B^**) and their production and decay properties have been measured. In this paper we will focus on measurements of the CKM matrix elements: |V_cb|, |V_ub|, |V_td| and |V_ts|. We will show how all these measurements, together with theoretical developments, have significantly improved our knowledge on the flavour sector of the Standard Model. (authors)

[en] The DELPHI RICH has been operated successfully at LEP I energies. With the increase of the centre of mass energy at LEP II the changed running conditions set new challenges: a very short period at the Z⁰ pole to provide calibration data and a long data taking period at high energy with the low event rate typical for operation away from the pole. These conditions require to revise the strategy for calibration and alignment of the DELPHI RICH. The most relevant improvement was the development of a new alignment program. In addition, the detector stability had to be monitored more carefully due to the long data-taking periods. As a result it will be shown that a similar data quality has been obtained as during LEP I operation. The new procedures also decrease dramatically the time necessary to perform the detector analysis

No abstract available

[en] A small TPC has been read out by means of a MediPix2 readout chip as direct anode. A Micromegas foil was placed 50 μm above the chip, and electron multiplication occurred in the gap. With a He/Isobutane 80/20 mixture, gas multiplication factors up to tens of thousands were achieved, resulting in an efficiency for detecting single electrons of better than 90%. We recorded many frames containing 2D images with tracks from cosmic muons. Along these tracks, electron clusters were observed, as well as δ-rays

[en] The DELPHI detector at LEP is equipped with RICH detectors which can be exploited for tagging decays of the Z boson into ss pairs. High momentum K^± identified with the RICH have been used both for a double tag of the s quark and for a single tag using the φ(1020) meson. (orig.)

[en] A small TPC has been read out by means of a Medipix2 chip as direct anode. A Micromegas foil was placed 50μm above the chip, and electron multiplication occurred in the gap. With a He/isobutane 80/20 mixture, gas multiplication factors up to tens of thousands were achieved, resulting in an efficiency for detecting single electrons of better than 90%. With this new readout technology for gas-filled detectors we recorded many image frames containing 2D images with tracks from cosmic muons. Along these tracks, electron clusters were observed, as well as δ-rays. With a gas layer thickness of only 1mm, the device could be applied as vertex detector, outperforming all Si-based detectors

[en] Proton-antiproton elastic scattering was measured at the CERN SPS Collider at the centre-of-mass energy √s = 546 GeV in the Coulomb interference region. The data provide information on the phase of the hadronic amplitude in the forward direction. The conventional analysis gives for the ratio ρ of the real to the imaginary part of the hadronic amplitude the result ρ = 0.24±0.04. (orig.)

[en] By placing a Micromegas gas gain grid on top of a CMOS pixel readout circuit (MediPix2), we developed a device which acts as a pixel-segmented direct anode in gas-filled detectors. With a He/Isobutane 80/20 mixture (capable of achieving gas gain factors up to 20x10³) and employing a drift length of 15mm, signals from radioactive sources and cosmic radiation were measured. Single primary electrons originating from the passage of cosmic muons through the gas volume were detected with an efficiency higher than 90%

[en] Proton-antiproton elastic scattering was measured at the centre-of-mass energy √s=630 GeV in the four-momentum transfer range 0.7<=-t<=2.2 GeV². The new data confirm our previous results at √s=546 GeV on the presence of a break in the t-distribution at -tapprox.=0.9 GeV² which is followed by a shoulder, and extend the momentum transfer range to larger values. The t-dependence of the differential cross section beyond the break is discussed. (orig.)