Updated precision measurement of the average lifetime of B hadrons

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 \tau_{\mathrm{B}} = 1.582 \pm 0.011\ \mathrm{(stat.)} \pm 0.027\ \mathrm{(syst.)}\ \mathrm{ps.} Combining this result with the previous result based on charged particle impact parameter distributions yields \tau_{\mathrm{B}} = 1.575 \pm 0.010\ \mathrm{(stat.)} \pm 0.026\ \mathrm{(syst.)}\ \mathrm{ps.

Crystal collimation studies at the Tevatron (T-980)

Bent-crystal channeling is a technique with a potential to increase beam-halo collimation efficiency in high-energy colliders. First measurements at the Tevatron in 2005 have shown that using a thin silicon crystal to deflect the 1-TeV proton beam halo onto a secondary collimator improves the system performance by reducing the machine impedance, beam losses in the collider detectors and irradiation of the superconducting magnets, all in agreement with simulations. Recent results, obtained with an improved goniometer and enhanced beam diagnostics, are reported here for dedicated beam studies and first full collider stores along with simulation results and plans for substantial enhancement of the T-980 experimental setup

A measurement of B+ and B0 lifetimes using Mathematical expression events

A measurement of B meson lifetimes is presented using data collected from 1991 to 1993 by the DELPHI detector at the LEP collider. Samples of events with a D meson and a lepton in the same jet are selected where {Mathematical expression} and D*ℓ+ events originate mainly from the semileptonic decays of B+ and B0 mesons, respectively. From the reconstructed B decay length and the estimated B momentum, taking into account the dilution due to B decays into {Mathematical expression}, the following B meson lifetimes and lifetime ratio are measured: {Mathematical expression} and an average lifetime of B+ and B0 mesons is obtained: {Mathematical expression} © 1995 Springer-Verlag

Strange baryon production in Z hadronic decays

A study of the production of strange octet and decuplet baryons in hadronic decays of the Z recorded by the DELPHI detector at LEP is presented. This includes the first measurement of the ∑± average multiplicity. The total and differential cross sections, the event topology and the baryon-antibaryon correlations are compared with current hadronization models. © 1995 Springer-Verlag

Search for the lightest chargino at s**(1/2) = 130-GeV and 136-GeV in DELPHI

A search for pair production of the lightest chargino at \rs= 130.4 and 136.3~GeV has been carried out using the data sample corresponding to the 5.92~${\rm pb}^{-1}$ recorded by the DELPHI detector during the high energy run of LEP in the last period of 1995. The theoretical reference model has been the Mi\-ni\-mal Supersymmetric Standard Model with R-parity conservation. The three topologies expected for the decay of a pair of charginos, namely two acoplanar leptons plus missing energy (\ll), two jets and an isolated lepton plus missing energy (\jjl) and missing energy in a hadronic environment (\jj), were investigated. No evidence of a signal was found. Lower mass limits were derived for various scenarios, including the case of a low mass difference between the chargino and the neutralino and of a light sneutrino. The mass limits range between 56.3~GeV/${\rm c}^2$ and the kinematic limit