C. Bruschini

Performance of an electromagnetic liquid krypton calorimeter based on a ribbon electrode tower structure

The NA48 collaboration is preparing a new experiment at CERN aiming to study CP violation in the K0-K0 system with an accuracy of 2 × 10−4 in the parameter Re(ϵ′/ϵ). Decays in two π0s will be recorded by a quasi-homogeneous liquid krypton calorimeter. A liquid krypton calorimeter has been chosen to combine good energy, position and time resolution with precise charge calibration and long-term stability. The prototype calorimeter incorporating the final design of the electrode read-out structure is presented in this paper. An energy resolution of ≃3.5%√E with a constant term smaller than 0.5% has been obtained. The time resolution was found to be better than 300 ps above 15 GeV.

WA92 : A FIXED TARGET EXPERIMENT TO TRIGGER ON AND IDENTIFY BEAUTY PARTICLE DECAYS

Abstract We describe the detectors and trigger system used in the CERN WA92 experiment. The experiment was designed to study the production and decay of beauty particles from 350 GeV/ c π − interactions in copper and tungsten targets. Charged particle tracking is performed using the omega spectrometer. Silicon microstrip detectors are used to provide precise tracking information in the region of the production and the decay of heavy-flavoured particles and to trigger on the resulting high impact parameter tracks. The precision of vertex reconstruction corresponds to ±3.7% of the mean B-decay proper lifetime. Lepton and high transverse momentum hadron signals are also used in the trigger, which accepts 23% of B-decays and rejects 98.4% of non-beauty interactions.

STUDY OF CHARM CORRELATIONS IN PI(-)-N INTERACTIONS AT ROOT-S-APPROXIMATE-TO-26 GEV

Abstract We report on the associated production of charmed hadrons in π−-nucleon interactions at s ≃26 GeV at the CERN Ω′ spectrometer. Results on the azimuthal correlation of charmed particle pairs are presented and compared to the predictions of Next-to-Leading-Order QCD calculations.

Measurement of the beauty production cross section in 350 GeV / c π-Cu interactions

Abstract Using a sample of 108 triggered events, produced in π−−Cu interactions at 350 GeV/c, we have identified 26 beauty events. The estimated background in this sample is 0.6 ± 0.6 events. From these data, assuming a linear A-dependence, we measure a beauty production cross section integrated over all χF of 5.7−1.1+1.3 (stat.)−0.5+0.6 (syst.) nb/N.

Search for the decay D0 → μ+μ−

Abstract We have searched for the decay D 0 → μ + μ − among 1.25 × 10 5 μ + μ − pairs produced by 350 GeV/ c π − particles interacting in copper and tungsten targets. Using a high-resolution silicon-microstrip detector followed by a large-acceptance magnetic spectrometer and a muon filter we are able to discriminate between prompt and non-prompt muons and to measure dimuon masses. No candidate compatible with a D 0 → μ + μ − decay has been found, allowing us to set an upper limit on the branching fraction B( D 0 → μ + μ − ) of 7.6 × 10 −6 at the 90% confidence level.

WA92: A fixed target experiment to study beauty in hadronic interactions

Abstract The essential feature of the described experimental techniques is the use of two specially designed pieces of hardware: a high precision “decay detector” and a fast secondary vertex trigger processor. Experiment WA92 should be able to obtain a sufficient data sample to measure lifetimes of B ± and B 0 and the B hadroproduction cross section.

Search for the decay D0 ---> mu+ mu-

Abstract We have searched for the decay D 0 → μ + μ − among 1.25 × 10 5 μ + μ − pairs produced by 350 GeV/ c π − particles interacting in copper and tungsten targets. Using a high-resolution silicon-microstrip detector followed by a large-acceptance magnetic spectrometer and a muon filter we are able to discriminate between prompt and non-prompt muons and to measure dimuon masses. No candidate compatible with a D 0 → μ + μ − decay has been found, allowing us to set an upper limit on the branching fraction B( D 0 → μ + μ − ) of 7.6 × 10 −6 at the 90% confidence level.