7 research outputs found
Aufbau und Charakterisierung des schnellen Kontrollsystem fuer das Experiment HERA - B
No full textThe experiment HERA-B is currently under construction at the Deutsches Elektronen Synchrotron DESY in Hamburg and, upon completion, will investigate CP-violation in decays of B-mesons. The central challenges for this experiment are a high density of particle tracks in the detector (about 200 tracks per event) and an extremely small signal-to-background-ratio (10"-"1"1 for the decay channel B#->#J/#psi#K_s"0#->#l"+l"-#pi#"+#pi#"-). Data from 540,000 channels must be processed an event rate of 10 MHz and a first level trigger rate of 50 kHz without deadtime. A novel fast control system has been developed to distribute time references, trigger information and test signals to the front end electroncis of all detector components as well as for some first level trigger control functions. This thesis starts with an introduction to the experiment and a detailed description of the data acquisition system which leads to the requirements for the fast control system. The motivation is followed by a description of the fast control hard- and software. The time references and trigger signals, which are distributed by the system, are characterized. Successful synchronization of the detector components is shown by means of data from the 1998 HERA - B -operation. Finally some possibilities the system provides for investigating the first level trigger and potential biases the fast control system might give to HERA - B measurements are discussed. (orig.)SIGLEAvailable from TIB Hannover: RR 8919(1999-016) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
Inclusive V 0 production cross sections from 920 GeV fixed target proton-nucleus collisions
No full textInclusive differential cross sections dσpA/dxF and dσpA/dp2t
for the production of K0S, Λ, and Λ particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to √s = 41.6 GeV in the proton-nucleon system. The ratios of differential cross sections dσpA(K0 S)/dσpA(Λ) and dσpA( ¯ Λ)/dσpA(Λ) are measured to be 6.2 ± 0.5 and 0.66 ± 0.07, respectively, for xF ≈−0.06. No significant dependence upon the target material is observed.
Within errors, the slopes of the transverse momentum distributions dσpA/dp2t also show no significant
dependence upon the target material. The dependence of the extrapolated total cross sections σpA on the atomic mass A of the target material is discussed, and the deduced cross sections per nucleon σpN are compared with results obtained at other energies
J/ψ production via χc decays in 920 GeV pA interactions
No full textUsing data collected by the HERA-B experiment, we have measured the fraction of J/ψ's produced via radiative χc decays in interactions of 920 GeV protons with carbon and titanium targets. We obtained Rχc= 0.32±0.06stat±0.04sys for the fraction of J/ψ from χc decays averaged over proton–carbon and proton–titanium collisions. This result is in agreement with previous measurements and is compared with theoretical predictions
Measurement of the b(b)over-bar production cross section in 920 GeV fixed-target proton-nucleus collisions
No full textUsing the HERA-B detector, the b (b) over bar production cross section has been measured in 920 GeV proton collisions on carbon and titanium targets. The b (b) over bar production was tagged via inclusive bottom quark decays into J/psi by exploiting the longitudinal separation of J/psi --> l(+)l(-) decay vertices from the primary proton-nucleus interaction. Both e(+)e(-) and mu(+)mu(-) channels have been reconstructed and the combined analysis yields the cross section sigma(b (b) over bar) = 32(-12)(+14)(stat) (+6)(-7)(sys) nb/nucleon
production via chi() decays in 920-GeV pA interactions
No full textUsing data collected by the HERA- B experiment, we have measured the fraction of J / ψ 's produced via radiative χ c decays in interactions of 920 GeV protons with carbon and titanium targets. We obtained R χ c = 0.32±0.06 stat ±0.04 sys for the fraction of J / ψ from χ c decays averaged over proton–carbon and proton–titanium collisions. This result is in agreement with previous measurements and is compared with theoretical predictions
