G. Bohm

The Outer Tracker detector of the HERA-B experiment. Part II: Front-end electronics

The HERA-B Outer Tracker is a large detector with 112674 drift chamber channels. It is exposed to a particle flux of up to 2x10^5/cm^2/s thus coping with conditions similar to those expected for the LHC experiments. The front-end readout system, based on the ASD-8 chip and a customized TDC chip, is designed to fulfil the requirements on low noise, high sensitivity, rate tolerance, and high integration density. The TDC system is based on an ASIC which digitizes the time in bins of about 0.5 ns within a total of 256 bins. The chip also comprises a pipeline to store data from 128 events which is required for a deadtime-free trigger and data acquisition system. We report on the development, installation, and commissioning of the front-end electronics, including the grounding and noise suppression schemes, and discuss its performance in the HERA-B experiment.

Aging studies for the large honeycomb drift tube system of the Outer Tracker of HERA-B

Abstract The HERA-B Outer Tracker consists of drift tubes folded from polycarbonate foil and is operated with Ar/CF4/CO2 as drift gas. The detector has to stand radiation levels which are similar to LHC conditions. The first prototypes exposed to radiation in HERA-B suffered severe radiation damage due to the development of self-sustaining currents (Malter effect). In a subsequent extended R&D program major changes to the original concept for the drift tubes (surface conductivity, drift gas, production materials) have been developed and validated for use in harsh radiation environments. In the test program various aging effects (such as Malter currents, gain loss due to anode aging and etching of the anode gold surface) were observed, and cures by tuning of operation parameters were developed.

Improved measurement of the bb production cross section in 920 GeV fixed-target proton-nucleus collisions

A new measurement of the b-bbar production cross section in 920 GeV proton-nucleus collisions is presented by the HERA-B collaboration. The b-bbar production is tagged via inclusive bottom quark decays into J/psi mesons, by exploiting the longitudinal separation of J/psi->ll decay vertices from the primary proton-nucleus interaction point. Both e+e- and mu+mu- channels are reconstructed, for a total of 83 +- 12 inclusive b->J/psi X events found. The combined analysis yields a b-bbar to prompt J/psi cross section ratio of

The Outer Tracker detector of the HERA-B experiment—Part I: Detector

{\frac{{\Delta\sigma(bbbar)}}{{\Delta\sigma_{\jpsi}}}} = 0.032\pm 0.005 \stat \pm 0.004 \sys

Humidity dependence of anode corrosion in HERA-B Outer Tracker chambers operated with Ar/CF4/CO2

measured in the x_f acceptance (-0.35 <x_f <0.15), extrapolated to

The outer tracker detector of the HERA-B experiment. Part III: Operation and performance

\sigma(bbbar) = 14.9 \pm 2.2 \stat \pm 2.4 \sys

Observations on cathode aging (Malter effect) in honeycomb drift chambers under high irradiation load

nb/nucleon in the total phase space.