HERA-B detector components

The HERA-B Detector


Disclaimer:

This is a prepreliminary version. All information has to be checked. Especially the ownerships are not assumed to be complete.

Components:

TARGET:   (Target homepage)   (Pictures of the target setup)   (NIM A446, 190 (2000)) (NIM A456, 206 (2001))

The target assembly consists of two wire stations separated by 4 cm along the beam line, each containing 4 target wires of different materials. A servo system automatically steers the target wires during a run in order to maintain a constant interaction rate.

Vertex Detector:   (VDS homepage)   (Pictures of the VDS)   (NIM A501, 39 (2003))   (NIM A511, 24 (2003))   (NIM A439, 442 (2000))

The Vertex Detector System (VDS) is realized by a system of 20 Roman pots containing seven planar stations (4 stereo views) of double-sided silicon micro-strip detectors (50 mm * 70 mm, 50 mu pitch) that are operated in a vacuum vessel at 10 to 15 mm distance from the proton beam. An additional station is mounted immediately behind the 3 mm thick Al window of the vacuum vessel.

Inner Tracker:   (ITR homepage)   (Pictures of the ITR)   (NIM A446, 324 (2000))   (NIM A392, 105 (1997))

The HERA-B Inner Tracker system, which is built by groups from the universities of Heidelberg, Siegen and Zuerich, consists of 184 detectors. The detectors are composed of Microstrip Gas Chambers (MSGC) with a pre-amplifying device in the gas volume, the Gas Electron Multiplier (GEM). The system includes 140k analog and 10k trigger channels.

Outer Tracker:   (OTR homepage)   (Pictures of the OTR)   (NIM A446, 317 (2000))   (NIM A515, 155 (2003))

The Outer Tracker (OTR) of HERA-B serves charged particle detection from the outer acceptance limit of the experiment down to a distance of 20 cm from the HERA proton beam. At positions between 2 and 13 m from the HERA-B target 13 planar drift chambers of increasing size are placed perpendicular to the beam. Each chamber contains several layers which measure different stereo views and are composed of honeycomb drift tube modules with cell diameters of 5 and 10 mm. The electronic readout system provides drift time information from 115000 channels. Other essential support systems supply HV and gas to the detector.

High pt chambers:   (High pt homepage)

The pretrigger logic reads in signals from 18000 pads distributed among three chamber stations. Each station is divided into two regions: a small inner region nearest the beam which is covered by gas pixel chambers being developed at Institut of Theoretical and Experimental Physics (ITEP, Moscow), and a large outer region surrounding the inner region, which is covered by straw tube chambers with pad readout being developed at University of Cincinnati.


Ring Imaging Cherenkov Counter:   (RICH homepage)   (Pictures of the RICH)
  (NIM A446, 299 (2000))   (NIM A453, 289 (2000))   (NIM A516, 445 (2004))

The HERA-B RICH uses C4F10 as radiator gas and a large 24 m2 spherical mirror for imaging. The photon detector employs 2240 Hamamatsu multi-anode photomultipliers with a total of 27000 channels. To match anode dimension (4.5 mm) and dispersion error and to solve the PMT packing problem we used a 2 : 1 reducing two-lens telescope in front of each PMT. The design performance of the RICH was fully reached: the average number of photons for a =1 particle detected in the RICH was found to be 35.4; a single-photon resolution of 0.65 mrad was reached. We used stand-alone ring finding algorithms to measure the angle and of tracks. With the position information of the target and that of clusters in the electromagnetic calorimeter we were able to identify electrons, pions, kaons and protons.

Transition Radiation Detector:   (TRD homepage)
  (NIM A408, 289 (1998))

The Transition Radiation Detector (TRD) is a part of the Electron Identification System of the HERA-B experiment. The TRD is based on a fine-grain structure of polypropylene fibre radiator with Kapton straw proportional detectors.

Electromagnetic Calorimeter:   (ECAL homepage)   (Pictures of the ECAL)
  (NIM A446, 246 (2000))   (NIM A461, 332 (2001))

The ECAL is based on "shashlik" sampling calorimeter technology, consisting of scintillator layers sandwiched between metal absorbers. It is built as a matrix of 5956 "shashlik" calorimeter cells. The cells are squares having different side sizes in order to match the granularity requirements. This leads to identify three different regions: Inner, Middle and Outer. In the radially innermost section, W is used as absorber and Pb everywhere else.

Muon System:   (Muon homepage)   (Pictures of the Muon layer 1)   (Pictures of the Muon layers 2-4)
  (IEEE Trans. on Nucl Sci.46, 126 (1999))   (NIM A461, 104 (2001))

The Muon system is segmented into four superlayers interleaved with iron-loaded concrete and steel shielding after the third and fourth superlayers. The first two superlayers have three layers of tube chambers with 0deg and ±20deg stereo angles. The last two superlayers consist of one 0deg layer with pad chambers. Each of the superlayers is equipped with pixel chambers in the central region. Coincidences between pad or pixel signals in the last two superlayer are used for the pre-trigger. Signals from anode wires from all superlayers except the second provide information for the first level trigger hardware.

July-01-04 J. Spengler