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The Lund group participates in the PHENIX collaboration, one of two large experiments at RHIC, the Relativistic Heavy Ion Collider at Brookhaven National Laboratory, USA. RHIC started to deliver colliding beams of gold in the summer of 2000.
A three-dimensional cutaway of the PHENIX detector, showing the location of the various detector subsystems. Note the standard sized human setting the scale.
(Click on picture to enlarge... [61kB])
The PHENIX experiment focuses on the electromagnetic and leptonic probes of a Quark Gluon Plasma by mesurements of direct thermal photons and lepton pairs (virtual photons). These probe particles are of particular interest as messengers from the plasma state due to their rare interaction with the hadronic final state. Continuum spectra of photons and lepton pairs are accesible as well as the vector mesons,
via their dileptonic decay channels. A set of hadronic probes allow studies of the properties of very dense and hot hadronic matter on the hadronic side of the phase transition.The experiment is built around an axial field dipole magnet which allows electron measurements in two 90 degree arms with
0.35. Muons are detected at larger rapidities in one arm at forward rapidities. Efforts are in progress to increase the coverage for dimuon pairs by a second identical muon arm placed in the opposite direction. Total multiplicity and rapidity densities are measured over almost six units of rapidity with Si-pad and Si-strip detectors placed close to the beams. Electron pairs are measured in the two tracking arms at mid rapidity. Electrons are identified by measurements of Cerenkov radiation (RICH), dE/dx and Transition radiation , Time of Flight and response in the electromagnetic calorimeter combined with the momentum determined in the tracking system. An overall hadron rejection factor better than 1/10000 is achieved. About 30% of the electron arms are equipped with leadglass (12000 in total) detectors for high resolution photon detection specially designed for detection of the direct thermal photon component.
The detector development efforts by the Lund group for PHENIX have concentrated on the problem of pattern recognition in tracking at high multiplicities by three planes of space point measuring pad chambers. We discuss the project of equipping these wire chambers with a pixel readout system separately under the description of the detector development program.
You can find more information on the PHENIX home page at BNL.
Read about the new interesting observations at RHIC.