Relativistic Heavy Ion Collider

PHENIX ( Pioneering High Energy Nuclear Interactions eXperiment ) is one of the four experiments, the plasma research at Brookhaven National Laboratory for the quark gluon. PHENIX focuses on the measurement of leptonic and electromagnetic observables (in contrast to STAR, which searches for hadronic signals). PHENIX is also designed to investigate the spin structure of the proton.

PHENIX consists of many different detectors. Photons, leptons and hadrons at mid- rapidity also be measured with the central spectrometer, while muons are measured in the forward direction by a Myonenspektrometer, which is located in the beam direction on either side of the collision point.

(2005 ) to work on the experiment 550 scientists from 62 institutions from 13 countries. From Germany, the University of Münster is involved in PHENIX.

Individual detectors

Global detectors

Beam -Beam Counter

The two identical Beam -Beam Counter ( BBC ) located in the beam direction on either side of the collision point. The detector consists of quartz Cherenkov detectors and serves time and location and other parameters of a particle collision to determine.

Zero-Degree Calorimeter

The two identical Zero Degree Calorimeter ( ZDC ) are also located in the beam direction, but to a much greater distance ( 18.25 m) than the BBC. The detector support, the BBC in determining the centrality of collisions.

Multiplicity - Vertex Detector

The Multiplicity Vertex Detector ( MVD) surrounding the collision region. This highly segmented silicon detector measures the vertex position with high precision and also serves to determine the number of particles.

Central spectrometer

The central spectrometer is disposed concentrically about the beam axis at the point of collision. It consists of two arms ( eastern arm and western arm ), each covering an azimuth angle of 90 degrees. The Central spectrometer is a large magnet.

Drift Chamber

The inner detector of the spectrometer, the central drift chamber (DC). It helps to measure the position of charged particles and their deflection in a magnetic field.

Pad Chamber

A first Padkammer Adjoining the drift chamber in both arms ( PC). More Padkammern are located in both arms in front of the calorimeter (see below), in the western arm also is such a detector directly behind the RICH (see below). The Padkammer helps to reconstruct the tracks of charged particles, also it serves as a veto detector for such particles in front of the calorimeter.

Ring Imaging Cherenkov Detector

Behind the first PC is located in both arms of a Ring Imaging Cherenkov Detector ( RICH ). This detector can distinguish with the aid of the light cone of Cerenkov radiation that hit a ring on mirror in the detector electrons and charged pions. The RICH is filled with this gas, by which the speed of light is reduced.

Electromagnetic Calorimeter

The Electromagnetic Calorimeter ( emcal ) is the outermost detector in both arms. It consists of eight sectors, two of which are Bleiglaskalorimeter ( PBGL ), the other six are lead - scintillator sandwich calorimeter ( PBSC ). These calorimeters are used for energy and position measurement of photons and electrons. Through their fine segmentation to reach this a good spatial and energy resolution, including the ability to measure neutral pions up to transverse momenta of about 20 GeV / c.

Muon spectrometer

Muon Tracker

The muon tracker ( MuTR ) are located along the beam axis on either side of the collision point. They open like a funnel to the outside. With the help of three drift chambers, the tracking of muons is made possible in a radial magnetic field.

Muon ID

At the muon tracker each one muon identification detector connects ( Muid ). With the help of absorber plates hadrons are absorbed, so that the detector detected particles are almost exclusively muons (99.9 %), but must have a minimum energy of 1.9 GeV, otherwise they would also suppressed.

Important results

Like the other RHIC experiments PHENIX was a strong suppression (compared to the expectation from proton-proton collisions ) of particles with high transverse momentum in gold-gold collisions at the highest energies (200 GeV per nucleon ) demonstrate for the first time. This suppression is explained by the strong interaction of hard scattered partons with the resultant dense and hot state of matter ( quark-gluon plasma). It could also be shown that in such a gold-gold collisions one of two opposite particle jets caused by hard scattering more or less disappears.