Nuclear and Heavy Ion Physics - Experimental

Stony Brook's strong program in experimental nuclear physics devoted to the investigation of multi-GeV collisions of relativistic heavy ions. It allows study of fundamental properties of nuclear matter under extreme conditions which deviate strongly from those of the ground state of stable nuclei. Stony Brook physicists are studying in the laboratory the properties of matter as it existed a few microsecond after the Big Bang. The current experimental programs is performed by the Relativistic Heavy Ion Group.

Relativistic Heavy Ion Group

The nature of nuclear matter at very high temperatures is the focus of relativistic heavy ion physics, where an experimental program is underway to study effects of the liberating of individual quarks from their nucleon "bags" into a quark-gluon plasma (QGP)- deconfined and thermalized form of strongly interacting matter. The main emphasis of the group is the participation in the PHENIX experiment at RHIC , the Relativistic Heavy Ion Collider at Brookhaven National Laboratory on Long Island. RHIC is a world-class scientific research facility that began operation in 2000. The group's initial research on superdense matter began at lower energies at the AGS (BNL) and at CERN, and is now focused on the highest energy density created in a laboratory, which are achieved at RHIC. This hot, dense matter is produced by colliding very heavy nuclei (gold at RHIC) at ultra-relativistic energies.

Two gold ions colliding at RHIC. Computer simulation...

• investigating the QCD prediction of a deconfined phase of matter, the QGP;
• exploring the physics of this new state of matter.

PHENIX and the other RHIC detectors also study the physics of polarized proton collisions. The main goal here is to uncover the secrets of the spin structure of the proton. Currently it is known that the three quarks do not carry alone the spin of the proton. Some contribution to the spin might be carried by the gluons, sea quarks, some combination of these or by some others as yet undiscovered mechanism.

... and reality. Tracks of charged particles produced in central gold-gold collisions as it seen by PHENIX.

The detection of the QGP requires a complex "state of-the-art" detector system. The PHENIX detectors allow to measure many different species of elementary particles produced in the collisions. In particular, PHENIX can detect photons, leptons (electrons and muons) and lepton pairs. These particles undergo only electromagnetic interactions with the residual bulk of the matter and thus carry clear information about the very early, dense stage of heavy ion collisions.
The Stony Brook group participated in the design and construction of the PHENIX Ring Imaging Cherenkov detector (RICH), Drift Chamber and its electronics. We participate in the data taking and develop software for data analysis. After 3 years of RHIC operation the PHENIX experiment has already obtained a set of intriguing and exciting results. Information about them can be found at PHENIX Results page.

From Physical Review Letters, Volume 88, Number 2, page 022301-1, 14 January 2002: "Transverse momentum spectra for charged hadrons and for neutral pions in the range 1 GeV/c < pt < 5 GeV/c have been measured by the PHENIX experiment at RHIC in Au + Au collisions. At high pt the spectra from peripheral nuclear collisions are consistent with scaling the spectra from p + p collisions by the average number of binary nucleon-nucleon collisions. The spectra from central collisions are significantly suppressed when compared to the binary-scaled p + p expectation, and also when compared to similarly binary-scaled peripheral collisions, indicating a novel nuclear- medium effect in central nuclear collisions at RHIC energies." The cover of this PRL issue shows the figure from PHENIX article.

We are teasing nature's secrets out of the data and publishing the results for all to see. Recently, the group has embarked on a program to upgrade the PHENIX detectors to handle higher luminosities, reduce background and directly measure particles containing heavy quarks.

PHENIX Drift Chamber constructed at Stony Brook on its way from the basement of the Physics building to BNL.

The proximity of Stony Brook to RHIC is a tremendous advantage and allows flexibility in combining research with courses and other departmental activities. Since 1997, students from our group received four Master Degrees for working on PHENIX hardware, three Master Degrees for working on computing and software developments. More than ten graduate students received the Ph.D. in Physics for works in relativistic heavy ion physics.
Right now the group consists of 4 professors, senior research scientist, research support specialist, 3 postdocs and 15 graduate students. The group is really international: citizens of France, Germany, Italy, Greece, Russia, Israel, India, China and USA are gathered for the strong joint effort of making New Physics in 21-st century.

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