New Results from RHIC Highlight 2004 DNP Meeting
Scientists reported new evidence for the experimental observation of a quark gluon plasma at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) at the 2004 fall meeting of the APS Division of Nuclear Physics (DNP), held October 28-30 in Chicago, Illinois. Other recent RHIC results presented at the meeting included the first experiments with a polarized hydrogen jet target. The meeting also featured a special session on the future of nuclear physics and nuclear science education.
Quark Gluon Plasmas. The quark-gluon plasma (QGP) is a new state of matter that may have been observed in ultra-relativistic nucleus-nucleus collisions at RHIC. Several scientists presented results from the most recent experiments in heavy-ion physics at very high energies. There is strong evidence for the observance of a new state of matter with unique long and short wavelength properties, which is believed to be a QGP, albeit somewhat different than the weakly interacting plasma that scientists expected to find at asymptotically large energy densities.
Polarized Hydrogen Jets. Targets of pure spin-polarized hydrogen have proven useful to study nucleon structure functions at DESY, as well as nucleon-nucleon and three-body interactions at the Indiana Cyclotron Facility and the COSY accelerator at Jülich. This is because experiments with polarized proton beams at very high energies require a means to measure the polarization of the stored beam to an accuracy of a few percent. A polarized hydrogen jet target was recently installed at the RHIC facility to successfully observe pp elastic scatting of a 100 GeV proton beam by polarized hydrogen atoms. The results nonetheless had some limitations in terms of absolute accuracy, and further improvements are expected to be made.
Degenerate Fermi Gases. Scientists at Duke University have developed an all-optical approach to trap lithium-6 atoms using ultrastable CO2 lasers. The atoms are evaporatively cooled to produce a highly degenerate, strongly interacting sample of a Fermi gas, split equally between spin-up and spin-down atoms. Ultracold, strongly interacting Fermi gases provide useful models for exotic systems in Nature, including high-temperature superconductors, neutron stars, and QGPs.
The Future of Nuclear Physics. The growing evidence that neutrinos have mass has caused nuclear physicists to contemplate the first significant revision to the Standard Model in several decades. Stuart Freedman (University of California, Berkeley) described the conclusions and recommendations of a recent study of the present and future of the US neutrino program, sponsored jointly by the APS Divisions of Nuclear Physics, Particles and Fields, Astrophysics, and Physics of Beams.
A concurrent need to prepare the next generation of nuclear physicists led to a similar study assessing current nuclear science education efforts at the NSF and DOE by an NSAC subcommittee. Rutgers University's Jolie Cizewski discussed preliminary findings and recommendations of the report, which was based on surveys of undergraduate and graduate students, postdocs, and recent PhDs in nuclear physics, and includes projected employment demographics. The subcommittee also looked at ways nuclear scientists could participate in K-12 education and public outreach.