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NSD ProgramsRelativistic Nuclear CollisionsProgram Head: Hans Georg Ritter The Relativistic Nuclear Collisions (RNC) program at LBNL conducts research to create dense nuclear matter to search for the quark-gluon plasma and characterize its properties, using high energy nuclear collisions to excite the QCD ground state (vacuum) over a macroscopic volume. The conceptual questions to be addressed are: What is the phase structure of QCD? Is there a phase transition to a QGP? Is there a chiral phase transition? Are the chiral and the QGP phase transitions identical? Understanding these questions is of fundamental interest and is a central part of the U.S. Nuclear Science Long Range Plan. The main focus of our research program is the STAR experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. We are playing a leading role in the operation and data analysis and are leaders in the effort to extend the physics capabilities of STAR through upgrades over the next decade. RNC physicists are also leading the initiative by US groups to participate in the ALICE experiment at the LHC and to build a large area electromagnetic calorimeter for the experiment. The STAR experiment is designed to study relativistic heavy ion collisions over a large acceptance and a wide dynamic range of species and energies. This allows us to investigate bulk properties of nuclear matter through the measurement of a very large fraction of the particles produced in the reaction, and at the same time study rare probes, such as high pT particles. Considerable excitement has been generated by the suppression of hadron yields at high transverse momentum and of the disappearance of back-to-back jets in central Au+Au collisions. The analysis of data from the recent d+Au run has led to the exclusion of the saturation model and confirmation of final state interactions as the cause for these phenomena. The analysis of single and multiple strange particles and their collective properties has led to new results on the suppression of baryons at moderately high transverse momentum, giving also the first indication of collective behavior at the parton level. The RNC has played a leading role in all of these efforts. RHIC has collided beams of polarized protons. This marks the start of a new generation of measurements to advance the knowledge and understanding of the nucleon spin structure. The RNC program has formed a group that will play a key role in the STAR measurement of the gluon helicity contribution to the proton spin. The ALICE experiment at the Large Hadron Collider at CERN presents a new opportunity for the study of jet production, jet energy loss, and aspects of gluon saturation at very high center of mass energies. RNC scientists are leading the development of an experimental program that will extend the present hard probes program in ALICE. New detector technologies have opened new frontiers of scientific discovery. The STAR TPC is testimony to our achievements in this area. One challenge for the STAR detector is to improve the vertex resolution in order to enable the measurement of open charm. We are developing a novel high resolution pixel vertex detector based on CMOS technology with an innovative support structure. Analyzing the large amount of data accumulated with the STAR detector is a formidable challenge. New concepts for data handling and storage are needed and are being developed. Grid technology has led to improved data management for RHIC computing. PDSF, the STAR data analysis center operated by NERSC at LBNL, is being used widely by a large number of STAR collaborators and other groups. By design, activities at PDSF complement those at the RHIC Computing Facility (RCF) at BNL. It is used by the entire collaboration and has had a tremendous impact on the physics productivity of STAR. Its capacity is expected to grow with the growing need of STAR for computing and data handling. NSD Programs:
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