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May 3, 2006 Current Issue | About SGTW | Subscribe | Archive | Contact SGTW  
PHENIX Data Fly With GridFTP

Mass spectrum of μ+μ- pairs in the PHENIX detector showing clear evidence of the J/Ψ resonance. Image Courtesy PHENIX Collaboration.
The hunt for the quark-gluon plasma, a state of matter that may have existed in the very early universe, is getting a little help from a common grid tool. During the current run of the Relativistic Heavy Ion Collider at Brookhaven National Laboratory, the PHENIX nuclear physics experiment is using GridFTP to transfer data automatically between BNL and Vanderbilt University.

Physicists study the quark-gluon plasma and other nuclear physics phenomena by examining what happens when beams of nuclei collide in the center of the massive PHENIX detector. While identifying new states of matter requires a detailed analysis of years' worth of data, a partial analysis of each day's data gives experimenters insight into the health of the detector and of the beams, ensuring that they collect high-quality data. With PHENIX's computing resources at BNL busy analyzing previously collected data, such partial analyses must take place remotely.

"We've come to rely on these daily remote analyses for real-time data monitoring and quality assurance, and for the jump-start it gives us on our physics analysis," explains PHENIX spokesperson Bill Zajc. "Looking at the partial data sets sharpens our analysis tools, so that they are ready to be used on the full data set as soon as it is available."

The PHENIX collaboration first experimented with GridFTP in 2005, when 270 TB of data was transferred from BNL to Japan for analysis. During the current RHIC run, they have turned again to GridFTP to make use of available resources at Vanderbilt's Advanced Computing Center for Research and Education. Twice a day, data are automatically transferred from BNL to Vanderbilt, where they are automatically analyzed. The results are then transferred back to BNL every 24 hours using GridFTP.

"The analysis we do is focused on the J/Ψ meson," explains Vanderbilt physics professor Charles Maguire. "We can tell a lot about how well the experiment is going by studying graphs of just that one particle. Measurements of the J/Ψ exploit all the technology of the PHENIX detector and use all the steps in the analysis chain." Experimenters at RHIC will be able to see if something is amiss in the PHENIX hardware or software that may not be obvious in the quicker checks that are performed at the experimental site.

Analysis of the J/Ψ is also interesting for the experiment's ultimate goal of discovering the quark-gluon plasma. A decrease in the number of observed J/Ψ mesons, and an increase in the amount of other types of particles, may be a signal for the new state of matter. That analysis will take many more months and much more data to complete, but will be helped along by the daily analyses taking place at Vanderbilt.

Learn more at the PHENIX Web site.

—Katie Yurkewicz