Flemming Videbaek on Brookhaven National Lab's BRAHMS Experiment
Special Topic of Hadron Colliders Interview, February 2011
Page: < 1 | 2 >
What we know is that there is a limit to this—that you cannot increase the density to infinity. At some point it has to become saturated, and that affects the particle production and results in this suppression. The publication reporting on this is the 2004 Physical Review Letters paper, " Evolution of the nuclear modification factors with rapidity and centrality in d+Au collisions," (Arsene I, et al., 93[24]: art. no. 242303).
The most-cited of the BRAHMS papers is your white paper in Nuclear Physics A in 2005 (Arsene I, et al., "Quark-gluon plasma and color glass condensate at RHIC? The perspective from the BRAHMS experiment," 757[1-2]: 1-27). Tell us about these white papers and what was in the BRAHMS paper.
It was decided in discussions between then Associate Laboratory Director for Nuclear and High Energy Physics, Thomas Kirk, and the 4 spokespersons for the RHIC experiments that after four years of running that it would be good to gather what we had learned from RHIC so far, and we would discuss the data from the experiments that had either just been published or were ready to be published.
It took us maybe six months to write the paper. All the experiments agreed to a timetable, and then we prepared the papers independently, so no one knew what the other collaborations were writing or what they would conclude. We all met in June 2004 at a one-day meeting in Port Jefferson, NY, and each experiment presented the main findings in their paper. Then the papers were finished and submitted together to Nuclear Physics A.
At the time we started writing these papers, we had touched on a couple of these key measurements, mainly this suppression in gold-gold collisions relative to proton-proton, and we had explored this issue about stopping and suppression at forward angles in deuteron-gold collisions and that's what we discussed. The other experiments had other significant measurements—the elliptic flow and the suppression of the production of high-momentum particles at mid-rapidity relative to expectations from elementary proton-proton collisions.
The paper with the second most citations from BRAHMS is the 2003 article in Physical Review Letters on the transverse-momentum spectra (Arsene I, et al., " Transverse-momentum spectra in Au plus Au and d plus Au collisions at root s(NN)=200 GeV and the pseudorapidity dependence of high-p(T) suppression," 91[7]: art. no. 072305). What was the story with this paper and what were you reporting here?
PHENIX Detector Under
Construction
Courtesy of Brookhaven National
Laboratory
The PHENIX detector (shown here when under construction) at Brookhaven
National Laboratory's Relativistic Heavy Ion Collider (RHIC) records many
different particles emerging from RHIC collisions, including photons,
electrons, muons, and quark-containing particles called hadrons.
The interview series
with Brookhaven National Labs >
This is another simultaneous and joint publication of results from the RHIC experiments. This was the first reporting of results from the deuteron-gold collisions. That particular running of RHIC was early in 2003—January and February. All the experiments set out to analyze the data to see whether deuteron-gold showed any suppression of particle production near mid-rapidity or not as a control experiment for the earlier gold-gold runs.
In this paper, we reported the results of the non-suppression of deuteron-gold spectra at mid-rapidity compared to gold-gold, and the three other experiments showed similar results. It was joint confirmation that the hot and dense medium seen in gold-gold has features we did not expect—namely, that high-transverse-energy particles lose more energy than expected.
These results were presented at a joint colloquium at Brookhaven, and four papers—one from each experiment—were published in the same issue of Physical Review Letters.
BRAHMS only ran for a few years after that. When was it retired and what physics did you do after the white paper was published?
We completed the experiment in 2005, with the exception of a small dedicated effort in 2006 to measure proton-proton collisions at lower energy. The top energy of RHIC is 200 GeV; this data was taken at 63 GeV, and the goal was to measure what's called the spin-asymmetry in proton-proton collisions. In this case, we did it at very forward angles and high momentum.
We only started talking about this idea around 2000 as something that would be possible to do with RHIC within the BRAHMS experiment: a nice little measurement that fits into a completely different part of physics, this idea of transverse spin polarization.
Where did the BRAHMS physicists go after the experiment was concluded?
Well, I was also group leader for the Brookhaven members of BRAHMS, and most of those physicists are now members of STAR. We had a number of foreign collaborators and institutes involved. We had people from Denmark, Norway, France, etc. Most of those are now working with the ALICE experiment at the Large Hadron Collider (LHC). We also had collaborators from the University of Kansas, and they're now with the CMS experiment at the LHC.
What do you consider the most challenging aspect of being a group leader in this kind of research?
Brookhaven From The Air
Courtesy of Brookhaven National
Laboratory
Aerial view of Brookhaven National Laboratory taken in August 2007. The
Relativistic Heavy Ion Collider (top, center) is 2.4 miles in
circumference, and dominates Brookhaven's 5,265-acre campus.
The interview series
with Brookhaven National Labs >
As the group leader and spokesperson, certainly one of the challenging aspects is to keep enough people focused on this experiment after the first three or four years of running. In the beginning everybody is enthusiastic, but then some groups start making other plans, and that takes away from the effort we can put into the experiment.
Would you do something different with BRAHMS, would you have designed it differently, knowing what you now know about the physics?
I think so. If we had known in the beginning about this idea of doing these forward measurements of deuteron-gold collisions and also about the work in proton-proton physics, we could have designed the part of the detector sitting in the forward direction somewhat differently. It would have been nice to go back and see if we could increase the aperture of the detector by maybe a factor of 10 or so, and we could have made significant measurements in that direction.
But overall I think the technical execution of the experiment was good. It was nice detector technology. And I'm quite pleased with what we've accomplished with this small group of physicists. We were probably around 50 people total. And, you can see from the publications, we have seven or eight articles with more than 50 citations. Overall, we have close to 30 publications. We had 14 Ph.D. theses and maybe 20 Master's theses.
It was a very productive time, although maybe it was a little long—you think about proposing the experiment in 1990 and you don't start taking data until 2000. But of all the physics I've done in my career, these last fifteen years have been the most exciting.
Now that the physics spotlight has moved over to CERN and the LHC do you have any regrets that you're not involved with one of those experiments?
I did have a desire to work at the LHC. We started an effort where a number of people from Brookhaven were going to participate in the heavy-ion part of ATLAS since the high-energy physics group at the laboratory is a major player in that experiment. It was started at a low level and, in the end, it did not get sufficient support to be a strong effort. Brookhaven decided it should be a small effort, with just a few of the people from the heavy-ion groups at Brookhaven. Thus I decided instead to join the STAR experiment. STAR is an exciting experiment, and for the next several years there will still be exciting new physics coming out of RHIC.
Dr. Flemming Videbaek
Brookhaven National Laboratory
Upton, NY USA
Page: < 1 | 2 >
BROOKHAVEN NATIONAL LAB'S MOST CURRENT MOST-CITED PAPER IN ESSENTIAL SCIENCE INDICATORS:
- Yao WM, et al., "Review of particle physics," J. Phys. G-Nucl. Particle Phys. 33(1): 1-+ Sp. Iss. SI July 2006 with 2,980 cites.
- Most-cited paper on the BRAHMS experiment: Arsene I, et al., "Quark-gluon plasma and color glass condensate at RHIC? The perspective from the BRAHMS experiment," Nucl. Phys. A 757 (1-2): 1-27, 8 August 2005 with 554 cites.
Source: Essential Science Indicators from Clarivate.
ADDITIONAL INFORMATION:
-
Menu for the institutional interview series with Brookhaven National Lab from the Special Topic of Hadron Colliders.
KEYWORDS: BROOKHAVEN NATIONAL LAB, NUCLEAR PHYSICS, PARTICLE PHYSICS, RHIC, RELATIVISTIC HEAVY ION COLLIDER, BRAHMS, BROAD RANGE HADRON MAGNETIC SPECTROMETERS, PARTICLE PRODUCTION, ANGLES, SOLID-ANGLE DEVICE, INCIDENT NUCLEONS, HOT DENSE MATTER, DEUTERON-GOLD COLLISIONS, HIGH-TRANSVERSE MOMENTUM, COLOR GLASS CONDENSATE, NUCLEAR WAVE FUNCTION, GLUONS, ELLIPTIC FLOW, JET MEASUREMENTS, GOLD-GOLD COLLISIONS, PROTON-PROTON COLLISIONS, SPIN ASYMMETRY, DETECTOR TECHNOLOGY, STAR, LHC, ATLAS.
Page: < 1 | 2 >