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A look inside RHIC, Brookhaven’s little big bang machine

The views expressed are those of the author and are not necessarily those of Scientific American.


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In the high-energy physics community, all eyes have been on Europe for some time, as the Large Hadron Collider, or LHC, has proceeded in fits and starts to become, in 2009, the most powerful atom smasher the world has ever seen. But as the LHC has taken shape in an underground tunnel outside Geneva, colliders stateside have been fading into retirement. At the start of 2008 the U.S. had four colliders; if Fermilab’s Tevatron shuts down as planned in 2011, the U.S. will soon be down to one: the Relativistic Heavy-Ion Collider, or RHIC, at Brookhaven National Laboratory in Upton, N.Y.

That point was made by RHIC physicist Ed O’Brien on March 10, when lab personnel led a group of reporters on a tour of the Long Island facility last week. RHIC accelerates gold ions (atoms stripped of some of their electrons) to nearly light speed as they race around a 3.8-kilometer ring—roughly the size of the Indianapolis Motor Speedway, as physicist Todd Satogata noted. RHIC is one of the largest colliders in the world: for comparison, Cornell University’s recently retired CESR collider was 0.77 kilometers in circumference, the Tevatron’s ring is 6.3 kilometers, and the mammoth LHC ring is 27 kilometers. (Like the Large Hadron Collider, RHIC saw its share of apocalyptic hand-wringing before start-up, thanks in part to an offhand remark made by physicist Frank Wilczek in Scientific American in 1999.)

At detectors around the RHIC ring, clockwise gold-ion beams plow into counterclockwise beams, and the detectors track the subatomic debris to investigate the physics of the interaction. Because the collider was turned off for a maintenance day, the media group got a peek inside the STAR [pictured above] and PHENIX detectors—two massive instruments that fill their chambers so tightly, they are almost impossible to see in full. RHIC emergency button

RHIC had recently been in the news following the February announcement that the quark–gluon plasma created from ion collisions in the detectors reaches temperatures of roughly four trillion degrees Celsius. That plasma "flows more freely than any fluid known to mankind," but it lasts just yoctoseconds, said Brookhaven physicist Peter Steinberg. Wait—yoctoseconds? "I would advise you to Wikipedia it," Steinberg added. Consider it done: a yoctosecond is one septillionth of a second, or 10–24 seconds.

Even that ferocious fireball is relatively tame given how small a volume it fills, Steinberg noted. A high-speed ion collision in RHIC packs about the same energy as a midair crash between two mosquitoes—the much slower speed of the mosquito crash is offset by the vastly greater mass of an insect compared to an atom. Out of the quark–gluon plasma appears a shower of recognizable particles, which allows RHIC physicists to unwind that yoctosecond-scale process, much of which is not directly observable. "No one’s ever seen a quark; you can’t see a gluon," Steinberg said, noting that their existence is inferred from the behavior of larger composites such as protons and neutrons. "We live our lives," he added, "as if they exist as particles."

One of RHIC’s missions is to investigate the nature of the proton, specifically the origin of its quantum-mechanical spin, or angular momentum, which happens to be the same as the electron’s, a fact that Steinberg called "totally weird." The spin could be wrapped up in the individual spin of the proton’s constituent quarks or in their orbital motion within the proton’s structure. "There are lots of places for the spin to be," Steinberg said, adding that the harder physicists look, the murkier the picture becomes. "It’s one of the most amazing null results I’ve seen, I think," he said. RHIC’s ability to swap in spin-polarized protons for gold ions in its collisions makes the collider uniquely positioned to investigate this wrinkle of nuclear physics, even though the Tevatron and the LHC have more brute strength.

Brookhaven physicists have been deeply involved in building and operating the LHC and its support infrastructure, which the lab demonstrated by hosting a video chat (albeit a choppy one) with three Brookhaven physicists currently stationed at CERN, the European lab for particle physics that runs the LHC. It’s only natural that domestic physicists would want to hitch their wagon to the so-called big bang machine over in Europe, for which expectations are sky-high. "The questions that we’re addressing at the LHC are the most fundamental that we know of," said Howard Gordon, a Brookhaven physicist who leads the U.S. program office for ATLAS, one of the two all-purpose detectors at the LHC. Among the issues LHC researchers hope to resolve: finding the Higgs boson, a hypothetical particle that lends other particles mass; identifying the signature of dark matter particles, the mysterious stuff that fills the universe but has yet to be directly observed; and looking for the extra dimensions beyond the traditional four (three dimensions of space, one of time) that string theory would require. If there are indeed extra dimensions to be found, Gordon says, the signal from the LHC "would be unmistakable."

Between RHIC and the LHC, Brookhaven will soon find itself deluged with petabytes of experimental data. The computing facility is one of two tier 1 centers for LHC data in the U.S., meaning that it sits one rung below CERN (the tier 0 center) on the network hierarchy. According to Brookhaven’s Ofer Rind, the facility has about 10,000 computing cores, lined up in a library of rack systems, dedicated to RHIC and ATLAS alone. The computing facility, running at capacity, pulls about 4.5 megawatts, enough to power about 3,500 U.S. homes. Much of that electricity is tied up in cooling systems to pull waste heat away from the computers—always a challenge for large-scale computing centers. "We turn electricity into science and heating," Rind said, "and I won’t say which one we do more."

Photographs © John Matson/Scientific American





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  1. 1. jtdwyer 6:16 pm 03/17/2010

    Once the LHC fails to detect the Higgs boson, the older, smaller colliders will seem like a real bargain.

    As I understand, there is no real basis for a Higgs boson, it’s just presumed to exist since successful quantum theories presume that the recognized fundamental force(s) are all manifested as characteristic properties of matter.

    Except for emission velocity, since particles are only detected when their momentum is absorbed. Particles in motion have not been proven to exist.

    So, this energy that imparts motion, which is not a detected characteristic property of particles, could in some way be related to mass, which is also not a detected characteristic property of particles. In that case there would be no Higgs boson to mediate mass between particles.

    Meanwhile, the only real candidate for the Higgs field, some undefined process necessary to impart mass to specific particles as the were produced during the big bang, is the temporally varying density of the universe. But, I’m just guessing.

    Link to this
  2. 2. chrisstevens 9:52 pm 03/17/2010

    So, fundamental particles, matter, quanta etc have neither mass nor motion………… thanks, now it’s all as clear as mud.
    When I lie awake at night my theory of everything seems clear, I just can’t remember it when I wake up the next morning.
    Something along the lines of an infinite, scalar and fractal universe/multiverse for all sizes from Planck to infinity, where time is simultaneous and synchronous, gravity is the product of infinite quanta, ordinary matter is the condensing out of Dark Matter at visible wavelengths………… by this point I’m usually asleep.

    Link to this
  3. 3. new illuminati 11:05 pm 03/17/2010

    If you investigate the nature and structure of holograms everything will become much clearer – while you’re awake.

    Link to this
  4. 4. jtdwyer 12:26 am 03/18/2010

    chrisstevens – Give me a wake-up call when the Higgs boson has been detected. Then perhaps particle physics can explain all that it now purports to.

    In the meantime the LHC can create ever more massive variants of previously detected particles in search of phantom particles: dark matter, Higgs, etc.

    Link to this
  5. 5. ronmoore 7:58 am 03/18/2010

    You can follow the Tevatron on Facebook or Twitter.

    Link to this
  6. 6. zlm313 1:58 pm 03/18/2010

    Hi,

    The LHC is going to do a whole lot more than just look for the Higgs boson. ALICE at the LHC is going to be doing very similar physics to RHIC (from the end of the year) but at higher energy. For now, we are looking at seemingly very basic things like, how many particles could be produced in proton-proton collisions…but as we go up in energy to a region that has never been seen (some time in the next few weeks we should have the first at new energies!), things get very hazy and theories that are otherwise very powerful start to diverge and seem a little hopeless. One of the most interesting things we will do is look at proton-proton collisions with extremely high energy density (producing more particles than any previous proton-proton collisions have been observed to produce) – no theorists seem to be able to agree on exactly how they expect systems like this to behave. In heavy ion collisions RHIC has seen striking evidence for Quark Gluon Plasma, and we are still unclear on its properties, and how well we understand its identifying markers. This physics to me is FAR more interesting than the Higgs boson. Higgs is the icing on a very perfectly made cake we call Electroweak theory. Unfortunately, a cake that looks good doesn’t always taste good, and if we are wrong, LHC will illuminate that. However, comparatively, Quantum ChromoDynamics (the theory of quarks and gluons) is a tasty treat that hasn’t left the oven yet. RHIC and LHC still have many years of work to do in this field and that’s why I like it!

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  7. 7. jtdwyer 3:19 pm 03/18/2010

    zlm313 – I’m sure some good basic science at the LHC will yield valuable new information – good luck.

    However, while high energy nucleon collisions may approach the energy of the big bang, that energy is not contained: only some of the conditions of the big bang are produced. The processes that created matter from energy cannot be reproduced by collisions – only the disintegration of matter.

    The Higgs particle based theory of mass appears to be weakly founded and certainly unsuccessful, but not only is it still revered after more than 50 years, but no alternatives seem to receive any consideration.

    As for looking for dark matter – forget about it!

    So much PR nonsense has been spieled out regarding the LHC it can’t possibly meet the public’s expectations of it, but good luck with it.

    Link to this
  8. 8. jtdwyer 4:27 pm 03/18/2010

    zlm313 – If the LHC can produce a confirmed Quark Gluon Plasma and condense nucleons from it, I will certainly applaud – it will have been worth every penny (I presume mostly spent by the EU)!

    I consider this not only a more worthy but more realist objective for the LHC than all the other highly publicized fantasies. I hope it can determine more exacting boundaries for physical reality than are now available.

    Link to this
  9. 9. NIRVANA 6:01 pm 03/18/2010

    Yes if we know how we come how we be,don’t forget how we will go too.Every thing created,state,and transform.That all.NIRVANA

    Link to this
  10. 10. jack.123 2:08 am 03/20/2010

    What about LHC finding other dimensions.

    Link to this

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