Particle Physics

In LHC’s Shadow, America’s Collider Awakens

The Relativistic Heavy Ion Collider recently fired up for its 15th run to take a deeper look at the building blocks of atoms.

Thomas Lin/Quanta Magazine

The 2.5-mile tunnel of the Relativistic Heavy Ion Collider.

America’s last major particle collider lies coiled beneath the pine barrens and sparse outbuildings of Brookhaven National Laboratory on Long Island, N.Y. The Relativistic Heavy Ion Collider (RHIC), as it’s called, recently came out of hibernation equipped with new gear for spilling the secrets of atoms.

RHIC pales next to Europe’s Large Hadron Collider when it comes to the energy with which its particles collide — energy that determines whether collisions will give rise to new, exotic particles. But the machine clings to relevance (and Department of Energy funding) by forgoing the new in favor of a closer look at the mysterious familiar: the quarks and gluons that comprise the cores of atoms, and thus 99 percent of all visible matter, about which several things are not known.

Thomas Lin/Quanta Magazine

Gene Van Buren in front of the STAR detector.

In a typical run, gold nuclei fly in opposite directions through RHIC’s central artery at 99.995 percent the speed of light before slamming together with the energy of colliding mosquitoes — objects 10 trillion times their weight — inside the two main detectors, STAR and PHENIX. The crash momentarily produces a several-trillion-degree droplet of “quark-gluon plasma” — matter in which quarks and gluons shed their individuality and form a single, flowing entity. It was here at RHIC in the early 2000s that experiments first definitively recreated this strange liquid, which researchers believe filled the universe in its infancy.

At RHIC, the plasma droplet survives for about a hundred-thousandth of a billionth of a billionth of a second before cooling and condensing into individual particles. Measurements over the years, along with calculations that exploit the plasma’s peculiar mathematical relationship to black holes, have revealed that it is an almost “perfect” liquid, possessing the lowest viscosity (or internal friction) allowed by quantum physics.

Thomas Lin/Quanta Magazine

A monitor in the control room for the STAR detector displays debris from a gold-gold collision (other collisions, such as proton-gold and proton-proton, also occur).

With gold nuclei and their nearly 200 constituent protons and neutrons, scientists take a shotgun approach to the problem of initiating contact between quantum-scale targets. A collision can produce thousands of particles. “It’s like trying to reconstruct a firecracker from the debris,” said Gene Van Buren, co-leader of STAR’s computing group.

Thomas Lin/Quanta Magazine

The PHENIX detector.

The strong force, which binds quarks together into protons and neutrons and those objects into atomic nuclei, is conveyed through the exchange of gluons. But the equations that describe the strong force are so difficult to solve that physicists do not have a complete understanding of quark-gluon dynamics. For example, quark-gluon plasma droplets form much faster than expected during collisions. For RHIC’s 15th run, which began Feb. 10, scientists have upgraded the PHENIX detector with a new tungsten-silicon hybrid tracking device to help detect radiation from gluons deep inside the colliding particles. “One idea is that we have the wrong picture of gluon distribution,” explained PHENIX scientist Barbara Jacak, who is a professor of physics at the University of California, Berkeley. A super-dense gluon “field,” rather than discrete gluons, might permeate the protons, she said.

As the world’s only polarized proton collider, RHIC also aims to address what’s known as the “spin crisis,” an unresolved question concerning a property of particles called “spin.” A proton’s three quarks only account for one-fifth of its spin, suggesting the lion’s share comes from the spins of gluons and from quarks and gluons orbiting one another. By colliding protons as they spin in a range of directions, scientists hope to identify the spins and orbits of their component parts.

Thomas Lin/Quanta Magazine

A section of the beam pipe mounted for display. Particles travel through the central tube.

The future of RHIC, which employs 850 people and costs the Department of Energy about $160 million annually, is uncertain. In a 2012 white paper making the case for continued operations, scientists argued that “RHIC is in its prime” with new upgrades poised to answer key questions in nuclear physics. Yet a panel of scientists recommended shuttering the collider in the stead of two other nuclear physics facilities vying for the same funding. So far, all three laboratories have made the cut, yet every run of RHIC could be its last.

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  • I deem it’s very interesting to get a closer look at the mysterious familiar: the quarks and gluons that comprise the cores of atoms. That’s the Phisics I do love.

  • The panel of scientists vehemently recommended keeping all three nuclear physics facilities, and that only if a sacrificial lamb was necessary that RHIC would be the difficult choice.

  • By colliding large atoms (gold at atomic weight 197), RHIC is the only machine capable of investigating nuclear colligative properties that have direct implication in Big Bang nucleosynthesis of dark matter- dark energy and all that we see and don’t see. LHC concentration on proton (atomic weight 1) collisions will miss this colligative approach and continue to produce results indicative of only a small part of the universe creation problem. The RHIC loss would be devastating to the scientific pursuit of universe knowledge.

  • Large Hadron Collider (LHC) worked since 10 September 2008 till 14 February 2013. Tevatron worked since 1 December 1970, till 30 September 2011. Enormous resources were spent, but any essentially new results weren’t received. Neither superpartners, nor additional dimensions, neither gravitons, nor black holes, neither dark matter, nor dark energy, etc., etc. weren’t found. As for the Higgs, the assertion that the boson found in the 124 – 126 GeV, is this particle, is highly doubtful.

    The Higgs field permeates the vacuum of space, which means the mass of the boson and the stability of the vacuum are closely intertwined. The much celebrated particle has a mass of about 126 GeV – light enough to raise fears of instability. Higgs boson could have destroyed the cosmos shortly after it was born, causing the universe to collapse just after the Big Bang.

    All well-known elementary bosons (photons, W and Z bosons, gluons) are gauge. In all likelihood, the found by LHC 124-126 particle represents a meson multiplet.

    Therefore, it is likely that Run Two of LHC will not bring any new fundamental results, too.

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