Iowa State University Scientists Poised To Explore The Birth Of The Universe

This will be possible with the completion of a new $600-million Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory on Long Island, N.Y. RHIC will be dedicated, Monday, Oct. 4, in a U.S. Department of Energy ceremony.

The new accelerator will enable physicists to create an exotic form of matter called the "quark-gluon plasma" that existed for only a few microseconds (millionths of a second) after the birth of the universe. Physicists will have the first opportunity to peer back in time to the moment of creation by recreating the "quark-gluon plasma." They believe that all matter in the universe today was originally in the form of this plasma.

"We want to find out what happened at the birth of the universe," said Iowa State University physics professor John Hill. "To do that, we want to see if we can 'replay' the creation story in the laboratory."

Hill is a senior member on the ISU/Ames Lab team that developed the first-level trigger, a major component of the PHENIX detector, the largest of four detectors that will be used to record and analyze data coming from RHIC. Other team members are faculty John Lajoie, Marzia Rosati, and Fred Wohn (retired) of ISU's Physics and Astronomy Department; engineers Del Bluhm, Harold Skank, Gary Sleege and Bill Thomas of Ames Laboratory's Engineering Services Department; and scientists Sasha Lebedev, Athan Petridis and Lynn Wood.

Physicists believe that at the very moment of creation, about 15 billion years ago, the universe was very small, very dense and billions of times hotter than the surface of the Sun or even a supernova (exploding star). The universe was so hot that individual protons and neutrons that makeup ordinary matter had not yet come into existence, but their basic constituents (quarks and gluons) swirled about in a hot "soup" (the quark-gluon plasma).

"As the universe expanded and cooled," Hill said, "the plasma went through a phase transition of unknown character resulting in the formation of neutrons and protons, which led much later to the formation of atoms and life as we know it."

When it is up and running, RHIC will take two beams of gold atoms that have been completely stripped of their atomic electrons and accelerate them to 99.995 percent of the speed of light. The two beams of gold nuclei, travelling in opposite directions will be slammed into each other, creating particle collisions at total energies of 40 TeV (trillion electron volts) and temperatures of 1.5 trillion degrees (about 100 times that of a hydrogen atomic bomb).

"With temperatures that high, a billion times hotter than the surface of our Sun, protons and neutrons of atomic nuclei will melt back into their bizarre building blocks, the quarks and the gluons that hold the quarks together," Hill said. Recreating the quark-gluon plasma and watching how it transforms into protons and neutrons will help physicists pin down the fundamental theories of how matter evolved into its present day form and the forces holding it together.

Four detectors will be stationed around RHIC's 2.4-mile (3.8-km) circumference. The detectors are designed to search for a wide range of signs of the plasma's existence since the best signal indicating plasma formation is unknown. The PHENIX detector, for example, is dedicated to looking at hundreds of particle trajectories and searching for particles that interact with matter primarily through the electromagnetic and weak interactions. A second large detector, called STAR, will measure thousands of particle trajectories, looking for telltale signs of strange subatomic species, such as K mesons, lambdas and omegas, which are products of the quark-gluon plasma, Hill said. Two smaller detectors will be used to monitor other byproducts.

The $90-million PHENIX detector is about three stories high, has the square footage area of a mid-sized house and weighs 4,000 tons. It is the result of an eight-year collaboration between some 450 scientists from around the world. While its outer shell is made up of steel and huge high-powered magnets, inside will be a series of delicate and complex sensors and instruments designed to look for matter in its strangest forms.

The Iowa State/Ames Lab team, designed, tested, built and will maintain the detector's first-level trigger. The $2.4-million trigger, is a series of more than 200 sophisticated, electronic printed circuit boards and high-speed electronics. Each has the computing power of a personal computer and uses high-level circuitry to monitor the mini-explosions that occur when gold nuclei collide. Physicists believe that the head-on collisions of gold beams in RHIC will be the ones most likely to yield the quark-gluon plasma. Identifying and monitoring these collisions is no small task.

The trigger will have to sort through up to 100,000 collisions per second, Hill said. It will take 4 microseconds to determine electronically whether a collision meets the requirements of being a direct hit. The trigger will dump collisions that don't meet the requirements and record data on those that do. The trigger will process data at the rate of 1,000 Gbits per second, a rate equivalent to processing all of the information in the Library of Congress every minute. Furthermore, each gold-on-gold collision will emit debris (thousands of nuclear particles) from which physicists will be looking for the subtle signatures of a quark-gluon plasma.

"Without the first-level trigger, serious data taking with PHENIX is not possible," Hill said. "The fact that we were chosen to develop this essential piece of hardware is a testament to the talented electronics engineers in Ames Lab engineering services. They designed the electronics that can sort through and intelligently select the right collisions for further study."

Overall, Hill said RHIC will be a very powerful tool that will enable physicists for the first time to peer back in time to the very instant of the big bang. Verifying the actual existence of the quark-gluon plasma and determining how it transformed into common matter are questions that need to be answered before the history and evolution of our universe can be fully understood.

"RHIC will help us see where most everything in our universe came from and it will provide clues as to how they formed and why the universe is of the form it is today," Hill said.

Ames Laboratory is operated for the Department of Energy by Iowa State University.

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Editors: For more information on the Relativistic Heavy Ion Collider, as well as images of the PHENIX detector, visit http://www.rhic.bnl.gov.