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Mari N. Jensen
Researchers will give a public lecture at Wednesday, Sept. 10 at 7:30 p.m.
University of Arizona physicists are part of the international team working on the world’s biggest scientific experiment.
On the morning of Sept. 10, the Large Hadron Collider will begin operation by sending a beam of sub-atomic particles around a 17-mile underground tunnel beneath the border of France and Switzerland.
As the beam streaks around the tunnel at close to the speed of light, it will pass through two main detectors. The one called ATLAS has key components that were designed and built by UA physicists.
The Large Hadron Collider, or LHC, is the largest and most powerful particle accelerator ever built.
The experiments conducted using the LHC will provide fundamental discoveries about the matter that makes up our universe.
The UA is the only university in Arizona involved with the LHC. The LHC is operated by the European Organization for Nuclear Research, known as CERN.
To celebrate the LHC's first beam, the UA physics department will hold the public lecture, "From the Big Bang to Dark Matter: Turning on the Large Hadron Collider," on Wednesday, Sept. 10 at 7:30 p.m. in Room 201 of the Physics-Atmospheric Sciences Building on the UA campus.
Elliott Cheu, associate dean of the UA’s College of Science, professor of physics and member of the Large Hadron Collider-ATLAS team, will give the lecture.
Robert N. Shelton, UA president and professor of physics, will deliver the opening remarks.
In addition to Cheu, the UA's LHC-ATLAS team includes UA physics professors John Rutherfoord, Michael Shupe and Kenneth Johns and Erich Varnes, a UA associate professor of physics.
Shupe and Rutherfoord have been working on the project for 14 years. The team also includes seven UA postdoctoral and graduate students, three engineers and two technicians.
In his lecture, Cheu will discuss UA's participation in building the world's largest scientific instrument and explain how the experiments to be conducted inside the LHC will reveal secrets about our world.
When it is operating at full strength, the LHC will produce beams of protons seven times more energetic and about 30 times more intense than any previous machine. Two beams will shoot around the 17-mile underground particle racetrack and collide head-on, creating 600 million collisions per second.
When the protons smash together, they will break apart and elementary particles, the smallest building blocks of matter, will shoot off in all directions.
The aftermath of the collisions will simulate some of the conditions that occurred one-trillionth of a second after the Big Bang that started the universe.
One goal of the experiment will be to understand the origin of mass, Cheu said.
The collisions will occur at enormous energies and therefore create immense masses, according to Einstein's famous E=mc2 formula.
One massive particle that has been predicted but never seen before is the Higgs particle.
"If we find the Higgs, that will be fantastic – and that will be confirmation of what we expect," Cheu said. "But if we don't find it, that may be confirmation of more exotic theories."
Kenneth Johns said another goal of the LHC is figuring out the origin of dark matter.
"Twenty-five percent of the universe is composed of something we don't know or understand," he said.
To detect particles that might be the Higgs, dark matter or things as yet unnamed, the proton beams will be focused so that the collisions happen inside one of the six detectors.
The UA team had key roles in the construction of two subsystems of the ATLAS detector, shorthand for A Toroidal LHC Apparatus. At 150 feet long, 82 feet in diameter and weighing more than 7,700 tons, ATLAS is the world's largest-volume particle physics detector ever built.
The ATLAS Collaboration, like other pieces of equipment that make up the LHC, involves an international team of scientists. The international effort involved 2,500 scientists from 37 countries. The 650 participants in the US-ATLAS team come from 43 American universities and national laboratories and represent 21 states.
Rutherfoord, Shupe and other members of the UA's ATLAS team led the design, construction and installation of the Forward Calorimeter, an instrument that measures the position and the tremendous energies of the particles given off when the proton beams collide.
Cheu, Johns and others were responsible for instrumentation for the Cathode Strip Chambers that will detect the high-energy particles called muons.
The collisions at the LHC will occur at a fixed energy. Using the ATLAS detector, the researchers will be able to measure the total number of particles and their energies produced in the collisions. The difference between the measured and produced energy is called the missing energy.
The missing energy will indicate that things like dark matter were created, Cheu said.
Shupe, head of the UA department of physics, said that with earlier particle accelerators, some of the most interesting findings were not expected. He anticipates that the same kinds of unanticipated discoveries will occur with the LHC.
All members of the UA-ATLAS team are in the UA's physics department. Other members of the team are doctoral students Xiaowen Lei, Caleb Parnell-Lampen and Chiara Paleari; Peter Loch, an associate research scientist; Alexandre Savine and Joel Steinberg, research engineers; Walter Lampl, an assistant research scientist; Venkatesh Kaushik, a research associate; Leif Shaver, a staff engineer, senior; Dan Tompkins, an engineer; Michael Starr, a test technician; and Robert Walker, an engineering aide.
Mari N. Jensen