Michigan integral to world's largest physics experiment

After 20 years of construction, a machine that could either verify or nullify the prevailing theory of particle physics is about to begin its mission.

A view of the ATLAS instrument, one of two main particle detectors on the Large Hadron Collider. A U-M physicist and students were involved in designing and building major components of ATLAS. (Photo by Claudia Marcelloni, CERN)

CERN's epic Large Hadron Collider (LHC) project currently involves 25 University physicists and students. More than 100 U-M researchers have been involved in the project over the years. CERN is the European Organization for Nuclear Research, located in Geneva, Switzerland.

The historic multibillion-dollar project aims to answer lingering questions about the laws of nature and the nature of matter by smashing protons and other particles together and examining the wreckage.

The collider — the world's largest — is scheduled to send the first proton beam zipping through its 17-mile tunnel Sept. 10. Scientists expect it will take four-eight weeks to adjust the beams to produce particle collisions. They hope to observe the first collisions between Oct. 8-Nov. 5.

"The Large Hadron Collider should address some of the most fundamental questions facing science now," says Homer Neal, the Samuel A. Goudsmit Professor of Physics and the Institutional Representative for the ATLAS Experiment at LHC. "This is an extremely exciting time to be involved with the project and with so many bright and dedicated faculty colleagues and sharp post-docs and students. It's been a long wait."

ATLAS is one of two large particle detectors on the collider. Michigan physicists and students helped design and build it. ATLAS and CMS, the other large particle detector, are looking for the same new particles, but in different ways. They back each other up, but they also will compete.

Neal has been working at CERN periodically for 40 years. He also was on the board of overseers of the Superconducting Super Collider project in Texas that was scrapped in 1993 during the early stages of construction.

"Many of us who have been eager to search for the Higgs boson and to explore other particles have been waiting not just during the period we've been working on the CERN LHC, but even before then, as we watched the Texas project undergo years of planning and then crumble," Neal says.

The Higgs boson particle is perhaps the most sought-after prize of the project. The Standard Model of particle physics theorizes that it gives other particles mass. This theory says the Higgs creates a field with which the particles with mass interact. Particles without mass don't interact with this field. The Higgs should be detectable at the energies the collider is capable of producing. If scientists find it, their Standard Model survives.

"If it does not exist," Neal says, "we'll clearly have to go back to the drawing board. That would shake the foundation of how we believe the smallest components of matter interact with each other and how mass itself is created. But even this outcome would be extremely exciting and would launch new avenues of exploration."

Michigan researchers built components of ATLAS called muon detectors that Bing Zhou, professor in the Department of Physics, says should play a lead role in finding the Higgs.

"These muon detectors will have the best chance of finding the signal for decay of the Higgs boson through the muon final states," says Zhou, who is leader of U.S. ATLAS muon detector development and construction.

In addition to Neal and Zhou, other U-M physicists involved in the ATLAS experiment are professors Dan Amidei, J. Chapman, Jianming Qian and Rudolf Thun. Six research scientists and four engineers are involved, as are six post-doctoral and seven graduate students. More than 50 undergraduate students have been involved as well.