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David Hedin
David Hedin

An aerial view of Fermilab. Click on the photo
for a larger view.


An elementary quest

NIU physicist Hedin explains
significance of the Higgs boson

March 23, 2009

by Tom Parisi

You’ll have to excuse NIU Physicist David Hedin if he gets a little excited over all that’s happening at Fermi National Accelerator Laboratory in west-suburban Batavia.

Over the decades, researchers at Fermilab – including Hedin and other NIU scientists and student researchers – have helped shed new light on how the universe works at its smallest and most basic level.

For Hedin, a 54-year-old Distinguished Research Professor at NIU, the quest to understand elementary particles, or nature’s building blocks, has covered the good part of three decades.

“I get carried away sometimes,” he says, adding that as of next month, he will have spent half of his life working with Fermilab’s DZero scientific collaboration. “I’m either very persistent or I lack imagination.”

Persistence on the part of hundreds of scientists has paid off at Fermilab, which is now in hot pursuit of the elusive Higgs boson, an elementary particle sometimes referred to as the holy grail of particle physics.

The Standard Model of particle physics – the best explanation scientists have of the origins of the universe – predicts the existence of the Higgs boson. Its detection would confirm the existence of the Higgs field, which is thought to permeate the universe. When elementary particles interact with this field, they gain mass.

Without mass, all particles would travel at the speed of light, never sticking together, and only these tiny mass-less particles would populate the universe.

Fermilab made headlines earlier this month when it announced a string of experimental results that narrow the territory where the Higgs boson might be found.

The latest analyses of data from the CDF and DZero collider experiments measure the mass of the W boson particle and the production of individual top quarks. Both the W boson and top quarks are heavy particles.

“We can study mass by measuring the properties of the heaviest particles,” Hedin says. “It is thought that interactions between the Higgs boson and other particles cause their mass differences. The heavier the particle, the larger its interaction with the Higgs. The mass of these heavy particles is related and measurements of the W and top quark mass can be used to predict the Higgs mass.”

It takes a monumental scientific effort to create and detect elementary particles.

CDF is an international experiment of 602 physicists from 63 institutions in 15 countries; DZero is an international experiment conducted by 550 physicists from 90 institutions in 18 countries.

Both collaborations conduct their work using the Tevatron, the world’s most powerful particle accelerator, which hurls protons and antiprotons toward each other at nearly the speed of light. The scientists study the resulting collisions for evidence of new subatomic particles and forces.

NIU has been a member of the DZero collaboration since 1986.

In addition to Hedin, current NIU researchers involved in the collaboration include physicists Jerry Blazey, Dhiman Chakraborty, Michael Fortner, Alexandre Dychkant and Sergey Uzunyan; and graduate students Martin Braunlich, Diego Menezes and Lei Feng. Additionally, NIU physicist Steve Martin works in developing the underlying theory of particle interactions and the role of the Higgs boson.

“Since 2001, when upgrades were completed, the Tevatron has been collecting data 24 hours a day and usually seven days a week, including on Thanksgiving and Christmas,” Hedin says. “It requires that all 600 DZero physicists on the experiment take responsibility for such things as individual detector operations, maintenance and software algorithms.

“This type of physics cannot be done by individuals but requires dedicated teams that are willing to spend years and even decades to add to our knowledge of fundamental physics.”

It’s an important quest. Hedin believes the discovery of the Higgs boson would open new frontiers in science.

“We know from looking at the heavens that there is new fundamental physics to be discovered,” he says. “About 95 percent of the universe seems to be composed of dark matter and dark energy, and we are without any understanding of the basic nature of these two components. When the Higgs boson is discovered, its properties, including its mass, will provide us with more clues to the nature of this new fundamental physics.”