Friday, July 09, 2010

A holiday for neutrinos

How a South Dakota company town turned science community

When physicists from institutions all over the U.S. rolled into the town of Lead (pronounced Leed), South Dakota in 2001, they were greeted by a banner stretching across Main Street declaring "Welcome Scientists." The townspeople may not all have completely understood what a neutrino detector was, but many recognized the future of their town might be saved by one.

What the physicists would eventually propose resulted in Lead's selection as the site of a new underground national laboratory. The town, as well as the entire state of South Dakota, has celebrated Neutrino Day on the second Saturday in July to commemorate the decision ever since.

For the previous 125 years, Lead's identity had been wrapped around the Homestake Co. Black Hills gold mine. The Homestake Mine was the deepest, largest and the most productive gold mine in the western world. To support its mine, the company had built the town's school, power plant, utilities, hospital, mill and even an opera house. At its highest point, the Black Hills mine employed 4,000 people-the entire population of the town is now a mere 3,000. The mine produced 2.5 million pounds of gold-more than $1 billion worth-in its lifetime, but declining prices and an increased cost of doing business made the company decide to close the 1.5 mile deep mine in 2000.

Physicists saw an opportunity in Black Hills. Neutrinos are notoriously difficult to detect and are thought to be important to dark matter and numerous other mysteries in our universe. Deep beneath the tallest peaks east of the Rockies, a new national lab would be able to search unabated by noise from the outside world. And because neutrinos can pass through solid matter, they can penetrate the earth to be detected.

Another physicist had seen this same opportunity in Homestake 40 years earlier. Raymond Davis Jr. had designed an experiment to detect neutrinos coming from the sun from nearly 5,000 feet down in the then active gold mine. While Davis headed up the experiment, fellow astrophysicst John Bahcall calculated the rate the experiment should detect neutrinos at. The experiment was successful in that it became the first to detect and count solar neutrinos, but the number of neutrinos it detected was one-third of what Bahcall had predicted. While both maintained the numbers were accurate and no mistake was made, it would take decades to confirm that they were in fact both right.

The answer to the now famous solar neutrino problem was that the tiny particles changed "flavors," into three different types on their way to earth from the sun. The Homestake experiment could only detect one of these types. In 2002, Davis shared the Nobel Prize in Physics for his work.

After the turn of the millennium, a number of sites across the country had been proposed as sites for a new national underground lab, called the Deep Underground Science and Engineering Laboratory (DUSEL). The Homestake site would eventually win out, bringing the town of Lead along with it and the project has been in the developing stages since it got final NSF approval in 2007. Thus far the project has been supported by $70 million from T. Denny Sanford, a South Dakota businessperson and owner of First National Bank and Premier Bankcard, as well as $35 million of state money from South Dakota. The project is eventually expected to receive $550-million in NSF money to complete the project.

To celebrate the town's future in the sciences, Lead has celebrated Neutrino Day since 2001. Last year South Dakota Governor Mike Rounds declared Neutrino Day for the second Saturday in July. The town will celebrate its tradition with science festivities of all sorts this weekend including; science art exhibits, lectures and presentations for public audiences, Q&A with scientists, tours of some parts of the mine, hands-on activities for kids, documentaries on the lab and underground science, and a "science café" staffed by SD Public Radio. In the past, it's even crowned a Miss Neutrino.

If you happen to be in South Dakota, you can find more info here.

But you can follow a live webcast as well here.

1 comment: