Ghost-particle hunter wins physics prize

STOCKHOLM (AP):

Belgian-born scientist Francis Halzen won the Nobel Prize in physics Tuesday for his efforts to demystify a rare group of neutrinos, tiny cosmic particles that researchers believe offer clues to how the universe evolved.

Halzen said he had been told he was among the favourites for the prize since he first published about cosmic neutrinos in 2013. In any given year, he thought he had a one in 20 chance to win a Nobel.

“And I just had to live long enough, so here I am,” the 82-year-old said.

Halzen, a physicist at the University of Wisconsin-Madison in the US, said the research was a huge collaborative effort. He was working on a new research proposal when the Nobel Physics Committee called.

“I hope that this prize will help getting it approved,” he told the committee by phone from Italy, in a call broadcast at the news conference announcing the winner. The comment elicited chuckles from the audience.

Neutrinos are tiny cosmic particles with no electric charge and extraordinarily small mass, making them difficult to detect. Yet they are everywhere. They spew from stars like the sun, and trillions zip through our bodies every second.

Scientists cannot glimpse the mysterious ghost particles zooming around on their own, so they measure what happens when the particles collide with other bits of matter. Neutrinos bump into other particles only rarely, so scientists build large detectors to improve their odds of catching collisions.

Halzen had the idea to turn the vast Antarctic ice into such a detector. The Nobel committee said his work was instrumental to the construction of the IceCube Neutrino Observatory in Antarctica, which glimpsed the first high-energy neutrinos from faraway galaxies.

“This experiment in the Antarctic is a revolutionary way of understanding the universe that we didn’t have before,” said Michael Moloney, chief executive officer for the American Institute of Physics.

When a neutrino interacts with ice in the detector, it produces a flash of light that’s picked up by sensors. The transparent ice makes it easier for scientists to find faint signals from the particles, and the sensors are buried about 8,200 feet (2,500 metres) deep to protect against interference from cosmic rays and radiation.

“People always thought this was a cute idea, right, but it would never work,” Halzen said at a news conference hosted by his university. “The greatest surprise is that we did make it work.”

Neutrinos can help scientists understand the universe

Halzen helped pull back the curtain on an elusive crew of neutrinos that scientists say carry clues about the development of other galaxies and the universe as a whole.

He said the work was painstakingly slow because the team had to differentiate between neutrinos from the cosmos and neutrinos that are emitted in Earth’s atmosphere.

“We actually detect 3,000 charged particles every second, and in these 3,000 a second, we have to find one every day, then like one a month we are totally sure of. That is the mathematics of the problem.”

He likened the Antarctic observatory to “a big eye made out of ice that can look at the universe in neutrinos, rather than in light.”

Supported by the National Science Foundation and run by Halzen’s university in Wisconsin, the IceCube Neutrino Observatory involves more than 400 scientists in 14 countries.