UH research way down under


POSTED: Monday, March 23, 2009

A University of Hawaii scientist and colleagues are looking for “;lightning bolts”; in data collected by a balloon flown more than 30 days over Antarctica.

This would provide evidence of ultrahigh-energy neutrinos—subatomic particles from cosmic rays detected only by interactions or collisions with matter.

Scientists believe the behavior of invisible elementary particles could give them clues to the origin of the universe.

Antarctica is the only place where they can be detected interacting deep within the ice because the ice sheets are completely transparent to radio waves, said Peter Gorham, physics and astronomy professor.

“;When a cosmic neutrino coming to us from some exotic galaxy across the universe collides with an ice molecule ... it suddenly dumps all of its energy—equivalent to a billion-billion volts—into the ice,”; he explained in an interview. “;The result is kind of a lightning bolt within the solid ice, about 10 meters long. And it produces a very strong 'crack' of radio waves, an ultrashort impulse less than a billionth of a second long.”;

Even if just a handful of neutrinos were recorded, “;these would represent the first glimpse of the highest energy sources in the universe,”; he said.

Gorham led an international team that launched the Antarctic Impulsive Transient Antenna balloon—ANITA—Dec. 21 in McMurdo, Antarctica.

It was the second successful balloon flight by principal investigator Gorham and his group to hunt for ultrahigh-energy cosmic-ray neutrinos with a radio telescope. The first, in 2007, detected six ultrahigh-energy cosmic rays but no neutrinos.

The 4,200-pound ANITA II payload was recovered after landing by parachute Jan. 20 on the Ross Ice Shelf, and the data arrived at UH on Feb. 12.

“;The quality looks excellent,”; Gorham said. “;We have calibration work to do before we can start the neutrino analysis, but it looks like we are starting with the right stuff.”;

Collaborating institutions will begin scrutinizing the data to select “;the neutrino 'needles' from the huge haystack of events (recorded),”; he said.

ANITA II, a polyethylene balloon with more than 29 million cubic feet of helium, had 40 large antennas and a 24-foot-tall payload. From 22 miles above the ice, the instruments can pick up radio impulses that spread through the ice up to the surface, Gorham said.

“;If you had eyes that could 'see' radio waves, you could shine a radio flashlight right through the ice and easily see the continent beneath. The ice would be as clear as glass, even where it is several miles deep.”;

An earlier UH project, DUMAND, sought to detect neutrino collisions in deep sea water off Keahole Point on the Big Island but was shut down in 1995 after technical trouble.