UCLA scientists discover new data on detecting dark matter
By Marcus Torrey
April 22, 2011 2:33 a.m.
Housed a mile beneath a mountain in Italy is the Gran Sasso National Laboratory.
The scientists who research there possess an extensive knowledge of physics ““ a knowledge they use to help them detect dark matter.
This mysterious, invisible type of matter makes up 25 percent of the known universe, said UCLA physics Professor Katsushi Arisaka. Compare that to regular matter, which only constitutes 5 percent of the universe.
Dark matter is responsible for the gravitational force that brought regular matter together to form stars and planets, said Hanguo Wang, a UCLA physics researcher.
Although it has not yet been directly observed by human eyes, dark matter is closer than ever to being discovered because of a collaborative effort between UCLA, Columbia University and a host of other research institutions that have been jointly working on the XENON100 experiment.
The experiment derives its name from the noble gas xenon, said Arisaka, who works on the project. Researchers filled a tub, which acts as a dark matter detector, with more than 100 pounds of liquid xenon and sheltered it in the Gran Sasso laboratory.
UCLA researchers joined the project halfway through the construction of the detector and mainly contributed by completing the unfinished half and analyzing data.
Arisaka said the detector works by creating a flash of light when dark matter particles go through xenon atoms and react with their nuclei.
But since dark matter interacts so infrequently, the noise created by background radiation makes this occurrence nearly impossible to distinguish.
“You have to go to a radiation-free environment,” Arisaka said.
The Gran Sasso lab was selected as the experiment’s location because cosmic radiation has a difficult time penetrating deep underground, although dark matter does not.
Though the XENON100 experiment has not detected any dark matter, Arisaka said the researchers have still advanced a step forward by figuring out a way to distinguish between interactions of dark matter and those caused by background radiation.
Xenon has proven to be on par with the best detector methods currently researched. Wang, who also works on the XENON100 team, said the next step will be to build an even larger tub to house a greater amount of xenon.
Emilija Pantic, a UCLA postdoctoral scholar and XENON100 researcher, said the future project will have a larger target mass. This will allow for greater exposure in less time ““ something other types of detectors can’t achieve.
“Our real contribution (to this type of research) will be to make the best detector,” Arisaka said.
While Wang said a better understanding of dark matter won’t affect day-to-day life, he emphasized that it is important to understand such a large part of the universe.
