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A team of international scientists studying neutrinos havedetermined enigmatic neutrinos behave like other elementaryparticles at the quantum level. Indeed, the Enriched Xenon Observatory 200 (EXO-200), aninternational collaboration led by Stanford University and the U.S.Department of Energy's (DOE) SLAC National Accelerator Laboratory,recently kicked off one of the most sensitive searches ever for amysterious mechanism known as "neutrinoless double-betadecay" in which two neutrinos, acting as particle andantiparticle, do not emerge from the nucleus. If this decay were observed, it would signal that neutrinos have adifferent quantum structure than other elementary particles. However, EXO-200, which is capable of detecting decays that happen,on average, only once every 10^25 years (1 quadrillion times theage of the universe), did not observe this decay, which constitutesthe strongest evidence yet that neutrinos behave like otherparticles. "The result could only have been more exciting if we'd beenhit by a stroke of luck and detected neutrinoless double-betadecay," explained Giorgio Gratta, a professor of physics atStanford University and spokesperson for EXO-200. "In theregion where double-beta decay was expected, the detector recordedonly one event. That means the background activity is very low andthe detector is very sensitive. It's great news to say that we seenothing!" To be sure, EXO-200 has been able to all but rule out a previous,highly controversial result claiming to have detected the decay,while narrowing down the mass of the neutrino to less than 140- to380- thousandths of an electronvolt (the unit of mass used inparticle physics). For comparison, the minuscule electron has amass of roughly 500,000 electronvolts. According to Gratta, at the heart of EXO-200 is a thin-walledcylinder made of extremely pure copper. It is full of about 200kilograms (about 440 pounds) of liquid xenon and buried 2,150 feetdeep at the DOE's Waste Isolation Pilot Plant (WIPP), a New Mexicosalt bed where low-level radioactive waste is stored. The xenon - in particular the isotope xenon-136, which makes up thelion's share of the xenon in EXO-200 - is one of the few substancesthat can theoretically undergo the decay. Constructing theexperiment of exceedingly pure materials and locating itunderground ensured that all other traces of radioactivity andcosmic radiation are eliminated or kept at a minimum. EXO-200 will take data for a few more years and in the future, theteam hopes to expand the technique to a several-ton version thatwould be even more sensitive at observing the nearly imperceptiblephysical processes that have been theorized. I am an expert from cobled-downlight.com, while we provides the quality product, such as China Flat Panel Led Light , China Led High Bay Lighting, Cob Led Track Light,and more.
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