World's smallest neutrino detector observes "elusive interactions" of particles

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WASHINGTON, Aug. 3 (Xinhua) -- Scientists using the world's smallest neutrino detector reported Thursday that they have observed the "elusive interactions" of the ghostly particles with the nucleus of an atom for the first time.

The research, performed at the U.S. Department of Energy's Oak Ridge National Laboratory (ORNL) and published in the U.S. journal Science, confirmed a neutrino interaction process predicted by theorists 43 years ago, but never seen.

"The one-of-a-kind particle physics experiment at Oak Ridge National Laboratory was the first to measure coherent scattering of low-energy neutrinos off nuclei," ORNL physicist Jason Newby, technical coordinator for the so-called COHERENT experiment, said in a statement.

Neutrinos, often referred to as "ghost particles," are a challenge to study because their interactions with matter are so rare.

Particularly elusive has been what's known as coherent elastic neutrino-nucleus scattering, which occurs when a neutrino bumps off the nucleus of an atom.

In the new study, the researchers designed the detector that is a cesium iodide scintillator crystal doped with sodium to increase the prominence of light signals from neutrino interactions.

They installed the detector at ORNL's Spallation Neutron Source (SNS), which produces neutrons for scientific research and also generates a high flux of neutrinos as a byproduct.

"Placing the detector at SNS, a mere 65 feet (20 meters) from the neutrino source, vastly improved the chances of interactions," the study said.

"That signal is as tough to spot as a bowling ball's tiny recoil after a ping-pong ball hits it," it said.

Meanwhile, the new design allowed the researchers to decrease the detector's weight to just 14.5 kilograms, enough for a researcher to carry.

In comparison, the world's most famous neutrino observatories are equipped with thousands of tons of detector material.

The COHERENT experiment involves more than 80 researchers from 19 institutions and four nations and has been in operation for more than one year at ORNL.

Through measuring coherent elastic neutrino-nucleus scattering, physicists hope to better understand the properties of the mysterious particle.

"Neutrinos are one of the most mysterious particles," said physicist Juan Collar of the University of Chicago who led the design of the detector. "We ignore many things about them. We know they have mass, but we don't know exactly how much." Enditem

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