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Last Update: 2010-03-19 Source: Research Headlines
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Scientists discover new heavy antimatter
A global team of scientists has discovered the heaviest known antinucleus and the first-ever antinucleus containing an anti-strange quark by investigating high-energy collisions of gold ions at the Relativistic Heavy Ion Collider (RHIC) located at the US Department of Energy's (DOE) Brookhaven National Laboratory. The findings of the study were presented in the journal Science.
The scientists said this new antinucleus, found at the RHIC's STAR detector, is a negatively charged state of antimatter containing an antiproton, an antineutron, and an anti-Lambda particle.
'This experimental discovery may have unprecedented consequences for our view of the world,' said Horst Stöcker, a professor of theoretical physics and vice president of the Helmholtz Association of the German National Laboratories. 'This antimatter pushes open the door to new dimensions in the nuclear chart — an idea that just a few years ago, would have been viewed as impossible.'
The scientists pointed out that all terrestrial nuclei are composed of protons and neutrons, which in turn have only up and down quarks. Most people use the Periodic Table of Elements which is arranged based on the number of protons that determine the chemical properties of each element. Physicists, for their part, use a three-dimensional chart which is more complex but offers information about the number of neutrons that can change in various isotopes of the same element, and a quantum number that experts call 'strangeness', which is contingent on strange quarks being present.
Experts define hypernuclei as nuclei that contain one or more strange quarks. The strangeness value equals zero for ordinary matter with no strange quarks and a flat chart. Hypernuclei emerge above the plane of the chart, according to them. Based on the findings of this latest study, the new antihypernucleus generates a key sample of normal hypernuclei and could shed light on the structure of collapsed stars.
'The strangeness value could be non-zero in the core of collapsed stars,' explained co-lead author Dr Jinhui Chen from Kent State University in the US and the Shanghai Institute of Applied Physics in China. 'So the present measurements at RHIC will help us distinguish between models that describe these exotic states of matter'.
According to the scientists, not only can the discovery of the antinucleus help experts clarify models of neutron stars but it could also encourage scientists to launch more investigations into the violations of fundamental symmetries between matter and antimatter that emerged in the early universe.
They added that collisions at RHIC momentarily generate conditions that existed just seconds after the Big Bang, the expansion which experts believe to be the point of the universe's origin nearly 14 billion years ago.
'Understanding precisely how and why there's a predominance of matter over antimatter remains a major unsolved problem of physics,' said co-lead author Dr Zhangbu Xu from the Brookhaven National Laboratory in New York. 'A solution will require measurements of subtle deviations from perfect symmetry between matter and antimatter, and there are good prospects for future antimatter measurements at RHIC to address this key issue.'
Collaborating on the STAR experiment were scientists from Brazil, China, Croatia, the Czech Republic, France, Germany, India, the Netherlands, Poland, Russia, South Korea, the UK and the US.