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The elusive masses of up, down and strange quarks pinned down
Monday, 03 May 2010 21:16
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| Astronomy - Astrophysics |
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Quarks, the elementary particles that make up protons and neutrons, have been notoriously difficult to nail down - much less weigh - until now. A research group co-founded by Cornell physics professor G. Peter Lepage has calculated, with a razor-thin margin of error, the mass of the three lightest and, therefore, most elusive quarks: up, down and strange. The findings reduce the uncertainty of the quark masses by 10 to 20 times down to a few percent. Scientists have known the mass of a proton for almost a century, but getting the mass of the individual quarks inside has been an ongoing challenge. The quarks are held together by the so-called strong force -- so powerful that it's impossible to separate and study them. They exist in a soup of other quarks, antiquarks and gluons, which are another type of elementary particle. To determine the quark masses, Lepage explained, it was necessary to fully understand the strong force. They tackled the problem with large supercomputers that allowed them to simulate the behavior of quarks and gluons inside such particles as protons. There are six types of quarks, and they have an astonishingly wide range of masses: Up/down, Strange/Charm and Top/Buttom The lightest is the up quark, which is 470 times lighter than a proton. The heaviest is the top quark, which is 180 times heavier than a proton - or almost as heavy as an entire atom of lead! Up: 2MeV (Previously est. 3MeV) "So why these huge ratios between masses? This is one of the big mysteries in theoretical physics right now," Lepage said. "Indeed it is unclear why quarks have mass at all." He added that the new Large Hadron Collider in Geneva was built to address this question. Result Source: Cornell University |
