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How many quarks are in<br>protons and neutrons?

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protons and neutrons?)

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(What is the charge of an up quark
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What is the charge of an up quark<br>and of down quark?

What kinds of quarks are protons and neutrons made of? What was the old name for the Top and Bottom quark?

Protons are made of two Up and one Down quark. The neutron is made of two Down and one Up quark. The Up quarks have a 2/3 positive charge and the Down has a 1/3 negative charge. Fractional charges are a pretty funny concept, but remember we (humans) made up the unit of charge that a proton has, so its very possible that there could be a smaller division of charge. If you add those charges you will see that sum is positive one for the proton and 0 for the neutron.

Truth and Beauty quarks were called T and B when originally proposed, to be Top and Bottom in analogy with the nucleon quarks that had just been renamed the Up and Down quarks. (Originally P and N had been used, but this led to confusion with the nucleons.) Very soon after the proposal T and B was made, somebody, maybe MGM, decided to call them Truth and Beauty. This nomenclature remained standard for several years. The term Beauty is still often used for the B quark. The Cornell accelerator was called a "Beauty factory" which sounds much nicer than a "Bottom factory." After the B was discovered and years went by without the T, people started to say "the quark model has no truth." This was true, but did not sound nice. This incident caused the name Truth to be dropped and Top and Bottom again became standard. Now that the T quark is well established, the name Truth can safely be brought back, but I don't know if it will, since MGM does other things now.

A Theoretician, who formulates ideas or theories, suggests that to explain certain natural phenomena, a certain particle must exist. Other scientists and experimentalists do experiments to look for that particle. In the early 1960's a theoretician, Murray Gell-Mann, proposed the quark theory. He named the quarks then even though they had never been observed. It took experimentalists nearly 30 years to find proof of the existence of all six quarks. The Top was the last quark discovered in two experiments called CDF and D0 at a sister lab to Jefferson Lab, Fermilab, outside Chicago. They announced their discovery in April, 1994. Many particles have been discovered by accident during an experiment looking at something else. The experimenter then gets to name that particle, therefore a lot of particles have awfully silly names.

Author:

Brian Kross, Chief Detector Engineer (Other answers by Brian Kross)

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