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Quark Model of the Nucleus
Transcript of Quark Model of the Nucleus
Christopher Cych Quark Model of the Nucleus Modern Atomic Structure/Theory Basic Nucleus
Review How was the nucleus discovered? Quarks Rutherford Continued Quark "Flavors" Color . The accepted atomic theories should be familiar to us . The role of the nucleus is to direct all activities that occur in a cell/atom Ernest Rutherford experiment . Rutherford concluded that the gold foil must mostly be comprised of empty space. What is a quark? . The quark "flavors" are:
1. Up quark
2. Down quark
3. Strange quark
4. Charm quark
5. Top quark
6. Bottom quark . The six quark "flavors" have three "colors" each . Basic atomic structure: Atoms consist of a positively charged nucleus, along with the negatively charged electrons that surround it . The nucleus consists of positively charged protons and neutrally charged neutrons . A strong nuclear force binds the protons and neutrons together . The number of protons in a nucleus is also known as the atomic number of the atom . The number of protons in the nucleus equals the number of electrons surrounding it . The atomic mass of an atom is equal to the atomic number plus the number of neutrons in the nucleus . In 1911, Rutherford conducted the well-known experiement to discover the nucleus. In the experiment, alpha particles were launched at a thin layer of gold foil. Most of the particles would break through the foil, but some did not. . These regions were the most dense/heavy, which Rutherford named as the nucleus. . Gell-Mann got the name "quark" from a line from James Joyce's "Finnegans Wake".
The line reads:
Three "quarks" for Muster Mark!
Sure he hasn't got much of a bark
And sure any he has it's all beside the mark. Up and Down Quarks . Most common quarks, contained in protons and neutrons . Protons contain two up quarks and one down quark
. Neutrons contain two down quarks and one up quark Up quark . Symbol: U
. Charge: + 2/3
. Spin: 1/2 Down Quark . Symbol: D
. Charge: -1/3
. Spin: 1/2 Charm quark . First discovered with the discovery of the J/Psi particle, a meson with pair of a charm quark and an anti-charm quark. This particle was the first found to contain this new quark Charm Quark . Symbol: C
. Charge: +2/3
. Spin: 1/2 Strange quark . During a study of cosmic ray interactions in 1947, a product of a proton collided with a nucleus and was found to live much more than was expected when it collided. . This particle was named the lambda particle, but the property that caused it to live so much longer was called "strangeness" and this name stuck to be the name of one of the quarks from which the lambda particle is constructed. . Symbol: S
. Charge: -1/3
. Spin: 1/2 Top and Bottom quark Top quark . Symbol: T
. Charge: +2/3
. Spin: 1/2 Bottom quark . Symbol: B
. Charge: -1/3
. Spin: 1/2 . The top quark was discovered when the collision products of protons with equally energetic anti-protons collided and the top quark was found to have a mass of 180 times more than the mass of the proton . The bottom quark was discovered through a lab experiment that led to the discovery of the Upisilon meson, which contained the bottom-anti-bottom quark pair. Scientists that formulated the Quark Model Murray Gell-Mann He is the author of The Quark and the Jaguar, published in 1994, in which his ideas on simplicity and complexity are presented to a general readership. He was able to discover quarks with some 100 kinds of particles in collisions involving atomic nuclei. Gell-Mann subsequently found that all of those particles, including the neutron and proton, are composed of fundamental building blocks that he named "quarks," with very unusual properties. George Zweig Russian scientist that proposed, along with Murray Gell-Mann, that all nuclear particles are merely different arrangements of a few simple parts—the quarks. In the late 1960's and early 1970's, experiments showed that protons and neutrons are made up of smaller particles, thus confirming the existence of quarks. Quark Model of the nucleus versus Modern Model Recap Similarities
Key Points Any Questions? Citations Joyce, James. A Shorter Finnegan's Wake. New York: The Viking Press, 1967. Print.
Unknown author. "How was the nucleus of an atom discovered?". Curiosity.com. Discovery
Communications. Web. Accessed 2/19/13. http://curiosity.discovery.com/question/nucleus-atom-discovered
Unknown author. "ABC's of Nuclear Science". www.lbl.gov. Last updated 3/30/07. Unknown publisher. Web. Accessed 2/19/13. http://www.lbl.gov/abc/Basic.html
Unknown author. "Quarks". hyperphysics.phy-astr.gsu.edu. Unknown publisher. Web. Accessed 2/5/13. http://hyperphysics.phy-astr.gsu.edu/hbase/particles/quark.html . Before the discovery of quarks, many scientists believed that atoms alone consisted of three basic particles, but there was also the question of whether these particles were made of even smaller, more basic building blocks. . Quarks are these even smaller particles. . Quarks can be thought of as separate, independent particles or they can be considered together as making up a larger particle, such as the proton or neutron. . Neutrons and Protons are combinations of three different kinds of quarks. . Flavor is used to describe the differences in these properties and to identify the different kinds of quarks . Each flavor of quark can come in three different forms, these different forms are known as color. . Color is just another way of classifying quarks according to the way they combine; this has nothing to do with actual color, it was deemed the best analogy possible. . Red, blue, and green are perhaps the most popular set of quark colors. Color Force . Quarks are held together by a force in the larger particles . Like electrical charges that repel and attract each other, so do quarks Properties of Quarks . There are only two electrical charges, positive and negative. . There is another particle that actually carries the force, since force in a way glues the quarks together, this particle is called gluon. . Overall the gluon is the force that holds the quarks in a larger particle together. Anti Quark . The anti-quark is an identical quark with the opposite color and an opposite electrical charge . The entire family of quarks have one unusual feature in common and that is that they all have fractional charges. . A combination of three quarks is a baryon . A combination of two quarks is a meson leptons are tiny particles not made of quarks .Combinations of quarks are labeled as "colorless" . The spin of a quark refers to the particles being able to coexist; the Pauli Exclusion Principle states that the particles cannot share the same spin. .The symbol of a quark shows what "flavor" it is, and how it appears in diagrams. Gell-Mann cont. Gell-Mann also formulated the "eightfold way", which classified the many particles he discovered through his atomic nuclei collision experiment. In this sense, it is similar to how the periodic table classifies elements. Berger, Melvin, and Gregory C. Wenzel. Atoms, Molecules, and Quarks. New York: Putnam, 1986. Print. Keith, Michael. "Quarks and Antiquarks". www.egglescliffe.org.uk. Unknown publisher, published 2001. Web. Accessed 4/24/13. http://www.egglescliffe.org.uk/physics/particles/mkquark/quarks.html
Unknown author. "The Color Force". hyperphysics.phy-astr.edu. Unknown publisher and publishing date. Web. Accessed 4/24/13. http://hyperphysics.phy-astr.gsu.edu/hbase/forces/color.html Hawking, S. W. The Illustrated A Brief History of Time. New York: Bantam, 1996. Print