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Hexaquark
In particle physics hexaquarks, alternatively known as sexaquarks, are a large family of hypothetical particles, each particle consisting of six quarks or antiquarks of any flavours. Six constituent quarks in any of several combinations could yield a colour charge of zero; for example a hexaquark might contain either six quarks, resembling two baryons bound together (a dibaryon), or three quarks and three antiquarks. Once formed, dibaryons are predicted to be fairly stable by the standards of particle physics. A number of experiments have been suggested to detect dibaryon decays and interactions. In the 1990s, several candidate dibaryon decays were observed but they were not confirmed. There is a theory that strange particles such as hyperons and dibaryons could form in the interior of a neutron star, changing its mass–radius ratio in ways that might be detectable. Accordingly, measurements of neutron stars could set constraints on possible dibaryon properties. A large fracti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exotic Hadron
Exotic hadrons are subatomic particles composed of quarks and gluons, but which – unlike "well-known" hadrons such as protons, neutrons and mesons – consist of more than three valence quarks. By contrast, "ordinary" hadrons contain just two or three quarks. Hadrons with explicit valence gluon content would also be considered exotic. In theory, there is no limit on the number of quarks in a hadron, as long as the hadron's color charge is white, or color-neutral. Consistent with ordinary hadrons, exotic hadrons are classified as being either fermions, like ordinary baryons, or bosons, like ordinary mesons. According to this classification scheme, pentaquarks, containing five valence quarks, are exotic baryons, while tetraquarks (four valence quarks) and hexaquarks (six quarks, consisting of either a dibaryon or three quark-antiquark pairs) would be considered exotic mesons. Tetraquark and pentaquark particles are believed to have been observed and are being investigated; Hexaquar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentaquark
A pentaquark is a human-made subatomic particle, consisting of four quarks and one antiquark bound together; they are not known to occur naturally, or exist outside of experiments specifically carried out to create them. As quarks have a baryon number of , and antiquarks of , the pentaquark would have a total baryon number of 1, and thus would be a baryon. Further, because it has five quarks instead of the usual three found in regular baryons ( 'triquarks'), it is classified as an exotic baryon. The name pentaquark was coined by Claude Gignoux ''et al.'' (1987) and Harry J. Lipkin in 1987; however, the possibility of five-quark particles was identified as early as 1964 when Murray Gell-Mann first postulated the existence of quarks. Although predicted for decades, pentaquarks proved surprisingly difficult to discover and some physicists were beginning to suspect that an unknown law of nature prevented their production. The first claim of pentaquark discovery was recorded ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Particle Physics
Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and bosons (force-carrying particles). There are three generations of fermions, but ordinary matter is made only from the first fermion generation. The first generation consists of up and down quarks which form protons and neutrons, and electrons and electron neutrinos. The three fundamental interactions known to be mediated by bosons are electromagnetism, the weak interaction, and the strong interaction. Quarks cannot exist on their own but form hadrons. Hadrons that contain an odd number of quarks are called baryons and those that contain an even number are called mesons. Two baryons, the proton and the neutron, make up most of the mass of ordinary matter. Mesons are unstable and the longest-lived last for only a few hundredths of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert Jaffe
Robert Loren Jaffe (born May 23, 1946) is an American physicist and the Jane and Otto Morningstar Professor of Physics at the Massachusetts Institute of Technology (MIT). He was formerly director of the MIT Center for Theoretical Physics. Biography Jaffe was born in Bath, Maine, USA, in 1946 and educated in public schools in Stamford, Connecticut. He received his Bachelor of Arts, A.B. degree in physics, summa cum laude, from Princeton University, where he was valedictorian of the Class of 1968. He received his Master of Science, M.S. and Doctor of Philosophy, Ph.D. degrees from Stanford University in 1971 and 1972, respectively. At Stanford he founded the Stanford Workshops on Political and Social Issues. In 1972, Jaffe moved to MIT as a postdoctoral research associate in the Center for Theoretical Physics; he joined the faculty in 1974. From 1975 until 1979, he was an Alfred P. Sloan Foundation Research Fellow. Jaffe has spent sabbatical years at the Stanford Linear Accelerator ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Soviet Astronomy
''Astronomy Reports'' (Russian: ''Астрономический журнал'', ''Astronomicheskii Zhurnal''), is a Russian, monthly, peer reviewed, scientific journal. This journal tends to focus its publishing efforts on original research regarding astronomical topics. Other types of reporting are also included such as chronicles, proceedings of international conferences, and book reviews. Founded in 1924, it is described as the most prominent astronomy journal during the age of the Soviet Union. Originally a print version, it is also available online. The editor-in-chief was Alexander A. Boyarchuk, Institute of Astronomy of the Russian Academy of Sciences, Moscow, Russia. Former title This journal, currently titled "''Astronomy Reports''", continues with the same Russian title as when it was known in English as ''Soviet Astronomy''. The former ''Soviet Astronomy'' shares exactly the same Russian name as this journal, exactly the same print issn, but the US Library of Congre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Review Letters
''Physical Review Letters'' (''PRL''), established in 1958, is a peer-reviewed, scientific journal that is published 52 times per year by the American Physical Society. As also confirmed by various measurement standards, which include the ''Journal Citation Reports'' impact factor and the journal ''h''-index proposed by Google Scholar, many physicists and other scientists consider ''Physical Review Letters'' to be one of the most prestigious journals in the field of physics. ''According to Google Scholar, PRL is the journal with the 9th journal h-index among all scientific journals'' ''PRL'' is published as a print journal, and is in electronic format, online and CD-ROM. Its focus is rapid dissemination of significant, or notable, results of fundamental research on all topics related to all fields of physics. This is accomplished by rapid publication of short reports, called "Letters". Papers are published and available electronically one article at a time. When published in s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dineutron
Neutronium (sometimes shortened to neutrium, also referred to as neutrite) is a hypothetical substance composed purely of neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...s. The word was coined by scientist Andreas von Antropoff in 1926 (before the 1932 discovery of the neutron) for the hypothetical "element of atomic number zero" (with zero protons in its nucleus) that he placed at the head of the periodic table (denoted by -, or Nu). However, the meaning of the term has semantic change, changed over time, and from the last half of the 20th century onward it has been also used to refer to extremely dense substances resembling the neutron-degenerate matter theorized to exist in the cores of neutron stars; hereinafter "''degenerate'' neutronium" will refer to this. In neutro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diproton
Although there are nine known isotopes of helium (2He) (standard atomic weight: ), only helium-3 () and helium-4 () are stable. All radioisotopes are short-lived, the longest-lived being with a half-life of . The least stable is , with a half-life of (), although it is possible that may have an even shorter half-life. In the Earth's atmosphere, the ratio of to is . However, the isotopic abundance of helium varies greatly depending on its origin. In the Local Interstellar Cloud, the proportion of to is , which is times higher than that of atmospheric helium. Rocks from the Earth's crust have isotope ratios varying by as much as a factor of ten; this is used in geology to investigate the origin of rocks and the composition of the Earth's mantle. The different formation processes of the two stable isotopes of helium produce the differing isotope abundances. Equal mixtures of liquid and below separate into two immiscible phases due to differences in quantum statistics: at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deuteron
Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1). The nucleus of a deuterium atom, called a deuteron, contains one proton and one neutron, whereas the far more common protium has no neutrons in the nucleus. Deuterium has a natural abundance in Earth's oceans of about one atom of deuterium among all atoms of hydrogen (see heavy water). Thus deuterium accounts for approximately 0.0156% by number (0.0312% by mass) of all the naturally occurring hydrogen in the oceans, while protium accounts for more than 99.98%. The abundance of deuterium changes slightly from one kind of natural water to another (see Vienna Standard Mean Ocean Water). (Tritium is yet another hydrogen isotope, with two neutrons, that is far more rare and is radioactive.) The name ''deuterium'' is derived from the Greek , meaning "second", to denote the two particles composing the nucleus. Deuteri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baryonic Dark Matter
In astronomy and cosmology, baryonic dark matter is dark matter composed of baryons. Only a small proportion of the dark matter in the universe is likely to be baryonic. Characteristics As "dark matter", baryonic dark matter is undetectable by its emitted radiation, but its presence can be inferred from gravitational effects on visible matter. This form of dark matter is composed of "baryons", heavy subatomic particles such as protons and neutrons and combinations of these, including non-emitting ordinary atoms. Presence Baryonic dark matter may occur in non-luminous gas or in Massive Astrophysical Compact Halo Objects (MACHOs) – condensed objects such as black holes, neutron stars, white dwarfs, very faint stars, or non-luminous objects like planets and brown dwarfs. Estimates of quantity The total amount of baryonic dark matter can be inferred from models of Big Bang nucleosynthesis, and observations of the cosmic microwave background. Both indicate that the amount of baryo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metastability
In chemistry and physics, metastability denotes an intermediate Energy level, energetic state within a dynamical system other than the system's ground state, state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. If the ball is only slightly pushed, it will settle back into its hollow, but a stronger push may start the ball rolling down the slope. Bowling pins show similar metastability by either merely wobbling for a moment or tipping over completely. A common example of metastability in science is isomerisation. Higher energy isomers are long lived because they are prevented from rearranging to their preferred ground state by (possibly large) barriers in the potential energy. During a metastable state of finite lifetime, all state-describing parameters reach and hold stationary values. In isolation: *the state of least energy is the only one the system will inhabit for an indefinite length of time, until more external energy is added ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
