Tau Particle, Tauon

"The tau (τ), also called the tau lepton, tau particle or tauon, is an elementary particle similar to the electron, with negative electric charge and aspin of ¹⁄₂. Together with the electron, the muon, and the three neutrinos, it is classified as a lepton. Like all elementary particles, the tau has a corresponding antiparticle of opposite charge but equal mass and spin, which in the tau's case is the antitau (also called the positive tau). Tau particles are denoted by τ− and the antitau by τ+."

"Tau leptons have a lifetime of 2.9×10⁻¹³ s and a mass of 1,777 MeV/c² (compared to 105.7 MeV/c² for muons and 0.511 MeV/c² for electrons). Since their interactions are very similar to those of the electron, a tau can be thought of as a much heavier version of the electron. Because of their greater mass, tau particles do not emit as much bremsstrahlung radiation as electrons; consequently they are potentially highly penetrating, much more so than electrons. However, because of their short lifetime, the range of the tau is mainly set by their decay length, which is too small for bremsstrahlung to be noticeable: their penetrating power appears only at ultra high energy (above PeV energies)."

Promethium

Promethium ( /prɵˈmiːθiəm/ pro-mee-thee-əm), originally prometheum, is a chemical element with the symbol Pm and atomic number 61. It is notable for being the only element besides technetium all of whose isotopes are radioactive but which is followed in the periodic table by chemical elements with stable isotopes. Chemically, promethium is a lanthanide, which forms salts when combined with other elements. Promethium shows only one stable oxidation state of +3; however, a few +2 compounds may exist.

There are three possible sources for promethium: rare decays of natural (primordial) neodymium (producing promethium-150), europium (promethium-147), and uranium (various isotopes). The most stable isotope, promethium-145, has a very low rate of alpha decay, so that the alpha half-life is long enough for the presence of primordial promethium to be theoretically possible; however, this has not been experimentally confirmed. Practical applications exist only for chemical compounds of promethium-147, which are used in luminous paint, atomic batteries and thickness measurement devices. Since natural promethium is exceedingly scarce, the element is typically synthesized by bombarding uranium-235 (enriched uranium) with thermal neutrons (for promethium-147).

Charm Quark

"The charm quark or c quark (from its symbol, c) is the third most massive of all quarks, a type of elementary particle. Charm quarks are found in hadrons, which are subatomic particles made of quarks. Example of hadrons containing charm quarks include the J/ψ meson (J/ψ), D mesons (D),charmed Sigma baryons (Σc), and other charmed particles."

"It, along with the strange quark is part of the second generation of matter, and has an electric charge of +²⁄₃ e and a bare mass of1.29+0.05
−0.11 GeV/c².^[1] Like all quarks, the charm quark is an elementary fermion with spin-¹⁄₂, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. The antiparticle of the charm quark is the charm antiquark (sometimes called anticharm quark or simply anticharm), which differs from it only in that some of its properties have equal magnitude but opposite sign.

Europium

"Europium ( /jʊˈroʊpiəm/ ew-roh-pee-əm) is a chemical element with the symbol Eu and atomic number 63. It is named after the continent of Europe. It is a moderately hard silvery metal which readily oxidizes in air and water. Being a typical member of the lanthanide series, europium usually assumes the oxidation state +3, but the oxidation state +2 is also common: all europium compounds with oxidation state +2 are slightly reducing. Europium has no significant biological role and is relatively non-toxic compared to other heavy metals. Most applications of europium exploit the phosphorescence of europium compounds."

"Europium is a ductile metal with a hardness similar to that of lead. It crystallizes in a body-centered cubic lattice.^[2]Some properties of europium are strongly influenced by its half-filled electron shell. Europium has the second lowest melting point and the lowest density of all lanthanides."

"Europium becomes a superconductor when it is cooled below 1.8 K and compressed to above 80 GPa. This is because europium is divalent in the metallic state,^[3] and is converted into the trivalent state by the applied pressure. In the divalent state, the strong local magnetic moment (J = ⁷/₂) suppresses the superconductivity, which is induced by eliminating this local moment (J = 0 in Eu³⁺)."

Positron

The positron or antielectron is the antiparticle or the antimatter counterpartDiscovery of the Positron of the electron. The positron has an electric charge of +1e, a spinof ½, and has the same mass as an electron. When a low-energy positron collides with a low-energy electron, annihilation occurs, resulting in the production of two or more gamma ray photons (see electron–positron annihilation).

Positrons may be generated by positron emission radioactive decay (through weak interactions), or by pair production from a sufficiently energetic photon.

In 1928, Paul Dirac published a paper^[2] proposing that electrons can have both a positive charge and negative energy. This paper introduced the Dirac equation, a unification of quantum mechanics, special relativity, and the then-new concept of electron spin to explain the Zeeman effect. The paper did not explicitly predict a new particle, but did allow for electrons having either positive or negative energy as solutions. The positive-energy solution explained experimental results, but Dirac was puzzled by the equally valid negative-energy solution that the mathematical model allowed. Quantum mechanics did not allow the negative energy solution to simply be ignored, as classical mechanics often did in such equations; the dual solution implied the possibility of an electron spontaneously jumping between positive and negative energy states. However, no such transition had yet been observed experimentally. He referred to the issues raised by this conflict between theory and observation as "difficulties" that were "unresolved".

Polonium

"Polonium ( /pɵˈloʊniəm/ po-loh-nee-əm) is a chemical element with the symbol Po and atomic number 84, discovered in 1898 by Marie and Pierre Curie. A rare and highly radioactive element with no stable isotopes, polonium is chemically similar to bismuth and tellurium, and it occurs in uranium ores. Applications of polonium are few, and include heaters in space probes, antistatic devices, and sources of neutrons and alpha particles. Because of its position in the periodic table, polonium is sometimes referred to as a metalloid,^[1] however others note that on the basis of its properties and behavior it is 'unambiguously a metal'".

"Polonium is a radioactive element that exists in two metallic allotropes. The alpha form is the only known example of a simple cubic crystal structure in a single atom basis, with an edge length of 335.2 picometers; the beta form isrhombohedral.^[6][7][8] The structure of polonium has been characterized by X-ray diffraction^[9][10] and electron diffraction."

^"210Po (in common with ²³⁸Pu) has the ability to become airborne with ease: if a sample is heated in air to 55 °C (131 °F), 50% of it is vaporized in 45 hours, even though the melting point of polonium is 254 °C (489 °F) and its boiling point is 962 °C (1763 °F).^[12][13] More than one hypothesis exists for how polonium does this; one suggestion is that small clusters of polonium atoms are spalled off by the alpha decay."

Pions

"In particle physics, a pion (short for pi meson, denoted with π) is any of three subatomic particles: π0, π+, and π−. Pions are the lightest mesons and they play an important role in explaining the low-energy properties of the strong nuclear force."

"Pions are mesons with zero spin, and they are composed of first-generation quarks. In the quark model, an up quark and an anti-down quark make up a π+, whereas a down quark and an anti-up quark make up the π−, and these are the antiparticles of one another. The uncharged pions are combinations of an up quark with an anti-up quark or a down quark with an anti-down quark, have identical quantum numbers, and hence they are only found in superpositions. The lowest-energy superposition of these is the π0, which is its own antiparticle. Together, the pions form a triplet of isospin. Each pion has isospin (I = 1) and third-component isospin equal to its charge (I_z = +1, 0 or −1)."

Up Quark

"The up quark or u quark (symbol: u) is the lightest of all quarks, a type of elementary particle, and a major constituent of matter. It, along with the down quark, forms the neutrons (one up quark, two down quarks) and protons (two up quarks, one down quark) of atomic nuclei. It is part of the first generation of matter, has an electric charge of +²⁄₃ e and a bare mass of 1.5–3.3 MeV/c². Like all quarks, the up quark is an elementary fermion withspin-¹⁄₂, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. The antiparticle of the up quark is the up antiquark (sometimes called antiup quark or simply antiup), which differs from it only in that some of its properties have equal magnitude but opposite sign."

"Its existence (along with that of the down and strange quarks) was postulated in 1964 by Murray Gell-Mann and George Zweig to explain the  Eightfold Way classification scheme of hadrons. The up quark was first observed by experiments at the Stanford Linear Accelerator Center in 1968."

Tungsten

"Tungsten /ˈtʌŋstən/, also known as wolfram /ˈwʊlfrəm/ (wuul-frəm), is a chemical element with the chemical symbol W and atomic number 74. The word tungsten comes from the Swedish language tung sten directly translatable to heavy stone,^[3] though it is commonly called volfram in Swedish."

"A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as a metal in 1783. Its important ores include wolframite and scheelite. The free element is remarkable for its robustness, especially the fact that it has the highest melting point of all the non-alloyed metals and the second highest of all the elements after carbon. Also remarkable is its high density of 19.3 times that of water, comparable to that of uranium and gold, and much higher (about 1.7 times) than that of lead.^[4] Tungsten with minor amounts of impurities is often brittle^[5] and hard, making it difficult to work. However, very pure tungsten, though still hard, is more ductile, and can be cut with a hard-steel hacksaw."

Bosons

"In particle physics, Boson is a subatomic particle with integer spin (i.e., angular momentum in quantum-mechanical units of 0, 1, etc.) that is governed by Bose-Einstein statistics. Bosons include mesons (e.g., pions and kaons), nuclei of even mass number (e.g., helium-4), and the particles required to embody the fields of quantum field theory (e.g., photons and gluons). Bosons differ significantly from a group of subatomic particles known as fermions in that there is no limit to the number that can occupy the same quantum state. This behaviour gives rise, for example, to the remarkable properties of helium-4 when it is cooled to become a superfluid."

"Bosons contrast with fermions, which obey Fermi–Dirac statistics. Two or more fermions cannot occupy the same quantum state (see Pauli exclusion principle)."

"Since bosons with the same energy can occupy the same place in space, bosons are often force carrier particles. In contrast, fermions are usually associated with matter (although in quantum physics the distinction between the two concepts is not clear cut)."

"Bosons may be either elementary, like photons, or composite, like mesons."

"All observed bosons have integer spin, as opposed to fermions, which have half-integer spin. This is in accordance with the spin-statistics theorem, which states that in any reasonable relativistic quantum field theory, particles with integer spin are bosons, while particles with half-integer spin are fermions."