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Particle Physics press view slideshow click here then.

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Presentation on theme: "Particle Physics press view slideshow click here then."— Presentation transcript:

1 Particle Physics press view slideshow click here then

2 Pauli exclusion principle no two identical fermions (particles with half- integer spin) may occupy the same quantum state simultaneously. Back

3 Bosons Unlike fermions, bosons do not follow the Pauli exclusion principle, which makes them perfect for the job as force carriers. Explore more bosons Go back What is the Pauli Exclusion principle

4 Standard Model Bosons Fermions

5 Do not cheat ! Use only your mouse Mr. Crow is watching you…

6 Standard Model However, the Standard Model falls short of being a complete theory of fundamental interactions because it does not incorporate the physics of dark energy nor of the full theory of gravitation as described by general relativity. The theory does not contain any viable dark matter particle that possesses all of the required properties deduced from observational cosmology. It also does not correctly account for neutrino oscillations (and their non-zero masses). The Standard Model of particle physics, which was developed throughout the mid to late 20th century, is a theory concerning the electromagnetic, weak, and strong nuclear interactions, which mediate the dynamics of the known subatomic particles. Since then, discoveries of the bottom quark (1977), the top quark (1995) and the tau neutrino (2000) have given further evidence that the Standard Model is accurate theory. Let’s Start

7 Boson Family Z boson W ± bosons gluon Graviton Higgs boson

8 Higgs Boson The Higgs boson is a hypothetical elementary particle predicted by the Standard Model of particle physics. The Standard Model predicts the existence of a field (called the Higgs field) which has a non-zero amplitude in its ground state. The field can be pictured as a pool of molasses where Higgs bosons "stick" to the otherwise massless fundamental particles that travel through the field, converting them into particles with mass that form the components of atoms. As of December 2011, the Higgs boson has yet to be confirmed experimentally, despite large efforts invested in accelerator experiments at CERN and Fermilab. Like other massive particles (e.g. the top quark and W and Z bosons), Higgs bosons created in particle accelerators decay long before they reach any of the detectors. However, the Standard Model precisely predicts the possible modes of decay and their probabilities. This allows events in which a Higgs was created to be identified by examining the decay products. Back

9 The W and Z bosons (together known as the weak bosons) are the elementary particles that mediate the weak interaction; their symbols are W +, W −, and Z. Weak Bosons These bosons are among the heavyweights of the elementary particles. With masses of 80.4 GeV/c2 and 91.2 GeV/c2, respectively, the W and Z bosons are almost 100 times as massive as the proton - heavier, even, than entire atoms of iron. (This does not mean they are bigger than iron atoms. They still have zero size, but with lots of mass.) The masses of these bosons are significant because they act as the force carriers of the weak force, and the high mass thus limits the range. By way of contrast, the electromagnetic force has an infinite range because its force carrier, the photon, has zero rest mass; and the same is supposed of the hypothetical graviton. The emission of a W + or W − boson either raises or lowers the electric charge of the emitting particle by one unit, and also alters the spin by one unit. The neutral Z boson obviously cannot change the electric charge of any particle, nor can it change any other of the so-called "charges" (such as strangeness, color, charm, etc.). The emission or absorption of a Z boson can only change the spin, momentum, and energy of the other particle. Back

10 The photon is a quantum of light and all other forms of EM radiation, and the force carrier for the EM force. The photon is currently understood to be strictly massless, but if the photon is not a massless particle, it would not move at the exact speed of light in vacuum, c. Its speed would be lower and depend on its frequency. Relativity would be unaffected by this; the so-called speed of light, c, would then not be the actual speed at which light moves, but a constant of nature which is the maximum speed that any object could theoretically attain in space-time. Thus, it would still be the speed of space-time ripples (gravitational waves and gravitons), but it would not be the speed of photons. Because the photon is thought to have zero rest mass, the electromagnetic force has an infinite range Speed = c Back

11 + Gluons are elementary particles which act as the exchange particles for the strong force between quarks. There are eight independent types of gluons. Quarks carry three types of color charge; antiquarks carry three types of anticolor charge. Gluons may be thought of as carrying both color and anticolor. QCD considers there to be eight gluons of the possible nine color-anticolor combinations. The expulsion or absorption of gluons causes a color change in quarks. Back

12 The Mysterious: Graviton In physics, the graviton is a hypothetical elementary particle that mediates the force of gravitation in the framework of quantum field theory. If it exists, the graviton must be massless, because the gravitational force has unlimited range, and must be a spin 2 boson. Attempts to extend the Standard Model or other quantum field theories by adding gravitons run into serious theoretical difficulties at high energies. When calculating the probability that a particle will emit or absorb a graviton, the solutions give nonsensical answers. Since classical general relativity and quantum mechanics seem to be incompatible at such energies, from a theoretical point of gravity cannot be explained. One possible solution is to replace particles by strings. However, string theories cannot be disproved at the current time, and therefore may not count as “real” theories. Back

13 A fermion can be an elementary particle, such as the electron; or it can be a composite particle, such as the proton In contrast to bosons, only one fermion can occupy a particular quantum state at any given time (they follow the Pauli exclusion principle). If more than one fermion occupies the same physical space, at least one property of each fermion, such as its spin, must be different. Fermions are usually associated with matter. Back HadronsLeptons Fermions experience all four fundamental forces

14 Lepton family tree electron muon tau electron neutrino muon neutrino tau neutrino Lepton’s differ from their fermion brothers (the quarks) because leptons are not involved in the strong force Back

15 Electron e-e- The electron is a subatomic particle with a negative elementary electric charge. Electrons have the lowest mass of any charged lepton (or electrically charged particle of any type) and belong to the first-generation of fundamental particles. The second and third generation contain charged leptons, the muon and the tau, which are identical to the electron in charge, spin and interactions, but are more massive. Unlike the muon and tau, the electron is thought to be stable on theoretical grounds: the electron is the least massive particle with non-zero electric charge, so its decay would violate charge conservation. If it did decay, the experimental lower bound for the electron's mean lifetime is 4.6×10 26 years Back

16 Muon µ The muon is an unstable subatomic particle with a mean lifetime of 2.2 µs. This lifetime is comparatively long (the second longest known) and is due to being mediated by the weak interaction. Muons have a mass of MeV/c2, which is about 200 times the mass of an electron. Since the muon's interactions are very similar to those of the electron, a muon can be thought of as a much heavier version of the electron. Due to their greater mass, muons are not as sharply accelerated when they encounter electromagnetic fields, and do not emit as much radiation. The muon was the first elementary particle discovered that does not appear in ordinary atoms. Muons can, however, form muonic atoms (also called mu-mesic atoms), by replacing an electron in ordinary atoms Back

17 Tau Tau leptons have a lifetime of 2.9×10 −13 s and a mass of 1,777 MeV/c 2 The tau was detected in a series of experiments between 1974 and 1977 by Martin Lewis Perl with his colleagues at the SLAC-LBL group. The tau is the only lepton that can decay into hadrons—the other leptons do not have the necessary mass. Back

18 The Neutrinos The neutrino (meaning "small neutral one" in Italian) is denoted by the Greek letter ν. All evidence suggests that neutrinos have mass but that their mass is tiny even by the standards of subatomic particles. Their mass has never been measured accurately. Most neutrinos passing through the Earth emanate from the Sun. About 65 billion (6.5×1010) solar neutrinos per second pass through every square centimeter. Neutrinos cannot be detected directly, because they do not ionize the materials they are passing through because they do not carry an electric charge. Because they are neutral particles, antineutrinos and neutrinos may actually be the same particle. So far, there is no detection method for low energy neutrinos that can be uniquely distinguished from other causes. Neutrino detectors are often built underground in order to isolate the detector from cosmic ray and other background radiation. Back

19 Hadrons Made out of 100% quality quarks and antiquarks A hadron is a composite particle made of quarks and held together by the strong force. Hadrons are categorized into two families: baryons (made of three quarks) and mesons (made of one quark and one antiquark). Quarks -> <- Back Back

20 Quarks Pick a flavor Due to a phenomenon known as color confinement, quarks are never directly observed or found in isolation; they can only be found within baryons or mesons. Quarks have fractional electric charge values — either 1⁄3 or 2⁄3 times the elementary charge, depending on flavor. Since the electric charge of a hadron is the sum of the charges of the constituent quarks, all hadrons must have integer charges. A quark of one flavor can transform into a quark of another flavor only through the weak interaction, one of the four fundamental interactions in particle physics. By absorbing or emitting a W boson. Quarks possess a property called color charge. Check out color charge!color charge Back

21 The up quark is the lightest of all quarks. 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 was named an up quark because of the its spin. Up Quark Down Quark The up quark is the second lightest of all quarks. It, along with the up quark, forms the neutrons (one up quark, two down quarks) and protons (two up quarks, one down quark) of atomic nuclei. It was named a down quark because of the its spin. Back

22 The charm quark is the third most massive of all quarks, a type of elementary particle. They are named charm quarks, because the researchers were charmed to find them as they fit perfectly into the Standard Model. Charm Quark Strange Quark The strange quark is the third lightest of all quarks, a type of elementary particle. They are named strange quarks, because the researchers found the particles in cosmic rays and thought their long decay lifetime was strange. Back

23 The top quark was found in 1995 and is the most massive observed elementary particle. It has a mass of 172.9±1.5 GeV/c 2 which is about the same mass as an atom of tungsten. It almost exclusively decays to a W boson and a bottom quark, but it can also sometimes decay into a strange quark, and on the rarest of occasions, into a down quark. Top Quark The bottom quark also known as the beauty quark. The bottom quark was discovered in 1977 by Fermilab. On its discovery, there were efforts to name the bottom quark "beauty", but "bottom" became the predominant usage. Bottom Quark Back

24 Color Charge Quarks possess a property called color charge. There are three types of color charge, arbitrarily labeled blue, green, and red. Each of them is complemented by an anticolor—antiblue, antigreen, and antired. Every quark carries a color, while every antiquark carries an anticolor. The color charge of a hadron should be white (R+B+G). However, hadrons are not always made of the right combination of color charged quarks. Therefore, the color charge of quarks can be changed by emitting or absorbing one of the eight gluons, which contain both a color and an anticolor charge. The continual passing of gluons is what creates the strong force. Back

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