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Technicolor (physics)
Technicolor theories are models of physics beyond the Standard Model that address electroweak gauge symmetry breaking, the mechanism through which W and Z bosons acquire masses. Early technicolor theories were modelled on quantum chromodynamics (QCD), the "color" theory of the strong nuclear force, which inspired their name. Instead of introducing elementary Higgs bosons to explain observed phenomena, technicolor models were introduced to dynamically generate masses for the W and Z bosons through new gauge interactions. Although asymptotically free at very high energies, these interactions must become strong and confining (and hence unobservable) at lower energies that have been experimentally probed. This dynamical approach is natural and avoids issues of quantum triviality and the hierarchy problem of the Standard Model. However, since the Higgs boson discovery at the CERN LHC in 2012, the original models are largely ruled out. Nonetheless, it remains a possibility ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physics Beyond The Standard Model
Physics beyond the Standard Model (BSM) refers to the theoretical developments needed to explain the deficiencies of the Standard Model, such as the inability to explain the fundamental parameters of the standard model, the strong CP problem, neutrino oscillations, baryon asymmetry, matter–antimatter asymmetry, and the nature of dark matter and dark energy. Another problem lies within the Quantum field theory, mathematical framework of the Standard Model itself: the Standard Model is inconsistent with that of general relativity, and one or both theories break down under certain conditions, such as Gravitational singularity, spacetime singularities like the Big Bang and black hole event horizons. Theories that lie beyond the Standard Model include various extensions of the standard model through supersymmetry, such as the Minimal Supersymmetric Standard Model (MSSM) and Next-to-Minimal Supersymmetric Standard Model (NMSSM), and entirely novel explanations, such as string theory, M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chiral Symmetry
A chiral phenomenon is one that is not identical to its mirror image (see the article on mathematical chirality). The spin of a particle may be used to define a handedness, or helicity, for that particle, which, in the case of a massless particle, is the same as chirality. A symmetry transformation between the two is called parity transformation. Invariance under parity transformation by a Dirac fermion is called chiral symmetry. Chirality and helicity The helicity of a particle is positive ("right-handed") if the direction of its spin is the same as the direction of its motion. It is negative ("left-handed") if the directions of spin and motion are opposite. So a standard clock, with its spin vector defined by the rotation of its hands, has left-handed helicity if tossed with its face directed forwards. Mathematically, ''helicity'' is the sign of the projection of the spin vector onto the momentum vector: "left" is negative, "right" is positive. The chirality of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supersymmetry
Supersymmetry is a Theory, theoretical framework in physics that suggests the existence of a symmetry between Particle physics, particles with integer Spin (physics), spin (''bosons'') and particles with half-integer spin (''fermions''). It proposes that for every known particle, there exists a partner particle with different spin properties. There have been multiple experiments on supersymmetry that have failed to provide evidence that it exists in nature. If evidence is found, supersymmetry could help explain certain phenomena, such as the nature of dark matter and the hierarchy problem in particle physics. A supersymmetric theory is a theory in which the equations for force and the equations for matter are identical. In theoretical physics, theoretical and mathematical physics, any theory with this property has the ''principle of supersymmetry'' (SUSY). Dozens of supersymmetric theories exist. In theory, supersymmetry is a type of Spacetime symmetries, spacetime symmetry betwe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Top Quark
The top quark, sometimes also referred to as the truth quark, (symbol: t) is the most massive of all observed elementary particles. It derives its mass from its coupling to the Higgs field. This coupling is very close to unity; in the Standard Model of particle physics, it is the largest (strongest) coupling at the scale of the weak interactions and above. The top quark was discovered in 1995 by the CDF and DØ experiments at Fermilab. Like all other quarks, the top quark is a fermion with spin-1/2 and participates in all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. It has an electric charge of + ''e''. It has a mass of , which is close to the rhenium atom mass. The antiparticle of the top quark is the top antiquark (symbol: , sometimes called ''antitop quark'' or simply ''antitop''), which differs from it only in that some of its properties have equal magnitude but opposite sign. The top quark interacts ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenomenology (particle Physics)
In physics, phenomenology is the application of theoretical physics to experimental data by making quantitative predictions based upon known theories. It is related to the philosophical notion of the same name in that these predictions describe anticipated behaviors for the phenomena in reality. Phenomenology stands in contrast with experimentation in the scientific method, in which the goal of the experiment is to test a scientific hypothesis instead of making predictions. Phenomenology is commonly applied to the field of particle physics, where it forms a bridge between the mathematical models of theoretical physics (such as quantum field theories and theories of the structure of space-time) and the results of the high-energy particle experiments. It is sometimes used in other fields such as in condensed matter physics and plasma physics, when there are no existing theories for the observed experimental data. Applications in particle physics Standard Model consequences W ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electroweak Scale
In particle physics, the electroweak scale, also known as the Fermi scale, is the energy scale around 246 GeV, a typical energy of processes described by the electroweak theory. The particular number 246 GeV is taken to be the vacuum expectation value v = (G_F \sqrt)^ of the Higgs field (where G_F is the Fermi coupling constant). In some cases the term ''electroweak scale'' is used to refer to the temperature of electroweak symmetry breaking, 159.5±1.5 GeV . In other cases, the term is used more loosely to refer to energies in a broad range around 102 - 103 GeV. This is within reach of the Large Hadron Collider (LHC), which is designed for about 104 GeV in proton–proton collisions. Interactions may have been above this scale during the electroweak epoch. In the unextended Standard Model, the transition from the electroweak epoch was not a first or a second order phase transition but a continuous crossover, preventing any baryogenesis. However many extensions to the sta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fine-tuning (physics)
In theoretical physics, fine-tuning is the process in which parameters of a model must be adjusted very precisely in order to fit with certain observations. Theories requiring fine-tuning are regarded as problematic in the absence of a known mechanism to explain why the parameters happen to have precisely the observed values that they return. The heuristic rule that parameters in a fundamental physical theory should not be too fine-tuned is called naturalness. Background The idea that naturalness will explain fine tuning was brought into question by Nima Arkani-Hamed, a theoretical physicist, in his talk "Why is there a Macroscopic Universe?", a lecture from the mini-series "Multiverse & Fine Tuning" from the "Philosophy of Cosmology" project, a University of Oxford and Cambridge Collaboration 2013. In it he describes how naturalness has usually provided a solution to problems in physics; and that it had usually done so earlier than expected. However, in addressing the proble ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electroweak
In particle physics, the electroweak interaction or electroweak force is the unified description of two of the fundamental interactions of nature: electromagnetism (electromagnetic interaction) and the weak interaction. Although these two forces appear very different at everyday low energies, the theory models them as two different aspects of the same force. Above the unification energy, on the order of 246 GeV,The particular number 246 GeV is taken to be the vacuum expectation value v = (G_\text \sqrt)^ of the Higgs field (where G_\text is the Fermi coupling constant). they would merge into a single force. Thus, if the temperature is high enough – approximately 1015 K – then the electromagnetic force and weak force merge into a combined electroweak force. During the quark epoch (shortly after the Big Bang), the electroweak force split into the electromagnetic and weak force. It is thought that the required temperature of 1015 K has not been see ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spontaneous Symmetry Breaking
Spontaneous symmetry breaking is a spontaneous process of symmetry breaking, by which a physical system in a symmetric state spontaneously ends up in an asymmetric state. In particular, it can describe systems where the equations of motion or the Lagrangian obey symmetries, but the lowest-energy vacuum solutions do not exhibit that same symmetry. When the system goes to one of those vacuum solutions, the symmetry is broken for perturbations around that vacuum even though the entire Lagrangian retains that symmetry. Overview The spontaneous symmetry breaking cannot happen in quantum mechanics that describes finite dimensional systems, due to Stone-von Neumann theorem (that states the uniqueness of Heisenberg commutation relations in finite dimensions). So spontaneous symmetry breaking can be observed only in infinite dimensional theories, as quantum field theories. By definition, spontaneous symmetry breaking requires the existence of physical laws which are invariant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Model
The Standard Model of particle physics is the Scientific theory, theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions – excluding gravity) in the universe and classifying all known elementary particles. It was developed in stages throughout the latter half of the 20th century, through the work of many scientists worldwide, with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks. Since then, proof of the top quark (1995), the tau neutrino (2000), and the Higgs boson (2012) have added further credence to the Standard Model. In addition, the Standard Model has predicted various properties of weak neutral currents and the W and Z bosons with great accuracy. Although the Standard Model is believed to be theoretically self-consistent and has demonstrated some success in providing experimental predictions, it leaves some physics be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electroweak Interaction
In particle physics, the electroweak interaction or electroweak force is the unified description of two of the fundamental interactions of nature: electromagnetism (electromagnetic interaction) and the weak interaction. Although these two forces appear very different at everyday low energies, the theory models them as two different aspects of the same force. Above the unification energy, on the order of 246 GeV,The particular number 246 GeV is taken to be the vacuum expectation value v = (G_\text \sqrt)^ of the Higgs field (where G_\text is the Fermi coupling constant). they would merge into a single force. Thus, if the temperature is high enough – approximately 1015 K – then the electromagnetic force and weak force merge into a combined electroweak force. During the quark epoch (shortly after the Big Bang), the electroweak force split into the electromagnetic and weak force. It is thought that the required temperature of 1015 K has not been seen w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Topcolor
Topcolor is a model in theoretical physics, of dynamical electroweak symmetry breaking in which the top quark and anti-top quark form a composite Higgs boson by a new force arising from massive "top gluons". The solution to composite Higgs models was actually anticipated in 1981, and found to be the Infrared fixed point for the top quark mass. Analogy with known physics The composite Higgs boson made from a bound pair of top-anti-top quarks is analogous to the phenomenon of superconductivity, where Cooper pairs are formed by the exchange of phonons. The pairing dynamics and its solution was treated in the Bardeen-Hill-Lindner model. The original topcolor naturally involved an extension of the standard model color gauge group to a product group SU(3)×SU(3)×SU(3)×... One of the gauge groups contains the top and bottom quarks, and has a sufficiently large coupling constant to cause the condensate to form. The topcolor model anticipates the idea of dimensional deconstruction an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
