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In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. The Standard Model presently recognizes seventeen distinct particles—twelve fermions and five bosons. As a consequence of flavor and color combinations and antimatter, the fermions and bosons are known to have 48 and 13 variations, respectively. Among the 61 elementary particles embraced by the Standard Model number: electrons and other leptons, quarks, and the fundamental bosons. Subatomic particles such as protons or neutrons, which contain two or more elementary particles, are known as composite particles.
Grand Unified Theory (GUT) is any model in particle physics that merges the electromagnetic, weak, and strong forces into a single force at high energies. Although this unified force has not been directly observed, many GUT models theorize its existence. If the unification of these three interactions is possible, it raises the possibility that there was a grand unification epoch in the very early universe in which these three fundamental interactions were not yet distinct.
Supersymmetry is a theoretical framework in physics that suggests the existence of a symmetry between particles with integer 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.
The Minimal Supersymmetric Standard Model (MSSM) is an extension to the Standard Model that realizes supersymmetry. MSSM is the minimal supersymmetrical model as it considers only "the [minimum] number of new particle states and new interactions consistent with "Reality". Supersymmetry pairs bosons with fermions, so every Standard Model particle has a superpartner. If discovered, such superparticles could be candidates for dark matter, and could provide evidence for grand unification or the viability of string theory. The failure to find evidence for MSSM using the Large Hadron Collider has strengthened an inclination to abandon it.
In theoretical physics, the hierarchy problem is the problem concerning the large discrepancy between aspects of the weak force and gravity. There is no scientific consensus on why, for example, the weak force is 1024 times stronger than gravity.
In particle physics, split supersymmetry is a proposal for physics beyond the Standard Model.
Savas Dimopoulos is a particle physicist at Stanford University. He worked at CERN from 1994 to 1997. Dimopoulos is well known for his work on constructing theories beyond the Standard Model.
In particle physics the little hierarchy problem in the Minimal Supersymmetric Standard Model (MSSM) is a refinement of the hierarchy problem. According to quantum field theory, the mass of the Higgs boson must be rather light for the electroweak theory to work. However, the loop corrections to the mass are naturally much greater; this is known as the hierarchy problem. New physical effects such as supersymmetry may in principle reduce the size of the loop corrections, making the theory natural. However, it is known from experiments that new physics such as superpartners does not occur at very low energy scales, so even if these new particles reduce the loop corrections, they do not reduce them enough to make the renormalized Higgs mass completely natural. The expected value of the Higgs mass is about 10 percent of the size of the loop corrections which shows that a certain "little" amount of fine-tuning seems necessary.
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, matter–antimatter asymmetry, and the nature of dark matter and dark energy. Another problem lies within the 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 spacetime singularities like the Big Bang and black hole event horizons.
In theoretical physics, the μ problem is a problem of supersymmetric theories, concerned with understanding the parameters of the theory.
In theoretical physics, unparticle physics is a speculative theory that conjectures a form of matter that cannot be explained in terms of particles using the Standard Model of particle physics, because its components are scale invariant.
Superstring theory is an attempt to explain all of the particles and fundamental forces of nature in one theory by modeling them as vibrations of tiny supersymmetric strings.
The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the quantum excitation of the Higgs field, one of the fields in particle physics theory. In the Standard Model, the Higgs particle is a massive scalar boson with zero spin, even (positive) parity, no electric charge, and no colour charge that couples to mass. It is also very unstable, decaying into other particles almost immediately upon generation.
Gian Francesco Giudice is an Italian theoretical physicist working at CERN in particle physics and cosmology.
Ali H. Chamseddine is a Lebanese physicist known for his contributions to particle physics, general relativity and mathematical physics. As of 2013, Chamseddine is a physics Professor at the American University of Beirut and the Institut des hautes études scientifiques.
Riccardo Barbieri is an Italian theoretical physicist and a professor at the Scuola Normale Superiore di Pisa. He has written more than two hundred research papers in the field of theoretical elementary particle physics, and has been particularly influential in physics beyond the Standard Model.
Riccardo Rattazzi is an Italian theoretical physicist and a professor at the École Polytechnique Fédérale de Lausanne. His main research interests are in physics beyond the Standard Model and in cosmology.
Probir Roy is an Indian particle physicist and a former professor at Tata Institute of Fundamental Research. He is also a senior scientist of the Indian National Science Academy at Bose Institute and a former Raja Ramanna fellow of Department of Atomic Energy at Saha Institute of Nuclear Physics.
Michael Dine is an American theoretical physicist, specializing in elementary particle physics, supersymmetry, string theory, and physics beyond the Standard Model.
Alessandro Strumia is an Italian physicist at the University of Pisa. His research focuses on high energy physics, beyond the Standard Model, studying the flavour of elementary particle, charge conjugation parity (CP) symmetry violations, and the Higgs boson. In September 2018, Strumia gave a controversial presentation at CERN's first Workshop on High Energy Theory and Gender, where he claimed that male, not female scientists, were the victims of discrimination on the part of universities.
References
- ↑ "Select Authentication System".
- ↑ Giudice, Gian F; Strumia, Alessandro (2011). "Probing High-Scale and Split Supersymmetry with Higgs Mass Measurements". Nuclear Physics B. 858 (1): 63–83. arXiv: 1108.6077 . Bibcode:2012NuPhB.858...63G. doi:10.1016/j.nuclphysb.2012.01.001. S2CID 119262976.
