Superpartner

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In particle physics, a superpartner (also sparticle) is a class of hypothetical elementary particles predicted by supersymmetry, which, among other applications, is one of the well-studied ways to extend the standard model of high-energy physics. [1] [2]

Contents

When considering extensions of the Standard Model, the s- prefix from sparticle is used to form names of superpartners of the Standard Model fermions (sfermions), [3] e.g. the stop squark. The superpartners of Standard Model bosons have an -ino (bosinos) [3] appended to their name, e.g. gluino, the set of all gauge superpartners are called the gauginos.

Theoretical predictions

According to the supersymmetry theory, each fermion should have a partner boson, the fermion's superpartner, and each boson should have a partner fermion. Exact unbroken supersymmetry would predict that a particle and its superpartners would have the same mass. No superpartners of the Standard Model particles have yet been found. This may indicate that supersymmetry is incorrect, or it may also be the result of the fact that supersymmetry is not an exact, unbroken symmetry of nature. If superpartners are found, their masses would indicate the scale at which supersymmetry is broken. [1] [4]

For particles that are real scalars (such as an axion), there is a fermion superpartner as well as a second, real scalar field. For axions, these particles are often referred to as axinos and saxions.

In extended supersymmetry there may be more than one superparticle for a given particle. For instance, with two copies of supersymmetry in four dimensions, a photon would have two fermion superpartners and a scalar superpartner.[ citation needed ]

In zero dimensions it is possible to have supersymmetry, but no superpartners. However, this is the only situation where supersymmetry does not imply the existence of superpartners.[ citation needed ]

Recreating superpartners

If the supersymmetry theory is correct, it should be possible to recreate these particles in high-energy particle accelerators. Doing so will not be an easy task; these particles may have masses up to a thousand times greater than their corresponding "real" particles. [1]

Some researchers have hoped the Large Hadron Collider at CERN might produce evidence for the existence of superpartner particles. [1] However, as of 2018, no such evidence has been found.

See also

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In a supersymmetric theory the equations for force and the equations for matter are identical. In theoretical and mathematical physics, any theory with this property has the principle of supersymmetry (SUSY). Dozens of supersymmetric theories exist. Supersymmetry is a spacetime symmetry between two basic classes of particles: bosons, which have an integer-valued spin and follow Bose–Einstein statistics, and fermions, which have a half-integer-valued spin and follow Fermi–Dirac statistics. In supersymmetry, each particle from one class would have an associated particle in the other, known as its superpartner, the spin of which differs by a half-integer. For example, if the electron exists in a supersymmetric theory, then there would be a particle called a "selectron", a bosonic partner of the electron. In the simplest supersymmetry theories, with perfectly "unbroken" supersymmetry, each pair of superpartners would share the same mass and internal quantum numbers besides spin. More complex supersymmetry theories have a spontaneously broken symmetry, allowing superpartners to differ in mass.

In supersymmetry, the neutralino is a hypothetical particle. In the Minimal Supersymmetric Standard Model (MSSM), a popular model of realization of supersymmetry at a low energy, there are four neutralinos that are fermions and are electrically neutral, the lightest of which is stable in an R-parity conserved scenario of MSSM. They are typically labeled
N͂0
1,
N͂0
2,
N͂0
3 and
N͂0
4 although sometimes is also used when is used to refer to charginos.

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Gaugino

In supersymmetry theories of particle physics, a gaugino is the hypothetical fermionic supersymmetric field quantum (superpartner) of a gauge field, as predicted by gauge theory combined with supersymmetry. All gauginos have spin 1/2, except for gravitino.

Split supersymmetry

In particle physics, split supersymmetry is a proposal for physics beyond the Standard Model.

In supersymmetric extension to the Standard Model (SM) of physics, a sfermion is a hypothetical spin-0 superpartner particle (sparticle) of its associated fermion. Each particle has a superpartner with spin that differs by 1/2. Fermions in the SM have spin-1/2 and, therefore, sfermions have spin 0.

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In particle physics, a stop squark, symbol
t͂
, is the superpartner of the top quark as predicted by supersymmetry (SUSY). It is a sfermion, which means it is a spin-0 boson. While the top quark is the heaviest known quark, the stop squark is actually often the lightest squark in many supersymmetry models.

Gordon L. Kane

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References

  1. 1 2 3 4 Langacker, Paul (November 22, 2010). Sprouse, Gene D. (ed.). "Meet a superpartner at the LHC". Physics . New York: American Physical Society. 3 (98): 98. Bibcode:2010PhyOJ...3...98L. doi: 10.1103/Physics.3.98 . ISSN   1943-2879. OCLC   233971234.
  2. ↑ Overbye, Dennis (May 15, 2007). "A Giant Takes On Physics' Biggest Questions". The New York Times . p. F1. ISSN   0362-4331. OCLC   1645522 . Retrieved 21 February 2011.
  3. 1 2 Alexander I. Studenikin (ed.), Particle Physics in Laboratory, Space and Universe, World Scientific, 2005, p. 327.
  4. ↑ Quigg, Chris (January 17, 2008). "Sidebar: Solving the Higgs Puzzle". Scientific American . Nature Publishing Group. ISSN   0036-8733. OCLC   1775222. Archived from the original on 2011-03-19. Retrieved 21 February 2011.
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