In
supersymmetric
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 theorie ...
extension to the
Standard Model
The Standard Model of particle physics is the theory describing three of the four known fundamental forces ( electromagnetic, weak and strong interactions - excluding gravity) in the universe and classifying all known elementary particles. I ...
(SM) of
physics
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which rel ...
, a sfermion is a hypothetical
spin-0
superpartner particle (sparticle) of its associated
fermion
In particle physics, a fermion is a particle that follows Fermi–Dirac statistics. Generally, it has a half-odd-integer spin: spin , spin , etc. In addition, these particles obey the Pauli exclusion principle. Fermions include all quarks and ...
. Each particle has a superpartner with spin that differs by . Fermions in the SM have
spin- and, therefore, sfermions have spin 0.
The name 'sfermion' was formed by the general rule of prefixing an 's' to the name of its superpartner, denoting that it is a
scalar particle with spin 0. For instance, the
electron
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary partic ...
's superpartner is the
selectron and the
top quark's superpartner is the
stop squark.
One corollary from supersymmetry is that sparticles have the same
gauge numbers as their SM partners. This means that sparticle–particle pairs have the same
color charge,
weak isospin
In particle physics, weak isospin is a quantum number relating to the weak interaction, and parallels the idea of isospin under the strong interaction. Weak isospin is usually given the symbol or , with the third component written as or . It ...
charge, and
hypercharge (and consequently
electric charge
Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respecti ...
). Unbroken supersymmetry also implies that sparticle–particle pairs have the same mass. This is evidently not the case, since these sparticles would have already been detected. Thus, sparticles must have different masses from the particle partners and supersymmetry is said to be broken.
Fundamental sfermions
Squarks
Squarks (also quarkinos) are the superpartners of
quark
A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All common ...
s. These include the sup squark, sdown squark, scharm squark, sstrange squark,
stop squark, and sbottom squark.
Sleptons
Sleptons are the superpartners of
leptons. These include the selectron, smuon, stau, and their corresponding sneutrino flavors.
See also
*
Minimal Supersymmetric Standard Model (MSSM)
References
*
{{Particles
Supersymmetric quantum field theory
Hypothetical elementary particles
Bosons
Subatomic particles with spin 0