Higgsino
Encyclopedia
In particle physics
, a Higgsino, symbol , is the hypothetical superpartner
of the Higgs boson
, as predicted by supersymmetry
. The Higgsino is a Dirac fermion
and that is a weak isodoublet
with hypercharge half under the Standard Model gauge symmetries. After electroweak symmetry breaking the Higgsino becomes a pair of neutral Majorana fermion
s called neutralino
s and a charged Dirac fermion called a chargino
(plus and minus). These states finally mix with the neutralinos (photino and zino
) and chargino (charged wino plus and minus) to form the predicted particles which are four neutralinos and two charginos (plus and minus each). Such a linear combination of the Higgsino, bino and wino makes up the lightest supersymmetric particle
(LSP), which is a particle physics candidate for the dark matter
of the universe. In order to be such a candidate, it must be neutral (i.e. a neutralino
rather than chargino
).
Particle physics
Particle physics is a branch of physics that studies the existence and interactions of particles that are the constituents of what is usually referred to as matter or radiation. In current understanding, particles are excitations of quantum fields and interact following their dynamics...
, a Higgsino, symbol , is the hypothetical superpartner
Superpartner
In particle physics, a superpartner is a hypothetical elementary particle. Supersymmetry is one of the synergistic theories in current high-energy physics which predicts the existence of these "shadow" particles....
of the Higgs boson
Higgs boson
The Higgs boson is a hypothetical massive elementary particle that is predicted to exist by the Standard Model of particle physics. Its existence is postulated as a means of resolving inconsistencies in the Standard Model...
, as predicted by supersymmetry
Supersymmetry
In particle physics, supersymmetry is a symmetry that relates elementary particles of one spin to other particles that differ by half a unit of spin and are known as superpartners...
. The Higgsino is a Dirac fermion
Dirac fermion
In particle physics, a Dirac fermion is a fermion which is not its own anti-particle. It is named for Paul Dirac. All fermions in the standard model, except possibly neutrinos, are Dirac fermions...
and that is a weak isodoublet
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 T or I with the third component written as Tz, T3, Iz or I3...
with hypercharge half under the Standard Model gauge symmetries. After electroweak symmetry breaking the Higgsino becomes a pair of neutral Majorana fermion
Majorana fermion
In physics, a Majorana fermion is a fermion which is its own anti-particle. The term is used in opposition to Dirac fermion, which describes particles that differ from their antiparticles...
s called neutralino
Neutralino
In particle physics, the neutralino is a hypothetical particle predicted by supersymmetry. There are four neutralinos that are fermions and are electrically neutral, the lightest of which is typically stable...
s and a charged Dirac fermion called a chargino
Chargino
In particle physics, the chargino is a hypothetical particle which refers to the mass eigenstates of a charged superpartner, i.e. any new electrically charged fermion predicted by supersymmetry. They are linear combinations of the charged wino and charged higgsinos...
(plus and minus). These states finally mix with the neutralinos (photino and zino
Gaugino
In particle physics, a gaugino is the hypothetical superpartner of a gauge field, as predicted by gauge theory combined with supersymmetry. They are fermions.In the minimal supersymmetric extension of the standard model the following gauginos exist:...
) and chargino (charged wino plus and minus) to form the predicted particles which are four neutralinos and two charginos (plus and minus each). Such a linear combination of the Higgsino, bino and wino makes up the lightest supersymmetric particle
Lightest Supersymmetric Particle
In particle physics, the Lightest Supersymmetric Particle is the generic name given to the lightest of the additional hypothetical particles found in supersymmetric models. In models with R-parity conservation, the LSP is stable. There is extensive observational evidence for an additional...
(LSP), which is a particle physics candidate for the dark matter
Dark matter
In astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly detected via optical or radio astronomy...
of the universe. In order to be such a candidate, it must be neutral (i.e. a neutralino
Neutralino
In particle physics, the neutralino is a hypothetical particle predicted by supersymmetry. There are four neutralinos that are fermions and are electrically neutral, the lightest of which is typically stable...
rather than chargino
Chargino
In particle physics, the chargino is a hypothetical particle which refers to the mass eigenstates of a charged superpartner, i.e. any new electrically charged fermion predicted by supersymmetry. They are linear combinations of the charged wino and charged higgsinos...
).