particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...

, for models with N=1 supersymmetry a higgsino, symbol , is the

superpartner 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. ...

of the

Higgs field 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 Stand ...

. A higgsino is a

Dirac fermion In physics, a Dirac fermion is a spin-½ particle (a fermion) which is different from its antiparticle. The vast majority of fermions – perhaps all – fall under this category. Description In particle physics, all fermions in the standard model ...

ic field with spin and it refers to a weak isodoublet with hypercharge half under the Standard Model gauge symmetries. After

electroweak symmetry breaking In the Standard Model of particle physics, the Higgs mechanism is essential to explain the generation mechanism of the property "mass" for gauge bosons. Without the Higgs mechanism, all bosons (one of the two classes of particles, the other bein ...

higgsino fields linearly mix with U(1) and SU(2) gauginos leading to four

neutralino 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 ...

s and two

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 (with spin 1/2) predicted by supersymmetry. They are linear combinations of t ...

s that refer to physical particles. While the two charginos are charged Dirac fermions (plus and minus each), the neutralinos are electrically neutral

Majorana fermion A Majorana fermion (, uploaded 19 April 2013, retrieved 5 October 2014; and also based on the pronunciation of physicist's name.), also referred to as a Majorana particle, is a fermion that is its own antiparticle. They were hypothesised by Et ...

s. In an

R-parity R-parity is a concept in particle physics. In the Minimal Supersymmetric Standard Model, baryon number and lepton number are no longer conserved by all of the renormalizable couplings in the theory. Since baryon number and lepton number conservatio ...

-conserving version of the

Minimal Supersymmetric Standard Model 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 inimumnumber of new particle states and new interactions con ...

, the lightest neutralino typically becomes the lightest supersymmetric particle (LSP). The LSP is a particle physics candidate for the

dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...

of the universe since it cannot decay to particles with lighter mass. A neutralino LSP, depending on its composition can be bino, wino or higgsino dominated in nature and can have different zones of mass values in order to satisfy the estimated dark matter relic density. Commonly, a higgsino dominated LSP is often referred as a higgsino, in spite of the fact that a higgsino is not a physical state in the true sense. In

natural Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are p ...

scenarios of SUSY, top squarks, bottom squarks,

gluinos In supersymmetry, a gluino (symbol ) is the hypothetical supersymmetric partner of a gluon. In supersymmetric theories, gluinos are Majorana fermions and interact via the strong force as a color octet. Gluinos have a lepton number 0, baryon numbe ...

, and higgsino-enriched neutralinos and charginos are expected to be relatively light, enhancing their production cross sections. Higgsino searches have been performed by both the

ATLAS An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth. Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geographic ...

and

CMS CMS may refer to: Computing * Call management system * CMS-2 (programming language), used by the United States Navy * Code Morphing Software, a technology used by Transmeta * Collection management system for a museum collection * Color manag ...

experiments at the

Large Hadron Collider The Large Hadron Collider (LHC) is the world's largest and highest-energy particle collider. It was built by the European Organization for Nuclear Research (CERN) between 1998 and 2008 in collaboration with over 10,000 scientists and hundred ...

CERN The European Organization for Nuclear Research, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in a northwestern suburb of Gene ...

, where physicists have searched for the direct electroweak pair production of Higgsinos. As of 2017, no experimental evidence for Higgsinos has been reported.

Mass

If dark matter is composed only of Higgsinos, then the Higgsino mass is 1.1

TeV TEV may refer to: * Transient Earth Voltage: a term for voltages appearing on the metal work of switchgear due to internal partial discharges * TeV, or teraelectronvolt or trillion electron volt, a measure of energy * Total Enterprise Value, a ...

. On the other hand, if dark matter has multiple components, then the Higgsino mass depends on the relevant multiverse distribution functions, making the mass of the Higgsino lighter.
::m_ħ ≈ 1.1(Ω_ħ/Ω_DM)^½ TeV

Footnotes

{{particles Supersymmetric quantum field theory Fermions Hypothetical elementary particles