In
supersymmetry, the
neutralino is a hypothetical particle. There are four neutralinos that are
fermions and are electrically neutral, the lightest of which is typically stable. They are typically labeled (the lightest), , and (the heaviest) although sometimes
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is also used when
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is used to refer to
charginos. These four states are mixtures of the
bino and the neutral
wino (which are the neutral electroweak
gauginos), and the neutral
higgsinos. As the neutralinos are
Majorana fermions, each of them is identical to its
antiparticle. Because these particles only interact with the weak vector bosons, they are not directly produced at
hadron colliders in copious numbers. They would primarily appear as particles in cascade decays of heavier particles (decays that happen in multiple steps) usually originating from
colored supersymmetric particles such as
squarks or
gluinos.