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 (scalar boson).
While the top quark is the heaviest known
quark, the stop squark is actually often the
lightest squark in many supersymmetry models.The
stop squark is a key ingredient of a wide
range of SUSY models that address the hierarchy
problem of the Standard Model (SM) in a natural
way.
A boson partner to the top quark would stabilize
the Higgs boson mass against quadratically
divergent quantum corrections, provided its
mass is close to the electroweak symmetry
breaking energy scale.
If this was the case then the stop squark
would be accessible at the Large Hadron Collider.
In the generic R-parity conserving Minimal
Supersymmetric Standard Model (MSSM) the scalar
partners of right-handed and left-handed top
quarks mix to form two stop mass eigenstates.
Depending on the specific details of the SUSY
model and the mass hierarchy of the sparticles,
the stop might decay into a bottom quark and
a chargino, with a subsequent decay of the
chargino into the lightest neutralino (which
is often the lightest supersymmetric particle).
Many searches for evidence of the stop squark
have been performed by both the ATLAS and
CMS experiments at the LHC but so far no signal
has been discovered
