Superpartner

In particle physics, a Superpartner (also sparticle) is a hypothetical elementary particle. Supersymmetry is one of the synergistic theories in current high-energy physics that predicts the existence of these "shadow" particles.

The word sparticle features the s- prefix which is used to form names of superpartners of the individual fermions, e.g. the stop squark.

Theoretical predictions

According to the supersymmetry theory, each fermion should have a partner boson, the fermion's superpartner, and each boson should have a partner fermion. Exact unbroken supersymmetry would predict that a particle and its superpartners would have the same mass. No superpartners of the Standard Model particles have yet been found. This may indicate that supersymmetry is incorrect, or it may also be the result of the fact that supersymmetry is not an exact, unbroken symmetry of nature. If superpartners are found, their masses would indicate the scale at which supersymmetry is broken.

For particles that are real scalars (such as an axion), there is a fermion superpartner as well as a second, real scalar field. For axions, these particles are often referred to as axinos and saxions.