String Theory: Supersymmetry Hypothesizes Superpartners

By Andrew Zimmerman Jones, Daniel Robbins

Under supersymmetry, the corresponding bosons and fermions are called superpartners. The superpartner of a standard particle is called a sparticle.

Because none of the existing particles are superpartners, this means that if supersymmetry is true, there are twice as many particles as we currently know about. For every standard particle, a sparticle that has never been detected experimentally must exist. The detection of sparticles will be one of the key pieces of evidence the Large Hadron Collider will look for.

If you read about a strangely named particle that you’ve never run into, it’s probably a sparticle. Because supersymmetry introduces so many new particles, it’s important to keep them straight. Physicists have introduced a Dr. Seuss-like naming convention to identify the hypothetical new particles:

  • The superpartner of a fermion begins with an “s” before the standard particle name; so the superpartner of an “electron” is the “selectron,” and the superpartner of the “quark” is the “squark.”

  • The superpartner of a boson ends in an “–ino,” so the superpartner of a “photon” is the “photino” and of the “graviton” is the “gravitino.”

This table shows the names of standard particles and their corresponding superpartner.

Some Superpartner Names
Standard Particle Superpartner
Lepton Slepton
Muon Smuon
Neutrino Sneutrino
Top Quark Stop Squark
Gluon Gluino
Higgs boson Higgsino
W boson Wino
Z boson Zino

Even though there is an elementary superpartner called a “sneutrino,” there exists no elementary particle called a “sneutron.”