Are there more Particles left to find?

Supersymmetry: Uniting the forces

Towards a superforce

Our understanding of the workings of the Universe often progress when unexpected connections are found between what appeared at first to be separate entities. A major breakthrough occurred in the 1860s when James Clerk Maxwell recognized the similarities between electricity and magnetism and developed his theory of a single electromagnetic force. A similar breakthrough came a century later, when theorists began to develop links between electromagnetism, with its obvious effects in everyday life, and the weak force, which normally hides within the atomic nucleus. Vital support for these ideas came first from the Gargamelle experiment at CERN, and then with the Nobel prize winning discovery of the W and Z particles, which carry the electroweak force. But take note – it is only at the higher energies explored in particle collisions at CERN and other laboratories that the electromagnetic and weak forces begin to act on equal terms.

So will other forces join the club at even higher energies? Experiments already show that the effect of the strong force becomes weaker as energies increase. This is a good indication that at incredibly high energies, the strengths of the electromagnetic, weak and strong forces may be the same. The energies involved are at least a thousand million times greater than particle accelerators can reach, but such conditions would have existed in the very early Universe, almost immediately (10^-34 s) after the Big Bang. Pushing the concept a step further, theorists even contemplate the possibility of including gravity at still higher energies, thereby unifying all the fundamental forces into a single force. This would have ruled the first instants of the Universe, before its different components separated out as the Universe cooled.

 

Enter superparticles

Although at present we cannot recreate conditions with energy high enough to test these ideas directly, we can look for the consequences of ‘grand unification’ at lower energies, for instance at the Large Hadron Collider. A very popular idea that allows the stong and electroweak forces to unite and become a single interaction at a common energy is called supersymmetry, or SUSY for short. SUSY provides a symmetry between matter and forces, and predicts that for each known particle there is a 'supersymmetric' partner. If this is correct, then supersymmetric particles should appear in collisions at the LHC.

Read more about Supersymmetry in CMS