The Large Hadron Collider (LHC) has raised awkward questions for theoretical physicists, with experiments so far showing no evidence for the existence of supersymmetry. Professor Geoffrey Taylor from the University of Melbourne says while the theory is not dead yet, it is running out of places to hide.
“It’s a beautiful model in some theoretical senses. If it were a true representation of reality it would solve all sorts of problems the LHC is looking to solve,” he said. “But there is not one skerrick of data yet which would suggest that we have to have supersymmetry. There’s no experimental evidence for supersymmetry.”
Supersymmetry predicts the existence of a host of new superparticles, each partnered with a particle from the standard model of physics; for example, quarks may have a corresponding supersymmetric particle known as a squark. The LHC, the world’s largest particle accelerator situated near Geneva in Switzerland, is smashing particles together to see and detect these superparticles. Though supersymmetry has existed in various forms since the 1960s, with many scientists hailing its aesthetic beauty and predictive powers, it has not been experimentally tested until now.
“There are many variants of supersymmetry and the different variants will end up with different predictions,” said Professor Taylor, director of Melbourne University’s ARC Centre of Excellence for Particle Physics. “The LHC has already in its very short history eliminated quite a bit of territory from where supersymmetry might lie; it hasn’t excluded all variants though.”
Supersymmetry, if correct, would help provide a “theory of everything” which reconciles general relativity, which explains physics on a large scale, with the standard model, which describes subatomic processes. It may also help explain the presence of dark matter – particles that appear to exist in the universe but which have not been found.