It was 3 years ago that particle physicists working with CERN at the Large Hadron Collider announced they had verified the existence of the Higgs-Boson. It was a pivotal moment in scientific history, demonstrating that the Standard Model of particle physics fundamental basis is solid. Prior to this announcement the LHC had been shut down for a planned upgrade, one that would see the energy of the resulting collisions doubled from 3.5TeV per beam to 7TeV. This upgrade was scheduled to take approximately 2 years and would open up new avenues for particle physics research. Just last week, almost 3 years to the day after the Higgs-Boson announcement, the LHC began collisions again. The question that’s on my mind, and I’m sure many others, is just what is LHC looking for now?
Whilst the verification of the Higgs-Boson adds a certain level of robustness to the Standard Model many researchers have theorized of physics beyond this model at the energies that the LHC is currently operating at. Of these models one that will be explored by the LHC in its current data collection run is Supersymmetry, a model which predicts that each particle which belongs to one of the two elementary classes (bosons or fermions) has a “superpartner” in the other. An example of this would be an electron, which is a fermion, would have a superpartner called a selectron which would be a boson. These particles share all the same properties with the exception of their spin and so should be easy to detect, theoretically. However no such particles have been detected, even in the same run where the Higgs-Boson was. The new, higher energy level of the LHC has the potential to create some of these particles and could provide evidence to support supersymmetry as a model.
Further to the supersymmetry model is every new particle physicist’s favourite theory: String Theory. Now I’ll have to be honest here I’m not exactly what you’d call String Theory’s biggest fan since, whilst it makes some amazing predictions, it has yet to be supported by any experimental evidence. At its core String Theory theorizes that all point like particles are made up of one-dimensional strings, often requiring the use of multi-dimensional physics (10 or 26 dimensions depending on which model you look at) in order to make them work. However since they’re almost purely mathematical in nature there has yet to be any links made between the model and the real world, precluding it from being tested. Whilst the LHC might provide insight into this I’m not exactly holding my breath but I’ll spin on a dime if they prove me wrong.
Lastly, and probably most excitingly for me, is the prospect of discovering the elusive dark matter particle. Due to its nature, I.E. only interacting with ordinary matter through gravity, we’re unlikely to be able to detect dark matter particles in the LHC directly. Instead, should the LHC generate a dark matter particle, we’ll be able to infer its existence by the energy it takes away from the collision. No such discrepancy was noted at the last run’s energy levels so it will be interesting to see if a doubling of the collision energy leads to the generation of a dark matter particle.
Suffice to say the LHC has a long life ahead of it with plenty of envelope pushing science to be done. This current upgrade is planned to last them for quite some time with the next one not scheduled to take place until 2022, more than enough time to generate mountains of data to either support or refute our current models for particle physics.