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.
It’s hard to understate the significance of the science that has been done because of the Large Hadron Collider. Whilst it’s famously known for discovering the Higgs-Boson, the particle which gives all other particles mass, it has a long list of achievements outside of that singular event. What makes these discoveries even more interesting is that the LHC has been operating at something of a disadvantage since it was first turned on over 6 years ago, operating at around half the potential energy it was capable of. Shortly after the discovery of the Higgs Boson the scientists and engineers at CERN have been working to bring it up to full capacity and with it the potential for some even more radical discoveries.
The doubling of the collision energy increases the potential for the LHC to generate even more exotic particles than it has previously, ones which can give us insights into some of the most perplexing mysteries in particle physics to date. One such source of intrigue is how our universe, which is composed of nearly entirely matter, came to be that way. Another seeks to explain why the universe seems to be riddled with matter that’s not directly observable but is seen through its gravitational effects throughout the universe. These, and many other questions, have potential to find answers in the newly upgraded LHC which is slated to come online this year.
In the beginning, the beginning of everything according to scientific theory, there existed both equal quantities of matter and antimatter. Upon annihilation these two entities should have completely destroyed each other, leaving behind a wake of energy with no matter to speak of. However casual observation will show that our world, and the rest of the universe, is dominated by matter. This strange preference for matter (dubbed the CP Violation) has perplexed scientists for decades however the newly upgraded LHC has the potential to shed some light on where the Universe’s strange preference comes from. The LHCb detector focuses on the decay of the Beauty Quark, a fundamental particle that decays in all manner of strange ways when created in a collider. Studying these decays could grant us insight into where the CP violation comes from and why we live in a matter dominated universe.
However what’s far more interesting (for me at least) is that the LHC could have the potential to generate dark matter, the highly pervasive as-of-yet unobserved substance that binds galaxies together via its gravitational influence. There’s numerous theories that posit dark matter being made up of WIMPs (Weakly Interacting Massive Particles) which could potentially be generated in the LHC. It’s highly unlikely that we’ll be able to detect them directly, their very nature means that they’re far more likely to simply pass through the detectors, however should we generate them their signature will be left on the reactions. Essentially we’ll be looking for a reaction that’s missing energy and then seeing if that can be explained by a WIMP being generated. Should we find that we’ll have a solid basis to further investigate this elusive form of matter, furthering our understanding of just what makes up our universe.
It’ll likely be another few years before we hear any further news from the LHC as it’s going to take time to generate the data and even longer to sift through it to find the reactions we’re looking for. However I’m very confident that the results will forever change the scientific landscape as either confirmation of current theories or evidence against them will provide dozens of more avenues for further research. That, to me, is the beauty of science, the never ending search for answers that inevitably lead to more questions, starting the process of discovery all over again.
You know what I most enjoy about science? The ever changing, always raging debate about how our models can be improved beyond what we currently have. Our scientific history is filled with models that made sense at the time with the knowledge we had then, only to be torn asunder by some new finding that forces us to rethink the way in which we modelled the observable universe before us. What I find most exciting are the times when we’re wrong as one experiment going completely awry can provide the required insight to shift our perspective considerably. Equally as exciting though is the prospect that we’ve modelled something almost perfectly and our experimental evidence confirms it.
Today we witness the latter with the Large Hadron Collider announcing that they’ve discovered a new particle and it looks suspiciously like the Higgs Boson:
“We observe in our data clear signs of a new particle, at the level of 5 sigma, in the mass region around 126 GeV. The outstanding performance of the LHC and ATLAS and the huge efforts of many people have brought us to this exciting stage,” said ATLAS experiment spokesperson Fabiola Gianotti, “but a little more time is needed to prepare these results for publication.”
“The results are preliminary but the 5 sigma signal at around 125 GeV we’re seeing is dramatic. This is indeed a new particle. We know it must be a boson and it’s the heaviest boson ever found,” said CMS experiment spokesperson Joe Incandela. “The implications are very significant and it is precisely for this reason that we must be extremely diligent in all of our studies and cross-checks.”
If you’re scratching your head as to why this discovery is so significant here’s a run down on what the Higgs Boson is in terms of the standard model of particle physics:
For the TLDR crowd the discovery of the Higgs Boson would fit our current model for understanding why particles have mass. Should the Higgs Boson not exist then our current understanding would be invalidated and we’d have to start testing other theories so our model could be made more accurate. For the most part there’s overwhelming evidence to support the standard model thanks to the previous work of other particle accelerators but the Higgs Boson represents the keystone of the whole model. Without it the rest of it needs a whole lot more explanation in order to make it work effectively.
Now whilst this is being lauded as the discovery of the Higgs Boson, and in all likelihood it is, there’s a non-zero chance that the CMS and ATLAS detectors at CERN have actually discovered another new particle that isn’t the Higgs Boson. That would be extremely interesting in and of itself as it would mean that the Higgs Boson, if it exists at all, would more than likely be at some mas even higher than first predicted. From what I can remember the current mass of the Higgs was on the upper limit of the LHC’s capabilities so if this turns out to be some kind of other particle, one that doesn’t exclude the Higgs from existing, we’d probably need to construct another particle accelerator in order to be able to detect it. That or the LHC would need to be upgraded which I admit is far more likely.
Regardless of the true nature of this new particle its discovery is something to get excited about as no matter what it is it means big things for the world of particle physics. The findings won’t see radical technology change or anything like that but it does mean we’re honing in on some of the fundamental aspects of our universe, something which I find incredibly thrilling. The next few months of data verification and probing the properties of this new particle will be a very interesting time and I can’t wait to hear more about this new boson.