The Large Hadron Collider has proven to be the boon to particle physics that everyone had imagined to be but it’s far from done yet. We’ll likely be getting great data out of the LHC for a couple decades to come, especially with the current and future upgrades that are planned. However it has its limit and considering the time it took to build the LHC many are looking towards what will replace it when the time comes. Trouble is that current colliders like the LHC can only get more powerful by being longer, something which the LHC struggled with at its 27KM length. However there are alternatives to current particle acceleration technologies and one of them is set to be trialled at the LHC next year.
The experiment is called AWAKE and was approved by the CERN board back in 2013. Recently however it was granted additional funding in order to pursue its goal. At its core the AWAKE experiment is a fundamentally different approach to particle acceleration, one that could dramatically reduce the size of accelerators. It won’t be the first accelerator of this type to ever be built, indeed proof of concept machines already exist at over a dozen facilities around the world, however it will be the first time CERN has experimented with the technology. All going well the experiment is slated to see first light sometime towards the end of next year with their proof of concept device.
Traditional particle colliders work on alternating electric fields to propel particles forward, much like a rail gun does with magnetic fields. Such fields place a lot of engineering constraints on the containment vessels with more powerful fields requiring more energy which can cause arcing if driven too high. To get around this particle accelerators typically favour length over field strength, allowing the particles a much longer time to accelerate before collision. AWAKE however works on a different principle, one called Plasma Wakefield Acceleration.
In a Wakefield accelerator instead of particles being directly accelerated by an electric field they’re instead injected into a specially constructed plasma. First a set of charged particles, or laser light, is sent through the plasma. This then sets off an oscillation within the plasma creating alternating regions of positive and negative charge. Then when electrons are injected into this oscillating plasma they’re accelerated, chasing the positive regions which are quickly collapsing and reforming in front of them. In essence the electrons surf on the oscillating wave, allowing them to achieve much greater velocities in a much quicker time. The AWAKE project has a great animation of the experiment here.
The results of this experiment will be key to the construction of future accelerators as there’s only so much further we can go with current technology. Wakefield based accelerators have the potential to push us beyond the current energy collision limits, opening up the possibility of understanding physics beyond our current standard model. Such information is key to understanding our universe as it stands today as there is so much beauty and knowledge still out there, just waiting for us to discover it.
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.