 In the last video, we ended with a potential method for producing the Higgs boson. In this video, we're going to talk about some of the technology that made this method possible. We'll start with charged particles. The reason for this is that charged particles interact with the electromagnetic force. Since we know how to produce and control electric and magnetic fields, we can use this knowledge to manipulate the particles we hope to accelerate. Let's start with a very simple example. Say we have two metal plates. The plates are very wide and closely spaced. Each plate is charged. One is positively charged and one is negatively charged. The charge on each plate is evenly distributed. You'll have an electric field between the two plates. The whole setup looks something like this. Let's say there's a tiny hole in the center of both plates. What happens if we inject a proton with positive charge through the hole in the left plate? Well, it's going to experience a force that pushes it towards the negative plate. That force is proportional to the strength of the electric field. Remember f equals ma? Well, as a result of that force, the proton will accelerate towards the negative plate straight towards the little exit hole we've installed. When it leaves the electric field region, it will be traveling faster than it was when it first entered the field region. The voltage we use to create the electric field determines how fast that proton will be going when it leaves the electric field region. So the higher the voltage of our power source, the faster that proton will travel. If we use a one-volt power source to generate our electric field, the accelerated proton will have an energy of one electron volt and so on. So higher voltages allows to accelerate particles to higher energies. But there's a limit to how much voltage we can apply to a setup like this. So we need to use some other tricks to accelerate particles to very high energies. The first is simple. We have a series of identical plates all set up in a row. As the particle passes through each set of plates, it gains energy. The final amount of energy the particle has depends on how many identical sets of plates it needs to pass through. Now the technology we currently use to accelerate particles is a little more sophisticated than this. But the basic idea is the same. An electromagnetic field is used to apply force to charge particles repeatedly so they gain energy. This is a pretty expensive way to accelerate particles though, particularly if you need to achieve high energies. So the biggest accelerators use a few tricks to pass particles through the same acceleration regions repeatedly. How do they do this? Well, let's have a look at the shape of an accelerator like the LHC. Basically, a portion of this ring is the accelerated equation. It can be concentrated in one area of the ring, or it can be interspaced throughout the ring. The beam of charge particles is kept in the ring via very strong magnets so particles can repeatedly be passed through the accelerated region. When they have enough energy, those same accelerated particles can either be injected into bigger accelerator rings, again using magnetic fields to guide the particles, or eventually be transported to collision stations within VAS detectors where the outcomes of collisions can be observed. The key to this last bit, the collisions, is that particles can be accelerated in both directions in these rings since we can manipulate the fields in the accelerator sections. So we can keep accelerating both beams of particles until we're ready to initiate a collision. What you generally have is something like this. So you have your ring. You have two vacuum tubes in which the particles actually travel. Each of those vacuum tubes represents a direction for those particles. You'll then have a detector station where the two bunches of particles traveling in different directions can actually be collided together. This is made possible using not just the electromagnetic acceleration regions, but also a series of magnetic fields to guide the particles around the paths. At the LHC, particles can, in principle, be accelerated to energies up to 7 TeV. That's 7 trillion electron volts. This is possible because the LHC is the biggest and most technologically advanced ring in a series of accelerator rings at CERN. Because two accelerated beams can be collided head-on in the LHC, that means reactions with a total of 14 TeV in the center of mass energy can, in principle, be studied. So the whole accelerator complex at CERN looks like this. There is a lot going on in this picture. But we'll focus only on a bit that's relevant for the Higgs search. We begin with protons, which are injected into Linux 2, which I have underlined here. The protons get accelerated to 50 MeV, and these are then injected into the booster, where they get accelerated to 1.4 GeV. After this, the protons get sent to the proton synchrotron, which accelerates the protons even more to 25 GeV. Next, the super proton synchrotron, or SPS, is used to get the protons to 450 GeV. Finally, they get injected into the LHC, where they travel in two different accelerator tubes and directions. At this final step, they get accelerated to up to 70 TeV. In this diagram, Alice, CMS, LHCV, and Atlas are all detector stations. These are the regions where collision between the two proton beams can happen. It's in these detector stations where discoveries are made. There are typically a bunch of different layers to each of these detector stations, each of which aims to measure the properties of all the particles produced in a given reaction. There are huge facilities involving collaborations between lots of different people from all over the world. To give you an idea of how big these detectors are, here is CMS, one of the detector stations involved in the Higgs search. Note the worker in the middle. He gives you some idea of the kind of scale for the whole enterprise. Now that you have an idea of the tools used in the Higgs search, we should finish our original story. The LHCs first started running experiments in September 2008. Two of the detector stations on the LHC, Atlas and CMS, were focused on the search for the Higgs boson. On July 4th, 2012, both collaborations announced that they had strong evidence of a particle that looked like the Higgs boson in the energy region between 125 and 126 GV. In August, they made the announcement official by publishing two papers. These papers, the cumulative work of thousands of people in many nations, provided experimental evidence of the discovery of the Higgs boson, and made it possible for Higgs and Engelbert to receive the Nobel Prize in Physics in 2013. So at this stage, you might be asking, well, what's next? We're still studying the Higgs boson. We don't know as much as we'd like to know about its properties. But there are other kinds of experiments going on in places like LHC. For example, people are studying the Quark-Gluon plasma. That's the state of matter that was thought to exist in the early stages of the universe when quarks and gluons were not tightly bound together. The other things that people are looking for include searches for phenomena that are not explained within the standard model. For example, dark matter and dark energy. And finally, people are always looking for science that the standard model is not quite the full story. Perhaps there's something more to what we've just told you. With that, we end this series of videos on the standard model in the Big Bang. I really hope you've enjoyed the videos and have learned something really interesting about the matter that makes up our universe and ultimately shapes us. Bye.