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So two guys walk into a bar.
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Really?
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No, seriously.
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Two guys walk into a bar,
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an ice cream bar:
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Dave, a physicist working on the Large Hadron Collider at CERN,
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the European laboratory for particle physics,
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and Steve, a blues singer.
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"Dave, how's it going?"
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"Steve, good to see you!"
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"Two scoops of chocolate almond for me."
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"Vanilla shake."
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"Hey, I just saw something about the LHC on TV.
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You guys found bozo in your detector?"
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"Well, not exactly.
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We found a boson,
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probably the Higgs boson."
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"What's that?"
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"It's a particle."
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"Don't you find particles all the time?"
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"Yes, but this one means
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that the Higgs field might really exist."
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"Field? What field?"
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"The Higgs field.
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It's named after Peter Higgs,
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although many others contributed to the idea.
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It isn't a field, like where you grow corn,
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but a hypothetical, invisible kind of force field
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that pervades the whole universe."
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"Hmmmm, okay.
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If it pervades the whole universe,
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how come I've never seen it?
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That's a bit strange."
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"Well, actually, it's not that strange.
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Think of the air around us.
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We can't see it or smell it.
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Well, perhaps in some places we can.
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But we can detect its presence with sophisticated equipment,
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like our own bodies.
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So the fact that we can't see something
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just makes it a bit harder to determine
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whether its really there or not."
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"Alright, go on."
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"So, we believe this Higgs field is all around us,
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everywhere in the universe.
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And what it does is rather special -
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it gives mass to elementary particles."
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"What's an elementary particle?"
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"An elementary particle is what we call
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particles that have no structure,
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they can't be divided,
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they're the basic building blocks of the universe."
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"I thought those were atoms."
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"Well, atoms are actually made of smaller components,
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protons, neutrons, and electrons.
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While electrons are fundamental particles,
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neutrons and protons are not.
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They are made up of other fundamental particles called quarks."
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"Sounds like Russian dolls.
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Does it ever end?"
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"Actually, we don't really know.
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But our current understanding
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is called the Standard Model.
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In it, there are two types of fundamental particles:
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the fermions, that make up matter,
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and the bosons, that carry forces.
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We often order these particles
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according to their properties, such as mass.
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We can measure the masses of the particles,
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but we never really knew where this mass came from
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or why they have the masses they do."
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"So how does this Higgs field thing explain mass?"
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"Well, when a particle passes through the Higgs field,
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it interacts and gets mass.
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The more it interacts, the more mass it has."
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"OK, I kind of get that, but is it really that important?
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I mean, what if there were no Higgs field?"
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"If there were no Higgs field,
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the world wouldn't exist at all.
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There would be no stars, no planets, no air, no anything,
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not even that spoon or the ice cream you're eating."
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"Oh, that would be bad.
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Okay, but where does this Higgs boson fit into things?"
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"Alright, now, you see the cherry in my shake?"
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"Can I have it?"
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"No, not yet. We have to use it as an analogy first."
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"Oh, right, the cherry's the Higgs boson."
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"No, not quite.
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The cherry is a particle moving through the Higgs field, the shake.
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The shake gives the cherry its mass."
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"I get it. Okay, so the molecules of the shake are the Higgs bosons!"
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"Well, you're getting closer.
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It takes an excitation of the Higgs field
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to produce the Higgs boson.
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So, for example, if I were to add energy
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by, say, dropping this cherry in the shake,"
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"Ah, then the drops that spill on the bar
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are the Higgs bosons."
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"Almost! The splash itself is the Higgs boson."
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"Are you serious?"
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"Well, that's what quantum mechanics teaches us.
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In fact, all particles are excitations of fields."
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"Okay, right. Well, I kind of see why you like particle physics,
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it's quite cool,
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strange, but cool."
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"Yeah, you could call it a bit strange,
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it's not like everyday life.
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The Higgs boson is an excitation of the Higgs field.
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By finding the Higgs boson,
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we know that the Higgs field exists."
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"Right. So now you found it,
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we know this Higgs field exists.
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You must be done.
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Is there anything left of particle physics?"
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"Actually, we've just begun.
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It's a bit like, you know, when Columbus thought
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he had found a new route to India.
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He'd, indeed, found something new,
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but not quite what he was expecting.
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So, first, we need to make sure that the boson we found
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is actually the Higgs boson.
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It seems to fit, but we need to measure
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its properties to be sure."
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"How'd you do that?"
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"Take a lot more data.
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This new boson lives for only a very short time
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before it breaks down or decays
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into lighter, more stable particles.
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By measuring these particles,
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you learn about the properties of the boson."
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"And what exactly are you looking for?"
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"Well, the Standard Model predicts how often
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and in what ways the Higgs boson would decay
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to the various, lighter particles.
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So we want to see if the particle we have found
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is the one predicted by the Standard Model
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or if it fits into other possible theoretical models."
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"And if it fits a different model?"
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"That would be even more exciting!
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In fact, that's how science advances.
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We replace old models with new ones
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if they better explain our observations."
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"Right, so it seems like finding this Higgs boson
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gives a direction for exploration,
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a bit like that Columbus guy heading west."
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"Exactly! And this is really just the beginning."