What were they looking for?

Particle physics as a subject is all about understanding the most basic building blocks of the universe.

And this is a journey that began 130 years ago with the discovery of the electron.

And since then, we've been zooming in and zooming in and zooming in on matter.

We've discovered the nucleus, inside that protons and neutrons, inside that quarks, and then most recently the Higgs boson.

And every time we've gone to sort of zoom in further to shorter distances, we've discovered new particles.

In a very broad sense, what we're looking for are new basic ingredients of our universe.

And potentially also give us an insight into this strange world of dark matter and dark energy?

Yeah, but physicists

just went for something more prosaic in the end, bottom and top.

But because we study these things at LHCB, we'd rather be beauty physicists than bottom physicists.

Sure, that's fair.

But yeah, why are these things interesting? Well, the beauty quark It's the fifth heaviest quark.

So there's this weird thing, and this is another thing we don't understand about the Standard Model.

We are made of basically three particles, electrons and the up and the down quark.

What does it actually look like? What's the kind of structure of it? And how do these investigations take place?

Harry, how accurate were Higgs's predictions and what does the confirmation of the Higgs boson mean for physics?

I mean, his predictions were clearly accurate.

I mean, one of the things that is amazing, I think, and almost unique about fundamental physics is this ability to predict the existence of phenomena or objects that have never been seen and then you see them.

And this happened in the 1920s and 30s when antimatter was predicted purely on theoretical grounds.

And similarly, the Higgs boson was predicted by Higgs and others in the 1960s.

What it didn't tell us was what the mass of the Higgs boson was.

So when the LHC switched on, Physicists were very confident they would find it if it was there, but they didn't know exactly at what energy scale.

Harry, something that I'd like you to try and answer, if you can tell us in a bit more detail what antimatter is.

Harry, how accurate were Higgs's predictions and what does the confirmation of the Higgs boson mean for physics?

I mean, his predictions were clearly accurate.

I mean, one of the things that is amazing, I think, and almost unique about fundamental physics is this ability to predict the existence of phenomena or objects that have never been seen and then you see them.

And this happened in the 1920s and 30s when antimatter was predicted purely on theoretical grounds.

And similarly, the Higgs boson was predicted by Higgs and others in the 1960s.

What it didn't tell us was what the mass of the Higgs boson was.

So when the LHC switched on, Physicists were very confident they would find it if it was there, but they didn't know exactly at what energy scale.

Harry, something that I'd like you to try and answer, if you can tell us in a bit more detail what antimatter

Harry, what was it that the Greeks and the ancient classicists, how were they conceiving of nothingness?

Well, I think Democritus said he was the guy that came up with the idea of an atom, that if you take matter and you cut it and you cut it, eventually you'll get to something that you can't cut anymore, the smallest thing.

And he said the universe is atoms and the void.

So it's stuff and the absence of stuff, and that's what the universe is made from.

But other people disagreed with that.

I think Aristotle said there was no such thing as nothing.

The first sort of scientific ideas really come with people like Robert Boyle, where they start to pump air out of glass containers and they discover that candles go out or that if you ring a bell in a vacuum, you can't hear it.

don't want that.

It's at great expense, but Dr. Cliff told Roland that that's how they make sure that the LHC continues to be a smashing success.

The LHC, it's the biggest scientific instrument ever built by human beings.

By some measure, it's the biggest machine that's ever been built by human beings.

It, it's a gigantic circular particle collider.

It's 27 kilometers in circumference, and it's buried about 100 meters on average underneath the Swiss-French countryside just outside Geneva, which is the loc- location of CERN, the European Organization for Nuclear Research.

So, I mean, what the LHC is, is, you know, it's a gigantic accelerator.

What it does is it takes protons, which are the nuclei of hydrogen atoms, it whizzes them round this 27-kilometer ring, and they get faster and faster every time they orbit the ring.

And, uh, I suppose you, you need to persuade us that it is still producing in- the kind of information we're paying you for.

Um, why, why, why do you want to?

I mean, the reason that this stuff is interesting is it really tests a, a really deep fundamental principle of the universe, which is the symmetry that relates matter and antimatter to each other.

And there is this big mystery, which is that according to our current theory of particle physics, in the very early universe, you should have made equal quantities of matter and antimatter, and then they would have annihilated each other, and we would end up with a universe that contains nothing but radiation, just some photons zipping about.

But we live in this incredibly rich universe with lots of stuff in it, and that is a fundamental mystery that we just do not understand, and we're trying to understand that in various different ways.

But one of the ways you can understand that is by trapping antimatter stably and then performing precision measurements on this stuff.

And what they're doing at the base experiment is measuring the properties of antiprotons, so measuring, in particular, something called its magnetic moment, which is, uh, basically how magnetic are these little particles, and comparing it to the ordinary proton.

But the problem they have at the antimatter factory is there are these stray magnetic fields caused by the decelerator that they use to slow these antiprotons down.

What, what can we expect to see once it reboots there and people like you at LHCb get back to work?

They are also wrapped up in some of its deepest mysteries.

Yeah, I mean, so neutrinos, they're probably quite unfamiliar.

If you know any particle physics or any atomic physics, you're probably familiar with the idea that an atom has electrons going around the outside.

These are negatively charged particles, and inside the center of the atom, there's this positively charged nucleus.

Well, neutrinos are sort of partners of the electron, right? in some sense, but they have no electric charge.

And because they have no electric charge, they very, very rarely interact with ordinary matter.

So the reason that ordinary matter holds together, the reason that we can touch objects is because the particles that make up that stuff have electric charge, and that holds them together and allows them to interact with each other.

Can you briefly explain those two, and maybe is the James Webb telescope the answer to resolving that tension? How do you see

(laughs)

... and the sea, and, and bits of rock.

And it relieves his hay fever.

And there's this lovely description of he's sort of...

in the middle of the night, he's been doing these calculations and he has the kind of key realization that, that Fay's been, been describing.

And there's this lovely quote from him where he says...

I think it gives a sense of what it's like to make a breakthrough like this.

But what about the man? Uh, one of the things about the man is that the politics of the 1930 affected him and, and his position with regard to Germany.

So talk about the status of G-2, why that's so important, and what would it mean to really have a fifth force? What would that

mean? due to physics, even to the philosophy of science.

Just to explain what G-2 is for the benefit of anyone who doesn't know, there's this particle called the muon, which is a heavy version of the electron, doesn't exist normally, but we can create it in experiments.

And it behaves like a little bar magnet.

So the muon spins just like an electron.

And because it's charged, that angular momentum comes up with an associated magnetic field.

And the strength of the magnetism of the muon depends not just on the muon, but on the contents of the vacuum around it.

So talk about that effort as one of the key players in this endeavor.

Why?

I mean, I wish I could claim responsibility for the existence of the universe. (laughs) Well, I mean, yeah. This is a big problem, as you say, 'cause like we see this in experiments. When we bang particles together, uh, at the Large Hadron Collider, you always see equal numbers of particles and antiparticles being made. So this is what happens. So the question is, how did you get this asymmetry? And there was a Russian physicist back in the '70s, I think, called Andrei Sakharov who came up with three conditions that had to be satisfied to allow matter to win this battle with antimatter in the early universe. The first one, pretty obviously, is you need a process that makes more particles than antiparticles. That's number one. The second one, though, is this condition known as CP violation. So CH- CP stands for charge parity, which is a sort of symmetry that ref- relates matter to antimatter. It's kind of like a mirror. If you sh- put matter in the CP mirror, uh, it shows up as antimatter. So what we're looking for are processes that violate this symmetry. And these B mesons that the question are asked about, so these are particles which contain a beauty quark and another quark, so like, uh, paired up with an antiquark usually. And there are a particular type of these particles that do this really weird dance where you create one of these B mesons, and as it travels through your experiment, it oscillates backwards and forwards between matter and antimatter. So it will flip its identity, uh, with this very nice sort of periodic way. And you can... What you then do is you watch how often does it decay in the matter state and how often does it decay in the antimatter state? And you measure the difference. And if you see a difference, that tells you that the laws of the universe violate this, this CP symmetry, this symmetry between matter and antimatter. So this is the kind of key ingredient, one of the key ingredients we need to explain this mystery.

You know, hit the black hole, and it just disappears into the singularity. That question reminds me of earlier in our conversation. Uh, so Harry, you were t- you studied particles that decayed in a trillionth of a second. It seems to me, that can be a trillionth of a second only at a certain speed, because the faster a particle goes, the longer it would take to decay because its timeframe is shifted relative to the observer. So, you can't just declare a trillionth of a second without specifying a speed, or is that, that particle at rest?

So that, that trillionth of a second is from the particle's point of view, so in the frame of the particle. So the particle's at rest basically. So if you were the particle, you'd live a trillionth of a second. But from our point of view in the lab, as you say, these things are going close to the speed of light, so they live way longer. So they actually will travel... They live long enough because of this relativistic time dilation to fly a centimeter or so in the experiment, which, if they just lived a trillionth of a second, they wouldn't go anywhere near that far. So, you're absolutely right. I mean, like, relativity, special relativity I should say, is, you know, fundamental to colliders because what they basically do is they are E=MC² machines. They take E, energy, kinetic energy in these accelerator particles, they bang them together, and they make M, they make new particles, new matter effectively. So, like, it's absolutely fundamental to what we're doing. But the question about black holes, that's really general relativity. And there were some ideas back when the LHC switched on that if there were extra dimensions of space, so extra directions that you can move in, that it would be possible to create microscopic black holes at the LHC. And this led to a load of tabloid stories about the LHC is gonna create a black hole, it's gonna swallow Geneva and then swallow the rest of the planet and we're all gonna disappear. And so this caused such, like, a big storm, and the British uni- the British tabloid press actually really got hold of this story. CERN had to create this health and safety report, which is the most exciting risk assessment you'll ever read. And it basically describes these various hazards, one of which is, like, a black hole that swallows the Earth. The other is the creation of a bubble universe that expands to destroy the entire of reality. So they had this risk assessment where the destruction of the universe was one of the possible outcomes. And they basically said, "This is very unlikely to happen, and so it's all fine." Um...