Large Hadron Collider starts 3rd run to unravel more mysteries about the Universe

JUANA SUMMERS, HOST:

A giant machine was brought back to life today. The Large Hadron Collider, or LHC, made history in 2012 when scientists used it to prove the existence of a particle called the Higgs boson and with it the secret behind what gives all particles mass. The LHC is a nearly 17-mile ring buried underground near Geneva, and after years on pause, scientists still have high hopes for what it can uncover. I spoke with Sarah Demers, a Yale physics professor who works at the LHC earlier, and I asked her what it is like to be underground when the machine is running.

SARAH DEMERS: Well, I think it's always really cool, obviously, but I guess I'm biased. The truth is, when the Large Hadron Collider is running, we can't go underground.

SUMMERS: Oh.

DEMERS: We can't get near those collisions because the radioactivity is pretty high because of all of those particles that are being created. So we are safely 100 meters above the detectors and the collider and operating the control rooms here from the surface in the control rooms and satellite control rooms.

SUMMERS: So as I understand it, this is the LHC's third run. What types of questions are scientists hoping to answer this time around?

DEMERS: Well, at this point, we have the Higgs boson in hand. And so we're both trying to understand it better by making more careful measurements of the way it's produced and the way that it decays because we still have some open questions. You know, we've had the Higgs for a couple of years now. We've done some measurements, but we need more data in order to really complete the picture. At the same time, we're turning around and using the Higgs boson to go hunting for other physics questions that we have. We're thinking about the Higgs as a portal into exploring dark matter, as just one really exciting example.

And also, we're using the fact that we're at higher energy in this run. We hit a world-breaking 13.6 TeV, so that's the highest that we've managed in the world in terms of human-made collisions. And so that higher energy gives us more space to explore. I like to think about it as if you're climbing up a mountain. The higher up you're able to go, the further you can see. And so from our perspective in particle physics, we just reached a new peak.

SUMMERS: You mentioned dark matter and hoping to learn a little bit more about that. What do you hope to uncover about dark matter on this run? And I should ask, what is dark matter?

DEMERS: So I wish we knew. And I think even if we made just one step forward in trying to answer that question, we would be making real progress. It's interesting how we can understand so much about the matter that surround us. We've catalogued it, categorized it. We can make predictions about it and measurements of it so well. But when we look out into the universe, we have multiple pieces of evidence that tell us we're missing a huge amount of matter out there. We know so little about it. It's invisible to us. We've labeled it dark matter.

We have fundamental questions about it. Is it even particles? If it is particles, what kinds of masses do they have? And when we think about trying to explore and answer questions about dark matter at the LHC, I think it would be making tremendous progress just to even rule out some things, to be able to say, ah, OK, well, it's not that. We're just trying to move forward in any direction we can on this really challenging, enticing question.

SUMMERS: Physicist Sarah Demers works at the Large Hadron Collider. Thank you so much for your time.

DEMERS: Thank you.

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