Dominique Dulièpre
Welcome to Longitude Sound Bytes where we bring innovative insights from around the world directly to you.

Hi, I’m Dominique Dulièpre, Longitude fellow and graduate student at Rice University studying Electrical and Computer Engineering.

We are exploring roles, projects, and approaches of individuals to experimentation and contemplation in scientific and creative fields. For this episode, I had the opportunity to speak with Peter Denton.

Peter Denton is an associate physicist at Brookhaven National Laboratory, where I interned as an undergraduate. He studies neutrinos; Neutrinos are among the most abundant particles that have mass in the universe. These particles almost never interact with other matter which makes them difficult to detect. Trillions of neutrinos from the sun stream through our body every second, but we can’t feel them.

Join me as I engage in conversation with Peter Denton about the current works toward the Deep Underground Neutrino Experiment.  Enjoy listening!

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Peter Denton
After I did my bachelor’s in math and physics at Rice, I did a PhD at Vanderbilt, in physics, focusing on theoretical particle physics. That just means looking at particles, the kind of the smallest things, and then in looking at them in the most extreme environments, to see how, you know, our understanding of them breaks, if it is correct, is it not correct. I studied that at Vanderbilt in Nashville.

So right now, I work at Brookhaven Lab, which is on Long Island, near, near-ish to New York City. There’s a number of programs for undergraduates and graduates, international high school students as well, to come to Brookhaven lab, and I think some of the other labs do this as well. We bring in just a huge number of students each year, at different levels, to engage with scientists, but also with like, the hardware, like the state of the art, you know, whatever machine, to run little, experiments. You give them little projects, and sometimes it is actually contributing to research, but sometimes it’s just getting a feel for what it is, because, a lot of people don’t understand, I find, really kind of the idea of what research is. It sounds like you’ve already gotten this experience a little bit. People kind of understand, like, what a business is, or like, what a doctor or a lawyer or things like that, what do they do, like there’s TV shows about them. So, we all kind of have some vague idea of what these things are, like the research is different from those things. And it’s very hard to understand that without experiencing it. And so even if it’s in kind of a very simple, confined, and you draw a box around a little problem, and you say, Okay, go work on this problem, it still provides the experience and it’s different from doing your math and physics and engineering homework in school, whether in master’s program or in undergrad, or even in high school. Those homework problems, you know, it’s a well-defined problem. There’s a beginning, there’s an end, the answer is probably in the last chapter of your textbook, but in research, there’s no guarantee there is an answer. I just come up with an interesting question. How do I do that? You know, I don’t know. It requires some level of creativity. In fact, I would say that being successful in research is largely creative efforts, very similar to the arts. And then you have to generate a new solution out of, out of the ether, so to speak, see if this works. They obviously have to have the technical skills in terms of math or hardware or whatever, to execute it, and see if it maybe be the homework problem for you, you know, you’ll do it in a day, because the procedure of things are well defined. And so, once you understand there is a solution, and that it is achievable, then that makes things much simpler. But that’s why I think these research programs for students are so essential, even if a person doesn’t become a research scientist, just to have an understanding of what that looks like.

Dominique
I certainly believe that also provides them the benefit of getting first-hand experience. So, they can certainly hit the ground running after graduation. They essentially have the direction, whether research or industry.

Peter
Exactly.

Dominique
Can you tell me a bit about, briefly, your experience at DUNE? And how would you describe your experience at Fermilab?

Peter
The U.S. is building a particle physics experiment. It’s the biggest particle physics experiment in the U.S. called DUNE. There’re also other names like LBNF, which are associated with it, but we can just basically call the whole thing DUNE, like the movie, a novel, but it stands for the Deep Underground Neutrino Experiment, not a desert planet and space. It consists of a number of separate components that are, each of which by themselves would be considered their own experiment in a typical thing.

The primary part is at Fermilab, which is a national lab outside of Chicago, where they have a big accelerator complex. So, they’re used to accelerating particles to very high with low energies, to get a lot of oomph, so they can do a lot of cool stuff. And they have experience with that. And they’re going to have to redesign that in a number of ways. And then they’re also building separately, a very big detector. But typically, the detectors are like in the same place as the accelerators. But for these kinds of experiments, these kinds of neutrino oscillation experiments, you often put the detector like several states away. So, this detector will be in South Dakota, in a former gold mine. So, they dug very deep, they dug out a lot of gold, and then the gold extraction kind of stopped. Of course, they’re looking at that relative to the price of gold and they said, Alright, we’re done with the mine. And basically, as soon as that happened, physicists jumped right in and moved in. And there’ve been experiments, smaller experiments there for years looking for different things because being underground is advantageous for a number of reasons. But now that they’re fully out, they’re prepared to start building huge underground caverns and stick giant detectors in there. The underground caverns are actually mostly done. I think they’re about 90% excavated. I think the target completion date is late January.

There are these two separate parts that compose what is DUNE. Now my role in it is, I would say, somewhat peripheral. I’m a theorist. So, I’m not building things, I am not very good at building things. But I think about things in different ways to put things together in ways that people haven’t thought of before. And so, a lot of that is related to DUNE although some of it is related to other experiments and other physics topics.

Dominique
What exactly are neutrinos?

Peter
The neutrino is neutral, so it’s electrically neutral, which means it doesn’t interact, in the same way that electrons interact. Electrons interact with everything. That’s why we can do chemistry, we can build semiconductors. We can manipulate electrons super well and do all kinds of cool stuff with them. Neutrinos, now so much. The neutrino, even though it’s electrically neutral, doesn’t interact very much. In physics, that’s what we think about is how does stuff interact? And exactly how does that happen? How likely is it? And like, what kind of angles and kind of energy do they come in with and go out with and what’s the probability for this to happen or that to happen, whatever. We calculate all this stuff. Now, there’s two other particles I mentioned, like an electron called the muon, and tau. I like to think of them as like the fat or cousins. Electrons are like the skinny little kid or whatever. And then about 200 times heavier is the Muon. And then another factor of, I think about 20 times heavier is the Tau. But at the fundamental level, they’re all kind of the same thing. But it turns out that because their masses are different, they act a little bit differently. So heavier particles can decay into lighter particles, if that’s allowed by certain rules. So, the muon and the tau, they decay fairly readily. So, they’re not stable. So that’s just hanging around. Electrons, obviously, just hanging around because there’s nothing lighter for them to decay to, they’re pretty light on the scheme of things. So, when a neutrino interacts, it will produce either an electron, a muon or a tau and since they look differently, we can measure them in a detector. We build detectors that are designed to say, oh, electron interacts this way. Muon, because it’s heavier, it does something different. And tau also does something different.

Dominique
So, there are multiple sources from which we can detect them. How much information can our detectors at DUNE actually provide in terms of differentiating whether they are coming from Earth resources or stars supernovaing?

Peter
Yeah, yeah. Good. So yeah, exactly. So, there’s a lot of sources of neutrinos. I mentioned nuclear reactors. That’s how the neutrinos were discovered. They’re also produced in the atmosphere, there’s a kind of background radiation raining down on us. It’s not, it’s not great for us, but we get it all the time. This is just part of life. And they’re also produced in the sun quite abundantly. Occasionally, stars run out of fuel, and they explode and turns out that produces a bucket load of neutrinos. And how do you know, you know, when you detect something, first, you have to know it’s a neutrino and not another particle. Right? That’s, that’s, that’s the first problem. And even once you know that, you say, well, where’s it coming from? So, there’s a bunch of different techniques and when you design your experiment, of course you design with these things in mind.

DUNE’s primary goal is actually detecting human made neutrinos. So, from a controlled source. So, what they do is they, they smash particles together at Fermilab near Chicago. And this produces a bunch of a bunch of particles, which eventually produces neutrinos. So that’s basically anything you produce is going to produce neutrinos. So, this is how the source at Fermilab works. It’s just producing a sort of what we call a beam of neutrinos. It’s kind of broad, but it’s most of the neutrinos go in the forward direction, along some axis, which is hopefully going to be pointed correctly at South Dakota. And the thing about this beam is that well, okay, so on your detector, you have some 3D sort of spatial reconstruction, and you can kind of tell where, because you see all the secondary particles going in one direction. So, they’re all going up or down or left to right or whatever, well, you know where Fermilab is. So, they should be going in a way that corresponds to coming from that direction, they should be going west-ish. And that if all of a sudden, particles are going west-ish, you know that the neutrino that you just detected came from Fermilab. Obviously, you have to get the direction exactly right. In addition, the beam is pulsed. So, it shoots neutrinos for a short period of time, and there’s an empty spot. You also have the timing information. So, you know how far away it is how long it takes for them to get there, you count for that, and it’s it has to come in this small-time window here and not in this big-time window here. There’s some duty factor of, where basically, if they come in this big chunk of time, then you know that it’s not a neutrino from Fermilab. So, you combine this information and then you do some statistical things, and you say, we are 99% sure that this is a neutrino from Fermilab. But there’s other things as well.

So, if it comes from a supernova, like you mentioned, those neutrinos tend to be lower energy than those from DUNE aside from Fermilab. You have a different detection strategy in the first place just for how they look in the detector, but also DUNE will see a lot of neutrinos, hundreds to 1000s in a timespan of like two seconds. Well, normally the rate is like, you know, I don’t know, one a day or something like that from Fermilab. It’s very rare. It’s not very often. So, if you’re seeing, you know, a couple of day, or whatever the rate is, and while you’re checking your watch, is there another one going to come today or not, but then you all of a sudden see in like two seconds, you see, like 500 neutrinos, and they’re not coming from the direction of Fermilab. They come from some random direction. They’re lower energy, but they’re all coming from kind of the same direction. Then you think, that must be a transient burst effect. That doesn’t necessarily immediately mean it’s a supernova, but you can combine this with other information and put it together. And if that happens, there’s actually a number of neutrino detectors around the world that will see it. They’ll send out an alert. You can actually sign up for this online. And I recommend anybody does this. It’s called SNEWS. S, n, e, w, s, the Supernova Early Warning System. And you can just sign in, type in your email address. They never send an alert. The last supernova nearby seen was in 1987, there’s not been one since then. We are waiting patiently. It’s been 35 years, we think we’re due, but you know, that’s not how these things work. But then the point is that we’ll get into neutrino information from a supernova, before we get the information via visible light. And that’s because outside the supernova, there’s a bunch of dust until the neutrinos, because they don’t interact very much, when I said they’re little, they just truck right through it, they just come through it at very near the speed of light. But the visible stuff, it kind of bounces around for a while. So, the optical telescopes won’t see it until potentially hours later. So, there’s this like, really small sliver of time, and you need that neutrino information, and you get that you then use triangulation, you then use pointing, use a variety of different things. And so, we’re pretty sure there’s a supernova, you know, near-ish nearby, in that direction, everyone with a telescope and that means you at home with your telescope, or binoculars or your eyeballs should go look in the direction that they say, and see if you see, suddenly a new star appear in the sky. Because that’s, that’s possible. And that has happened before, but now we have the capability to know in advance. That’s never happened before. That would be just an amazing thing. And DUNE will play a big part of that for sure.

Dominique
I like to think of it as you snooze, you lose – the ability to observe.

Peter
Yeah, that’s awesome.

Dominique
Which was the precursor to a black hole in a white dwarf. So, it’s pretty important.

Peter
Yeah, exactly. So, supernova can form a black hole, sometimes, we don’t really know very well how often that happens. It can form a neutron star, which is like a really compact bunch of neutrons and stuff, basically, that’s just super energetic, and doing a bunch of crazy stuff. And seeing these things form, in some sense, would be amazing. I mean, there’s so much, so much to know, and we’d love to be able to get at, but you can never do these kinds of things at the earth. So, we have to use astrophysical environments to do this. And neutrinos play a huge role, provided that you can detect them, and they’re a pain to detect for we’re building bigger and more sophisticated detectors all the time.

Dominique
What are some upcoming milestones or experiments that you’re most looking forward to?

Peter
Yeah, that’s a great question. There’s a couple of things coming up. There’s currently experiments like DUNE. So, DUNE is expected to turn on in the next, let’s say, five-ish years. But there’s experiments that are doing a similar thing right now. One at Fermilab, it’s called NOvA and there’s another one in Japan called T2K. And they’re doing the same thing, but with less precise detectors and less powerful beams. And so, they’re putting out results. They haven’t put out results in a couple of years. So ,I think they’re hopefully due, so I’m crossing my fingers, they’re gonna put up something soon. And they’re measuring stuff, you know, not nearly as well as DUNE will, but we’re still getting information. And they provide indications for what kinds of things to expect at DUNE. Oh, maybe, maybe the numbers are a little bit, you know, maybe the parameters are a little bit more this way so, you know, we should have that in mind. DUNE, measuring the things we want to measure. DUNE will be a little bit easier or a little bit harder. So, I’m hoping that with the next data release from these current, what are called long baseline neutrino oscillation experiments, that they will start to migrate towards each other. Do they migrate more towards the one or the other one, you know, how does it work? You know, I don’t know. I mean, this is its research, right? We don’t know how it goes, could go in either way. And I think that’s something that I’m anticipating for some time, and I’m very much hoping that they will come out with something soon.

Dominique
What advice would you give to young scientists aspiring to pursue a career in physics?

Peter
Obviously, you’ve got to do well in your classes. You’ve got to learn differential equations, linear algebra, and so on. Maybe more math, depending on what areas you’re interested in. You have to learn programming. There’s very few physicists who have successful careers without pretty good programming abilities. I am not saying you have to be like a computer scientist and writing your own compilers or whatever. But you know, high performance computing, using supercomputers. This is a standard tool of physics today. You’ve got to learn that stuff. And also getting involved in research by doing some research things as well, there’s a number of opportunities there.

I would say that some of the biggest problems that young scientists have, where things start to go awry, is in and I would say in two kinds of main areas. One is, in having an awareness of what a career in research looks like, it doesn’t look like a career in business or in, you know, other professional careers like law or medicine or whatever. It’s a very different kind of career trajectory. And it’s a little bit different in every field. But you know, just very briefly kind of a standard career trajectory, as you get a bachelors, of course, you go to graduate school, you get a master’s and a PhD that may be together or separate, then you do postdocs. This typically involves moving, quite possibly moving around the world. I’m American, but I did my postdoc in Denmark, because that’s where I got a postdoc. You do one, two, three, some number of those, these are each a couple of years. And then you get a hopefully a, you know, permanent tenure track job. So, there’s some kind of trajectory, there’s some kind of steps that you have to accomplish, and also looks a little bit differently in different countries, in Europe, in different places, it follows a different trajectory. That’s one thing.

The other thing is what are often called like soft skills. Networking, giving talks, writing. You think, Oh, I’m getting into physics, because it doesn’t involve people and sometimes that’s very nice. But that’s, of course not true. In order to be successful, you have to network, you’re just the same as your friends going into finance, or engineering or whatever, you got to go out and meet people and make a good impression. And make sure they remember you. You also have to give talks, this is a big part of the job, you stand in front of a room of 30 people or 100 people or 300 people and tell them about your research. And they’re gonna ask tricky questions, and you got to be able to answer it on the spot. And people who do this, well leave a good impression on the audience. And maybe one of them when it comes time to hire somebody decides to hire you. That definitely happens. Also writing and we write a lot people who can write good papers that are easy to read, it makes a big difference. And people remember those people much better than you know if you struggle with it a little bit. So, you know, I spent time in literature classes in school because I liked it. But I also got a lot of practice writing, and it’s definitely paid off a lot for me. I don’t think you can get by just taking only math and physics and be fine. It is necessary, I would say to have a successful career in particle physics, to be able to write well to stand up and speak in front of people and to network well.

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Dominique
We hope you enjoyed our episode. What stood out for me from this conversation was how much information neutrinos provide about our universe. Supernovae Early Warning System, SNEWS for short, can inform us on the life and health of the core of our sun before its light makes its way to us. The SNEWS can even inform us of supernovae. In the transition to black holes or neutron star. It can even lead to the examining of the essence of dark matter and dark energy for scientists.

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