One-on-one with Soeren Prell, ISU physics professor

Soeren Prell is a physics professor at Iowa State and was present at the conference where the discoveries on the Higgs boson particle research were announced.

Aimee Burch

ISU professor Soeren Prell was present for one of the biggest announcements of the century. He presented his findings at the conference where scientists announced recent results concerning the Higgs boson particle. Prell talked about this momentous occasion with the Daily.

How did you get to go to the conference? What was it like to be there during this momentous occasion?

[laughter] Lots of questions… Okay… I presented results there for one of my experiments. And the other one of my two experiments was one of the two experiments that announced the discovery of a new particle in the search for the Higgs boson.

It was when the conference started on July 4, and that was also when they had the famous press conference at CERN. And it was streamed into the auditorium there in Melbourne, [Australia]. So after we had registered there — it was a huge auditorium, I think there were some 700 plus people there or so — it was pretty exciting because we didn’t know exactly what would be presented. Being a member of the ATLAS, [the A Toroidal LHC Apparatus,] collaboration, I knew what our results were [laughter] but I did of course not know what the end results of the CMS, [the Compact Muon Solenoid,] collaboration were. We had a little bit of an idea because last year in December, the results based on the 2011 data were made public. And there was a little bit of a hint that there would be something but not enough to say conclusively, and so we were all hoping that this wouldn’t go away as a statistical fluctuation but rather be more substantial now. And indeed this was exactly what happened.

I don’t know if you’d had a chance to look a little bit into the media at what has been said, and this is quite a big thing because people have been waiting for this for more or less 40 years to happen. I’m not involved that long in high energy physics, but some people there in the auditorium were — even the person who this particle was named after was there, so he was quite excited as well. He was at CERN. Peter Higgs was from Edinburgh. And so he was there, and I’m sure being quite enjoyed that this would be announced.

What was the atmosphere like after the news conference was over? Were a lot of people jumping up and down?

Ah, well… The organizers had a welcome reception, so we had a glass of champagne, and we were discussing things. But the results… I mean, sometimes the results are not that convincing. There’s a lot of discussion if there could be a possible different interpretation of the of the data, perhaps. But this, I think that the results spoke for themselves. There’s clearly something there. It has been found in the search in the Higgs boson. But we do not yet [know] whether it is indeed the Higgs boson. One person in this talk said it could be an impostor. It looks like the Higgs boson, [laughter] but it may not be the Higgs boson.

Now, the theoretical framework that has predicted every result in the last 30 years that we have measured what we call the Standard Model of particle physics tells us everything about the Higgs boson, except the mass. It didn’t tell us how heavy it was, so we didn’t know exactly where to look. And so now that we have found it, there’s a lot of cross-examination that we can do to confirm that it is the Higgs boson. Because, if it is the Higgs boson, it will decay with a certain probability one way, and a different probability another way and yet another way. At least we can test how often it does decay this way, how often that way and so forth. It also tells us a little bit about other properties of the particle. One property is called spin — and it tells us that it shouldn’t have any spin — and this is something that we can test also. So the Higgs program has basically started with the discovery of the Higgs.

Now the big job is to convince ourselves that this new particle that we see there is indeed the one that we have been looking for the last so many decades. This is by no means clear. I mean, this gets a little bit confused sometimes. Some people say very convincingly this is the Higgs boson, but we’re not quite there yet. We have to convince ourselves that this is indeed the case. And some of the properties when people look into the future will be tested at machines and accelerators, perhaps beyond the Large Hadron Collider. But for the next decade or so, we will need to collect a lot of data to test a large number of conditions that have been met. But ultimately, there’s more that can be tested that will not be possible at the Large Hadron Collider, and we may have to look for the next type of accelerator then.

So you said that there are going to be ongoing tests? Will you be involved in any of those? What will you or Iowa State be doing for the future of this?

Right. The ATLAS and CMS experiments have a rather large program of measurements that they want to make. One part of this program is the study of the Higgs boson. The other part of this program tries to address other questions that particle physics may be able to answer. So, the Higgs boson is responsible that the elementary particles obtain mass. The other big questions, for example, if you look at the Universe — we see that stars and all the matter that we see in the universe is maybe just one-sixth of the matter that exists. The other five-sixths is called “dark matter.” What that basically means … it doesn’t interact with anything. We don’t know what it is, but there is a potential particle physics explanation. It may just be a new kind of particle that sits around in galaxies and makes them very heavy, but we cannot see them. For example, there are people in the ATLAS and CMS collaborations that try to look and see if these dark matter particles are being produced at the Large Hadron Collider and then detect them and determine their properties.

There’s another question: why is the universe made of matter at all? There’s matter, and in the laboratory we can also make something called “anti-matter.” And this [is] not science fiction stuff — we do it actually every day. And if matter and anti-matter collide, they annihilate into pure energy. And if you do it the other way around — if you have a lot of energy — you can create matter, anti-matter. For example, we would expect that even the universe is half made of matter, anti-matter. Well, there’s no anti-matter: It’s gone.

And that’s a big question of why is that happening. And my previous experiment studying that both studies are being done in a different way, but looking [and] trying to answer the same basic question in ATLAS and CMS. There’s a big problem. And yes, our group will [be] and is already involved also in the future, involved in the measurement of the properties of the Higgs boson. But we’re also looking into trying to test some of the hypotheses that have been put up that explain these other phenomenon. So we’re also trying to set up analyses which would, maybe, show signatures of dark matter particles.

There’s another area that we are involved in — with the Standard Model we can group particles, like in the periodic system of the elements, except we don’t have atoms; we have quarks and leptons. Instead of having a lot of them — [laughter] I don’t know how many there [are] in the periodic off the top of my head — but in the Standard Model of particle physics, there’s just what we call three generations. And those are the ones that we’ve seen so far. But there may be a fourth one.

So we’re looking for that as well. We’re developing techniques that not necessarily only test a specific hypothesis but look more generally at the phenomena that we can see something that sticks out. Once we see something, then we will try to interpret it and how it fits into the hypotheses that have been made or not. But basically, we’re trying to look for deviations from the Standard Model. We think there is, for example, the Standard Model itself has no explanation for dark matter. And so they’re trying to look for something that violates the predictions of the Standard Model, and once we see it, then we try to see if any of the other hypotheses have something to say about it.