Q&A: Dr. Jay Dittmann

Let’s start at the beginning. What is a high-energy particle collider, and what is its purpose? 

A particle collider is a tool used by scientists to study the fundamental properties of nature. The Large Hadron Collider (LHC) at CERN accelerates protons in opposite directions around an enormous ring to create collisions we can observe and study. Through these collisions, we learn about the forces that cause various types of subatomic particles to interact. 

So, you’re basically looking for things which happen as a result of those collisions you hadn’t seen before?

Correct. We already have theories that predict what takes place when you collide protons together. With a particle collider, we produce billions of collisions, analyze data from them, and then compare the result to what the theories predict.

How has it compared so far?

By and large, there has been spectacular agreement between the theoretical predictions and our measurements. But sometimes there are minor differences, and that usually is a sign that there’s some aspect of the theory that isn’t quite right, or that the theory is incomplete in some way.  

Are there other things that the collision of subatomic particles can tell you?

Yes. Sometimes we see evidence that these collisions produce particles we have never observed before. Often, this search for new particles could lead to a whole new understanding of some aspect of nature. For example, at Baylor, our drive for many years has been the search for supersymmetry. 

Just what is supersymmetry?

According to our current understanding of the universe, there is a set of particles that are the building blocks for everything. Basically, supersymmetry says that every one of those particles has a partner. These partners are particles we have not yet seen any evidence of, but if the number of particles were doubled according to supersymmetry, then mathematically, there would be some wonderful properties that kick in which would explain certain mysteries about the universe.

What kind of mysteries?

One mystery is the origin of something called “dark matter.” It seems as though there’s some invisible matter in the universe that we can’t see, but no one quite understands what it is. If supersymmetry does exist, it could provide an explanation for this dark matter, and that would tie back in with the origins of the universe.

So, the focus of the research done by you and your colleagues here at Baylor has been to look for evidence of supersymmetry?

Yes, and it’s been going very well. Our group has been involved in several data analyses in which we have searched for evidence of supersymmetry in different forms. Of course, it would be huge if we actually did discover clear evidence of it, but even without extraordinary results, each new study we make advances the tools we use, so we apply our expertise to the next new cycle of data that we collect.

How large do particle colliders have to be to create the kinds of collisions and data that can help you figure out things such as supersymmetry?

Over time, particle colliders have grown because a larger size gives us more energy in the collisions. The LHC has the highest energy of any collider in the world, and it also happens to be the largest. It’s roughly circular in shape and around 27 kilometers (about 17 miles) in circumference. The higher the collision energy, the better the chance for a new discovery like supersymmetry.

Can you see a particle collider from above ground?

No. If you looked at an aerial view of the city of Geneva, Switzerland, with all the mountains and lakes in the area, you wouldn’t see any evidence of it. The CERN particle collider is underground, passing directly underneath buildings and farms and roads. The place where I live is actually in the middle of the circular ring.

Is the CERN collider similar to the particle collider they began building around Waxahachie (north of Waco) years ago, but then discontinued?

Yes, it is. That project would have been the highest energy collider of its time, but it was canceled, and the Large Hadron Collider at CERN became the one with the highest energy instead.

How long have you been living in Geneva and working at CERN?

In 2015 I became the deputy manager of the Hadron Calorimeter Project, which is one part of the Compact Muon Solenoid (CMS) detector here at CERN. When I became the manager of that project in January 2020, I moved to Geneva full time, thanks to a research leave given to me by Baylor. Within two months, however, everything in the world changed. My expectation was that I would be primarily living in Geneva, and traveling back to Waco every three months or so for visits. But because of COVID, I will have been at CERN for a year and a half, returning to Baylor just before the start of the Fall 2021 semester.

Let’s back up for a minute. How did Baylor become involved with the CERN particle collider?

Eleven years ago, we were not involved with CERN at all. There are certain procedures that any new university group must follow in order to join the CMS collaboration, one of them being that there must be at least two faculty researchers joining the experiment from each university. For years I was the only person at Baylor doing experimental high-energy physics research, but when Dr. Ken Hatakeyama joined the physics faculty in 2009, we could finally apply. We did, and in 2010 the CMS collaboration accepted our application and Baylor became a collaborating university. Today we’re among about 200 collaborating institutions, including universities here in Texas such as Texas A&M, Rice and Texas Tech. 

What part of the CERN collider has the Baylor team been working on?

Baylor’s involvement on the CMS experiment at CERN has increased substantially, and we contribute in a number of different areas. One main area of involvement is the Hadron Calorimeter Project.

What exactly is the Hadron Calorimeter, and what part does it play in the overall operation of the CMS detector?

The Hadron Calorimeter is one of the main systems of CMS, and its purpose is to measure the energy of individual particles called hadrons, which emerge from the proton collisions. It’s hard to think of the calorimeter as a single piece of laboratory apparatus, because the entire detector is something like five stories tall, and the calorimeter has pieces that are spread out throughout the entire structure. To give you an idea of its size, imagine that you walked into the huge Baylor Sciences Building atrium –– the detector would entirely fill up the space, all the way up to the ceiling. The Baylor team has built and installed parts of this huge apparatus, and part of my job here is leading the effort to make sure the Hadron Calorimeter operates properly and is prepared to take data when we resume particle collisions at CERN in February 2022.

Are you and Dr. Hatakeyama still the only ones working on high-energy physics research and involved with CERN at Baylor?

Since Baylor became affiliated with CMS, we have hired a third faculty member, Dr. Andrew Brinkerhoff. He started at Baylor a couple of years ago and brings expertise that complements the activities that Ken and I were already working on. That has allowed us to push into new areas of study. At the moment, we also have several postdoctoral researchers, as well as a number of graduate students — typically about six PhD students at a time, at different stages of their research programs.  

How exactly are Baylor graduate students involved in all this research?

We try to offer our students the best possible physics experience by having them spend time at the CERN laboratory, testing and installing significant portions of the experimental apparatus. Previously, our work was focused at Fermilab, which is a high-energy physics laboratory located near Chicago. From about 2003 to 2010, I would send graduate students to live there for a period of time. Since 2010, our graduate students have gone to CERN from a few months to a year. 

What about undergraduate physics students? Are they involved in any way?

Definitely. Altogether, we have had six undergraduate physics students spend their summers at CERN, participating in beam tests of new detector electronics. Working at CERN is an awesome experience that we’ve been able to share.

Are you and your two colleagues taking what things you’re learning at CERN and bringing that into the classes you teach at Baylor?

Yes, we definitely are. All three of us have taught introductory physics courses, and even though the subject matter of those courses tends to be rather general, it’s possible to bring in a lot of examples from our research at CERN. Students are always very interested to hear about these huge particle colliders and detectors. We also have a senior-level course called Nuclear and Particle Physics, in which we cover this exciting area of physics in much more detail.

Are there any practical, immediate applications to some of the discoveries being made by you and your fellow physicists?

High-energy physics is an area of basic science. Many times the results are very specialized. But sometimes, what we learn is then taken up by engineers and put to a more practical use. For example, when certain fundamental particles were discovered in the 1900s, no one understood that they could be used for medical imaging, but then those techniques advanced. Our large particle detectors share technology with the devices used to perform CT and MRI scans. 

Any other examples?

There are similar practical applications that probably aren’t fully realized yet. For example, high-energy physics leads the way in data science where many of our analyses rely on cutting edge, machine learning applications. That’s one area where, of course, Baylor is committed to investing resources. Our physics team is also making innovative use of certain new forms of technology, such as using graphical processing units for scientific computation. As you might know, the World Wide Web was born at CERN because scientists realized, “Hey, we need a better way to communicate with one another.”

Those are some wonderful byproducts of physics research.

It’s like that. The science itself can lead to interesting and useful technology, but that can take decades. However, in the process of doing science, we often will find a need for certain tools that don’t exist yet –– so we just invent them. Physicists will be the first to use them, and then the applications will spread more broadly.

You of course are very familiar with Baylor’s current efforts to elevate its research profile. Is Baylor’s involvement in this international program at CERN helping us in the eyes of the research community in the United States and the world?

Our area of physics — high-energy physics — is very collaborative in nature. In order to do this kind of physics at all, you need huge, complicated devices that require a team effort among many universities across the world. By being involved in this area of physics, Baylor has formed a network of colleagues throughout the United States and the world whom we know well and work closely with. My colleagues and I know faculty members in physics departments across the country, and that makes it very useful to exchange students between schools. For example, our undergraduate students will go on to graduate programs at these other universities, and vice versa.

So, this has been a win-win all around, it seems.

I think the main point is that over the past 10 years, Baylor has built a strong reputation in this community of worldwide scholars. This has been great for Baylor as we strive to obtain research grant funding. The nature of this type of science also yields many scientific publications from our collaboration with other universities. All of this helps Baylor as we aim to achieve Tier 1 status. It is a great pleasure for us to share this research with our students and train a new generation of scientists.