CERN: Not just particle physics, an 'incubator' for specialists

As part of the recent 70th-anniversary of CERN and close collaboration with the Institute of Particle and Nuclear Physics at Charles University, we spoke to Czech experimental particle physicist Martin Rybář, who works on the ATLAS experiment at CERN and is an active science communicator. The skilled researcher popularises science at events like Colours of Ostrava.

“If CERN wants to remain at the cutting edge... building a new advanced particle accelerator is essential. But it’s not just about catering to a niche group of scientists searching for dark matter. Its construction will drive technological advancements with significant societal impact,” Martin Rybář says.

You’ve just returned from CERN after almost three weeks. What were you doing there?

My summer stay at CERN was a bit unusual this time because it wasn’t directly related to my research. Instead, I was on shift duty, which is mandatory for every country or institution with scientists working at CERN. Everyone at CERN works on their own research but is also required to contribute to the general upkeep. In my case, I was ensuring that the detector our research group works on remained operational. We’re also involved in updating the software that processes and prepares the accelerator's data for analysis.

So, in addition to working with your research data, you take turns with your colleagues to help maintain the equipment essential to your experiments?

Exactly. Without that agreement or approach, things wouldn’t work. Otherwise, everyone would want to focus solely on physics, and nobody would handle the operations. During my last stay, I was responsible for the trigger system, which selects which collisions to store and which to discard. Out of nearly a billion collisions per second, only a few thousand can be saved. The various subsystems of the detector are monitored from a control room full of screens, much like a NASA command centre. Most of the time, PhD students with limited system knowledge staff this room. When something unusual happens, they call the experts – in this case, me. I was constantly on call to help solve problems and ensure the detector subsystems functioned correctly.

The control room at CERN, where Martin Rybář worked required shifts during the summer. Spot the rubber ducky!

That sounds hectic.

It can be, but it’s also fun. It’s a change of environment, switching to shift work, and I learn new things constantly because I have to communicate with others to solve problems as they arise. It’s quite different from analysing data.

Now that you're back in the Czech Republic, how much does your work at CERN influence your research at The Faculty of Mathematics and Physics?

I’m an experimental particle physicist, so I investigate what the universe is made of at the most fundamental level. To do this, I rely on experiments. I’m fortunate to be part of the ATLAS collaboration, one of the large detectors at CERN’s LHC (Large Hadron Collider), the world’s most powerful particle accelerator. I’ve been involved with this project since my master’s thesis.

How should we understand the LHC?

Imagine a subway tunnel with a 27-kilometre circumference, located about 100 metres underground between the Jura Mountains in France and Lake Geneva in Switzerland. Ninety per cent of the time, we accelerate protons at the LHC, causing them to collide at four specific points. From the energy of these collisions, we can create new particles.

Once a year, though, the LHC switches to accelerating lead nuclei, which is when I head to CERN.

You work with lead nuclei?

Right. My colleagues and I study collisions of lead nuclei to create quark-gluon plasma, a material 100,000 times hotter than the Sun’s core. We believe this state of matter existed in the first microseconds after the universe’s formation. These collisions are essentially miniature big bangs, and our research has cosmological implications.

When will the LHC switch to lead nuclei again?

It always happens in the autumn, so I’ll be heading back to CERN shortly for these measurements.

"It's not high-tech or Silicon Valley," laughs the physicist who has been working at CERN since his doctoral studies.

What’s CERN like?

Imagine it as a large industrial site. The LHC has a 27-kilometre circumference and sits 100 metres underground, so the area above is much larger than the fenced-off section with office buildings and development halls. The buildings themselves still look like they did when they were built in the mid-20th century. The focus at CERN is on science, not high-tech office spaces.

Why is the LHC underground?

That’s a question I often put to students during my talks. People usually think it’s to keep the accelerator away from civilisation or to shield it from cosmic rays, but neither is true. In Switzerland, it’s simply cheaper to dig a tunnel than to buy land on the surface.

Could CERN be considered the European equivalent of Silicon Valley?

Not at all (laughs)! Most of CERN’s funding, which comes from member countries, goes into scientific projects, the construction of accelerators, and infrastructure. The office buildings remain basic, and many halls are dedicated to testing magnets and detectors. During the recent energy crisis caused by the war in Ukraine, CERN saved so much electricity that it even turned off the lights in the offices. After all, running the LHC requires enormous energy, which is supplied by French nuclear power stations. So, CERN tried to conserve wherever possible, and I found myself navigating a maze of dark corridors, feeling like I was in a computer game.

As a student, you co-authored a highly-cited paper, second only to the discovery of the Higgs boson. How did that happen?

There were very few scientists working on lead collisions at the time, so as a first-year PhD student, I had the opportunity to work on some very exciting experiments. That’s still true today – we remain a small group compared to those studying proton collisions. I collaborated with my colleague Martin Spousta and a professor from Columbia University, Brian Cole, along with his student Aaron. We focused on jet physics, and the first data we received showed something so interesting that we quickly published it. People in the ATLAS collaboration were sceptical at first, but after a thorough review, the paper was published in just two weeks – an incredibly fast turnaround for CERN standards.

Here, Forum photographed Martin Rybář not at CERN but at Kampus Hybernská in Prague. 

When did you start to engage in popular physics?

My interest in science was awakened in childhood and led me to astronomy. In Blansko, Moravia, where I come from, I had an interesting friend—my neighbour—who was a year older and was constantly exploring something new. At the age of 14, he built a telescope, and I started observing the sky with him. He soon lost interest, but I continued in his place and have mostly stuck with it ever since. During high school, I participated in a Summer Astronomy Expedition in Úpice, a kind of camp for young naturalists. Gradually, I became a leader there and also started working as a demonstrator at the Brno Observatory, where I talked to visitors about the night sky. I continued to lead the Summer Astronomy Expedition even while studying at Matfyz and began to give more and more lectures about the universe. Moreover, my supervisor was Associate Professor Jiří Dolejší, who is also very involved in popularisation and opened up opportunities for me in the field of particle physics.

Additionally, I was often pleasantly surprised by how interested my friends outside of physics and science were in what I and my classmates were doing. We thought we could organise a lecture for them, and that's how the Science to Go project was born; back then, it was called Science Goes to the Countryside. We held the pilot edition at the home of my colleague and friend David Píša. We bought a keg of beer and talked about physics… Gradually, this developed into a platform for lectures taking place at various locations across the Czech Republic, aimed at giving young scientists space to talk about what they do.

What motivates you to keep popularising science?

It energises me to engage people. It’s rewarding to spark their interest, and I believe it’s part of my job. Science is expensive, so it’s only right to explain to the public what their contributions are funding. Our field is full of extremes – accelerators are huge, powerful, and operate at extreme temperatures. People are naturally curious about them, and CERN, like NASA, holds a place in popular culture.

How do you balance public outreach with your scientific work?

It’s been a busy year. I helped develop the Big Bang Stage programme at Colours of Ostrava, mixing science and art with things like science-themed slam poetry and illustrators’ competitions. I enjoy exploring different contexts for physics – it helps me stay creative and not get lost in data analysis alone.

How important is building a new, more powerful accelerator for particle physics? Is there anything left to discover at the LHC?

If we thought nothing was left to discover, we’d shut the LHC down (laughs). The LHC has two crucial parameters – the energy of the collisions and the number of collisions. The higher the energy, the better the chance of producing exotic particles like the Higgs boson. One of the big questions in particle physics is the existence of dark matter. We know it makes up about 25% of the universe, but we don’t know what it is.

Can the LHC help us find dark matter?

Yes, we hope to create and identify these particles. The LHC will continue until 2026, then undergo upgrades to increase the number of collisions. But higher energy is needed to explore new particles, which is why we need a new accelerator. Building it will drive forward technological progress, not just in physics but across many fields.

We start from the current theory known as the Standard Model, which describes the behaviour of particles and the forces between them. However, it has its own issues. We know it is not a final theory. Various physicists are proposing ideas to extend the Standard Model, which typically leads to the assumption that there should be additional particles.

The LHC tests these theories. However, it can only verify those for which it has the technical capacity. That’s why it's important to work on the implementation of an even more powerful accelerator.

Yes. To create these new particles, you need either a greater energy from the colliding particles, which cannot be achieved at the LHC—we can no longer accelerate protons to a higher speed, and therefore to a higher energy. However, we can carry out even more collisions there.

Is this an area where the LHC can still improve?

Exactly. The more collisions we have, the more data we can obtain, which through statistical analysis allows us to determine the likelihood of a certain particle existing, such as the already discovered Higgs boson. The more data we have, the more likely we are to uncover processes that are rarer and can be observed. This is currently the goal of the LHC, whose operation is planned until 2026. After that, there will be a three-year shutdown during which all the detectors and the LHC itself will be upgraded. As a result, we should then obtain nearly an order of magnitude greater number of collisions and thus more data.

Of course, it may also happen that we discover nothing new. Because the amount of data is not everything; energy is still an extremely important condition, which is why we should build a new accelerator. If CERN wants to remain a top-tier institution and not a second-rate laboratory, it is essential to construct a new accelerator. Yes, it is expensive. But CERN currently has a budget similar to that of a medium-sized European university. If the amount needed to build a new accelerator is divided among all the countries contributing to CERN's operation, it isn't that much.

The construction of such colossal facilities is often a political matter, where the developers refer to societal demand. By popularising the topic of particle physics, you are actually preparing the conditions for their construction.

Yes. As I said: if I want the public to pay for it, I need to explain to them why they should pay and what the significance is. Another significant argument for building a new accelerator is that it can advance not only particle physics research but also many other areas of human activity. The future accelerator is designed with parameters that cannot be built today. However, because CERN needs it, it drives development in companies and technology forward.

This perspective motivates me personally to continue working. Of course, I always have some minimal chance of discovering something new. But it is much more likely that through my work, my students will learn something new. Most of those I have mentored did not become particle physicists. They moved into the private sector, where they apply their knowledge of particle physics. I have a friend who uses software derived from CERN to build robots for medical purposes. Thus, CERN serves as a kind of breeding ground for specialists in various fields. You learn to think critically, analyse data, and acquire many other skills that can be applied in areas ranging from finance to industry to medicine. So it’s not just about fulfilling the demands of a small group of eccentrics searching for dark matter. The realisation of a new accelerator has much larger technological and thus societal impacts.