Three VUB particle physicists were recently appointed to the physics coordination group of the Compact Muon Solenoid (CMS) detector (one of the two detectors at the Large Hadron Collider (LHC)), at CERN. One of them is Professor Freya Blekman, who will continue in her role as communication officer, coordinating the distribution of more than 100 scientific papers every year. We sat down for a chat, online of course.
Professor Blekman obtained her M.Sc and Ph.D from the University of Amsterdam, and after several posts as Research Associate in the US and the UK, she joined the VUB in 2010. She is a professor in elementary particle physics, with a focus on searches for physics beyond the standard model in the top quark[1] sector with the CMS experiment and future colliders.
COVID-19 has impacted her work to some degree as it has most of us: no travel, which is a big change as she’s normally on the road quite a lot, ‘train-ing’ to the UK (where she’s a visiting lecturer at the University of Oxford, and has strong collaboration with the University of Bristol), or to Switzerland, to CERN. Overall though, the work within the CMS experiment group is already structured through online collaborations. It has to be; there are some 3,000 people at CMS from 150 universities from across the world.
VUB: How did you end up working at CERN, working on the CMS experiment?
Freya Blekman: “I settled on studying physics two weeks before classes started. I had to choose between physics and biology. I opted for physics, wanting to do bio-physics, but during my first year we went to CERN, and I saw those big machines, and I thought: this is what I want to do. It is the reason why now, as a professor, I really want our students to visit CERN. This is the peculiarity of our work: most of our colleagues go down the corridor to their lab; we have to go to Switzerland to visit our lab, but then.. it is a truly impressive lab!”
As a Master’s student she spent 3 months at CERN, where she started working on the CMS experiment. Next, she ended up at the Fermilab (US) for her Ph.D. It was right at the time when they discovered the top quark and she specialised in this particle, about which nothing was known at the time. She’s been learning more about it ever since, focussing on searches in the top quark sector. After her Ph.D she went back to the CMS experiment at CERN.
The 4 July 2012-moment
On 4 July 2012 the world heard that the Higgs boson was discovered. A big moment in particle physics, but she does think it is a shame it was detected. Discovering the Higgs boson, which confirmed the model predicted in 1964 by Peter Higgs, François Englert (who both were awarded the Nobel Prize in Physics in 2013) and other scientists, was truly amazing, but it would’ve EVEN been more exciting if it hadn’t been found. As Stephen Hawking said at the time, physics would be far more interesting if it had not been found. In other words, physicists would have had to rethink many of the fundamental ideas about particles and forces, which is exciting."
Freya Blekman: “When new particles are discovered, your work isn’t done. You need to test them, use them and measure them. The excitement isn’t per se discovering them, but understanding them, and this is what we’re doing right now, and for that we need a lot of LHC data.”
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VUB: What has happened since that moment at CERN? What other discoveries have been made?
Freya Blekman: “In a few weeks’ time we’ll produce our 1,000th result. A lot of our results aren’t maybe as exciting for the general public. We continue our search for new particles. The problem is that before the Higgs boson was discovered, there were many different scenarios out there. The discovery of the Higgs boson narrowed these down, but there are still plenty of scenarios at play. I often say there are more scenarios than there are experimental particle physicists! Even with the Higgs boson, we know that the standard model[2] is very predictive, but it is also what we call an effective theory. I.e., it has the same status as e.g. Newtonian physics has with respect to general relativity: it describes gravity very well, but it isn’t the full picture. Similarly, we know with the standard model that eventually when you go to really high energies or really small distances or very strong forces, it will stop working. We can’t describe the extreme scenarios. It all depends on which of the extra scenarios you need to add to the standard model.”
“Supersymmetry is one of those scenarios”, Professor Blekman continues. “Most of the scenarios out there are inspired by the big questions: why is there dark matter? And is dark matter a particle? Why is the Higgs boson the way it is? Why do all the different particles have different masses? Why do the particles behave the way they do? Are there connections between the particles within the three groups? And why are there three groups of particles, and not two or five? We don’t know. We don’t have that big picture yet.”
What’s next?
VUB: Have you seen a surge in interest in particle physics because of programmes like the documentaries made by Professor Brian Cox, which bring physics closer to general audiences?
Freya Blekman: “There is definitely a Brian Cox-effect! The science is very exciting and very diverse. It’s challenging, and people don’t per se anticipate this. In our work, we see a shortage of people with a STEM background. At CERN, we train people with different skill sets to interpret data, build detectors, analyse data. CERN is also very aware of their role in society – its training centre is there for people working in AI, network and internet engineering, detection and camera technology, data processing, project management. People who work at CERN have a very diverse skill set.
VUB: What’s next for the LHC, because it was closed down in 2018?
Freya Blekman: “It was closed in December 2018 for big maintenance works, yes, and is now slated to reopen in May or June 2021. We’re actually prepping for the next major upgrade in 2025-2027. Part of the components that are to be used then are being built in Brussels as we speak.
VUB: What’s next for you now?
Freya Blekman: “In 2 weeks’ time our 1,000th paper comes out. And I’m also chairing the course council for physics and astronomy to ensure our students still get their classes, etc. That will keep me busy. I’m working on future colliders. I’d really like Belgium to get its foot in the door. There’s an EU strategy due, but it’s important that Belgium is involved, especially the VUB where we are the lead in this kind of physics. I’m leading the work on the Future Circular Collider, but more students and post-docs should be involved. Funding is the problem though. It’s highly competitive. It’s also difficult to explain that you need to work now on an accelerator that will only be there in 2040, but if you don’t start now, there won’t be one!”
Two days after we spoke with Professor Blekman, CERN announced its updated strategy for the future of particle physics in Europe. It says, “The highest scientific priorities identified in this update are the study of the Higgs boson… and the exploration of the high-energy frontier.” The press release continues to say that the updated strategy “highlights the need to pursue an electron-positron collider acting as a “Higgs factory” at the highest priority facility after the LHC.” It’s clear there is a lot to look forward to in the near and long-term future!
[1] The top quark is a unique particle due to its phenomenally high mass. It is the heaviest of the known elementary particles. The top quark is the sixth and last one to be discovered in 1995 at the Tevatron accelerator at the Fermilab.
[2] The standard model in particle physics is the theory describing three of the four known fundamental forces in the universe, as well as classifying all known elementary particles. It is seen as a theoretically self-consistent model that has shown huge success in providing experimental predictions, but some phenomena are still left unexplained.