‘I was always interested in the structure of things’: particle physicist Çiğdem İşsever on the importance of thinking about physics early

Çiğdem İşsever is an elementary particle physicist who works with the Large Hadron Collider detector ATLAS. She tells Rob Lea about her work at CERN and the importance of early and engaging science communication

The 2012 discovery of the Higgs boson at CERN’s Large Hadron Collider (LHC) was a momentous achievement. Despite completing the so-called Standard Model of particle physics, the discovery of this particle opened up the search for physics beyond the Standard Model and the elements of nature that assist the Higgs boson in granting all other matter particles their mass. One researcher who is taking a deeper look at the Higgs boson is the experimental particle physicist Çiğdem İşsever – lead scientist in the particle physics group at Deutsches Elektronen-Synchrotron (DESY) in Hamburg, and the experimental high-energy physics group at Humboldt University of Berlin.

After obtaining her degree in physics and completing a PhD in natural sciences at the University of Dortmund in Germany by 2001, İşsever was a postdoc at DESY and at the University of California, Santa Barbara in the US. From 2004 to 2019, she was based at the University of Oxford, where from 2014 she held a professorship in elementary particle physics. She then became head of physics and from 2015 taught at Lincoln College, Oxford, before moving back to DESY in 2019.

As a member of the ATLAS collaboration at CERN since 2004, İşsever’s research has focused on how the Higgs boson defines our reality. “My main focus is to shed light, experimentally, on the so-called Higgs mechanism, which explains how elementary particles and gauge bosons acquire mass in nature,” explains İşsever.

The Higgs mechanism is a key parameter of the Higgs boson, which particle physicists are trying to experimentally constrain, to gain important insight about the shape of the so-called Higgs potential. Determining if the Higgs potential is exactly as predicted by our theories or “if nature has chosen a different shape for it influences the very physics that determines the shape of our universe and even its eventual fate,” she explains.

What lies within

İşsever was fascinated by the inner workings of nature from a very young age. “I was always interested in how things are made, or why something is the way it is,” she says. “My father is not a physicist, but when I was in the first or second year of primary school, we would talk like adults about physics. He would discuss with me how nuclear reactors split the atom and if it was possible to bring it back together.”

As a child of six or seven, İşsever recalls industriously dissecting the vegetables on her plate, to reveal their inner structure. “This might sound really weird, but I wouldn’t just eat vegetables and fruit… I would really carefully cut them open. Look where the seeds are, see how many chambers a tomato has.”

This early fascination with the natural world on small scales deeply influenced İşsever and led to her interest in science communication. Keen to inspire young minds, and help children engage with science from a early age, the ATLAScraft project was developed by İşsever together with her husband and fellow DESY physicist Steven Worm, and physicist Becky Parker, from Queen Mary University, London. The project was a collaboration between the University of Birmingham, University of Oxford, the Institute for Research in Schools and the Abingdon Science Partnership, with technical expertise from CERN.

ATLAScraft provides users a map of CERN, the ATLAS detector and the LHC; all which have been created in the hugely popular computer game Minecraft. The idea behind the project was to bring the LHC and its scientific endeavours to a whole new generation, but it was also about breaking cultural stereotypes, especially getting more women in physics.

“Children decide quite early in their life, as early as primary school, if science is for them or not,” İşsever explains. They decided to visit pupils between five and 11, and “talk to them before they buy into science-related stereotypes of the male scientist and his female assistant,” says İşsever, adding that “When we went to schools in the UK to talk about our physics, I would be the main presenter of the physics concept, and Steve would be my sidekick. This was something we did deliberately to challenge these stereotypes.” Thanks to ATLAScraft, you can now take a virtual tour of ATLAS, via a 3D interactive map complete with the buildings, beamline tunnels and the actual ATLAS detector, all within Minecraft.

Pairing up

This year İşsever will also be involved in CERN’s 70th anniversary celebrations. She sees these as further opportunities to communicate CERN’s discoveries to a wider audience. However, İşsever’s research is still her prevailing passion. She is currently excited about her work to discover Higgs “pair production” at the LHC. Experimentally detecting these pairs of Higgs bosons is a crucial step in understanding how the Higgs boson may interact with itself, as this will determine the shape of the potential of the Higgs field.

“This hasn’t yet happened. When it does, if we collect enough data, we should be able to constrain the Higgs coupling as a parameter,” says İşsever. She adds that this search could also lead to the discovery of physics beyond the Standard Model. “To me, this represents the true thrill of discovering something new, which would be amazing.”

When it comes to the future of CERN and particle physics in general, the proposed successor to the LHC – the Future Circular Collider (FCC) – is an interesting prospect. More than 90 km in diameter – three times that of the LHC – the FCC would allow for a significant upgrade in collision energies.

While she acknowledges how useful the FCC would be, İşsever believes that a less energetic electron–positron collider, could be vital as a next step. Such an instrument could lead to a deeper understanding of the Higgs boson and its associated phenomena, as well as allowing particle physicists to “infer the energy scale we should investigate with future machines,” she adds.

Looking ahead

Beyond the Higgs boson, İşsever is also involved with the Large Hadron Collider forward (LHCf) experiment, that captures and measures forward-travelling particles that escape “standard” detectors like ATLAS. LHCf could help build a better understanding of the cosmic rays that bombard the atmosphere of Earth from space.

İşsever also acknowledges the importance of non-collider experiments, even though they are unlikely to end the collider-dominated era of particle physics. “Collider experiments are much more general-purpose experiments. If you think of, for example, the ATLAS experiment, it’s not just one experiment. At any time, there are something like 200 or more analyses going on in parallel. You can think of each of them as an individual experiment. So, it is a very efficient way to perform experimental physics.”