An Italian particle physicist, Fabiola Gianotti, 58, has been the director general of Cern since January 2016. Previously she led a collaboration of around 3,000 physicists from 38 countries which co-discovered the Higgs boson in 2012. Last month Cern published plans for a €20bn successor to the Large Hadron Collider.
What’s up with the Large Hadron Collider (LHC)?
The LHC is in shutdown because we are going to upgrade the accelerator complex. We’ll upgrade the injectors and the experiments and resume taking data in 2021 with higher intensity beams. We’ll run for three more years and then shut down again until 2026 to upgrade the LHC for the high-luminosity phase. Higher luminosity means more collisions. We can study fundamental particles in much more detail. We’ll be producing about 15m Higgs bosons per year.
When the LHC switched on, physicists talked of finding the Higgs boson, dark matter and even extra dimensions. Are you disappointed not to have found more than the Higgs?
Yes and no. Yes, because discovering new particles is fantastic. It’s very glamorous and fascinating and it means we have found new physics. No, in the sense that we know the open questions are difficult. It’s not obvious that we’ll find the answers with one collider. Research requires a lot of patience. And physics is not just about discoveries. The discoveries are the most glamorous part of it, but extremely precise measurements of known phenomena, ruling out scenarios for physics beyond the Standard Model, or a given theory, are important too. The discoveries make the front pages of the newspapers while precise measurements of a known particle don’t, but scientifically they are just as important.
A theory called supersymmetry predicts the existence of partners for the particles we know already. It would explain why the Higgs is light, and perhaps even tell us what makes up dark matter. The LHC has found no sign of it. Is supersymmetry dead?
I don’t know. Maybe supersymmetry exists but we haven’t seen it because we don’t have enough data, or it’s at an energy the LHC cannot reach, or at an energy no collider on Earth will ever reach. Or it’s the wrong theory. I can’t tell you. But, for me, it is important not to run behind a particular theory. We don’t know what answer nature has for the open questions. We don’t know if supersymmetry is the answer to the dark matter question or if it’s something else. If the answer is supersymmetry, then supersymmetric particles will show up either in the LHC, or in the next machine, or in some other way.
You led the collaboration that announced the discovery of the Higgs boson on 4 July 2012. What was that like?
It was the most exciting time of my scientific life. There is nothing more rewarding for a research physicist than to discover a new particle. And it’s a very special one. The Higgs boson was the missing component of the Standard Model. But getting to the discovery was a really a long path. It required the effort of thousands of physicists and engineers to conceive and then build the LHC and detectors, which are marvels of technology. When we realised what technologies we needed, it really looked like mission impossible. But in the end, we managed to build a fantastic machine with fantastic experiments. The performance is beyond our most optimistic expectations. It has been hard work, it has been teamwork and it was a fantastic discovery. All these elements together made it special for me.
It must have been an extremely intense time.
In the month leading up to the discovery we were working nights and days. The buildings at Cern where [we were working] were fully populated at night with people having pizzas at 3am. We had to go through thousands of checks, cross-checks and verifications. It was a very good lesson for the young people on how you get there, how much effort is behind it, how careful, how serious and how rigorous you have to be before you go public with a discovery.
Last year, Cern suspended an Italian physicist, Alessandro Strumia of Pisa University, for comments he made at a workshop on gender and high-energy physics. He claimed that men, not women, are discriminated against and that he was passed over for a job that a woman in the audience got, despite him having more citations.
He was suspended from Cern not for his ideas, because there is freedom of expression at Cern, but for publicly attacking colleagues in the audience. You don’t use a seminar, where you are invited to talk and to express your ideas, in front of an audience of young people, to launch personal attacks on your colleagues. This is a violation of our code of conduct that, as a first principle, is based on respect.
Have you faced discrimination in your career?
I never felt discriminated against, but some of my female colleagues were not so lucky. I don’t think I had to go through more difficult choices, more difficult steps, in my career because I am a woman. At least, I didn’t realise it if I did. I felt I had the same opportunities as my male colleagues. But again, I know female colleagues and friends who were not so lucky and did not have the same opportunities as men. There is still a lot to be done. We have to do a lot not only for gender diversity, but for diversity in general. Diversity is an asset of humanity, it’s our richness, and we have to use it in the best possible way.
Last summer, your name came up as one of five women in the running to be Italy’s transitional prime minister. Are you tempted to go into politics?
No. I can tell you that the newspaper headlines came as a surprise to me. I was not contacted about it. I am a scientist, I like doing physics. What I like about my job as director general, and it’s a fantastic job, is that I still have time to do scientific work. I cannot run an analysis or develop a detector prototype as I used to, but I can contribute to strategic planning, follow Cern’s projects, and participate in technical and scientific discussions.
Last month Cern published designs for a €20bn Future Circular Collider that would be four times the size of the LHC. How do you justify such a machine?
The Future Circular Collider is not an approved project. Every six to seven years, European particle physicists get together to develop a roadmap for the future of the discipline. This time, there are two projects on the table for a post-LHC. The Compact Linear Collider, or Clic, is a 50km-long electron-positron collider that would start at 380GeV [giga electron volts] and ultimately reach 5TeV [tera electron volts]. The Future Circular Collider will be a ring of about 100km: it can provide electron-positron, proton-proton and ion collisions. Both will be discussed by the physicists. These are not projects that are built and operated in a couple of years. They are expensive, but the cost is spread over decades as it was with the LHC.
But what are they for?
It’s important to underline that we need to make progress in our understanding of fundamental physics. The fact that 95% of the universe is dark, is unknown to us, is a major embarrassment for scientists today. But it’s also very exciting: it means there are many, many new things to discover. Dark matter is a question mark. Nobody knows if it is very light or very heavy and there is no unique instrument to find it. Nobody knows if it will be found by cosmic surveys, or underground detectors looking for dark matter particles from the intergalactic halo, or colliders. We have to attack the problem from different sides. It is very important to develop the technology to reach the highest possible energy and build a financially feasible machine.
We should not underestimate that fundamental physics, not only in our field, is so ambitious in its goals that it is a driver of innovation. It requires development, construction and operation of instruments that require cutting-edge technologies, which benefit everybody. Not to mention the impact of educating and training thousands of scientists, most of whom go into society in other walks of life.
With so much of the universe unknown to us, is there still a place for God?
Science and religion are two separate endeavours. I’m an experimental physicist. My approach is based on what I see and what I measure.
Other countries want to build huge colliders. Why is it important for Cern to have another machine after the LHC?
A post-LHC will be a very important tool. It has a strong scientific motivation and will present extremely demanding and difficult challenges in terms of technology. That it’s a scientifically and technologically valuable project is demonstrated by the fact that other countries, other regions in the world, are discussing similar colliders. Japan is discussing the possibility of building a linear collider. China is considering a 100km circular collider. This really speaks to the importance of the project. With Cern, Europe has regained leadership in fundamental physics at the energy frontier and also in the advanced technologies that are needed to do these experiments. For me, it would be a real pity if that leadership were to go elsewhere in the world.