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EVEN if the entrance has been spruced up, and a spanking new tram runs from its front door into the centre of Geneva, from the outside, CERN could be mistaken for any other institute of higher learning in need of a lick of paint. Yet the flags of 23 nations fluttering by the main entrance, and the buzz of activity inside, tell a different story. Straddling the border between Switzerland and France, CERN is the world’s largest particle physics laboratory, an international scientific collaboration without parallel in its scale and ambition.

Established by international convention in the aftermath of the second world war, the European Council for Nuclear Research – known now by its French acronym – was intended to foster collaborative research into fundamental physics for peaceable purposes. Today, some 12,000 researchers from across the globe use its facilities each year, and it has been the scene of seminal scientific and technological breakthroughs – notably the World Wide Web, invented within its portals in 1989 to allow particle physicists to exchange data across borders.

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CERN’s greatest scientific triumph came in 2012, with the discovery of the Higgs boson at its 27-kilometre-circumference Large Hadron Collider (LHC) particle smasher. The Higgs is the particle that gives all other fundamental particles mass. That same year, CERN was granted independent observer status at the United Nations, bestowing the right to participate in the work of the UN’s General Assembly and to attend its sessions. It is just one of the myriad responsibilities with which its boss must grapple.

Richard Webb: How difficult is it to manage the thousands of physicists at CERN?

Fabiola Gianotti: Well, I’m a physicist myself, so I feel really at home. What is very nice in this place is that it is always about teamwork. We always try to get different points of view around the table.

The LHC is shut for an upgrade until 2021, and you have a decade or so’s worth of data since it started up in 2008. Are you happy with what it has achieved so far?

Of course, we are extremely happy. The discovery of the Higgs boson was a monumental one because this particle is very special, very different from the other 16 elementary particles that we had discovered and measured before.

The Higgs is related to the most obscure and problematic sector of the standard model, the theory that describes the elementary particles and their interactions. And it is a unique tool to look for physics beyond the standard model that could help us elucidate other mysteries.

But the LHC hasn’t discovered anything new and unexpected.

The precise measurement of the Higgs boson and many other well-known particles has allowed us to make a step forward in our understanding of fundamental physics. We didn’t discover new physics, true.

This may appear disappointing, because of course discovering new particles is always very glamorous and exciting. But being able to disprove some scenarios and hypotheses is important to help us guide our explorations towards the most promising directions.

Hasn’t the no-show of new particles broken the successful model of particle physics over the past few decades: theorists propose new particles and experimentalists find them?

It hasn’t always been like that in the history of particle physics. There have been times when theory has guided experiments, and there have been times when the experiments were discovering plenty of new particles and theory was trying to make sense of them. Now, perhaps more than ever, we need to make progress on the experimental side to give some hints to theorists about the most promising direction for developing new ideas.

The likes of supersymmetry, a theory that would fill in gaps in our understanding of the universe that the standard model of physics can’t, predict a bevy of new particles, but the LHC has detected no sign of them. Does that mean these theories have ceased to be viable?

We have to be very careful about that. I consider supersymmetry a very nice theory. The fact that we haven’t found any sign of it as yet may indicate two things. One, supersymmetry is wrong. Fine. Or, supersymmetry sits at an energy scale above where we are exploring now, or alternatively manifests itself through particles that are extremely light and extremely weakly interacting.

“It is the duty and the right of humanity to understand how nature works”

Our goal is not to run behind a given theory. Theories are good benchmarks, but nature may have chosen a completely different way. We have to address the open questions – and there are many, many of them – related to the Higgs boson and its mass, the problem of dark matter, the problem of matter-antimatter asymmetry, and so on.

You mention dark matter, this vast quantity of unseen matter that cosmological observations tell us must be there. The LHC hasn’t been able to make anything that looks like a dark matter particle. So where are they hiding?

Dark matter could be either extremely light or extremely heavy. The window that we have explored so far might not be large enough, or dark matter might not have the type of interaction that would be accessible to the LHC or to a future collider. Colliders are one tool that we have to explore dark matter, but not the only one.

Is fundamental physics in a bit of a funk, trying to think too much about established theories concerning things like dark matter and not about new ideas?

I think you are correct. We have to approach our explorations with a very open mind. That’s why the LHC experiments, in particular the two general-purpose experiments, ATLAS and CMS, have been built in a way that, in principle, allows them to detect any type of new particles, whether from an established theoretical scenario like supersymmetry or extra dimensions, or something new. It’s very important to be very broad and very open.

Earlier this year, CERN published plans for the , a larger version of the LHC. What convinces you that this is the way forward for particle physics?

First of all, CERN is doing design studies and R&D for two projects. One is a , which will smash electrons against positrons coming from the opposite direction. It will allow detailed studies of the Higgs boson and provide sensitivity to new physics up to very high energy scales. The other is the Future Circular Collider, which is a ring like the Large Hadron Collider but three times bigger.

However, they are not just bigger, they also come with much more sophisticated and powerful technologies that will allow us to make a big step up in the energy and intensity of the particle beams compared with previous colliders.

What is the benefit of that?

A Future Circular Collider can collide electron-positron beams and proton-proton beams in more than one experiment. An electron-positron collider would allow detailed studies of not just the Higgs boson, but other known particles. A proton-proton collider would allow the production and observation of heavy, new particles.

Some theoretical models suggest that there aren’t any more particles at the energy scales we can realistically reach with a collider. Wouldn’t it be a big gamble to build these things?

What is the goal of particle physics, and in particular of colliders? Is it to discover new particles, or to make a step forward in our understanding of fundamental physics? The LEP [Large Electron-Positron] Collider, which was the predecessor of the Large Hadron Collider, didn’t discover a single particle, and yet there are few projects in the history of particle physics that have progressed our understanding of fundamental interactions so much.

The goal of any scientific exploration is to make progress in our understanding of nature. Discovering a new particle is one way, but very precise measurement of known particles is as important, as is ruling out ideas that are unfounded.

What would you say to people who say it isn’t worth spending that amount of money on particle physics, that it should go on something like mitigating climate change?

Obviously, we should also be spending money on mitigating climate change. But one doesn’t exclude the other. I think it is the duty and the right of humanity to understand how nature works, how the universe evolved, and how it will evolve in the future. Pushing back the limits of knowledge is one of our aspirations and obligations.

Apart from that, science in general, and particle physics in particular, is a driver of innovation, because our goals are often so ambitious that they require the development of new technologies. From CERN alone, the spin-offs are huge: the World Wide Web, medical applications and many others.

And there is also another important role of science nowadays: to foster collaboration across borders and all over the world. In a fractured world with many forces pulling it apart rather than together, science is still an example of what humanity can do when we use our cultural diversity to work together and do something good.

Can that sort of ideal prosper in this fractious period in international relations?

I think science carries a good message of peace and of collaboration at a very delicate time. Perhaps even more than the arts, it brings together people from all over the world, because it is based on facts, and not on opinions. The laws of nature are the same here as in the UK, in the US, in China, so nobody can argue about them.

Science is a very strong glue that unites people of all cultures, traditions, passports, religions and political beliefs. We have scientists sitting around tables here at CERN whose countries will not sit around the table for political discussions. That is a very important message.

You mention the power of science to bring people together, but last year CERN was in the headlines for the wrong reasons when theorist Alessandro Strumia made disparaging comments about women in physics at a CERN seminar. Did that set your mission back?

That was an opportunity for us to re-emphasise the importance of diversity in all its facets. That isn’t just gender diversity, but diversity in terms of ethnicity, culture and so on. Diversity means giving everyone the same opportunities, and unfortunately in our work this is not true. We still have a gender gap, but also gaps between developed countries and developing countries, the rich and the poor. We live in a world where technology is expanding at a very fast pace and that brings the risk of exacerbating differences and inequalities.

What can a place like CERN do about that?

We can continue to promote, support and expand open science. What we do, what we publish, what we develop is open to everybody. In 1993 we made the web available for everyone to use and develop royalty-free, and that is still true today. We develop open-source software and hardware. We publish our results in open-access journals available to everyone, for free. Our data, once they are understood and well-calibrated, are available to everyone.

The other important component is education, training available to everybody and reaching out to countries that aren’t at the forefront of science and technology. We have many initiatives, for instance, a summer programme including students from less privileged countries. So we try in our little corner to do something good for the world.

What achievement are you most proud of, both personally and for CERN?

From the point of view of my scientific career, I had the fortune to be involved in the Large Hadron Collider project right from the beginning, developing the detector and analysis techniques for the ATLAS experiment and then being on the forefront at the time the Higgs boson was discovered. That was clearly a great satisfaction. I’ve been lucky enough to grow in this lab, and I am very grateful for what I got, not only as a physicist but also as a human being. It has helped me develop as an open and tolerant person. I think the atmosphere of this place is very special. There are a few places like it, but not so many. We should cherish them, because the world definitely and desperately needs them.