CERN Director on Finding Higgs: 'The Real Work Has only Just Begun'

In a SPIEGEL interview, physicist Rolf-Dieter Heuer, general director of the particle physics research center at CERN near Geneva, discusses the remaining unsolved mysteries in his field following the spectacular discovery of the Higgs boson.

Traces of proton-proton collisions measured by the European Organization for Nuclear Research in the search for Higgs boson. Zoom

Traces of proton-proton collisions measured by the European Organization for Nuclear Research in the search for Higgs boson.

SPIEGEL: Mr. Heuer, now that the Higgs boson has finally been discovered at CERN, are there plans to shut down the particle accelerator?

Heuer: By no means. We have achieved a breakthrough, but the real work has only just begun. We need to measure our find, observe its interaction with other particles and also determine its properties. And if, when doing that, we find something that contradicts our theory, then that will automatically open the door to a new type of physics. After all, our so-called Standard Model only describes 4 to 5 percent of our universe.

SPIEGEL: And the rest?

Heuer: About one-fourth is made up of dark matter. It's what keeps the rotating galaxies from simply flying apart. That cannot be explained with visible matter alone. What we call dark energy accounts for the almost three-fourths that remain. It causes the universe to expand at an ever faster rate. But we still don't understand the mechanism which expands space equally in all directions.

SPIEGEL: Could the Higgs provide new clues?

Heuer: The Higgs field, which is part of the particle, has a decisive characteristic that fits with dark energy: It works in all directions simultaneously.

SPIEGEL: So Higgs could be the bridgehead to the unknown?

Heuer: Precisely. We don't know if it has anything to do with dark energy. But we suspect that there is a similar field beyond the Standard Model -- the other end of the bridgehead, so to speak.

SPIEGEL: And what if Higgs doesn't do you the favor of revealing such secrets?

Heuer: We will still have found a particle that helps provide all other particles with mass. It finally proves that our Standard Model is completely accurate. What we must do now is find the hole in this model through which we can advance to the remaining 95 percent of the universe. We still don't know what role the particle we have found plays. It's like catching sight of your best friend from a distance. At first it could also be someone who looks a lot like that person, but it turns out to be someone totally different. You only find out for sure when you get closer.

SPIEGEL: What do you plan to do next?

Heuer: By the end of the year, we plan to fire protons at each other. Then we will shut down the accelerator for around two years for maintenance work. When it goes back into commission, things will get exciting: Step by step we will double the energy, allowing us to create particles with ever greater mass. And it could be that by doing so, we will also exceed the threshold to dark matter. That would open new doors.

SPIEGEL: What do you hope to find?

Heuer: Primarily the first traces of supersymmetry. That's the name of the theory which holds that every particle also has a shadow particle -- a mirror world predicted by the theory of anti-matter. Supersymmetry's lightest particle could be stable enough to be within the reach of our accelerator. That would be a good candidate for dark matter. If we find it, it would represent a massive leap forward.

SPIEGEL: Do you know exactly where you need to search? Or do you just look randomly?

Heuer: Both. We have to be entirely open to unexpected findings. Still, with supersymmetry, we already have a direction and our search is targeted. But it will no longer be as focused as it was with Higgs.

SPIEGEL: When searching for Higgs, you essentially had a ready-made profile of the particle, the one published by Peter Higgs in 1964. Does he deserve the Nobel prize?

Heuer: I think so. But there are also others who were working on similar models back then …

SPIEGEL: … while the Nobel rules only allow for a maximum of three prize winners at a time.

Heuer: Yes, that needs to be changed. In many areas of research -- from particle physics to genetics -- ever larger groups of people work together because that's the only way it can work. At some point, the time will have passed when individuals are capable of major discoveries.

SPIEGEL: How many researchers were involved in the long journey towards finding Higgs?

Heuer: In the end, between three and four thousand took part in each of the two major participating experiments.

SPIEGEL: Are such large groups able to change focus and commit to new goals? Or will each researcher soon go back to doing his or her own thing?

Heuer: No, our people will surely stick with it, especially now. The ability to work together has to be in the blood of particle physicists. They learn very early on that it is impossible to advance on one's own and that constant exchange is necessary.

SPIEGEL: Doesn't an individual's achievements get lost in the crowd?

Heuer: No, it is still very easy to identify an excellent physicist. Good people climb quickly -- just like in a company.

SPIEGEL: How large can research teams be and still remain manageable?

Heuer: Fifteen years ago, I led a project with 350 people. At the time we thought that was the upper end. Now we have 10 times as many. I would say the real limits we are experiencing are in technology and in the detectors that we are capable of building.

SPIEGEL: For how much longer will you be able to continue conducting experiments with the Large Hadron Collider? At which point will it have done its duty?

Heuer: We are planning up until 2030. It may be worthwhile to upgrade the machine again during the 2020s -- for a relatively low extra investment, we would then be able to collide considerably more particles. But it depends on what we have found by that time.

SPIEGEL: And afterwards? Will you need even bigger machines?

Heuer: It's the energy, and not the size, that is decisive. The closer we want to look, the faster we have to accelerate the particles. In our case, it's the protons. A lot suggests that our next undertaking will be an accelerator that fires electrons at positrons. That would open up a new view of matter, and of the Higgs particle. There are already plans for it. The main question is which region of the world would be ready to build such a machine?

Interview conducted by Manfred Dworschak

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    Physicist Rolf-Dieter Heuer, 64, is director general of the European Organization for Nuclear Research (CERN) near Geneva. He studied physics at the University of Stuttgart and obtained his doctorate at the University of Heidelberg. He began working at CERN in 1984.

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