Boson breakthrough

Researchers at the European Organization for Nuclear Research (CERN) have been hunting the elusive Higgs boson - using the world's largest particle accelerator, the Large Hadron Collider, for only three years. But the concept of the Higgs boson was formed as long ago as 1964 to solve an important problem in theoretical physics. It is thought to be part of a mechanism that gives fundamental particles mass - and without it, we might not even exist. But the problem has been finding it and proving its own existence.

CERN say they have come a significant step further.

At a press conference in Geneva on Wednesday, CERN's director general, Rolf-Dieter Heuer, said "As a layman I would say, I think we have it! You agree?" And all the scientists and reporters in the room broke out into cheers of congratulations.

"We have a discovery - we should state it. We have a discovery. We have observed a new particle consistent with a Higgs boson…," he continued.

But which one?

"That remains open. This is an historic day, but we are only at the beginning," said Heuer.

DW spoke to Professor Rolf-Dieter Heuer for more about the discovery and to find out what happens now.

DW: In terms of a lifetime as a particle physicist, what does this mean for you? How momentous is this day for you and your colleagues?

Rolf-Dieter Heuer: I'm not sure I've realized how momentous it is because we are pretty busy at the moment but I don't think there can be a much better moment in the life of a director general of such a fantastic laboratory with such excellent experiments… to be able to say that we have made the discovery of a new particle - a completely new particle - which is most probably very different from all the other particles. It's nearly a once in a lifetime experience I would say.

You say that you've found a new particle, and it's a boson, but what kind of boson? You've been very careful about that distinction - that this is not necessarily the Higgs boson, but that it could be.

Yes. The problem is that once you've made a discovery then you've done - well, it sounds strange and it's not quite true - but then you've done the easiest part, so to speak. Now, what comes is detailed work on finding out which properties the particle has. And only when we have pinned down the properties of this particle, then we can say it's the Higgs boson of the Standard Model. I'm pretty convinced it is a Higgs boson, but if there is, for example, super-symmetry realized in nature, then there is not only one Higgs boson, but at the minimum at least five. So, there can be many more Higgs bosons.

You just mentioned the Standard Model - perhaps you could explain the difference between a Standard Model Higgs and a different Higgs boson?

The Standard Model Higgs boson: up to today, we knew all its properties because they are predicted by the Standard Model - except whether it exists. That was the only thing we didn't know. That means, which mass it has. That's the only thing which was not given by the Standard Model.

The Standard Model, though, is this idea of the relationship of almost everything - is that correct?

No, no, only four to five percent. It only describes the visible universe. The Standard Model is, so to speak, the Period System of the microcosm. That means you have three families of two quarks and two leptons each - so, 12 particles - always including the anti-particles, plus the fourth particles, the matter particles, and in addition to fourth particles for the electromagnetic force, for the weak force and for the strong force - only gravity is outside. And this is all that you need for the Standard Model and to describe the visible world. The only problem with the Standard Model was that we did not yet have the mechanism with which these fundamental particles get their mass. And the key to that is the Higgs boson.

And at the press conference, you described this in terms of a cluster of journalists. I wonder whether you could repeat that because it was very neat!

Well, first of all, if a certain particle has a certain energy, then it moves with a certain velocity. So, the heavier the particle with the same energy, the slower it moves. This means that a particle with a zero mass moves at the speed of light and all other particles move slower the heavier they are. Now, suppose you have a party of journalists and they are all equally distributed in the room, and then somebody comes in, whom they don't know, and that person can move through the room with the velocity of light - mass zero. But now somebody comes in, whom the journalists know. They immediately - some of them - cluster around that person and through the interaction between the journalists and the person, the person slows down, and therefore the person acquires mass. And if the person is even better known to the journalists, they acquire even more mass. So, the better known to the journalists, the heavier the particle. This is exactly the Higgs mechanism.

There was a lot of talk at the press conference about putting this into laymen's terms - term that we normal people can understand. What does that tell you about what you're doing and the understanding of your work?

It tells me that we still have to work on ourselves - on the way that we are able to explain what we are doing. If you work at the very forefront of science, then you're working with things which are difficult to understand by the general public - after all, it took us years to get to such a level that we can do such research. But it tells me that the public is interested - I saw that today and I always see that in my outreach talks. But I realize that we have to work on ourselves to break down what we are doing into a language which is easier to understand without losing the charm of our science.

But is it really an issue of the science or is it an issue of this really being quite inconceivable for people as they go about their daily lives?

I think both things go together because, as I said, forefront science, basic science, is always difficult to understand for the layman. If you look out into the night sky, you see all the stars and the galaxies, you see the Milky Way, and you say, Wow, this is fantastic! You see all these pictures but you don't understand it, you cannot imagine what the distances are - already here the human imagination, not the knowledge, but the imagination fails. And you need some imagination to try to visualize for yourself what happened in the early universe. So, I think it's both. It's a science that is upfront, very far away, and science is difficult if you express it in equations. One has to learn to express it without equations - like with the Higgs mechanism and the cluster of journalists. We need more examples like this so that people can say, Oh, wow, that's not so difficult to understand from a logical point of view. You can express the logic without equations.

One of the other tools that has been used is this idea of the God Particle. Is it fair to say that the Higgs boson is the key to a lot?

As far as we know, the Higgs boson is the key to a lot - that's correct. Still, the word God Particle goes a bit too far! But it helped a lot in triggering fascination.

It also veers into the realms of this debate between the sciences and the religions - the idea of the God Particle - it's quite confrontational for a lot of people.

It's quite confrontational for a lot of people but it's quite an interesting boundary because this boundary is moving year by year. When people find new results in research the boundary moves and it's always moving in one direction. So, I think what we need is more dialogue between philosophers, scientists like physicists, and theologians to define a common language and then try to understand each other better.

You've said that the work really begins now and that what's exciting is what comes now - the future of your discoveries. But we also know that the Large Hadron Collider is shutting down for two years for maintenance. It will be back online in 2015. That doesn't mean that the work is on hold now, does it?

Oh, no, by now means - these guys are intelligent! At the moment, they're taking more data than they can look at this year. So, they're storing data in addition to that which they are looking at. And they will look at this [extra] data next year when we are not running. You also have to do all the refined analysis - you can't do that within a few months, you need quite some time for that, so there's a lot of analysis work that still has to go on next year and in 2014. And there's a lot of work to do on the experiments - so, it's not just the accelerator [the LHC] that's being maintained and refurbished, it's also the experiments.

Interview: Zulfikar Abbany
Editor: Michael Lawton