Steve Mirsky: Welcome to this special Nobel Prize edition of Science Talk, the podcast of Scientific American. I’m Steve Mirsky.
Staffan Normark: This year’s prize is about something very small that makes all the difference. The Royal Swedish Academy of Sciences has decided to award the 2013 Nobel Prize in Physics to Professor Francois Englert at University Libre de Bruxelles, Belgium, and Professor Peter Higgs at University of Edinburgh, United Kingdom.
Steve Mirsky: Staffan Normark, Permanent Secretary of the Royal Swedish Academy of Sciences at a Press Conference shortly before 7:00 a.m. U.S. Eastern Time this morning.
Staffan Normark: And the Academy Citation runs for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles and which recently was confirmed through the discoery of the predicted fundamental particle by the ATLAS and CMS experiments at CERN’s Large Hadron Collider. Professor Gunnar Ingelman will now gives us a short summary in English, please.
Gunnar Ingelman: This is a triumph, not only for Englert and Professor Higgs but for theoretical physics more generally and actually the whole research field of elementary particle physics. It also illustrates the scientific method namely to formulate theories based on mathematics in attempts to understand the laws of nature and testing them against experimental measurements.
In 1964 Francois Englert, together with his now deceased colleague, Robert Brout and Peter Higgs proposed independently of each other the theory to solve the fundamental problem of how particles acquire mass. Their theory became a cornerstone of the standard model for elementary particle physics which describes all matter as being built of a few kinds of basic metaparticles, and all forces in nature as mediated by a few kinds of force particles.
However, their theory required a totally new quantum field which should be manifested by a new and special kind of particle, the Higgs particle. This particle has now, at last, been observed last year by the ATLAS and CMS collaborations or experiments at the International CERN Laboratory outside Geneva in Switzerland.
Staffan Normark: Thank you Professor Ingelman, and now I turn to Professor Olga Botner.
Gunnar Ingelman: So this brings me to the 4th of July, 2012, which is a day that marks a new era in particle physics and this is not only because Francois Englert and Peter Higgs met for the first time ever in front of the packed auditorium at CERN but mainly because their ideas on mass of the fundamental particles had just been confirmed but let us start by going 50 years back in time.
In the Autumn 1964 Englert, together with Robert Brout who is now no longer with us and Peter Higgs independently published two manuscripts explaining how certain particles can obtain mass.
So both made the contribution to explaining the origin of mass and these contributions cannot be distinguished. Now what they did is central to the so-called standard model of particle physics and let me try to explain what the standard model of particle physics is about by taking this example of a fly.
So everything around us and we ourselves flowers, trees, stars, can be described in terms of a handful of constituents of matter and the forces acting between them, and so if you now look at the fly it consists of molecules. Each molecule consists of atoms and each atom has an atomic nucleus and, orbiting around the nucleus we have electrons.
Nuclei are not fundamental particles. The protons and neutrons have in turn fundamental constituents which they believe are indivisible and they are called quarks.
Now these fundamental matter particles interact by means of forces and within quantum mechanics we believe that these forces are mediated by quantum, by particles, and so we have the electromagnetic force mediated by photons which are massless; we have the weak nuclei force mediated by massive particles which are called W and Z and we have the strong nuclear force mediated by massless gluons.
Now all is well and good except that the theory behind the standard model with like all the mediator particles and all the matter particles to be massless; however, we all know they are not massless. I mean we are not massless, so something must be there in the background to give these particle mass.
So how can the world be so diverse? What is the origin of mass? Now the problem is that to make the standard model work we need theories which are basically symmetrical but these symmetries forbid particles to have mass.
If you try to put in mass by hand into the theories the theories will collapse and the standard model no longer works. So somehow the symmetries must be broken in such a way that keeps the good properties of the theory.
Now this is where the Mexican hat comes in. Now the Mexican hat symbolizes e-symmetry. If you think in terms of a hat you see a hat in front of you and suppose you had the bag which sits on top in the center of the hat, to you all the world looks symmetric.
All directions are equivalent; however, if you slide down into the valley then the world is no longer symmetric. There’s obviously one direction in which it’s easy to move which is around the center and there are directions in which it’s difficult to move and it’s up and along the brim, and so now we have a situation which was symmetric to begin with but which is no longer symmetric.
Now this Mexican hat symbolizes – illustrates a piece of mathematics. The Brout, Englert and Higgs added into the theory to show that you could have a theory which was inherently symmetric but with a ground state, the state of the lowest energy did not display the symmetry and this is what saved the standard model.
Now the theory made a concrete prediction, namely one, there should exist a new fundamental particle and, two, all the other particles in nature; the matter particles and the quantum mediating forces should gain mass; three interactions with these particles which brings us back to the 4th of July 2012.
Appearing in front of a packed auditorium at CERN the spokespersons of the experiments ATLAS and CMS announced the observation of a new fundamental particles in proton-proton collisions at the large hadron collider which had properties consistent with the long sought-after Higgs particle, and you can imagine that the whole auditorium exploded in applause.
Now the Higgs particle cannot be seen directly. It can only be reconstructed from its decays, from traces it leaves in particles, particle detectors. So from these traces you can reconstruct the particle mass and so what we have here is the final piece in the puzzle which is the standard model.
This is of course not the final piece in the puzzle of the universe. There’s still mysteries left: we don’t know where the dark mass is, we don’t know where the dark energy is, we don’t know if Higgs is the only Higgs particle that exists or there’s more Higgs particles. So obviously there are things to do for future generations of scientists. Thank you.
Staffan Normark: Thank you, Professor Botner. We will now see if we can get hold of Professor Englert. I just talked to him a few minutes ago. Are you there with us, Professor Englert?
Francois Englert: Yes, I’m on the phone.
Staffan Normark: Good day and congratulations. How do you feel right now?
Francois Englert: Well thank you very much, I feel very well of course. Now I’m very happy.
Staffan Normark: Yes, so I’m sitting here in the session hall at the Royal Swedish Academy of Sciences and I’ll have a large group of the people from the media –
Francois Englert: Yes.
Staffan Normark: -- in the international press and are you ready to take some questions from the press, Professor Englert?
Francois Englert: Yes, please, I will try to do what I can.
Staffan Normark: Okay. I have a question there.
Question: Yes, hello, Professor Englert. My name is Maria Gunther Axelsson. I am writing for the Swedish newspaper, Dagens Nyheter. Now that the standard model is complete which in your opinion is the biggest question remaining to be solved in physics?
Francois Englert: Well there are a few big questions, right, first the question which is still not solved is whether there is some involvements of symmetry which will manifest itself as energy which will not yet be reached.
This is the critical point of what will happen but, of course, there are other problems like which some of them may be directly related; some other indirectly or maybe not related which is the problem of dark matter is probably somehow hopefully related to particle physics.
The problem of dark energy is a more tricky problem which one way or another leads us to what is in my opinion the most and the fundamental problem which is not solved today despite some progress which is a problem of quantum cavity or the quantization of cavity.
Question: Hello, congratulations. My name is Joanna Rose.
Francois Englert: Thank you, yes.
Question: I work for a Swedish popular science magazine, Forske Ramsteg, and I would like to ask you in the late 60’s when you worked on the theory –
Francois Englert: Yes.
Question: -- did you ever think about the discovery of the Higgs Boson?
Francois Englert: Oh yes but the whole thing at that time – well first the late 60’s is not really when the thing was done. It was the beginning of the 60’s and in ’64. It was published after a lot of thought. At that time we thought that we’re going to solve this way the problem of short-ray forces which was completely unsolved at that time, and which obviously is related to the problem of the original mass.
So the Boson by itself is something that is the experimental test on the existence of the whole mechanism and one had to wait, and certainly we had to wait first before the theory itself was applied to something which is a standard model which took some time.
It had – it took some time to first prove the consistency of our theory which was up to the beginning of the 70’s the standard model was being done and only after that could one look for a test because a standard model was wonderfully made, except for the missing element which was that Boson whose condensation is what gives the mass particle and the short-ray forces.
Staffan Normark: Okay, do we have another question, case?
Question: Yes, hi, congratulations, this is Marlyn from the Associated Press.
Francois Englert: Thank you.
Question: Of course this was highly-anticipated by all of us but how did you feel when you found out about the award and what are you planning to do with the prize money?
Francois Englert: Well, when the first or second question, I don’t know. My concern, no. The first part of the question was what about?
Question: Just how does it feel to have won a Nobel Prize? I mean –
Francois Englert: Well, you may imagine that it’s not – this is not very unpleasant, of course. I am very, very happy to have that recognition of this extraordinary reward and so I’m very happy of it. What can I say more?
Question: Okay, thank you.
Staffan Normark: Okay, thank you very much and thank you very much. I think this was the last question from the press here and thank you, Professor Englert and once again congratulations and we look forward to see you in Stockholm in December for the Nobel Prize ceremony, thank you.
Francois Englert: Thank you.
Staffan Normark: Bye.
Steve Mirsky: Olga Botner of the Nobel Committee for Physics then spoke with an unidentified interviewer about this year’s prize.
Unidentified: These are two scientists; Englert and Higgs who actually wrote the theory in the 60’s – 1964, so they had to wait even longer for the prize. Why so?
Gunnar Ingelman: So there’s a theory, there are a lot of theories out there. There’s a lot of theories out there but in the end it’s the interplay between experiment and theory which decides what nature has chosen as the grand scheme of things, and so it took 50 years for the prediction they made in 1964 to now come true, and the thing which makes the prize interesting right now, you’re asking why 50 years, is because of this observation of a new particle it’s – where the properties expected by the theory, so this is why sometimes you have to wait 50 years and sometimes the theory may turn out to not be true.
Unidentified: And this is the so-called Higgs particle.
Gunnar Ingelman: This is the so-called Higgs particle.
Unidentified: Yeah, many people have heard about it. Why was it so hard to get it, to discover it?
Gunnar Ingelman: Well, there are several things. One thing is that the theory predicted that there ought to be a particle. It could tell us the properties of these particles or how it interacted with other particles, with matter particles and force carrier particles but it couldn’t tell us what the mass of this particle was, and so we didn’t know where to look and so actually for the past 50 years this particle has been looked for at every accelerator in existence.
So it has been looked for at the ISR, it has been looked for at the SPS. It’s at the left collider at the tebertron and this is – this was in ongoing hands so from other properties one could try to narrow the range of mass and have bits of both left and the tebertron.
So in the end we knew more or less that, if it existed, it had to be there, and then the LHC came in. It is the most powerful accelerator in existence, could produce enough energy to make this happen, and so we found the particle.
Unidentified: And they got it. Why is this particle so important?
Gunnar Ingelman: Well the particle in itself is not as important as the theory which is represents. So the theory tells us why we exist and all this because as I said in my story, this is a philosophical question then again but maybe tells us why we don’t float away like a photon. I mean we all know that we are massive, we know that we consist of atoms, and the atoms have atom nucleis, protons and electrons, and neutrons – this is what we consist of but according to the theories which existed before the mechanism was proposed all these particles ought to have been massless.
And we know that unfortunately we are massive, some are more massive than other people, but definitely not massless. So there was something wrong and the theory proposed a solution and this is why the theory is important and the particles is important as a manifestation of this theory.
Unidentified: So all particles get their masses from the Higgs theory and where does this Higgs particle exist? Is it here around us or where is it?
Gunnar Ingelman: Well I have to modify this a little bit. All particles that we consist of get mass from the Higgs particle. They’re particles which do not seem to interact with the Higgs particle, maybe the neutrinos, and so the standard model is not complete.
That, it is probably only a low energy approximation of something larger which also explains the mass of the neutrinos which also explains the dark matter, so at the moment we don’t know but electrons and protons and neutrons, the quarks inside them get mass by interacting with the Higgs; so one way of looking at it is to imagine that the Higgs field is something which pervades all the universe. It’s everywhere. It’s here in the room, it’s out in the black space, it’s everywhere and so every particle which moves through this field, and it’s forced to, will interact with the Higgs particles and in that way gets mass.
Unidentified: All the time now?
Gunnar Ingelman: All the time now.
Unidentified: And we don’t see it?
Gunnar Ingelman: We don’t – I mean we are born like that, right, so we wouldn’t feel the field.
Unidentified: But where does this field and the particle come from?
Gunnar Ingelman: Well this is something that we actually don’t know. I mean this must have happened in the big bang somehow that this is how our universe is constructed that there is this field. It is possible that this field was part of the inflation process which blew up the universe from a very tiny size to what we have today.
We also don’t know that. We don’t know if there’s only one Higgs field or maybe there’s more Higgs fields. So there’s still mysteries to be solved.
Unidentified: Yeah, this Higgs particle is so crucial to the whole universe and the discovery was so hard to make. Why didn’t the people who made the discovery get the Nobel Prize?
Gunnar Ingelman: Well this is, as you know, it’s a very difficult question for me to answer because we now are not at liberty to divulge the discussions which take place inside the Nobel Committee or inside in the academy when the decision is made but let me just tell you that the decision on the prize is based on primarily the will of Alfred Nobel, on the nominations which we receive this very year and then we, of course, take into account the prestige and the tradition of the prize.
Now weighing all of these things together we came up with the proposal of this year’s prize and now for the rest of the internal discussion we’ll have to wait 50 years.
Unidentified: And the Higgs particle has been said to be the last piece of the standard model puzzle for elementary particle physics. Is particle physics over now? Is it finished?
Gunnar Ingelman: The standard models, so far-so good but as I already told you there’s still unsolved things; one is the neutrinos, based on how they don’t fit completely into the standard model they do have mass but apparently they are not getting their mass through interactions with Higgs.
There’s also the question why the Higgs is so light. Maybe there are more Higgs particles. Maybe this is just one of them and there are more to be found. So today the belief is that the standard model is a low energy approximation of a more complete theory and this whole theory is what particle physics is after now.
So there are various speculations; super symmetry may be a possible extension of the standard model. There are also people speaking of extra dimensions so that our four-dimensional world is just what we perceive of a larger 10-dimensional world and the other dimensions are just tiny, rolled-up, and we don’t see them, so there are mainly speculations of that and like with the Higgs, you know, experiment will eventually show which theory is the right one.
Unidentified: Thank you very much for the time.
Gunnar Ingelman: You are most welcome.
Unidentified: And taking your time.
Gunnar Ingelman: Well worth it, thank you.
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