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Quarks and Quirks Among Friends

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Quarks and Quirks Among Friends hat could be worse WEST: I have here a sort of ‘~ractalized” experiments, where he showed that it would 66 than a bunch of table of discussion, thefirst topic being, take certain quantities of electricity that were physicists gathering “What isparticlephysics, and what are ifs integral multiples of each other to plate a w in a corner at a origins?” Perhaps the older gentlemen among mole of one element or another onto his cock~ail party to discuss physics’?” asks Pete us might want to answer that. electrodes. Carmthers. We at Los Alamos Science An even earlier contribution was Brown’s frankly didn’t know what could be CARRUTHERS: Everyone knows that older observation of the motion of minute parti- worse. .or better, for that matter. However gentlemen don’t know what particle physics cles suspended in liquid. We now know the we did find the idea of “a bunch of physicists is. chaotic motion he observed was caused by gathering in a corner to discuss physics” ZWEIG: Particle physics deals with the the random collision of these particles with quite intriguing. We felt we might gain some structure of matter. From the time people liquid molecules. insight and, at the same time, provide them began wondering what everything was made RABY: So Einstein’s study of Brownian mo- with an opportunity to say things that are of, whether it was particulate or continuous, tion is an instance of somebody doing par- never printed in technical journals. So we from that time on we had particle physics. ticle physics? gathered together a small bunch of four, Pete WESW In that sense of wondering about the ZWEIG: Absolutely. There’s a remarkable Carruthers, Stuart Raby, Richard Slansky, nature of matter, particle physics started description of Brown’s work by Darwin, who and Geoffrey West, found them a corner in with the Greeks, if not observationally, at was a friend of his. It’s interesting that the home of physicist and neurobiologist least philosophically. Darwin, incredible observer of nature George Zweig and turned them loose. We ZWEIG: I think one of the first experimental though he was, didn’t recognize the chaotic knew it would be informative; we didn’t contributions to particle physics came nature of the movement under Brown’s know it would be this entertaining. around 1830 with Faraday’s electroplating microscope; instead, he assumed he was see- 172 Summer/Fall 1984 LOS ALAMOS SCIENCE LOS ALAMOS SCIENCE Summer/Fall 1984 173 ing “the marvelous currents of protoplasm in nature, then it’s not a static thing. Atomic Dirac’s idea of viewing the proton and the some vegetable cell. ” When he asked Brown physics atone point was particle physics, but electron as two different charge states of the what he was looking at, Brown said, “That is once you understood the atom, then you same object was a nice idea that satisfied all my little secret.” moved down a level to the nucleus, and so the desires for symmetries that lurk in the SLAN!3KY Quite a bit before Brown, New- forth. hearts of theorists, but it was wrong. And the ton explained the sharp shadows created by WEST Let’s bring it up to date, then. When reason it was wrong, of course, is that the light as being due to its particulate nature. would you say particle physics turned into proton is the wrong object to compare with That’s really not the explanation from our high-energy physics? the electron. It’s the quark and the electron present viewpoint, but it was based on what ZWEIG: With accelerators. that may turn out to be different states ofa he saw. SLANSKY. Well, it really began around single field, a hypothesis we call grand un- CARRUTHER% Newton was only half 1910 with the use of the cloud chambers to ification. wrong. Light, like everything else, does have detect cosmic rays; that is how Anderson WEST Well, it is certainly true that high- its particulate aspect. Newton just didn’t detected the positron in 1932. His discovery energy particle physics now is cloaked in the have a way of explaining its wave-like straightened out a basic concept in quantized language of quantized field theory, so much behavior. That brings us to the critical con- field theory, namely, what the antiparticle is. so that we call these theories the standard cept of field, which Faraday put forward so CARRUTHERS: Yes, in 1926 Dirac had model. clearly. You can speak of particulate struc- quantized the electromagnetic field and had CARRUTHERS But I think we’re overlook- ture, but when you bring in the field concept, given wave/particle duality a respectable ing the critical role of Rutherford in invent- you have a much richer, more subtle struc- mathematical framework. That framework ing particle physics. ture: fields are things that propagate like predicted the positron because the electron WEST: The experiments of alpha scattering waves but materialize themselves in terms of had to have a positively charged partner. on gold foils to discern the structure of the quanta. And that is the current wisdom of Actually, it was Oppenheimer who predicted atom. what particle physics is, namely, quantized the positron. Dirac wanted to interpret the ZWEIG: Rutherford established the fields. positive solution of his equation as a proton, paradigm we still use for probing the struc- Quantum field theory is the only concep- since there were spare protons sitting around ture of matter you just bounce one particle tual framework that pieces together the con- in the world. To make this interpretation off another and see what happens. cepts of special relativity and quantum the- plausible, he had to invoke all that hanky- CARRUTHERS In fact, particle physics is a ory, as well as the observed group structure panky about the negative energy sea being continuing dialogue (not always friendly) be- of the elementary particle spectrum. All these tilled-you could imagine that something tween experimentalists and theorists. Some- things live in this framework, and there’s was screwy. times theorists come up with something that nothing to disprove its structure. Nature SLANSKY Say what you will, Dirac’s idea is interesting but that experimentalists looks like a transformation process in the was a wonderful unification of all nature, suspect is wrong, even though they will win a framework of quantum field theory. Matter much more wonderful than we can envisage Nobel prize if they can find the thing. And is not just pointy little particle% it involves today. what the experimentalists do discover is fre- the more ethereal substance that people ZWEIG: Ignorance is bliss. quently rather different from what the sometimes call waves, which in this theory SLANSKY There were two particles, the theorists thought, which makes the theorists are subsumed into one unruly construct, the proton and the electron, and they were the go back and work some more. This is the way quantized field. basic structure of all matter, and they were, the field grows. We make lots of mistakes,we ZWEI(G: Particle physics wasn’t always in fact, manifestations of the same thing in build the wrong machines, committees de- quantized field theory. When I was a gradu- field theory. We have nothing on the horizon cide to do the wrong experiments, and ate student, a different philosophy governed: that promises such a magnificent unification journals refuse to publish the right theories. S-matrix theory and the bootstrap as that. The process only works because there are so hypothesis. RABY Weren’t the proton and the electron many objective entrepreneurs in the world CARRUTHERS That was a temporary supposed to have the same mass according to who are trying to find out how matter aberration. the equation? behaves under these rather extreme condi- ZWEIG: But a big aberration in our lives! S- WEST No, the negative energy sea was sup- tions. It is marvelous to have great synthetic matrix theory was not wrong, just largely posed to take care of that. minds like those of Newton and Galileo, but irrelevant. CARRUTHERS: It was not unlike the pres- they build not only on the work of unnamed RABY: If particle physics is the attempt to ent trick of explaining particle masses thousands of theorists but also on these understand the basic building blocks of through spontaneous symmetry breaking. countless experiments. 174 Summer/Fall 1984 LOS ALAMOS SCIENCE “To understand the universe that wefeel and touch, even down to its minutiae, you don’t have to know a damn thing about quarks.” ROUND TABLE WEST: Perhaps we should tell how weperson- ally got involved in physics, what drives us, why we stay with it. Because it is an awfully difficult fieh$ anda very frustratingjield. How do wejind the reality of it compared to our early romantic images? M’s start with Pete, who’s been interviewed many times and should be in practice. CARRUTHERS I was enormously inter- ested in biology as a child, but I decided that it was too hard, too formless. So I thought I’d do something easy like physics. Our town library didn’t even have modern quantum mechanics books. But I read the old quan- tum mechanics, and I read Jeans and Ed- dington and other inspirational books filled with flowery prose. I was very excited about the mysteries of the atom. It was ten years before I realized that I had been tricked. I had imagined I would go out and learn about the absolute truth, but after a little bit ofex- perience I saw that the “absolute truth” of this year is replaced next year by something that may not even resemble it, leaving you with only some small residue of value.
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