Samuel C. C. Ting, “Muons, Electrons and Gamma Rays” - LNS46 Symposium: On the Matter of Particles

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LOW: Good afternoon. Our speakers this afternoon, of course, need no introduction. Let me just say a few words anyway. We live in a time of rising expectations. And we physicists, I think, are no exception to what is going on in the rest of the world. Our expectations are rising also.

There's talk of a crisis in elementary particle physics, nothing to do, technological unemployment. Where are we going to go? All of those questions-- Of course, the crisis-- it's not really a crisis. It's a reflection of the tremendous success that this field has had over the last decade.

46 years ago-- the date we're celebrating, the date we're remembering, 46 years ago-- it would have been inconceivable to imagine that we would have the understanding, the knowledge of the subnuclear world that we now have. So it's hardly a crisis in that sense. It's a wonderful accomplishment. It's been reflected a great deal in the talks that we've heard.

Today, we have four speakers, all of whom played major parts in achieving this success and learning the things that we've learned over the last 25 years. It's an honor to have them with us. Looking at the titles, it seems to me the first three speakers are addressing the present, the past, and the future. And the last, Steve, is addressing all of the above. So we'll see.

The first speaker is Professor Sam Ting. And his title is, "Muons, Electrons, and Gamma Rays." Sam.

TING: It's 25 years ago, Viki hired me. At that time, I had quite a few offers. MIT was the only offer without tenure. But nevertheless, I sensed their great freedom for research, and, therefore, I decided to come here. In any case, I did not really understand what tenure was in the case.

What I would like to do today, in order not to waste your time, is to describe a little bit the sense Professor Becker, Professor Min Chen, and others have been doing, together with me, on physics of the electrons, muons, and photons.

The first period covers from '65 to '72, in the Deutches Elektonen Synchrotron in Hamburg. My personal interest in this field comes from reading a paper from Columbia, by Francis Low, whom I did not know at that time, on the possibility of an excited electron [? go to econ. ?] And that paper fascinated me a great deal.

As you all know, the physics of the electron positron, in fact, [INAUDIBLE] this morning, already since '48, '49, and '50s, through the work of Deutsch and Kendall and others, who have the simplest electron positron collider. And that is positronium.

In 1964, there was an experiment that shows electrodynamics was violated. The experiment that was carried out was a photoproduction of the electron positron pair in the field of Coloumb nucleus, where you have a momentum transfer, so-called Bethe-Heitler pair, a momentum transfer of 1 TeV. And therefore, you probe the electron propagator to 10 to the minus 14 centimeter.

That experiment shows a violation of the electrodynamics, as a function of the e plus, e minus environments. Together with Professor Becker, we built a spectrometer, which has a magnet and detectors.

The detectors defined the aperture not the magnet. And also, two sets of Cherenkov counters, separated by magnets, so they're not counting the electrons from the first one-- does not enter the second one. And also, the electron are measured twice, once with the shower and the other time with the Cherenkov counter.

This is a picture of this first spectrometer we made. And this person is Stewart Smith, who is now the head of the physics department at Princeton University.

The measurement from us shows we had a small disagreement with earlier measurement. In other words, we agreed with the prediction of the electrodynamics, [? except ?] for the [? mass of ?] rho, the [? mass ?] [? of ?] phi, and with the deviation. This deviation come from the fact the photon changes after [? rho, ?] goes back to a photon, goes to the electron positron pair.

Indeed, at that time, there were a family of three vector mesons. They have the same quantum number as a photon except it has a mass not equal to 0, which I will call heavy photons. At that time, most of the people would discuss the vector dominance model. And I see Bernie Margolis is here. He did a lot of work on this.

And one can then relate that current with the quantities from contribution from rho, from omega, from phi. In this spirit, photoproduction of vector mesons will be deflective in nature. And this is an article or data taken from Scientific American. It shows photoproduction of pi plus [? phi ?] minus mass as a function of angle. The yield peaks at the rho and peaks more forward at heavy nuclei, like the classical diffraction scattering.

Analysis of this can be carried out in the following way. You have a photon with a coupling constant, let's say gamma v squared or 4 pi, and go into the nucleus, and go back to pi pair or k pairs.

And so this is red, therefore, it's a quantity of the vector meson nuclear cross-section, nuclear density, and a coupling. If you took the ratio, the coupling disappears. It's a measurement of the radius and vector meson nuclear cross-section.

The first thing we measured was the Woods' action potential. And I see Dave Saxon is here. And this is a very accurate measurement of the Saxon-Wood potential across all the nuclei. And the accuracy is 1.12 plus/minus 0.02 to A to the 1/3.

Once you have measured that, you can also look-- a vector meson decays to a photon, and decays to e plus, e minus. In which case, you have two couplings, one, photon goes back to meson, with a mass of the photon, and here, with a mass of the rho. And the question, therefore, are the two coupling constants the same?

This is the measurement of a photon go to e plus, e minus, photon go to rho, goes to a photon, goes to e plus, e minus. Clearly, because the final states are the same, they have the interference. Indeed, you see the interference. Interference is a measurement of this coupling constant, also the production phase.

The results of this series of experiments shows the coupling constant and the mass of the vector meson, from rho to e plus, e minus, is 0.5. And from diffraction scattering, where the photon mass is 0, it's also 0.5.

And furthermore, the rho, nuclear, and cross-sections, [? lepton ?] and nuclear cross-section-- at that time, there was a theory, by [? Dahl ?] and Weisskopf-- I hope Viki still remember-- and shows they are the same. And more important, the coupling constant is independent of the photon mass.

At that time, there was a puzzle. And that is, there were experiments at CEA and Cornell to look for a rho to the electron, omega to the electron, a diffraction pattern. And this pattern was looked for a long time but never observed.

It is difficult, because the branching region was very small, and, therefore, you need a high rejection. And furthermore, the width of omega is only 10 MeV. Therefore, you need a very good spectrometer. And a new spectrometer was built.

And from this, one indeed observes, e plus, e minus mass spectrum, it's not only rho, but a sharp peak from rho-omega interference. You can look the vector meson photon analogy once more.

And notice, rho goes to 2 pi. Omega goes to 3 pi, therefore, they do not interfere. But omega can go to a photon. Photon can go to a rho. Rho go to 2 pi. And therefore, there must be an omega go to 2 pi. And this, indeed, that was looked.

And I think, at that time, the most famous upper limit was set by Jack Steinberger and Günther Lütjens. And we have looked. Indeed, with a good spectrometer, if we do it very precisely, you see, on hydrogen and carbon and lead, the red spectrum is where the rho are long. The points and the blue lines are rho-omega interference due to pi.

A difficult measurement was carried out on phi to the electron pair, because the rate was very low. And it obtained a phi coupling constant and also phi nuclear and cross-section agrees with the quark model.

This series of experiments can be summarized in the following way. At that time, the so-called Weinberg's "First Sum Rule," which is the partial width of rho, partial width of omega, partial width of phi must have a triangular relation. And this is the phi measurement, omega measurement, and the red line's the rho measurement. Indeed, the measurement agrees with the Weinberg sum rule.

So to summarize, the early data work shows the decay of vector mesons comes SU3 theory. The electron radius is less than 10 to the minus 14 centimeter. And the question is, are there any more vector mesons at a higher mass?

I should mention, at that time, there are many young physicists working with us, Joseph Asbury, who is now the associate director of the Argonne, Professor Min Chen, Professor Becker, Wit Busza, Professor Smith at Princeton, and so forth. And there's Sadrozinski, Garry Sanders, and Sau-Lan Wu, and also Robin Marshall, who just received a distinguished chair in Manchester.

It's also interesting to report that the early measurement, was confirmed by e plus and minus collider. And for reasons I never understood, the collider result was not better than the earlier measurement by Becker and Chen and others.

Now we know photon and heavy photon are almost the same. And they do transform into each other. And we also learned how to use high intensity flux, of 10 to the 11 gamma ray per second, to obtain pi pair rejection larger than 10 to the a, and to have a mass resolution of 5 MeV.

And then the question is, as I just said, why should be only three heavy photon that all has a mass 1 GeV? And to go to higher mass, we went to Brookhaven. So let me now summarize the only two years I ever worked in the United States, namely, at Brookhaven.

At Brookhaven, life is somewhat difficult. Because from a proton on a beryllium, you produce many, many particles. The most difficult are the electron pair, because the radius is 1 part in 10 to the a. That means to obtain enough electron pair, you need 10 to the 12 protons. To have a pi pair rejection of 1%, you need a rejection of 1 part in 10 to the 10th.

This is the design of the spectrometer. Looks all the same, but, actually, it's a very difficult spectrometer. This is looking from the top. You have three magnets, two Cherenkov counter measures the electrons. And these detectors measure the coordinates and measures shower.

Bending is in the vertical plane. The horizontal coordinate measures theta. Bending is a vertical plane. And therefore, the bending, theta and phi are decoupled from each other.

So this is the spectrometer. Shows the magnet, Cherenkov counters, and position detectors. The target was arranged in a helium bag. And they are separated by 7.5 centimeter with 1.8 millimeter beryllium. And it's done in such a way so that the signal can be traced from one point. The background, from two different points, can be rejected.

The magnet was measured with a three-dimensional Hall probe, 100,000 points. In those days, there were no computers. And it was mostly done by hand. The detector is smaller than the magnet aperture, therefore, the detector defined acceptance. It's something we learned from [? Daisy. ?]

And the magnet bends the charged particle to an angle, so that the detector is never exposed to the target, never interfered with the neutrons and photons.

To have a rejection of 1 part in 10 to the 10, indeed, is quite difficult. When you have a Cherenkov counter, if a hadron go into a Cherenkov counter, it knocks the electron forward. And, therefore, the pion will disappear. The electron goes forward.

To reduce knock-on, we use hydrogen gas, which has a smaller number of electrons. And we put two magnets, so that the low energy electron does not enter the second Cherenkov counter. And these are very nicely made Cherenkov counters, with hydrogen, the very same on both sides, including a mirror, which is made at CERN workshop, 3 millimeters thick. And you see one, two, three photoelectrons.

Position-sensitive counter were made by Ulrich Becker. There are 10,000 wires. None of them broke during the experiment. Resolution is 1 millimeter. The three wires are 60 degrees apart, and, therefore, the sum is always a constant, and the rate is 20 megahertz, equivalent to 10 to the 36 luminosity. And they are designed such that output's always a very low voltage because of high radiation.

To have an electron, you must have an electron detector, and you must have a calibration. To calibrate this, we generate, artificially, from proton on a target at pi 0, get a photon e plus, e minus. [? Then ?] [? send ?] e plus into a Cherenkov counter, let the e minus go into the main spectrometer. A coincidence enables you to calibrate your detector on the electron, artificial electron beam.

Because you need 10 to the 12th protons, so you have a 10% target, therefore, 10 to the 12th particles are produced. To stop photons, electrons and muons, we use 5 tons of uranium, 100 tons of lead. And to stop the pion, kaon, and so forth, we used 10,000 tons of concrete so generously lent to us by Karl Strauch, from CEA.

And soft neutrons are still left all over. And we manage to convince Martin Deutsch, who was the laboratory nuclear science director, to buy five tons of soap to stop soft neutrons. And this shows, if you can see it, the location of the soap.

In fact, it's during this experiment, we began to know Martin Deutsch. And he really supported us and made an enormous effort to make this experiment possible.

It takes a whole week to set up the detector, because all of the Cherenkov counters must be mapped to make sure they are 100% efficient. All the chamber area are mapped to make sure they're 100%. All counter efficiency and timing are checked. And [? both ?] side on all shower counters are calibrated with artificial electron beam. All voltage are checked every 30 minutes. All magnets are reversed once a day, mainly because you want the rejection of 1 part in 10 to the 10th, a mass resolution of 1 part in 1,000.

It was also during this time, we began to know Herman Feshbach. And, since that was the first experiment we are inside US, we had then close interaction with the Laboratory Nuclear Science and, particularly, Dr. Fred Eppling. And I have benefited enormously from these three gentlemen.

So this is the result of this experiment. It shows a proton on a beryllium, as a function of e plus, [? give us ?] [INAUDIBLE] mass. Indeed, show a sharp peak, which we call the J particle.

The physicists in this experiment, there's Becker, Burger, Wit Burza helped to make sure the proposal get approved, Min Chen, Sau-Lan Wu, and then Jean-Jacques Aubert, who is now a professor in Marseilles, Walter Toki, a student of Becker's, now a professor at Colorado.

And there's a nice picture. This is Sau-Lan Wu. This is my wife, Susan. And there's Jean-Jacques Aubert and Walter Toki. Very young at that time.

After that, to look for higher mass particle, we did an experiment at CERN ISR. And essentially, it was a proton-proton collision. It goes to a photon, goes to a mu plus, mu minus. Going to look for a new quark and look for Q Q bar distributions.

ISR is a new concept. Rings of protons and protons collide, and, therefore, the center mass is equal to the laboratory. It's a new type of accelerator made possible through the personal, strong push by Victor Weisskopf, when he was director general.

This is the ISR experiment, where you have a proton-proton collision. These are magnetized ions from the [INAUDIBLE] cyclotron. And these are very large propulsion chambers developed by Ulrich Becker.

And this the first time we will enter into very large, solid [? angle ?] devices. I guess you can't see it. But we have to really take the accelerator apart in order to install this detector. And also, ever since that time, we have had a very pleasant collaboration with Karl Strauch and his group.

And there's the installation of the experiment. And it shows Ulrich Becker-- How much younger then. And also, this is a picture of Professor Min Chen under the detector. And this is the large chamber developed by Ulrich Becker. And it really made the subsequent experiment possible.

The process of collisions is known as Drell-Yan process. So the first result is to provide a very accurate check of PP interaction in a time-like region. And this is a direct comparison of scaling phenomena at s equal to 62, s equal to 44, and shows, indeed, the scaling phenomena is correct.

But also, the second thing is to see the effect of gluons. The first effect one can see is the following, where you have a PP, one goes to a photon, go to mu plus, mu minus. The other goes to a gluon.

If there's a gluon emission, as a function of energy, the transfers of momentum, or PT, will be increased. Indeed, this is the PT measured from us, and this is a measurement by Lederman group at Fermilab, and shows it fits to the QCD prediction.

The second QCD effect also concerning multiplicity. If you look at gluon emission, which is opposite to the mu pairs, [? a local ?] [? transfers ?] [? movement ?] of mu pairs in the opposite direction, from where the gluon energy increases, because of balance of momentum, and the multiplicity increases.

There were many young physicists working at ICR, Jim Branson, who is now a professor at University of California, Francois Vannucci, in Paris V, [? Soji ?] Sugimoto in Kyoto, Roberta Battiston, in Perugia, and Pierre Spillantini now is a professor in Florence.

After that, we faced the question, where shall we go for the next experiment, going to PETRA or PEP? I want to show this check, which I received from Victor Weisskopf, one of our [? author. ?] It says, lost bet as to who is first, PETRA or PEP. Viki, I still have this check.

WEISSKOPF: You didn't cash it?



TING: No. At PETRA, you have a 24 GeV e plus or 24 GeV e minus. It Goes to a photon, then goes to quarks, and the electron. PETRA is accelerator which has four places, TASSO, Mark-J, Jade, and Pluto and Cella, four detectors.

The Mark-J detector is a very simple detector. Basically, it's a colorimeter, a [? four-by ?] colorimeter. It measures hadrons, measures muons, measures the electrons and photons. So this is the Mark-J detector and shows the large chambers made by Becker and collaborators. Image resolution is about 25% and covers about 95% of the total energy.

During Mark-J, we had the first group of Chinese ever sent to the West. And I went to see Mr. Deng Xiaoping. He said, how about training some Chinese physicists for us? And I asked, how many? He said how about 100? And I had to explain to him, no, physicists are not soldiers. And you have to select them. And so he selected 10.

And now, the new director of the Institute of High Energy Physics and also the one in charge of the Beijing detector, in fact, most of the active high energy physicists come from this team.

Also, in 1981, Spain decided to rejoin High Energy Physics group and selected, in a national way, a group of physicists to start working with us. Juan Antonino Rubio now is in charge of the tau/charm factory. Bernardo Adeva is a professor in San Diego. Martinez is a professor in Barcelona. Most of them have returned to Spain and become very, very active there.

One of the things we learned is measuring e plus, e minus to mu-mu and tau-tau, check of QED, in the time-like region. In the space-like region, this e plus, e minus goes to e plus, e minus. And it's 1/s, and, therefore, you take out a propagator.

A 30 GeV, 20 GeV, 10 GeV shows a perfect agreement with QED, taking into account the [? re-data ?] corrections, of course. From this, you see the radius of the electron and mu and tau are less than 10 to the minus 14 centimeters.

And one of the important things was done by Greg Herten and Harvey Newman. Harvey Newman was educated by Lou Osborne, as you have heard. Gregor Herten and Min Chen also worked on this.

And that was first reported by Harvey Newman in the photon conference in Fermilab in August. And the basic idea is very simple. You have e plus, e minus go to anti-quark, quark, and gluon. Eventually, you see three lobes of jets.

The three loop of jet has no meaning. You always will see that. The important thing is the rate must agree with QCD and the shape must agree with QCD.

There was a paper published [? rather ?] [? rapidly ?] in September, 1979. Let me define. In the production plane, since the event has to be a planar, you have a q, gluon, q bar.

And following the terminology of Howard Georgi, you project the momentum in this axis, which we'll would call major, along the thrust axis, we'll call thrust. In the production plane, the events must be circular, and your core minor. And therefore, major minus minor is a flatness or oblateness. Oblateness essentially transfers momentum of the gluon. And therefore, it must be essentially 0 for jet events, in which case, major equal to minor, the event will be circular.

And based on 500 events, you see the rate indeed agrees with QCD. And without QCD, just a quark model, no matter what you change the parameter, you're not going to fit this data. And this is in the production plane. Perpendicular to the production plane, the shape also agrees with QCD.

That the shape agrees with QCD is very important, because there are many models essentially produce three jets. And these are the data. And this is the QCD. This is the phase space distribution. And this is Q Q bar distribution. Phase space, of course, also produces three jet patterns.

Indeed, with the increasing of oblateness or the transfers of momentum of gluon, you can see, gradually, with increasing, you begin to see the gluon jet. When the transfers of momentum to gluon is very small, you have no fragmentation. And gradually, you have a small jet. Eventually, you have a full three jet.

I mention this, because you will always see three jet events. And this is a three jet event. And this is a flat event at 12 GeV. But this event can be completely explained by a Q Q bar model without gluons.

Indeed, before we publish our result, there was an early result by TASSO, by Paul Soeding, which says they indeed find five [? flat ?] event, where the QCD predict nine. And they said, if the theory is correct, we must soon confirm this result with higher statistics and with much more improved evidence.

And there's a article by Gloria Lubkin-- I saw her. I see her here-- describing the support of QCD and gluons. And this is the data from Mark-J. And there, it said fairly clearly.

With time, people tend to forget who discovered what. And fortunately, at that time, Mr. Schopper was the director general. He got hold of everybody, together, and agreed to say that-- Schopper told us that Mark-J group was the first to report statistically significant evidence of the three jet pattern predicted QCD. After sometime, people tend to forget that.

But today, of course, things are very different. With higher energy, these are the data Professor Becker reported this morning. With high energy, the jet are much more collimated. And you can see the jets become much narrower.

A good experiment, in fact, also a very difficult one, was the electroweak effect from the existence of z0. Because of the existence of z0, the forward-backward asymmetry is a function of [? ga. ?] At this energy, it's about minus 10%, if we define theta as mu minus, which is back to e minus.

If you want to look for 10% effect, your systematic error has to be better than 1%. Because of that, the Mark-J detector actually can be rotated, both in phi direction and also in theta direction, to cancel all the systematic effects. The experiment e plus, e minus to mu plus, mu minus was the thesis of Jean-Pierre Revol, who's here, and also Gregor Herten.

And this is the measurement of e plus, e minus, two mu plus, mu minus. This was one year before the discovery of the Z and W. First, you have to make sure your detector has no asymmetry from cosmic rays, and, also, the low energy data must only be explained by QED. And then high energy cannot be explained by QED and agrees with the model of Glashow, Weinberg, and so on. And that also was reported in Physics Today and shows the curve which I just presented to you.

Indeed, we were able to manage to measure the asymmetry as a function of energy. Of course, over a very limited energy region, but, nevertheless, it agrees with the standard model.

And I think this was originally the work of Min Chen. With this very crude data, we were able to set a range of [? GeV ?] and [? ga ?] Together with the neutrino data, we said the [? GeV ?] [? ga ?] range in this region. Today, Ulrich Becker's data shows, now, we're in this point.

Much work was carried out on the physics of gluons. One of them is a determinant of the strong coupling constant. Strong coupling constant, essentially, is the rate of three jet versus two jet, because, in this case, you just measure this coupling.

The first order of the strong coupling constant is 0.2. To complete second order, you have to take into account not only the standard QED graph but also the three gluon vertex. When you properly take it into account, all the second order diagrams, your data completely agrees with QCD prediction.

This was work mostly done by Min Chen and Harvey Newman. And this is really very difficult work. Let me just give you a feeling what kind of systematic error that's involved. Using different fragmentation models, different detector parameters, gluon fragmentation function, cut-off energy transfers momentum in the Feynman field model or in the string model, And the change is in the 0.01 level.

And this is the difference in the change of the strong coupling constant as a function of the cut-off in the energy in the [? particle ?] level. And again, it was a difficult experiment. There's always disagreement.

What is plotted in here? This curve comes from Professor Min Chen, I believe, originally. It's alpha s as function of years. And this is the measurement by Min Chen and Newman. And these are the measurement by other groups.

At the beginning, they were factor of two different. Unfortunately, after '86, now everybody agree with each other. Let's say, with him.

We also look for new quarks. And new quarks can be looked by the so-called R. R is e plus, e minus to hadron versus e plus, e minus to mu. And they essentially measure quark charge. With different particles, you see sharp peaks, and you'll see a shoulder.

Those days, we know the first three quarks has a mass of 1 GeV, fourth quark has a mass of 3 GeV. The fifth quark has a mass of 9 GeV. And there was a paper by Glashow at that time. And it says the sixth quark, when you take into account QCD, must be a 38 GeV. It's in the Physical Review Letters.

And this is our measurement of R. And since we have managed to go to 46 GeV, and you really see nothing at all. When you take all the data into account of the electroweak effect and QCD corrections, and then you can set the size of the quark. And the size of the quark will be less than 10 to the minus 16 centimeters.

We also look for many new particles. And none, clearly, was found. There were many young physicists working with us at that time, Albrecht Boehm, HS Chen, Mr. Zhang, who is now the new director in Beijing. Peter Duinker is a professor at University of Amsterdam. Herten is at MIT. Jean-Pierre Revol and Wyslouch is also assistant professor here.

This is a picture of the very small Mark-J group. And there's Harvey Newman. Let me see. There's Mr. Zhang, who is the new director. This is Peter Duinker. This is Min Chen. This is my wife, Susan. There's Ulrich Becker and Jean-Pierre Revol. Everybody was younger then.

This morning, Ulrich Becker mentioned the effort at the lab, at the 27 GeV e plus, e minus collider. And there, we mentioned we have a L3 experiment. In the L3, there are many, many physicists.

Somewhat unfortunate, so many people, not only from the United States, from Bulgaria, from China, France, Germany, Holland, Hungary, India, Italy, Korea, Russia, Spain, Switzerland, and Taiwan. There are about 120 physicists from 16 US institutions. And this is during one of the group meetings, during the assembly of the experiment. And this is with one third of the physicists.

And I should mention, during this time, Robert Birgeneau, who was the head of the department and, also, at the beginning, Jerry Friedman, who was the director of the Laboratory of Nuclear Science, were most supportive to get this experiment underway.

These are really very difficult things. And particularly, Arthur Kerman really spent a rather large amount of effort to support this experiment. And this is a picture of Arthur Kerman with Tom Cabot during one of the visits to L3 experiment. And two years ago, I think, the MIT Corporation made the executive committee of the MIT Corporation come to visit L3. And this is during one of the receptions.

The experiment, now, had become rather large and somewhat complicated for L3. For example, in the last 18 months, 60 papers are being written or being published by 150 physicists. And that means, it's really no longer possible for a person to really understand everything in detail. Certainly not me.

And Ulrich Becker mentioned some of the major results, a number of neutrino species, a radius of leptons and quarks, the mass of Higgs, Z parameter, and precision determined the heavy quarks, measurement of quark mixing, a measurement of s.

And because this is a very precise detector, you can measure transaction metrics. There are many different ways to measure sine square W. All agree with each other. A model independent measured the number of neutrinos in the universe, lepton flavor violation, flavor independent of alpha s, e plus, e minus go to Z plus eta.

This has been a very difficult thing. Because, in the past, nobody's [? state ?] has agreed with them on the color or with QCD. And this is the first time we've managed to see this is really an experimental effect that previous results do not agree with QCD.

We obtained the branching ratio and also studied hard photon emission, J production, and the mass of excited electron is larger than 122 GeV.

Mr. Becker also mentioned, maybe someone will go to LEP 200. One of the first thing we can see, look for will be Higgs. Indeed, we have now a very large effort to ask LEP to go as high energy as one can. If you go 120 GeV, you can set the mass of Higgs already to 100.

If the machine's 220 GeV, you can set the mass of Higgs to 120 GeV. The second thing, it's a very precise test of the electroweak theory, the comparisons for W from 100 and LEP 200. LEP 100, with a field 10 to the 6th or 10 to the 7th event, you can measure the mass of the Z to 15 MeV. Measure the parameters, various parameters enable you to determine sines for W to 2 plus/minus 0.005.

And LEP 200 measures e plus, e minus to W pair by measuring the mass of W to 50 MeV. Since sine squared W is 1 minus mw divided by the mz, you determine sine square W to 0.003. This number must agree with this number.

The third thing if gauge cancellation, which Ulrich Becker also mentioned. And that is the three diagrams must cancel each other, so the cross-section is constant. And that is most sensitively measured by measuring the forward-backward asymmetry. And then particularly, if there's no triple boson coupling, the rate in the background region will vastly increase.

So since we come to MIT, the first thing we have done is to measure photon to the electron pair test QED to the [INAUDIBLE], define the radius 10 to minus 14, measure rho, omega, phi to e plus, e minus, check SU3.

Build a spectrometer that has a mass resolution of 1%, hydrogen rejection 1 part in 10 to the 8th, luminosity is about 10 to the 35. Measurement was always done twice, once with momentum, another time with shower.

At Brookhaven, the detector has a mass resolution of 1 part in 1,000. The rejection is 1 part in 10 to the 10th. The luminosity is 10 to the 36. Again, we develop a high rate chamber but duplicate the measurement to obtain the high rate.

ISR is the first time we enter into 2 pi detector with a very good rejection and developed large area chambers. At PETRA, that's the time we developed the 4 pi detector for discovery of gluon and e plus, e minus to mu plus, mu minus. We set the radius 10 to the minus 16.

Now we check the electroweak theory to 1%, through the P P bar mixings, set the mass of Higgs. We have a 4 pi detector that measures e, mu, gamma to 1%.

For the future, as Gregor Herten had mentioned, we will stay till '94 of '95 at LEP 100, field 10 to the 6th or 10 to the 7th. For three to four years, maybe five, to W pair, at which time, there are basically quite a few choices.

One choice, no LHC, in which case, the machine will go to 36 [INAUDIBLE] and 36 [INAUDIBLE], both at W and Z, and with a luminosity larger than 10 to the 36. Another possibility, in fact, indeed, may rightly [? happen ?] you for new discovery coming [? HERA ?] and to do EP. Another is the phase one, phase two of LEP, with Gregor Herten mentioned.

Let me just make a comment of EP. In this century since Rutherford, since Hofstadter, and Kendall, Friedman, Taylor, much work, much discovery has been made from EP.

At LHC, with 0.06 TeV electron, with 8 TeV proton, with a luminosity 10 to the 32, since the electron is stationary, and, therefore, the electron goes everywhere, and with the low luminosity, basically, you do not need to make any modification of L3, but, with the adding of a forward detector, measure protons. Compared to HERA, the center mass energy is factor 20 high.

And we have also looked into what the detector will look like for EP. Essentially, the BGO, vertex chamber, has calorimeter muon chamber. It can be kept the same, except, in the forward part, for the proton, we add a proton calorimeter.

Gregor mentioned, if you go to LHC, there's a very simple design by adding six Tesla coil and putting colorimeter and vertex chamber. In this way, because you have six Tesla coil, what will happen is you will trap all the mu, low energy particle, and let them go forward and backward. Only muons go out into your detector.

Another design is to measure the electrons and photons very precisely by putting crystals very, very far away from the vertex. The basic idea is very simple. At a distance of 3 meters, a 25 GeV pi 0 go to 2 gamma. The 2 gamma will be in 2 different crystals, and, therefore, you can reject the pi 0.

Well, I should mention, since there are many detectors now, we will proceed for L3 detector upgrade at PP or eP, only if we have a unique design, with unique resolution, unique design concept, not to the other general purpose detectors, and, also, a minimum cost. If we cannot achieve that, we probably will not proceed with this. And we will do something else.

I must mention that much of the result from our collaboration comes from doing instrumentation development, which is something Viki always think is very, very important. I totally agree with him. And all done by Ulrich Becker and collaborators.

Since '74, developed the high rate chambers, '76, large drift chamber, '79, drift tubes, now know as straw tubes, originally developed by him. In '82, he developed the L3 multisampling drift chambers. And now he has a continuing effort for R&D.

Now, finally, let me make a few small comments. From my personal experience, when I first come to MIT, the group only had four people. Now there are 600. In fact, when I first come to MIT, none of the research really was funded by DOE, at all.

Under the funding, we were talking about 10 to the 4. Now, it's 10 to the 8. And the detectors come from a few coincidence to half a million channels. Indeed, if you look, a number of physicists collaborate with me. And since I come to MIT, really, unfortunately, it has gone up so enormously.


TING: Not the [? right ?] population, no. Clearly, this cannot have been possible without a strong support of the Department of Energy and Bill Wallenmeyer, who is here, Bernie Hildebrand, Bill Hess, John O'Fallon, PK, and Enloe Ritter.

I have a nice picture of Bill Wallenmeyer, PK Williams. Had a conversation with my good friend Okun. He was doing one of the visits of L3. But unfortunately for us, after this visit, he decided to take $1 million out of our budget. It was probably because we served the wrong coffee.

And I also wanted to take this opportunity to thank the MIT administration and also the Dean of Sciences, as well as the MIT Physics Department, Vicki, Herman, Francis, Jerry Friedman, R. Birgeneau, Ernie Moniz, and also Peter Demos, Arthur, Fred Eppling, and the staff of Laboratory Nuclear Science, particularly most of the nonscientific staff. Because for them, it's not for us. We do things for fun.

And L3 has become very internationally visible. And this is a visit to L3 by the US Congress Committee on Science and Technology, just the Foreign International Collaboration Subcommittee. Anyway, they come with their own jet.

Finally, let me mention, in 28 years, the most rewarding thing I had was to win $40. My first $10 was October '65. I bet with Leon Lederman on how long it would take to complete the QED experiment. And the second was August '74, bet with $10 with Mel Schwartz on J particle. And the third was $20 from Viki. Thank you very much.