Glenn R. Young, “New States of Nuclear Matter” - LNS46 Symposium: On the Matter of Particles

YOUNG: There will be no jokes this morning about heavy ions given the speaker. Lee Grodzins suckered me-- oh, excuse me. Persuaded me to give this talk a couple weeks ago, or maybe a month back. Asked me to spend a little bit of time talking about life with the heavy ion group, as I'm going to rechristen it.

It was actually the-- when I was here, it was maybe still known as the Van de Graaff group, even though the last real Van de Graaff at MIT had been shut down about a year and a half before I came here, sometime in the very early '70s. So by the time I came here, the group had already turned into a user's group. But even so, we managed to continue running Van de Graaffs. We just had to go across Long Island Sound to get to them. So most of what I'm going to talk about in terms of what I was doing when I was here was actually done in user mode down at Brookhaven National Laboratory.

I was here from '73 to '78. I came from the University of Tennessee, partly on two sets of recommendations. One was a fellow who was a year ahead of me at UT named Tom DeGrande. Some of you in the theory department may remember Tom. He was a Knoxville native. And I was from a smaller town in East Tennessee. We got to know each other in senior mechanics class. It was only offered every other year, so he had come back to take it with us juniors.

The other thing that persuaded me to come here was a series of letters I had sometime in early '73. One set came from Dave Frisch, who was here in charge of getting graduate students in that year. The other was from Willie Fowler, who was, of course, Caltech, who was trying to persuade me to go out there and study nuclear astrophysics with him.

I was somewhat torn between the two decisions. I didn't get very strong advice one way or the other until David finally wrote me the third letter and said that he'd beat the Johnny Reb out of me and make me a Yankee yet if I'd just come up here and give him a chance. So given that challenge, I of course had to take him up on it. And came on up that fall.

When I got here, the group over in Building 58, which is where I was parked for a few years, was in the process of putting together a variant on an angle split-pole. This was being done down at Brookhaven. The variation was that instead of the usual two-pole magnet arrangement, which Harold had invented some few years prior, we had added a Wien filter in front of it. The idea being to be able to-- in addition to momentum focusing, you could also do M over q focusing. That was important for doing heavy iron physics, where you had to deal with a range of charge states and masses all at the same time.

Bill Buckner was still around then. And when he-- I came in and took my obligatory introduction to the laboratory. Bill asked me what I'd like to work on, since in his opinion all good graduate students had to get their hands dirty, preferably as quickly as possible. He managed to pry out of me that I'd spent the previous summer working at Eastman Kodak in one of the chemistry groups, a summer employment between undergraduate and graduate school. And one thing in particular I had done is run an NMR spectrometer all summer.

So he said, oh, that's wonderful. We'll put you to work. We have a NMR which we need to get running for this new spectrograph down at Brookhaven. Here it is. I expect, you know-- please rebuild it. Get the oscillator to work and the driver. And make us a few new probes and a few other little details.

So I took this job on not really knowing any better. It looked a little old. Fortunately, I was, at the time, had been hooked up as a teaching assistant to supplement my fellowship. I was under the supervision, I think, of Rainer Weiss at the time. And he'd sent me over to help out with the junior lab, which meant I had access to a nice, small compact electromagnet with a good field quality, so I could check this NMR.

And I proceeded to rebuild it. It was a little worrisome. Because I opened it, and it was all full of these things called vacuum tubes. Which proved to be problematic, because none of the stores had vacuum tubes anymore you could buy. And several of them didn't work anymore. This problem we solved somehow by going and talking to somebody back in the depths of the physics stockroom who certainly had a few of the necessary vintage tubes.

The thing that disconcerted me, though, is when Harold finally gave me the prints for the oscillator. And I realized that the prints had been drawn the year I was born. So this thing was not exactly the newest piece of equipment ever. Bill told me later he thought that you should work on things of your own vintage. And he certainly meant it.

After that, I-- after working with the group, I spent the next summer at Brookhaven under Harold's suggestion. We had an engineer from Denmark who'd come over. Name was Pierre Knudson, who needed some young fellow who didn't know any better to help him put the spectrograph together. I was of course put to work drilling holes, and wiring in power supplies, and all the other good things experimentalists learn how to do.

Harold came down the fall. And we tuned the whole thing up. And Harold finally decided that the acronym for the thing should be the Energy Mass Spectrograph, or EMS as I've marked on the slide. And Harold's rationale for wanting to call it the EMS was that, when it didn't work, we could just invert the two first letters of the name to call it the Mass Energy Spectrograph, or MES for short, which summarized maybe the first few shifts. But then it worked rather well. And we had a good time with it.

I'm going to, at this point, talk a little bit about some of the physics. I've got three things I've picked out from what I did here. I've listed the cast of characters that were over in-- we were partly spread between Building 58 and partly in Building 26 on the fourth and fifth floors. I spent a good bit of time when I came working with Eric Cosman, and Harold Enge, and Steve Steadman, who was here when I came here, still, as a senior scientist. And later became my thesis adviser about '75 when I finally decided I should pick a topic and think about getting out.

I worked with Lee also some on one topic I'll come to at the end. I've listed here all the graduate students and post-docs who I can remember working with and whose names I could flush out from the papers. There are about 20 people there, 12 of whom went on for a PhD. A few are postdocs. And there's some number of undergraduates. We always seemed to have a-- due to the pushing from Eric, we always had a fairly steady supply of UROP students working with us. And I was lucky to be able to help a few of them through their senior thesis, which was good training for a graduate student.

When I came in the door here, the topic that Karl van Bibber put me to work on as far as data reduction was looking at a series of resonances that had been found the previous year before I came. Looking at carbon-carbon reactions. What Eric had become interested in studying was, what happens if you took two heavy irons, and put them together, and asked the question if you excited any states of any particular special structure up in the compound nucleus.

This was a subject of some speculation. There had been a series of measurements made about a decade earlier by Bromley et al, looking at resonances near the Coulomb barrier. And Eric and Karl had managed to find through one of the last ever exposures using the MIT multi-gap. This was done at Brookhaven.

But if you shot carbon and carbon together and varied the bombarding energy from about 32 to 44 MeV in the lab-- this is shown down here at the bottom in terms of center of mass energy-- then lo and behold, if you look to the proton exit channel, which would give you states in sodium-23, you found particularly in one region a number of states-- especially these two at 907 and 984, and also a pair up around 12 and 14-- all of which seem to follow one another as you vary the bombarding energy, which was suggestive of resonance structure. Or as we liked to call them in the group, molecular states.

So we spent quite a bit of time-- this particular paper was published in '74. And after I'd been here about a year we had another one where we'd continue this process. This is the first paper, I think, I was involved with in the group. We worked with-- we'd gone out to Argonne over that winter, worked with John Erskine and Lee Greenwood. [INAUDIBLE], who was visiting at Brookhaven at the time, we had teamed up with him. And by that point, we'd managed to systematize things enough to where we had a fairly good idea of the whole landscape.

There was this one enormous figure, which kept up on the bulletin board over in Building 58, which we would add to sort of a every few weeks basis as we managed to get a few more states analyzed. What we've done is plot, again, as a function-- in this case, we've systematized it all as a function of excitation energy in magnesium-24, running up here along the top. And we've looked at a fairly large number of states. Particularly, Eric had had us look at the members of the ground state rotational band in sodium 23. The ground states of k by three halves plus state. These four states we've looked at, these two here were the ones that ha been most prominent earlier. And after a certain amount of analysis, we realized that we evidently had fairly good correlated structure with these three energies here. And maybe something starting to happen out here at the tail end, though it had gotten rather hard to see in these states.

We also were able to measure the duteron channels and find measurements in the literature of the inverse reaction of alpha neon, all of which seemed to go together. This finally led us to argue that perhaps you saw some evidence for systematic structure in this, which Eric suggested could be interpreted as a highly deformed rotational band. In fact we finally referred to it as a resonance rotational band. What I'm showing here is a plot quite favorite in high spin gamma physics where you plot the square of the angular momentum versus excitation energy. The ground state band in manganese 24 sits here. There's a clutter of low lying states that are well known. The threshold for carbon carbon starts here. What you find are these states whose span was slowly worked out in later years by other people.

So our guesses here are based on likelihoods of branching ratios and knowing what states were being populated in photon decays, all of which we'd measured. And you had the indication that perhaps you had a band here that was a series of states all collected and correspond to some rather deformed states in the carbon. We went on and studied this for a number of years further. I think Tom Cormier took his thesis on this data Al Lazarini took his thesis out of this set of data. Partly that show here where we've gone through and looked at a few other channels and found that we can match resonances and excitation functions with states that are preferentially populated in alpha decay from Silicon 28. And I think Bob LaDue went through and finally completed the elastic scattering measurements and a few other. And did a re-analysis of the reaction is shown here. The carbon carbon going to alpha neon for his thesis.

As I recall this one last piece of this work was probably finished around '82 or '83 as I recall. A number of years after I'd left. Simultaneous with that, even though I worked quite a bit on that, Tom Cormier had managed to build a time of flight spectrometer which we had installed at Brookhaven. And Tom had-- we'd started using it to measure heavy ion transfer reactions. Had done a few papers. But all in all had not learned anything particularly unusual from those reactions other than aspects of how to properly do DWVA when you have heavy ions whose recoils have to be dealt with properly. Which wasn't always done in the good old days of DP stripping. What we had found as we were getting this thing running, the rumors and papers started coming from our colleagues in France and also on some certain west coast lab somewhere out near San Francisco that if you looked at heavy ions and didn't restrict yourself just to the transfer region or the compound nucleus region but took a broad brush, there was a much broader structure that you might see. This was discussed at some detail yesterday by Professors [INAUDIBLE].

It's become known as deep or deeply inelastic scattering by that point. What one finds is that there is a considerable amount of nucleon and energy exchange without a fusion reaction or even a fusion reaction going on. Just to set a landscape, what I've done here is pull a plot from a paper that was sort of the beginnings of Carl van Bibers and my thesis. This was what we plot here is a massive reaction product.

Actually, this is not a linearized plot so the lines aren't terribly straight. But this coordinate is roughly mass and this coordinate is linearly proportional to energy of what comes out, which is the first sort of the easy information from time of flight spectrometer. The normal landscape on such a plot would have looked like this. You'd see a clutter of protons and alphas down here in the lower left corner. Of The normal evaporation products. A group of compound nuclei, which for an asymmetric system were going to be lumbering along at a fairly low energy. And then all the transfer and elastic products up around where the bean sat. And what you saw instead was this rather broad sweep.

In particular this distribution of strength right around the projectile mass. If you looked in detail at this group over here, you found that in fact you could understand most of that is compound nucleus decay. You're simply at such an energy that there's a lot of mass emission. But if you then came down and looked at the angular distributions in various windows of Q value, it's too broad to pick out particular states.

You would then find that the angler distributions didn't really match anything you knew very well. It turns out that if you recall these contra plots you saw yesterday, what I'm showing you here is simply some slices through these constant final state kinetic energy or Q value window as we chose to call it in this paper. What I've done is look at mass 17 groups and mass 12 groups and show you as things get more and more inelastic. This is nearly elastic reactions. And these are highly inelastic reactions pushing up near the kinematic limit for the reaction. You find things simply get more and more relaxed. Becoming fission like but never quite making it. It became a bit of an industry then to study exactly what was going on. This particular paper got as far as noticing that if you looked at how the most likely inelasticity, which is shown on the ordinate here varied as a function of mass transfer where not moving any mass at all corresponds to the middle.

You see a trend which suggests perhaps that what you're looking at is successive nucleon exchange which as these exchanges proceed, you tend to get more and more inelasticity. You finally tend to run up against the kinematic boundary, which is a bit mushy. This is the boundary you'd expect for two touching chart spheres that hadn't deformed. We went on and studied this for a number of years. Carl and I did theses looking at the polarization of the products which were admitted.

Steve Cunan's video yesterday showed you some evidence for how these things spin as they pull apart. Prow got interested in the polarization. I got interested in how much angular momentum, and therefore gamma were emitted. Other people got interested in exactly how the vision branch of this would work and how polarized those fragments were. How hard you could push. Did the neutrons come before the vision or after the vision? This occupied me for a number of years after I left here, in fact. Until roughly the mid-80s, at which point I changed gears rather thoroughly.

I wanted to talk about one last thing we did here. It was, the reason I'm going to bring this up is this was the first project that I did after I finished my thesis. Steve Steadman had allowed me a certain-- enough rope to hang myself my last few months here, I stayed on one year after I took my role as a post-doc. Just as I finished in that summer of '77, there came a paper out from our colleagues at MBI, some of whom I had worked with. Particularly [INAUDIBLE] I'd worked with at Brookhaven. They had decided to go off and see if there were any more interesting structures in high spin physics around the mass 150, 160 region where nuclei are known to be deformed if they're near the stability line. What they wanted to know is could you get well off of stability and find any evidence for isomerism. With the [INAUDIBLE] line, the line that tells you where the lowest excitation state is a function of angular momentum sits, would that line stay nice and smooth, as we knew from even new nuclei, or would it get jagged enough that you in fact would develop what were, in anticipation, Chris and [INAUDIBLE]? States which would say find themselves unable to decay by an e-2 transition, because the nearest e-2 state below it was in fact above it in excitation. Would the [INAUDIBLE] line get that jagged?

So the hypothesis was that these would form isomers, and what the group at MBI and GSI had done is simply take a survey of where such isomers like look. This isn't something you can really do until the mid-70s, because you needed an accelerator which would put heavy ions out in a controlled manner at energies right around the cooling barrier. You didn't need the bevel act which would tear things apart, you wanted the unilacker, a big tandem which would do things in a controlled way. What they found-- I should point out that apparatus a little bit-- is it's actually this devilishly simple. You simply bring a beam in on a target. You bury the target in this case in a bunch of lead. You then go some distance downstream, allow recoils to come down to a catcher, and then surround that with a number of number of sodium iodide detectors. So you're deliberately blind to the prompt radiation within shielding fraction, but you're able to see any particles which decay with isobaric lifetimes on the order of one to several hundred nanoseconds, which is roughly the recoil time of these ions to get from here to here.

What they found in fact, was you found an entire island of these things. What they show here is the usual nuclear physics plot of z running up this way, nucleon number running out this way. What they've marked in black are compound nuclei that were formed. They didn't know what the system was, they just knew that that reaction would lead to isomerism.

What's drawn in here in blue is the line of beta stability. What's drawn in green is a rough estimate of where the better known deformed nuclei sit. The rotational limit as it was called in that paper. You define that by asking for a four plus to two plus transition ratio of about three. After reading this, we went off looking and it turns out I spent a good part of the next few years studying those three red dots, which are dysprosium 151 and then two isotopes of erbium. I hoped on reading this paper one morning, we called the client at Rochester the next afternoon and asked him if we could come up and use his tandem. Peter Butler was at Oak Ridge at MIT at the time as a post-doc. He knew something about high spin physics.

So we went to Rochester, set up an experiment, worked very hard to get it set up. I've drawn a bit of a sketch here in the corner just to what it looked like. It's the same kind of arrangement. Though since we had a tandem, we had to get our time zero by sticking sodium iodides around the target. Then we put up some shielding and then germanium detectors, because we wanted to do spectroscopy.

There's a bit of a story about this tungsten shield here. I was at Brookhaven. I went over to AJS asking to borrow some tungsten blocks and gave me some after smearing the surface radioactivity. I happily took them away. I Then fortunately set up a little test over at the tandem with one of the germanium detectors to see if they really did shield properly. Tried to adjust the shielding, and found out that these were perfect anti shields. I then went back over to the AJS. Asked exactly which tungsten block they'd given me. They got a somewhat unhappy look on their face as they checked the records and realized that they hadn't handed me the shielding blocks. They'd of course given me a beam stop. This is a terrible story to tell in the present days of ESNH.

The unfortunate aspect of this was that the fellow realized that the beam stalk was stored in a box which they were using as a poker table. So there were bad jokes for a few weeks about real hot poker games over at the AJS ESNH office. About a week later, I noticed that same box well buried in the shield wall near Professor Ting's experiments.

Anyhow, we went off and I won't try to go through this level scheme. It was my first and last effort in constructing a level scheme. I decided that I'd chosen wisely by not becoming a high spin physicist. Kim Lister had most of the fun doing this in fact. But the interesting thing we found from that is when you study the shape of the [INAUDIBLE] band you in fact get a rather-- if you make one of these plots as I showed you earlier for carbon carbon. In this case the dysprosium 151 is the one we mentioned. We had measured what you usually find for an even even nucleus closer to stability. A nice smooth curve, and you see instead you get this very jagged dependence of where the states sit as a function of square of angular momentum. And if you in fact just draw a straight line through that, you get moments of inertia which are comfortably large.

There was a conference fairly soon thereafter when this was all discussed. And the only thing I can remember from that conference was Abe Klein continually asking Ben Mandelson what a rotating box of nucleons meant in quantum mechanics. I don't know if Ben ever did answer the question. Anyway we continued these studies. After I got to Oak Ridge, Kim had by that point gone to Brookhaven and Doug Horne, who was ahead of me at MIT, had also gone to Brookhaven. [INAUDIBLE] come from Pittsburgh. They asked me down for a summer. We did some more of this and had a good time.

Just to show you what the type thing we ended up studying, and how different these schemes are, we decided to do erbium 152 and 153, which are like the dysprosium case. Just add a pair of protons. If you look at the even even, case you get the usual rather beautiful [INAUDIBLE] sequence. Though those of you who know this game would notice that you're so far off stability that what you might call a backbend is it a suspiciously low spin value of six to eight instead of the usual 12 to 14. However if you stick that one last neutron in, as every good nuclear physicist knows, this lovely level scheme turns into this not so lovely level scheme. But to our eyes this was a thing of beauty because this showed isomers and that's what we wanted to study. So we had a good time doing that. If

You can in fact-- we went through in the paper. I think we proved that we must be getting near the end of the experimental program because in that paper we started making theoretical conjectures. Which is bad for a gang of four experimental post-docs to be doing. But we did it anyway. We couldn't resist taking the level schemes from dysprosium 150, which had been worked out in the interim, and the erbium we'd just measured-- knows that these two even even schemes are fairly similar. The difference being simply this pair of protons. You then in both cases tack on a neutron and the dysprosium 151, you end up with this sequence of states and spin parity values and the trained eye can quickly spot that it's actually rather similar to what happens over here in the erbium 153. The difference was we didn't run quite as long and managed to chase out the F7 have H9 half band there in the middle.

But we thought that was rather cute in terms of how things worked out that the structure didn't change so much. There's one last thing, and digging back through the literature I reread that paper. And in the discussion under experimental technique, there was a little phrase which I've pulled out here that mentions-- this is from the erbium 152 paper. We'd run some [INAUDIBLE] carbon reactions. That's good standard compound nucleus reaction where you let a few neutrons boil out and make your compound nuclei. And we comment here that reactions with the backing material made radium 216 lines, which leads into troublesome contaminants in this experiment. We usually with things like that, stop there, but of course Dog and Kim never let a data tape go unused. So a year later, a paper came out about radium 216 lines. They decided the tandem had to go down for repairs that year and so they were industrious fellows and analyzed the background. Almost Thomas Lonnroth came over from Finland to help us finish that effort.

Now before I say a few words about Rick, since Lee got me into this, I have to say how Lee got me into Berkeley and how I met Peter Butler and Lee. Lee had The idea late in my stay here that we ought to get into the then very current and timely effort to find super heavies. We spent a little bit of time thinking up how to do it. Lee suggested that we ought to get off and do something rather different from what had been done by other groups. We were simply trying to make things by compound nucleus extend reactions. Which is rather difficult up in high mass because it's difficult to make the nucleus cold enough that it won't sit and just boil neutrons off, find itself where it's unstable against doggone near everything. Fission decay, rapid alpha decay, and the like. His suggestion was to turn this instability to fission decay into a virtue.

And so what we decided to do is instead of trying to make things by compound nuclear routes, instead we'd try to make them by forming a heavy nucleus which decayed by fission. Lee's suggestion was that we take these beams of about eight and some odd MEV per nucleon-- actually this is around five-- of krypton, which were available now at the super hilac at Berkeley. Use those to bombard lead targets and then cock the target over at about 80 degrees. So that you'd be nice and thick for stopping the heavy fragments.

You could stop them in about two picoseconds. But you'd be rather open for looking at the fission fragments, which would come lumbering out. So we put this rather simple looking set up into the line at the hilac and I think took a few shots out there. Of course, everybody knows what the answer to the experiment is because fame and fortune were not ours. We ended up with the same results as everybody else. What I show you here is the operative figure from the paper where we plot the correlated energies from the two telescopes. One on this axis and then the three recoiled telescopes, each in their own box. And had there been large numbers of counts in these little windows which I show you here, then Peter would have been happy and Lee would have been famous, and so on.

But as it was, we joined the long list of people who were able to set limits. In our case, we were able to, however, set them at an interesting piece of phase space. No one had ever looked at things that were isomeric out to several hundred nanoseconds. The really nice thing about this technique is that you can observe until you're tired and turn the electronics off. So if you found things that were metastable, you would in fact see them in this. But we didn't, and I think we that cross section limits somewhere in the micro barn range as I recall. Well that's sort of what occupied me up till roughly 1985. It was this and similar studies which went on at Oak Ridge with the Holifield machine that was set up there. Some of were done in collaboration with Cormier and Horne, who I'd worked with here. And other people who I then met. I spent a few more years studying isomers with Yang Lee since he also ended up coming to Oak Ridge. In fact is still there now involved in the gammasphere program.

However somewhere in the mid 80s, I think it was '82 '83, I went to a talk at one of the early nucleus nucleus conferences. I think it was given by Miklos Jalousie where he described what had come out of the Bielefeld conference of that summer. And also some observations concerning what had been seen in recent cosmic ray events looking at heavy nuclei such as calcium and iron striking emulsion targets. What had been seen looked rather exciting and this all led to us going and reading the literature that winter. Bjorkin's paper about suggestions of how one might look for a deconfined state.

How it might be seen in the hydrodynamic scaling picture came out. And I decided at that point to shift gears in a fairly major way. Specifically we decided to join the relativistic heavy ion or what's now somehow become known the ultra relativistic heavy ion. It'll have to become relativistic I guess once the SSC going gets going. And start looking at very high energy collisions and see if you could see evidence for something quite different go on in nuclei. In this case use them as a hope for tool for finding evidence for quark deconfinement. How to describe that in the few minutes I've got left is a bit of a challenge. I finally decided it would be best to talk like this to deal with it a bit at the cartoon level.

So I had a few cartoons I've brought. What's meant by the following graph is just a discussion of how you might find a difference between-- discuss what goes on when you're looking at-- instead of say a familiar diamagnet of the type that we all know rather well from superconductivity. You have a situation where you've formed a condensate of electron pairs and you end up with a rather perfect diamagnet. You exclude say a magnetic field from the center of a super conductor there when you get down to what you might loosely refer to as a QED vacuum. The opposite possibly happens in QCD.

As I mentioned, Tom Degran had something to do with getting me to come here. And part of what he was doing while he was here was working on the bag model and occasionally would tell me stories about that was going and how one tried to understand this rather odd fact that quarks seemed to be real objects. That's how you would understand certain results that were seen at Slack and Brookhaven, but they didn't seem to show up. You had to understand why they should stay confined. You might choose to look at that as the few-- argue the QCD vacuum is also a condensate. In this case of blue long pairs and QQ bar pairs. And you end up with the inverse case of what you see in a superconductor instead of the small region forcing the fields, you get the vacuum confining the color electric fields down to the core of a hadron.

What you would then-- so you would then end up with a QCD vacuum which you should describe in electrical language as a color dielectric. What I have down here at the bottom is then a very crude correspondence chart between the two. And what you're describing and say the superconductivity is-- you're excluding a magnetic field on the inside, whereas what goes on of course in QCDs you exclude the color electric field from the outside. You can find it down to the volume of a hadron. But you could then ask what does it take to get yourself into a situation where that wasn't just confined to a hadron but rather was able to spread out over a somewhat larger volume of space.

Maybe one you could even hope to experiment with a bit. It's been conjectured that you in fact ought to do that. It ought to be able to be seen if you were able to compress nuclear matter or heat it up by some factor which if you expressed it in density terms might correspond to about a factor of four. You can come up with a cartoon, and it's nothing but that, of how such a phase diagram might look if you'll allow yourself to discuss thermodynamics and strongly interacting matter in the same sentence.

And you might express that as something which runs up along an axis which is labeled here as temperature. You can understand that by asking crudely where that scale comes from just by asking yourself what's the energy density inside of a proton, which is of the order of half a jev per cubic Fermi. And what's the energy density inside of an atomic nucleus, like a lead nucleus? And the answer in that case is 0.15 jev per cubic Fermi.

So you could argue to yourself that if you could crowd the lead to where everything was overlapping, and there was increased that energy density by about a factor of three per unit per Fermi cubed, you can come up with a rough estimate of the order of 300 MEV. Of course you can make a much more sophisticated estimate of where that should sit. Similarly, you can get a rough guess of where this break between normal matter we know and love and this conjectured plasma, carboline plasma as it's become known, you could estimate where that sits on the density scale by taking a bit of a look at just what the relative volume sizes are. Radius parameter nucleus is 1.2. It's 0.8 for a proton. If you take the ratio of those cubed, lo and behold you'll come up with about four.

This of course has had much more sophisticated investigation than that. Here I've picked something from one of the papers by the Columbia group, Norman Kris group who have done fairly large scale lattiscapes studies of QCD over the last number of years. And in fact as Professor Cunin discussed yesterday have built a rather large and specialized machine to do this. What's shown here is how the entropy in such a field theory runs as a function of beta, which is proportional to temperature in that theory. And you see a rather sharp run up of that at a specific point.

Whether or not this will actually turn out to be a nice first order of phase transition from what we know as nuclei to what we call a plasma, or whether it'll be more like the phase transition of no particular order, which is what we know for atomic plasma, of course remains to be seen. From the standpoint of what an experimentalist might think about, if you could do this, we hope, by colliding two very heavy ions at high energies. If you start here and here after they pass through each other. These nuclei are pancakes simply because of Lorentz contraction.

You might hope if you do this at high enough energies, such as at the energies that the machine being constructed at Brookhaven will do, that you might find yourself in a situation such as the barions, the network content, will be boosted out of the central region of phase space and you'll be left with a region covering a number of units of rapidity, which is best described as purely bluonic excitations. Not that you'd lack a few Q bars in that region, but you'd be free of the normal baryonic matter we're familiar with and be able to take a rather direct look at matter of that type.

Now such a machine is in fact under construction at Brookhaven. Those of you who remember the Isabel project will perhaps recognize the tunnel. This is known as the relativistic heavy ion collider. It is a machine which will be fed by the tandem and AGS complex, which I guess a few weeks ago managed to accelerate the goal nuclei that are needed for this project. It's currently under construction and expected to complete in about five years from today, as we stand. There may very well be a parallel effort go on at CERN. It's not quite clear how that will evolve, though I think we'll hear later today about discussions concerning the Large Hadron Collider, which would be concerns version of a machine of SSC type. It's been pointed out at CERN that since they are constructing injectors for lead beams and have put heavy ions through the SPS that you could just as well carry those out to the LHC.

So if that came to pass, instead of the 100 jev on 100 jev that we'll have at Rick, which should form the central region, it might very well be able-- be possible to get out to the center of mass energies on the order of 1 PEV if you add it all up. In more conventional units, that would be about three TEV per nucleon for lead ions. I think I can go on at some length about how one goes about detecting a quark log plasma. I think the only candidate answer to that is once we get through the exploratory phase in this particular branch of research, we'll know. That There has been a fairly large program started to do that at Brookhaven and at CERN. And I'm happy to notice from asking yesterday to Steve Stedman for a list of who is now in the heavy ion group that they're back to some dozen students who are in fact involved in that program. So a few years down the road we hope to see another good set of MIT graduates leading the way on this particular effort.