Questions and Answers from Virtual Ask-a-Scientist of February 2, 2002

More information about the program

Moderator (this is Robin Erbacher, researcher at Fermilab)
Welcome to the Virtual Ask-a-Scientist program. I am Robin, the moderator. Sitting next to me is Roger, the guest scientist for today. We are ready to begin when you are. Fire away!

Kevin
What, exactly do you do there at Fermilab?

Roger Dixon
I do a few different things here, but my main thing is my research. I am working with a group of people who are looking for what most of the Universe is made of. It turns out that whatever it is, it is missing. We would like to be able to detect it in a laboratory on earth. So, that is what I am spending most of my time doing here-- working on the Cryogenic Dark Matter Search (CDMS). Check out this link for more information on CDMS. http://cosmology.berkeley.edu/group/directdet/

Barbe
Is Fermilab currently running an experiment in the accelerator?

Moderator
Hi Barb, Yes, Fermilab is currently running two experiments in the Tevatron, the world's highest energy accelerator. We are colliding protons and antiprotons to study fundamental particles. Here is a link to a nice site that shows live events from the two experiments, CDF and Dzero, as well as the status of the accelerator itself. Check it out! http://www.fnal.gov/pub/now/index.html

Kyle
What exactly is Dark Matter? Do we know what kinds of properties it may have or importance it may be to the field of science?

Roger Dixon
Good question, Kyle. We don't know what dark matter is-- exactly. We see lots of evidence for it when we look out into the universe and see how things are moving out there. We think we understand the laws of gravity and that tells us there is a lot more out there than we can. But, we only have theories as to what it might be. The best one seems to be a kind of elementary particle that we have never detected directly on earth. We hope that it interacts weakly so we can detect it in detectors in the Laboratory. It is important to science because it influenced the way the entire universe evolved. Without it we would not have galaxies, stars, or structure.

Bill
Why do you have bison there at Fermilab?

Roger Dixon
We have bison at the laboratory because our first director, Bob Wilson, was from Wyoming and he was attempting to re-create the atmoshpere of the prairie here. It worked.

Moderator
We have a description of many of the natural aspects of the laboratory along with pictures on our website. Here is a description about the bison: http://www.fnal.gov/pub/about/campus/ecology/wildlife/bison.html

Mike A
What experiments at Fermilab are related to astrophysics?

Roger Dixon
We have 3 experiments at Fermilab that are astrophysics. The first is the Slaon digital sky survey which is mapping out a good bit of the sky using a telescope in New Mexico, my home. The second is the Pierre Auger project which is setting up in Argentina to look at very high energy cosmic rays in the hope of figuring out where they come from. Finally there is my own, CDMS, which is currently runniing under the campus at Stanford to look for dark matter. We are presently installing a better version of CDMS in an old iron mine in northern Minnesota where we hope to actually be able to detect the dark matter. We also have a terrific astrophysics theory department here.

Should be Sloan instead of Slaon-- I need a spell checker here!

Moderator
The Fermilab Astrophysics Theory group is indeed very active, and has a website at: http://www-astro-theory.fnal.gov/

Bill
Where will the next accelerator be sited?

Moderator
The next large accelerator in the world will be the LHC, the Large Hadron Collider. This is currently under construction at CERN, the European particle physics laboratory that is located near Geneva, Switzerland. The LHC expects to start taking data toward the end of this decade. The United States is collaborating on this experiment. After that, there is a proposal to build a Linear Collider, which will collide electrons and positrons, but the location has not been determined.

Mike A
What's the connection between sub atomic physics and astrophysics?

Roger Dixon
Good question. When it comes right now down to it, the whole universe is ultimately made up of particles, so it makes sense that we have to understand particle physics pretty darn good to understand what is going on in the Universe. Now let me give a specific example. Dark Matter-- sorry that is our theme-- we have good reasons to suspect that it is some kind of fundamental particle that we may also be able to produce in the laboratory. We haven't produced it yet, and we haven't detected it yet on earth, but we certainly see its effect on the universe. Note that understanding how the sun works was not possible until we understood a good deal of nuclear physics. We are learning more about it by studying things like neutrinos which are produced in the sun. It goes on and on.

Kyle
The concept of astrophysics and anti-matter is very interesting. What sort of college education is required to enter this field of work?

Moderator
The answer to this varies. It depends on what exactly you want to do. In general, to become an academic (laboratory physicist or university professor) you would have received a Ph.D. in physics from a University, and then would go on to become a postdoctoral research associate for a short term before being eligible for a permanent position. I am currently a Research Associate at Fermilab. If you just want to learn more about particle physics, there are lots of nice books and websites on the subject.

Rob
Reading through FermiNews, I see mostly male physicists. Are there many female physicists?

Moderator
Good question, Rob. I would say that there are not nearly as many female physicists as male, but our numbers are increasing. I'm female, and I really enjoy my work! As more women enter physics, the pathway becomes paved for future women. The numbers have been increasing steadily as more girls are exposed to science and realize what fun it can be!

Rob
Can someone please explain this whole antimatter thing?

Roger Dixon
No. But, we do know something about it-- like it actually exists, we make it at Fermilab, and we use it to collide with protons. It turns out that antimatter was predicted before it was found by a famous physicist named Dirac. He was a theorist. He was trying to put quantum mechanics and relativity together, and his equations had a whole set of solutions for particles that had not been observed. They had different properties, or opposite quantum numbers for than the particles that were known. It turns out that every particle has such an "anti" particle. Why the entire universe is matter and not antimatter is another good question, but then you didn't ask. We might know somethiing about this from our studies of and certain assymmetries we have found there, but I am off on a tangent.

Michael
What do you think will be the next big breakthrough at Fermilab?

Roger Dixon
I would just guess that it might be the discovery of the Higgs, but supersymmetry and dark matter (which may be the same things) would be another good possibility.

Michael
I'm particular interested in the medical applications of high energy physics. Can you point me to some good resources?

Moderator
There are too many applications of our work to medicine to describe here, but for example, the MRI that you would find at a hospital stands for Magnetic Resonance Imaging. In our field we call it NMR, nuclear magnetic resonance, and it is a useful tool both in physics and in medicine. Here at Fermilab we use our accelerator to treat cancers, with a wonderfully successful program. Here is more information about our work: http://www.fnal.gov/pub/pulse/

Mike A
Are the mechanics a solar system like ours subject to the same law of physics as particles at a sub-atomic level? Maybe this is naive, but at some level, is our sun like a giant nucleus and the planets like electrons?

Roger Dixon
The answer to your question is yes and no. The laws of physics are the same everywhere, and everyone must obey them. But, the primary force holding the solar system together is gravity while the primary forces holding an atom together are the electomagnetic and strong forces. It turns out these forces are much more important on the distance scales associated with an atom. Gravity is more important for large scales. Quantum mechanics also influences the way very small particles behave, so the behavior of an atom is very strange if a solar system is your norm.

Lori
I'm interested in taking my family to visit Fermilab. Can I?

Moderator
Fermilab used to be open to the public daily. Now we are in a heightened level of security, but we are slowly adding back our public programs. Unfortunately, there are still restrictions. There are guided tours available, and we have just restarted our live Ask-a-Scientist program, held at the Lederman Center on Saturdays from 1-3pm CST. You are welcome to join us there and speak with us. See http://www.fnal.gov/pub/visiting/tours/index.html for information about visiting Fermilab. In addition, we have an Art and Lecture Series to which the public can come. See http://www.fnal.gov/pub/events/culture.html for our cultural events. The public can attend Fermilab colloquia, as well, provided they go to the Lederman Center ahead of time to receive a visitor's badge, and provided they have a Fermilab contact.

Kyle
supersymmetry?

Roger Dixon
Supersymmetry is a theoretical idea that has yet to be verified by experiment. It turns out that several problems in particle physics would be cleared up if supersymmetry were to exist, so theorists tend to like the idea. But, it has not shown up yet in our particle physics experiments. One could argue that it should have. The theory predicts an entire set of particles that are the partners of the known particles, much like the case for antimatter. It may be that they are too heavy to have been discovered yet. We are still looking. Also the lightest supersymmetric particle could be the dark matter. There are good theoretical reasons for believing that this may be the case.

James
How much is Fermilab's annual budget?

Moderator
Our most recent annual budget is listed as $297 million dollars. Here is a nice link that describes some of our expenditures. http://www.fnal.gov/pub/about/organization/budget_statistics.html This may sounds like a lot of money, but relative to many other government programs, particularly defense, it is really small beans. But for a huge payoff in knowledge!

Artie
Can you suggest other interesting sites for high energy physics?

Moderator
Yes, there are plenty! As you may know, high energy physicists were responsible for inventing the world wide web. Tim Berners-Lee was working at CERN, the European high energy physics lab, and created a mechanism to make documents public. SLAC, the Stanford Linear Accelerator Center had the first website in the United States, after Berners-Lee called up and said "check this out!" Here is the link to the other high energy physics sites around the world: http://www.fnal.gov/pub/inquiring/othersites/index.html

Moderator
PS, Paul Kunz was the scientist at SLAC that created the first WWW connection with Berners-Lee.

James
I read something somewhere about a discovery at Fermilab that may go against the standard model? Is that true? Can you direct me to more info.

Moderator
There has recently been some exciting results from NuTeV, a neutrino experiment that was done here at Fermilab. The results from this analysis disagrees with previous results of the same measurement (but measured a different way) by 3 standard deviations! See the press release here: http://www.fnal.gov/pub/presspass/press_releases/NuTeV.html It is unclear if this result is due to a lack of theoretical understanding of some aspects of strong interactions or whether it really shows a problem with the Standard Model. Either way, the results are exciting!

Artie
Does an accelerator have to be that big?

Roger Dixon
Well, maybe we should talk a little bit about why accelerators have gotten bigger and bigger. There are only a couple of ways we learn about the "stuff" around us. We can touch it, we can hear it, etc., but one of the most fundamental ways we learn about things is through sight, and that is basically what we are doing with our accelerator. When you do this at home you use might use a flashlight. You shoot it at something you want to know about, the light bounces off, and your eyes detect part of it. Then you think you know something about the object. So, why don't we just use a flashlight at Fermilab. The answer is based in quantum mechanics, which tells us how very small objects behave. It turns out that quantum mechanics tells us that to learn about the smaller, or finer details of anything, you have to have beams of higher energy. The higher the energy, the finer the detail. So, we have to make high energy machines to get down to seeing objects like quarks. Why are high energy machines so large? It turns out that the higher that to accelerate particles to higher and higher energies, you have to pass them through a cavity that gives them a kick each time they go through. As the energy gets higher, it gets more and more difficult to bend them in a circle and bring them back to the cavity. This bending is accomplished by dipole magnets. Since you can only make the magnets so strong, you have to make the circle that the particles travel in larger and larger. And, that is why we have such large machines and want to build even larger ones.

Kyle
How does the research being done at FERMI Lab compare to what is being done at CERN in Switzerland? Is it possible to tell who is closer to the next big discovery like the Higgs particle?

Moderator
At CERN, the LEP experiments, in which electrons were collided with anti-electrons (or positrons), completed there work in about 1999, and are currently publishing their final results. Some of these experiments reported an excess of data in an interesting region of energy, and some people believe that this may be a "hint" of a higgs boson in their data. Currently the baton has been passed to the Tevatron, where we will be able to look at this energy region to see if we see similar signals, or if the signal isn't there. At the end of the decade, the LHC (large hadron collider) will come online and be able to reach even larger energies, and we hope to be certain by then about the existence of the Higgs in our currently accessible experiments.

Rob
Is it safe there?

Roger Dixon
Yes. Fermilab is as safe, or safer than most industrial complexes. Yes, we do have accidents. Things fall on peoples heads, they trip over cords, you get runover walking to work (this happened to me in January), but there are no unusual dangers here. Our safety systems don't allow us to be in the accelerator enclosure while the beam is on. That would not be a good idea. It is safe to be there when the beam is not on. That is what most people worry about.

Rob
What different types of physicists work at Fermilab?

Moderator
Good question. Primarily, the physicists are what we call "particle physicists" or "high energy physicists". These come in several types. Experimentalists are the ones that design, build, and run the experiments, as well as analyze the data. Phenomenologists typically combine theoretical knowledge and skill with the results from the experiments to make statements about theoretical predictions or the implications of results. Theorists often do some phenomenology, but they also do lots of calculations, from the accepted to the speculative. All of our work put together makes the field very strong. We also have accelerator physicists, engineers, nuclear physicists, astrophysicists, and atomic physicists that work here.

James
It seems like CDF andD0 are trying to do the same thing. Am I right about that? Why does there have to be two detectors?

Moderator
CDF and Dzero are both Tevatron experiments, and will both be looking at data in the next decade. Two experiments are always prefered over one for several reasons. First, it is good to have a cross-check for our results. For example, when one experiment started seeing a hint of the top quark in the 1990's, the other could check their data to find the evidence there as well. Also, since the detectors are different, and have different strengths and weaknesses, we consider them to be complementary to each other, and both are needed. Right now we are extremely happy to have two independent detectors, because in our field we need as much data (as much statistics) as possible, and with both experiments we can combine our results and reduce the errors on our resulting answers.

Artie
Seems like the site Fermilab resides on would be some pretty valuable farm land. Does Fermilab have to be there?

Roger Dixon
It turns out that Fermilab is on some pretty good farm land. At least I see some good looking corn growing out there. Part of the site is still farmed. The answer to your question is that Fermilab does not have to be here, but it has not made all that large an impact on the farming in the area-- not nearly so large as all the subdivisions that surround us. To my mind, the Laboratory has been great for the area because it has preserved a little open space where there is still some farming going on, there is forest, there are all sorts of wetlands birds and animals. It is great for the area. We need to set aside more land like this.

Tom K
I was looking at the live event displays. What do they show you?

Roger Dixon
They show you sample events that are being registered in our two big collider detectors at the Laboratory. If you look at the displays you see the data from the tracking chambers and calorimeters in a format that lets you see the tracks coming out from the interaction points and see the energies deposited in the calorimeter.

Julia
Can the energy of a photon be converted into mass?

Roger Dixon
The answer is yes-- more in a second. Okay, more details. It turns out that mass and energy can be converted to one another, no problem except that you have to obey both the law of conservation of energy and conservation of momentum. This puts a little constraint on you. Anyway, the most common way to convert a photon into mass is that you run it into some material and convert it into an electron and a positron. Of course, you also have to conserve a few other things, like charge. That is why it doesn't convert into just an electron for example.

William
I'd like to be a physicist. Is it a good job? How's the cash?

Moderator
Being a physicist is very challenging and time-consuming, but most of us really love what we do! It takes a lot of training and often takes a lot of time, even on the weekends and evenings. We also don't get paid a lot, compared with many business people, although it increases as your seniority goes up, particularly for professors and senior scientists. But we don't do this for the money. We do this because we are interested in exploring the nature of our universe, and of matter. :)

Kyle
What could the discovery of the Higg's mean for the fields of physics and chemistry?

Moderator
Hi Kyle, I don't know if it will imply anything, really, for the field of chemistry. For particle physics, it could mean a lot. If we find evidence for a Higgs boson, one of the first things we will try to discover is whether or not there is only *one* Higgs (the "Standard Model Higgs") or if there are more. There is a theory called "supersymmetry" or SUSY that suggest there should be four different Higgs-type particles. Both or either of these findings would have many implications for the Standard Model of particle physics.

Julia
Did the experiment that CDF ran in march of 2001 bring any new or unexpected results?

Moderator
Hi Julia, I work on CDF, and we are currently studying our detector ("commissioning it") as well as looking at the data that are coming in to see if there is anything interesting there! CDF and Dzero will likely both begin to publish first results from Run 2 of the Tevatron, which began in March 2001, by this summer. We have now had some time to understand how our detectors perform, and to begin to calibrate them (determine energy scales and so forth) so we are looking forward to a very successful run with lots of papers full of interesting results!

Artie
I've heard there's been digging and blasting around Fermilab lately. What's that all about?

Roger Dixon
It turns out that we are doing the construction for a very exciting project. We are building a neutrino beam that is aimed at the Soudan Laboratory in northern Minnesota. The neutrinos will be produced using a beam that comes from the main injector here. It will pass through a detector here on site and then cut a cord across the earth and finally pass through the Soudan Laboratory where another detector will register a few of the neutrinos. The idea is to compare the beam as it leaves here with the beam that passes through the detector up there. We believe that some of the neutrinos are changing into different kinds of neutrinos enroute. These changes are called neutrino oscillations, and we want to study them in detail. If they exist, and it seems they do, it means that the neutrino has a little bit of mass. There was a time not so long ago when we thought the neutrino was massless.

JuliaWow, what are the chanses that you will discover something new?

Moderator
Well, that depends on how generous Nature is! For example, if the Higgs particle exists at energies below around 180-190GeV, by the end of Run 2 we will hopefully be able to at least see first evidence for it, though we will not necessarily be able to claim "discovery". If SUSY exists, we hope to begin seeing evidence for it very soon.

Moderator
Geruce has asked about the CDF and Dzero experiments. Both experimental collaborations have nice websites. Here is the CDF website, click on For the Public: http://www-cdf.fnal.gov/ Here is the Dzero website: http://www-d0.fnal.gov/. Here is a link to live events from CDF and Dzero... your answer is coming: http://www.fnal.gov/pub/now/index.html

geruce
Thank You Very Much.

Artie
It seems like there's a lot of other things going on at Fermilab besides physics (concerts, art gallery, etc.). Does that take away from the focus?

Roger Dixon
No. You can't be focused 24 hours a day for very long. You will run down pretty quickly that way. Anyway, the idea of all the activities at the Laboratory is to create an atmosphere that is conducive to creativity and good work, whether it is scientific, engineering, or whatever.

James
I'm sorry, but I don't really understand what's the difference between and Astrophysist and a Particle physicist. Could you explain?

Roger Dixon
Particle physicist are primarily interested in studying fundamental particles in the laboratory, measuring all their properties, and all. An astrophysicist is interested in understanding what is going on in the cosmos. Of course, this is not possible with the benefit of the knowledge that comes from particle physics. As a result, many astrophysicists are pretty good particle physicists too.

geruce
Where could I find more informaton about the steps the particle beams go through before entering the Tevatron?

Moderator
Hi, we have lots of information about the accelerator complex here at Fermilab, including a cool picture of where it all begins (the Cockroft-Walton) at: http://www.fnal.gov/pub/inquiring/physics/accelerators/chainaccel.html

William
It seems like there's a lot of "flip-flopping" about Neutrinos (ha!). What's the latest thinking?

Roger Dixon
Yes, it appears that neutrinos are doing some flip-flopping. The three kinds, or flavors, of neutrinos can change from one to the other. This is relatively new information, and it is exciting to particle physicists because it is one of the indicators that the standard model of particle physics must be modified.

Kyle
I am curently a sophomore in high school. How do you think the fields you are currently studying will change as information is gathered and technology evolves? Will we be likely to find particles even more elusive than those being sought after now?

Moderator
Hello Kyle. High energy particle physics is very dependent upon technological innovations. As the energies and the "luminosities" (number of total particles) of the accelerators go up, the amount of data that comes in at any one time increases dramatically. We therefore need better and faster detectors and triggers, as well as faster computers and larger storage (disk and tape and processing speed) capabilities. High energy physicists also participate in developing new technologies specifically for our experiments!

Julia
There is a similar laboratory that is now being built at CERN, Switzerland. What is going to be Fermilab's main focus when it is open in 2007?

Moderator
This is a very good question. Right now it looks like the Tevatron may run past 2007, but this depends upon when the LHC at CERN begins to publish physics results. There are lots of proposals for experiments to be built and performed here at Fermilab, including very good fixed-target experiments. One highlight will be the NuMI-MINOS project that is under construction here at Fermilab. This is an experiment designed to study the increasingly interesting neutrino particles. In addition, currently the Mini-BooNE experiment is gearing up to be run beginning sometime this year (concurrent with the Tevatron, but during a downtime of the Tevatron) to study neutrinos as well!The future for Fermilab past this decade is now being discussed and debated. Many physicists in the U.S. would like to see the next big accelerator built here: a large Linear Collider that would collide electrons and positrons at high energies (500 GeV to perhaps 1.5 TeV or so). There are also proposals to build the linear collider in Germany and Japan, though, so who knows? Other scientists here would like to see a VLHC built here, an even higher energy hadron collider. But this would be on an even further time scale.

Lori
So Weakly Interacting Massive Particles are "WIMPs"? Who names these things?

Roger Dixon
Not me!!! Whoever did it is probably quite proud of themselves, but here I am doing research where I have to live with it. Anyway, when you write it out, it does make sense. That is what we are looking for-- weakly interacting particles that are probably heavy (WIPTAPHs-- there, that's better.) By the way, it used to be MACHOs vs. the WIMPs. MACHOs were thought to the the dark matter by some astronomers for a while. They are Massive Compact Halo Objects.

Tom K.
OK--Who REALLY discovered the Top Quark first? You can tell us.

Roger Dixon
I think it was James Joyce, but it is not well documented. Anyway, the real story is that CDMS saw evidence for it first, and then the Dzero and CDMS collaborations zoomed in on it at the same time and announced the discovery together.

Roger Dixon
I meant CDF-- I guess my bias for physics is really showing there.

Lori
Are there any opportunities there for high school students?

Moderator
Yes! If you are local, you can participate in Saturday Morning Physics, which Roger helps run: http://www.fnal.gov/pub/education/index.html In addition, there are summer programs for students interested in science. You can browse through on this link.

Julia
I'm looking at the webpage where you can see the CDF and D-0 results every 15 seconds. Do you run experiments all the time or are there different set times for that?

Moderator
Hi Julia, When the Tevatron is running (when there isn't "downtime" for repairs, upgrades, studies, or other experiments) we operate the accelerator, and thus the CDF and Dzero experiments, 24 hours per day, 7 days per week! This means that there are people "on shift" in the Main Control room that controls the accelerator, in the CDF control room, and in the D0 control room.

ronnie
I'm particularly interested in the architecture of Robert Wilson. Can you point me toward some info?

Roger Dixon
Here is the link: http://www.fnal.gov/pub/about/campus/architecture.html

Me
Can someone help me with a lesson plan on WAVES for 14-15year old highschool students. Thanks.

Moderator
We do have a lot of high school physics and science teachers that work with Fermilab through a program called Quarknet, along with other programs. They might be a good resource for help at the high school science level. Please send a note to the education office or to Quarknet at: http://www-ed.fnal.gov/ed_home.html or at: http://quarknet.fnal.gov/

Julia
Thank you very much for all the answers!

papageno
I've heard there are many photos and information about birds on the Fermilab site. Where can I find that?

Moderator
Hello Papageno! Please see: http://www.fnal.gov/pub/about/campus/ecology/wildlife/index.html

Julia
Is there a live "Ask-a-scientist" program at Fermi?

Moderator
Oh, you and I think alike! Yes, see my previous message: Saturdays at 1pm CST, use the Pine Street entrance to Fermilab and come to the Lederman Center!

Moderator
See you next time!

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