Questions and Answers from Virtual Ask-a-Scientist of March 31, 2004

More information about the program

Moderator
Welcome to Virtual Ask-a-Scientist! Adam and Jean-Roch are ready for your questions.

Bill
How has funding changed over the last five years for Fermi lab as a whole?

Adam Yurkewicz
Funding for physical sciences as a whole has been pretty flat over the last few years.

Bill
Does Fermilab have any experiments scheduled or recently completed that are in any way related to string theory?

GreenGrass
So, what's going to happen at Fermilab when the LHC at CERN comes online?

Adam Yurkewicz
D0 and CDF will wind down. A new experiment called BTev has been proposed (its one of the top priorities in the 20 year plan for the field). it may start running around that time (2007-2009?)

Jean-Roch Vlimant
Actually D0 and CDF are experiments that are looking for extra-dimension which is a necessary condition in String Theory

neutron dancer
Has anyone found the Higgs boson yet?

Jean-Roch Vlimant
Not yet, but high energy physicist are trying to set a limit on its production cross section ( probability of creation through interactions )

Bill
Any general comments on the validity of string theory? Strong points? Weak points? Where is the smart money betting?

Adam Yurkewicz
The strong points are that the fundamental forces can be unified in this theory (gravity, electromagnetism, and the weak and strong forces). on the weak side, the theory hasn't provided many predictions which are falsifiable by experiment. so we can't test it out very well yet!

Monty
If photons travel at the speed of light and at the speed of light time slows to a halt, would a photon have experienced any time since the big bang?

Adam Yurkewicz
The speed of light in a vacuum is always measured to be the same value by all observers, regardless of their motion. this is the idea behind the theory of special relativity.

GreenGrass
Do you think you'll find the Higgs at Fermilab?

Jean-Roch Vlimant
It is possible. Since the energy we are dealing with is far enough to create it. But the probability for its production is very low so we need to collect a lot of data.

Bill
Can you say anything about how the upcoming D0 & CDF experiments will address the extra-dimension issue?

Adam Yurkewicz
both experiments have already presented preliminary results on searches for extra dimensions. they haven't found anything yet. they will continue searching for the next several years.

Kalibyrn
This is pretty basic physics, but I am a beginner. Can you explain what radiation is and why it is dangerous? Thanks.

Adam Yurkewicz
Radiation comes in several forms. It can be particles like electrons or electromagnetic waves such as light. it is dangerous in high doses because it can enter your body and possibly damage the cells.

GreenGrass
Could you explain what happens with the Numi experiment? It goes all the way to Minnesota?

Jean-Roch Vlimant
The Numi experiment goal is to measure quantities for neutrino. Those particles interact weakly with matter, so it need to go from here to Minesota for them to interact with the earth and be detected in particular physical states.

Howie
I see that Fermilab is looking for a new director. What does it take to be a director at Fermilab?

Adam Yurkewicz
I would say it takes both good management skills as well as an excellent and broad knowledge of physics

Howie
How did each of you decide to become physicists?

Adam Yurkewicz
I had a great physics teacher in high school who had a passion for physics. in college, i took a few courses and was hooked.

Bill
What are the technical challenges for the up coming experiments?

Jean-Roch Vlimant
As for particules physics the challenge is two sided, first we need more and more energy to create particles not seen yet, and second, we need a lot of statictics to look for rare decays.

Paul
My nearly 11-year-old son Jake is sitting here with me and wants to know: I know that you use a particle accelerator to smash the same kinds of particles into each other. But why don't different kinds of particles smash into each other, too? Or do they?

Adam Yurkewicz
Here at Fermilab we collide beams of protons with beams of antiprotons. each beam has millions of particles in it. because they are so small, most of them completely miss each other. usually one proton hits one antiproton. sometimes a few collide at the same time. other accelerators collide electrons and positrons(SLAC at stanford) or gold atoms(brookhaven).

Howie
Thanks, Adam. How does it compare with what you thought it would be? Do you like your work?

Adam Yurkewicz
I enjoy the subject matter very much. it is also a treat to work with so many smart people who are interested in the same thing. in addition, at a large lab like fermilab many guest speakers come to give presentations which are very interesting.

Jean-Roch Vlimant
I decided to become a particle physicist because I always wanted to find the meaning of things, and working at atom or molecule level is not satisfactory for me.

Bill
Are the decays and interactions still searched for "manually" ?

Adam Yurkewicz
in the old days(before my time), bubble chambers were used which took photographs of each collisions. workers manually scanned through each one. now, we record the data with computers, and check it with computer programs. but we still make "event displays" of interesting interactions. i think there is a web site where you can see some of them.

Nathan
Can you give a status update on MINOS? When will start shooting neutrinos at minnesota?

Adam Yurkewicz
we are not sure here. we know it is soon. consensus here is about 2005.

GreenGrass
It seems like CDF and D0 are trying to do the same things. Why are there two experiments like this?

Jean-Roch Vlimant
We need two experiments so that results can be cross checked. It was the case for the Top quark discovery in 1995

Howie
Why does Brookhaven use gold atoms?

Adam Yurkewicz
because they are doing a different kind of physics. gold atoms have lots of protons and neutrons in them. inside each are quarks, and they are trying to collide the quarks to create a "quark-gluon" plasma. they didn't have to choose gold. they could have used another heavy element.

Paul
A question about radiation: If a country exploded a nuclear weapon, how fast and how far would the radiation spread? Would it be carried around the world, like dust sometimes is carried all the way here from a dust storm in Africa?

Jean-Roch Vlimant
Each radiation type is stopped by a certain amount of matter so it depends on a lot of parameters. As for dust is can be carried by the atmosphere and therefore go sometimes further away

Howie
Sheesh. Doesn't that get expensive?

Jean-Roch Vlimant
The amount of gold used for such an experiment is so small it does not turn that expensive

Bill
Does Fermilab get involved in the dark matter/energy questions?

Adam Yurkewicz
definitely. at d0 and cdf we search for new particles which may be the dark matter. we also have theorists who come up with new ideas about dark matter. there are also other experiments at fermilab which search for dark matter such as CDMS.

Nathan
Can you explain the difference between "energy" and "charge"? Are they not the same thing?

Jean-Roch Vlimant
Charge is how things react to electromagnetic fields and force. As for energy, if we beleive Einstein theroy energy is matter and vice-versa.

Bill
OK, thanks. I gather dark matter is matter that isn't bright so we don't "see" it. ... but what is dark energy?

Adam Yurkewicz
dark energy is the name for a different thing we don't understand. it encapsulates our ignorance about what causes the acceleration of the universe.

Howie
Jean-Roch--you don't sound like you're from around here. How do you like working at Fermilab? How do you like the area?

Jean-Roch Vlimant
FermiLab is a great place to work at. The site is ok, I like working here although I am away from home. I work too much and did not take time to visit the country that much, but Chicago is a great town.

GreenGrass
Could you explain a bit about what CDMS does?

Adam Yurkewicz
i don't know too much myself. they have detectors which just sit and wait for particles to float by and interact with the detector (as opposed to particle accelerators which actively smash particles). you can read about it http://ppd.fnal.gov/experiments/cdms go to the overview.

Adam Yurkewicz (Mar 31, 2004 8:46:53 PM)
i should add CDMS is located in Minnesota, but it is managed by Fermilab.

neutron dancer
What are you looking for in your research?

Adam Yurkewicz
My research is a search for supersymmetry. supersymmetry predicts a whole new series of particles. there is one new particle for every particle that we have already found. the new particles are sometimes called super partners or sparticles. we haven't found any yet.

Howie (Mar 31, 2004 8:54:29 PM)
So what are your predictions for the next "big thing" in physics?

Jean-Roch Vlimant
Of course the Higg boson is the next to come, but many theories are waiting for discoveries. In particular supersymetry and string theory. LHC will do the job I guess.

kevinmar
Hello. I was wondering about particles that "move backward in time". I know that this works out mathematically, but is this cosidered to be a likely explanation of antimatter?

Adam Yurkewicz
mathematically, this comes about because when you take the square root of a number you get both a positive and negative number. when the equations for electrons were worked out by Paul Dirac, the energies that they could have were a square root. so there were positive and negative solutions. His interpretation was that the negative answers represented positrons, which are just like electrons only with a positive mass. Richard Feynman said you can think about these antiparticles as regular particles that travel backwards in time.

Nathan
Is the search for sparticles different than the search for particles? How are the expirements different?

Jean-Roch Vlimant
The only thing we see in our detector is the results of their decay, we always ends up with basic particles whenever particles or "s" particles are involved.

Bill
Why is the Higg boson important?

Adam Yurkewicz
The Standard Model of particle physics as we now know it it has particles with no mass. in order to give the particles mass (since experiments show they need masses) a person named Peter Higgs came up with the idea that a Higgs field pervades the universe. When all the other particles interact wiuth this field, they get a mass. Some theory is needed to esplain how particles get mass, and the Higgs mechanism is the best one we curently have. One offshoot is that a particle called the Higgs boson must exist if this Higgs field does. So we are looking for the Higgs boson.

Howie
It seems like string theory is getting a lot of attention lately. Is that a good thing?

Jean-Roch Vlimant
String Therory is a great theory as Adam said. And it is getting a lot of attention because it will answer a lot of questions in a very "aesthetic" way.

Nathan
Is research being done at Fermilab to find the graviton particle?

Jean-Roch Vlimant
I think so. But its production is very rare and has not been seen yet.

Nathan
Isn't Fermilab planning, or bidding for a large straight line accelerator? What type of research will that be used for and how far along is that in the planning process?

Adam Yurkewicz
This is in the early planning stages. Right now, the world community is trying to decide exactly what to build and with what technology. it is a very challenging problem to build the machine. after a technology is chosen, several proposals will be made to build it at different sites. I am sure Fermilab will have a proposal. The reason we want this machine is to do very precise measurements at a higher energy than is currently possible. The machine will collide electrons with positrons.

Howie
re: String theory: So, you're saying it's an elegant solution? But, does that make it likely?

Jean-Roch Vlimant
Yes, it is an elegant way to unify all existent theory only starting with a few geometrical requirments.

demster
What is a Higgs field?

Adam Yurkewicz
The Higgs field is something proposed by Peter Higgs in response to a problem. The problem was that the current Standard Model of particle physics has particles with no mass. In order to give them mass, Peter Higgs proposed a new field, later called theh Higgs field, which fills the entire universe. When particles interact with it, they get a mass. If the field exists, a Higgs boson probably exists as well. we are currenbtly searching for it.

kevinmar
What is the state of the newest colliding beam at Fermilab? I read that it wasn't operating as well as many had hoped. What experiments are currently running on it?

Adam Yurkewicz
It has been performing better lately. Recently it set new world records for instantaneous luminosity which is a measure of how "bright" the particle beams are. Currently, CDF and D0 are studying collisions produced by the Tevatron.

demster
How close are you to finding the Higg's field?

Adam Yurkewicz
We probably won't know until we find it. An experiment at CERN, a laboratory in Switzerland, claimed they saw some preliminary evidence for it a few years ago, but then never claimed a discovery. We are looking in the same area they were looking (and beyond). Stay tuned. We may find it in the next few years. If not, the LHC at CERN will start a new experioment in 2007 or so that has an excellent chance.

Clo
Trying to understand everything...

Adam Yurkewicz
Physics can be very complicated. Follow up with questions if we are not clear. I have been studying physics for years and there is much more that I don't know than I do know.

Bill
Are there any particular imaginable, experimental results that would "clinch" string theory ?

Jean-Roch Vlimant
I don't think. High energy physics is a place where we can discover them. In accelerator or in cosmological observations.

kevinmar
Are there other large detectors planned for other sites in the world? LHC gets a lot of press, for good reason, but are there others even approaching that scale?

Adam Yurkewicz
Not really. As experiments get bigger, they get more expensive. As they get more expensive, they get fewer in number. Also, the number of people working on it is in the thousands, and there are only so many physicists in the world! Bug your politicians to fund more experiments.

Howie
I've heard talk of a new linear collider project. What's that all about? Why is that needed with the LHC coming online?

Jean-Roch Vlimant
LHC collider is a very powerfull machine, but the collision is not very "clean" because we use protons. In linear collider, the energy is a bit lower but the interaction does not contains a lot of background.

Bill
I must go. Thank you very much for your time and information. This is the best "reality show" I've seen.

Adam Yurkewicz
Thanks! Stop by again next month!

kevinmar
I'm trying to get our local politicians to build us a new school - we might have more luck with a detector!

Adam Yurkewicz
Both are very necessary in my opinion.

kevinmar
Back to LHC, why are protons not very "clean"?

Adam Yurkewicz
protons are made of 3 quarks. so colliding protons with other protons or antiprotons is actually colliding 3 quarks with 3 quarks. you can imagine the mess! colliding electrons with positrons is "cleaner" because electrons and positrons are not made of anything. they are fundamental particles.

demster
Thanks for the information!

Adam Yurkewicz
Sure, no problem!

Clo
(sorry for my bad english...) Why do you need to use "supersymetry" in the string theory ?

Jean-Roch Vlimant
Supersymetry is needed by String Theory because it makes it consistent with the existing therories. It has mathematical requirments that I don't remember.

Howie
I don't understand--why is "clean" better?

Adam Yurkewicz
Clean is better because it is easier for us to tell what is going on in the detector. The data is literally simpler for us to understand.

Howie
Does Fermilab seem a likely spot for the new linear accelerator?

Adam Yurkewicz
Fermilab is a good location because it is already staffed by people who have been succesfully building accelerators for decades. The actual location of the machine might be on the current property or it might be nearby.

kevinmar
Thanks for the chat! I have to go, but I'll be back next time.

Adam Yurkewicz
Thanks for your interest!

David
At least as far as we have been able to tell, electrons are not made of anything, right?

Jean-Roch Vlimant
Right. Its size is smaller than the current precision of the best experiemt. And no theory trying to make them of something is validate by experimental results.

Nathan
Re: Education. Do you think schools are not preparing our high school students with enough science foundation and critical thinking skills? Any observations?

Adam Yurkewicz
There was a fascinating talk on this very subject here just last week by Nobel Proze winner Leon Lederman. Look for it here: http://vmsstreamer1.fnal.gov/VMS_Site_02/Lectures/Colloquium/Lederman/index.htm

Adam Yurkewicz
Personally, I agree with some of what he said. Our education system has not been reformed in quite some time, and it could probably use it. The most important thing is critical thinking, as you said.

Howie
So, do you think your education served you well for being a physicist?

Adam Yurkewicz
I was fortunate to have some pretty good teachers. In terms of the problem solving skills, which are the most important, I was pretty well prepared. In terms of the actual skills, I had to learn many of them once I got here. I expect to need to continue to learn new skills throughout my life.

Nathan
Adam, Thanks for the great link. I look forward to seeing what Dr. Lederman has to say. I have the same problem with the stream.

Adam Yurkewicz
Too bad. Please follow up on it. I'm sure it will get fixed. It has some funny parts as well as the serious points. Dr. Lederman has a great sense of humor.

David
Lederman has been trying to get science curricula to teach "Physics First". So many of the curricula start somewhere else (say, with Earth Science) and then they have to tap dance around things because the phenomena is based so much on at least a conceptual understanding of physics

Adam Yurkewicz
That's right. In the talk I mentioned, he says that he has gotten some school districts to try things his way. San Diego is using it, and they are anxiously awaiting results that show whether the students did better.

Howie
What has Lederman been up to since leaving Fermilab?

Adam Yurkewicz
He has spent a lot of time trying to reform science education.

neutron dancer
what kinds of things do you do during the day?

Jean-Roch Vlimant
I am involved in the detector operation so I have to take care of the electronics and try and calibrate its response. I also have to take care of pieces of code that reads the data. And eventually I have to analyze data to get the physics signal out of it.

Howie
What are your person aspirations in physics? You're both quite young, right?

Adam Yurkewicz
Yes. Currently, I am writing my dissertation. After that, I'd like to continue to work at Fermilab for a while. The field of particle physics is very interesting, so I'd like to keep working on it.

David
Also, he was one of the founders of the Illinois Math and Science Academy, a state funded high school based in Aurora, Illinois, with a curriculum focused on science and math (see http://www.imsa.edu/ )

Jean-Roch Vlimant
Thanks for the information. I did not know that.

Howie
Do you think you'd ultimately like to work at the LHC?

Adam Yurkewicz
Yes, the potential for discovery there is very high. It will be an exciting time for us when it starts to collect data.

Howie
What are the implications of Grid computing? Soon, will you be able to "work at" the LHC while really working at Fermilab?

Jean-Roch Vlimant
It is already the case. But with maybe less amplitude that is aim at with Grid project. The interesting part of being on site is to interact quickly with people who knows the answer to your question. Although e-mail is widely use, some tricky things are difficult to explain.

Howie
Is that what US CMS is about?

Adam Yurkewicz
CMS experimenters are currently working on building a virtual control room in wilson hall here at Fermilab. There are also parts of the CMS detector being built here and shipped to CERN.

Howie
There seems to be a lot of excitement around B-TEV. What's that all about?

Adam Yurkewicz
BTev will be able to study B mesons in new ways. Many of the parameters of the Standard Model of particle physics will be studied more precisely than ever before. These precision measurements tend to make us more confident about our theories when they agree, and make us aware of possible problems with our theories when they disagee.

Nathan
No final question from me. I just want to thank Adam and Jean-Roch for their time tonight. Terrific resource. I will be back. Thanks.

Adam Yurkewicz
Thanks for your questions. It's been fun.

Howie
So, is this a new model for collaboration? Will more physicists work off site?

Jean-Roch Vlimant
Grid projects make it faster to process the huge amount of data that will be collected, gathering a lot of computer around the world. It will always be better to work on site, because communication is easier that way. Working on-site is a great experience and I can tell the difference.

neutron dancer
Thanks for all your answers!

Jean-Roch Vlimant
You are always welcome.

Moderator
Good night ! Thank you for participating in tonight's session!

Adam Yurkewicz
Good night everyone. Thanks for the questions.

Jean-Roch Vlimant
Good Night everyone, thanks for your attention.

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