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Dave Schmitz | Photo Courtesy of Fermilab
Particle physicist Dave Schmitz works on the MINERvA experiment at Fermi National Accelerator Lab -- he took some time to tell us why neutrinos (electrically neutral, subatomic particles) are important to the universe and why the time 1:32am has special meaning for his experiment. And, check out Dr. Schmitz’s talk yesterday -- “In One Ear and Out the Other: A Talk about Neutrino” -- as part of Fermilab’s 'Physics for Everyone' lecture series.
Question: What sparked your interest in pursuing a career in science?
I started my career in science relatively late. I originally started as an architectural engineering student in college. I didn't change to physics until late in my fourth year as an undergraduate. I had read several physics books for a public audience and became interested in learning more. I decided to enroll in a Physics III course as an elective towards my engineering degree. I remember my advisor thinking that I was completely nuts and only reluctantly signing my enrollment card. Maybe he was so hesitant because he feared I would not return to architecture.
That semester, the class touched on the concepts of relativity and quantum mechanics for the first time. My professor was very enthusiastic and would happily spend extra time out of class discussing anything I wanted. At the end of that semester I joined a research group studying neutrinos produced by distant cosmological sources that interacted in the polar ice cap at the South Pole. In December 2000, I had the thrill of traveling to the experiment for two weeks to deploy some new equipment. If I wasn't already hooked on a career in science, a trip to the bottom of the earth sealed the deal.
Q: You’re a physicist and a neutrino expert. Why did you choose this field?
DS: Neutrinos first sparked my interest as an undergraduate. The idea that neutrinos could be used to tell us something new and exciting about an object on the other side of the universe was pretty incredible to me. Then in graduate school I had the opportunity to work on an experiment that was searching for a completely new kind of neutrino that we had never even seen before. I worked on the MiniBooNE experiment at Fermilab which was searching for evidence of "sterile" neutrinos, a new type that did not interact via any of the currently known forces. It turns out there remain many interesting unanswered questions about the fundamental nature of the neutrino. We now know that neutrinos do have a tiny mass, but we have not been able to measure its value -- we only know that it isn't zero. There is also the possibility that neutrinos and their antiparticles (simply called antineutrinos) may behave differently in very subtle ways. We are planning experiments now to search for such differences, which could be a big part of the explanation for why the universe we live in is dominated by matter with little to no antimatter. In this way, neutrinos could fill in a critical piece to our understanding of how the universe has evolved into the amazing (and, thankfully, hospitable!) place we see around us.
Q: Do you have any advice for students who are interested in becoming scientists?
DS: Get involved in experimentation as early as you can. It really is a process and, like anything, it takes practice to get better at it. If you are really young, it can begin with doing small experiments at home. If you are an undergraduate college student interested in studying science in graduate school, then participating in some form of research at your university will really help open your eyes to the challenges and joys. It doesn't even need to be exactly what you will work on later (you don't even need to know exactly what you want to work on later), but the experience will be invaluable in any case. Also, take any opportunity you have to practice communicating with other people, about science or otherwise. Science is a collaborative effort and the skill of communicating what you are doing to others, experts or not, is really important.
Q: You work on the MINERvA neutrino experiment. What is your team working on right now? What was it like to be there when MINERvA witnessed its first neutrinos?
DS: MINERvA is designed to vastly improve our basic understanding of how neutrinos interact with other matter. Neutrinos interact with the nucleus but this interaction can be different for different nuclei (helium vs. carbon vs. oxygen vs. iron) and measuring these differences can tell us about the atomic nucleus as well as about the neutrino. These measurements are also critical for improving the reach of future experiments like the ones I mentioned above.
Right now the MINERvA collaboration is focusing on obtaining first physics results from our data, so it is a very exciting time for us. We have been working very hard for the past few years to build and test the detector in the neutrino beam, and now that operations are very stable we have been able to turn our attention toward analysis.
It feels great to be at this point when I can still remember so clearly the feeling of seeing MINERvA's very first neutrinos not so long ago. Actually, the day we first turned on the detector my parents happened to be visiting and so I had to drag myself away from the lab that evening before we saw confirmation that things were working to go to dinner with them. After dinner, I couldn't wait until the next morning and so I logged on to download the small amount of test data my colleagues had managed to record with the experiment after I left but were unable to analyze. Sitting on the couch next to my mother at around 11pm, I made a couple of tweaks to the analysis software and was finally able to make the graph that showed, plain as day, evidence for interactions that were being caused by the intense beam of neutrinos. The signature was so clear that even my mom, sitting next to me, got excited when she saw the graph, suspecting that it had to be something meaningful. I just looked up the email I subsequently sent out to the collaboration that night - it was sent at 1:32am.
Q: International collaboration is a key part of your field -- which projects are you watching (beside your own)?
DS: Oh, there are many. Everyone is, of course, watching the Large Hadron Collider to see what physics it will uncover. In neutrino physics, I'm hoping the next big result will come from one of the reactor neutrino experiments (Double Chooz, Daya Bay, Reno). These projects are looking for electron type neutrinos to convert (or oscillate, as we say) into other kinds of neutrinos. These experiments are trying to measure a very important but totally unknown parameter in neutrino physics, called theta13 ("theta one three"). It describes the extent to which the electron neutrino can oscillate into the other kinds and it is a key step to measuring the neutrino/antineutrino differences that I mentioned earlier.
Q: Neutrinos have fascinated a diverse history of characters, from Wolfgang Pauli to John Updike. What excites you the most about being part of this group?
DS: Neutrinos have developed a reputation for themselves by repeatedly surprising the science community. The first surprising thing was their simple existence. It was a rather desperate idea (his words) by Pauli to solve a problem seen in other experimental data. The neutrino was so difficult to observe that is took 25 years for particle physicists to figure it out and verify Pauli's idea. Since then it has been one surprise after another. Oh look, there is more than one kind of neutrino! Oh wow, they can actually transform into each other like an apple turning into an orange! I want to be a part of discovering the next surprise. Can they explain the dominance of matter over antimatter? Are there even more kinds of neutrinos that don't interact via any of the known forces?
Q: So why are neutrinos important for our sun and the evolution of the universe?
DS: Neutrinos participate in, and even dominate, a huge variety of processes happening throughout the universe. A supernova explosion, the most energetic explosion in the universe, gives off 99 percent of that energy in the form of neutrinos. So clearly neutrinos are important to what's going on at the end of a star's life, but stars produce neutrinos throughout their lifetime in the nuclear fusions which constantly occur in a star. The sun, for example, produces so many neutrinos that 100 billion of them pass through a space the size of your fingernail (one square centimeter) each second! From that you can estimate the incredible number that are passing through your entire body every second of every day, and yep, nighttime too.
Q: What can you never start a day at the lab without?
DS: Same as anyone, I'm afraid, coffee and email! But also Fermilab publishes a daily online newsletter called Fermilab Today. I make a point to read the three to four articles that are posted each day. The articles cover news from within the lab, letters from the Lab Director, other articles on a variety of topics affecting the laboratory and links to general particle physics news from around the world.
Q: When you’re not working in the lab, where can you be found?
DS: In the summer I spend all of my time outdoors. I play on a softball team and a flag football team with friends in Chicago. I always plan at least one camping and hiking trip each summer, anywhere from a weekend in a Wisconsin state park just a few hours away to two weeks hiking in the great National Parks of the west. But on most weekends I can definitely be found on the lakefront at Montrose Harbor in Chicago where I keep my sailboat, Hyperbole.
In the winter, well, just check the lab first.
Q: We did hear that you’re an avid sailor. What are the greatest joys and challenges of sailing?
DS: Sailing is an incredible combination of two things that I love. First, relaxation! Nothing is more relaxing than a beautiful summer evening out on Lake Michigan two miles from shore where the traffic and buzz of the big city can be seen in the distance but not heard at all. And the thing that makes sailing unique is that this relaxing activity if chock-full of mechanical and electronic gadgetry of various sophistications, planning and strategizing to get where you want to be with the wind nature happens to be providing (or not) at that moment, and the physics of forces and motion enabling a three-ton boat to be moved by a ten-knot breeze. These things, to me, only add to the obvious natural beauty of sailing.