Quantum Diaries

As I was typing those words in my last post, the thought actually crossed my mind, “Tell that to Tiger Woods.” I, for one, don’t have much interest in Tiger’s private life, and I’m not about to voice any opinions about it here.

But one tiny piece of his story did catch my attention yesterday while listening to NPR on the drive home from the lab. I looked it up when I got home and found dozens of hits, but the basic story is explained here on the web site of The Independent.

That’s right, Tiger has boosted the sales of a popular science book on physics written by British astrophysicist John Gribbin by virtue of keeping a copy in the back seat of his crashed SUV. I don’t know exactly how many copies have been sold but the book has apparently jumped overnight from an overall rating of 396,224th on the Amazon sales list to 2,268th place. That seems like a lot of book sales. Better still, the book was published ten years ago and is no longer in print. Therefore, only used copies are available, and it was reported that people have been spending up to $75 US for their little piece of Tiger Woods’ personal library.

I wonder if Gatorade and Nike will consider this anecdote when deciding whether to keep Tiger as their public face? I could not imagine a more bizarre way to test it, but “Get a Grip on Physics” seems to indicate that his testimonial is as influential as ever. Bizarre.

I couldn’t help it. At $5.50 for a matinee showing, I just had to hear it for myself. I recently went to see the newest Armageddon thriller to hit the big screen, 2012. I couldn’t resist because of this New York Times article about movie director Roland Emmerich and his tendency to destroy the world in his movies (Independence Day, The Day After Tomorrow). In particular, the article explains that in 2012 the earth tears itself apart when

A monster solar flare shoots invisible neutrinos into the earth’s core, cooking it like a Hot Pocket.

You have to love the Hot Pocket reference, but what drew me to see the movie was, of course, the neutrino as Hollywood star.

Sure enough, the film begins with an American scientist visiting a solar neutrino experiment located in a deep underground cavern in India.  After being told by the physicist running the detector about the increases in rate they have witnessed recently (I think he said a factor of two increase in neutrino interactions in the detector, but I’m not positive), they opened the hatch on top of the detector and, sure enough, the liquid inside was boiling. Oh, wow.

I also recently saw Angels and Demons since it came out on video.  In A&D, of course, as I blogged about forever ago, a small canister of antimatter is used as a weapon to threaten the Vatican City.   In that post, I talked about the antimatter we produce everyday here at Fermilab and how it compares to the claims in the movie.

Picture of the Sun using a "neutrino camera", the giant Super-Kamiokande neutrino detector in Japan.

So, how accurate is the science of 2012?  Well, not very, I’m afraid.  First, it is absolutely true that the Sun produces tremendous numbers of neutrinos and that many of them hit the Earth.  A common statistic to set the scale is that trillions of neutrinos from the Sun pass through the nail on your pinkie finger (about 1 sq. cm.) every second!  That’s a lot of neutrinos, but the key is that they pass right through.  And most of them pass right through the Earth’s core as well like it isn’t even there, moving on toward distant reaches of the galaxy with little to impede their journey.

I said most pass right through, because a small fraction of the neutrinos from the Sun certainly do interact with materials on Earth and deposit tiny amounts of energy. If they didn’t, then we would have no way of knowing they were there. I know the energy deposited by an interacting neutrino is impressively tiny, but I became curious about the temperature change that might be caused by a neutrino from the Sun interacting at Earth – exactly how far is it from making water boil?

So here’s the simplistic calculation that I did. The Super-Kamiokande neutrino detector in Japan is an enormous tank that holds about 25,000 tons of water. When a neutrino interacts with a hydrogen or oxygen nucleus in the water, the interaction gives off light which is detected.  A neutrino from the sun typically contains around 10 MeV of energy.  MeV is just a unit of energy measurement and 10 MeV is equal to about 16E-13 joules – a tiny amount. So I made the simplifying assumption that all of the energy from the neutrino goes into heat energy in the water to estimate the temperature increase of the water in Super-Kamiokande due to a single neutrino interaction. I used the specific heat formula from an old physics textbook:

change in Temperature = [(energy added) / (specific heat of H2O) x (mass H2O)]

T = (16E-13 J) / [(4180 J/kg*K) x (25,000,000 kg)] = 1.5E-23 K = 1.5E-23 degrees Celsius

Wow, okay, so assuming I didn’t screw that up (an enormous assumption) that indicates that each neutrino interaction increases the temperature of the water by about a 100 billionth of a trillionth of a degree. I think Super-Kamiokande sees about 4,000 solar neutrino events per year. So assuming no heat is dissipated (but it is), that’s an increase by 6E-20 degrees Celsius a year (0.00000000000000000006 C). You can see that it will take a whole lot more than a doubling of the solar neutrino rate to make a measurable change in the temperature of the detector, much less make water boil!  I’m pretty sure we’re safe from this particular form of Armageddon.

I think seeing major players from our theories of fundamental physics, like neutrinos and antimatter, show up on the big screen is pretty fun. Its true that the science of these movie plots is usually far from accurate, but if it gets anyone asking questions like “Is antimatter real?”, or “What are neutrinos and do they really come from the Sun?”, then I’m not inclined to complain too loudly.  Its interesting that, in these examples at least, the particles are all a threat to humans, but I suppose that’s Hollywood.  For now, I’m inclined to keep thinking that “all press is good press”.  Anyone know of a movie where subatomic particles magically save the world?

50-mile water route from Chicago to Racine, WI

The weather in Chicago has been pretty crummy for weeks now, but winter seems fast approaching when I finally give up on the possibility of more nice days and return the boat to its winter hibernation spot, Racine, WI.

Racine is about 50 miles north of Chicago and one immediately wonders why pick such a spot to return it to every winter. Coincidentally, I think the answer is a physics term:

inertia: a property of matter by which it continues in its existing state of rest or uniform motion in a straight line, unless that state is changed by an external force.

The sunrise over Lake Michigan on a chilly October morning.

The view back as we say goodbye to Chicago for the summer.

Basically, that’s where I found her six years ago and it seems easier to take it back each off season than to find a new location and transport the trailer which is far from road ready. Also, the marina there is very nice and extremely affordable compared to around the Chicago area. Finally, there is the matter of the 50 mile trip at the beginning and end of each season which is actually quite fun. In the spring we stopped over at Waukeegan Harbor on the way down and I wrote about it here on QD. On the return trip we usually barrel through in one 8-11 hour day on the water.

This time of year that typically means leaving before sunrise to get in to Racine well before dark. And I can assure you that it is freezing on the lake that early in the morning in October. I look relatively content in the photo to the left, but it did take six or seven layers of clothing, a winter hat and gloves, two pairs of wools socks, hot coffee, and that gorgeous sunrise to get me so cheery.

It ended up being a beautiful day, although it never really warmed up out on the water. We did make record time with a very strong tail wind the entire day, but eight hours after leaving Chicago the Main Street draw bridge as we entered the river in Racine was a welcome sight.

Bright and early tomorrow morning we’ll go up by car and take her out of the water, thus bringing summer of 2009 officially to a close 🙁

Main Street draw bridge in Racine, WI

Main Street bridge from Main Street.

Safely back in the Racine river.

One of the true joys of working in an internationally collaborative field like particle physics is the opportunity (necessity even) of getting together with colleagues from all over the world. For me, these meetings are an opportunity to look past my own day-to-day work and think about the exciting advances being made throughout the field.  And it is great to be reminded how my own work fits into a much much bigger picture. For most of us I think, even though we eventually become involved at a micro-level, it is exactly this big picture that drives us, that enticed us into fundamental science in the first place.

Courtyard of the Relais San Clemente hotel where the WIN 2009 workshop was hosted.

Last week I had the privilege of attending the 22nd hosting of the International Workshop on Weak Interactions and Neutrinos, known as WIN. The workshop was held at a beautiful hotel, the Relais San Clemente, outside of Perugia, Italy.

We were told during an opening session that a long-standing theme of the WIN conference series has been “maximum relaxation with minimum distraction” in order to harbor the free and easy exchange of scientific ideas between participants. This means that discussion is encouraged not just during formal presentations but over coffee breaks or at dinner. I, for one, ran into colleagues from past experiments and we discussed plans for further analysis of old data. I also met theoretical colleagues who are very interested in exactly the kinds of effects that the experiments I am currently working on will be studying. A continued relationship with such people should be invaluable to both groups. This, to me, is a great benefit of workshops like this where we all come together to discuss these issues in an environment absent of major distractions.

A discussion group session on neutrinos at WIN.

It was a great privilege for me as well that among participants this year were both the Director and Deputy Director of Fermilab, Pier Oddone and Young-Kee Kim. Pier wrote a column for Fermilab Today on Tuesday describing the conference and his plenary talk about a possible future facility here at Fermilab, the muon collider. My talk, on Current and Future Neutrino Cross-Section Experiments, immediately followed his on the second morning of the workshop, which was a great thrill for me (Although I was reminded the hard way that the second morning on an international trip is the peak of jet lag – whew, it was tough to get up and give my talk that morning!)

A coffee break where all could mingle and discuss freely.

A group at dinner in the city center of Perugia.

Typically, multi-day physics conferences (WIN lasted 6 days) include a half day without scheduled sessions. Often, an excursion is arranged for the participants to visit a nearby place of interest. For WIN ’09 that was the beautiful city of Assisi, Italy less than a one hour drive from Perugia. The conference organizers arranged for a bus to take anyone who wished to visit for a few hours in the afternoon. Assisi is famous for being the home of two people declared saints by the Catholic church, so there are two large cathedrals in the city to commemorate them. The Basilica of San Francesco (1181-1286 AD) is a particularly amazing site.

The Cathedral of San Francescso of Assisi.

A shot from the back of the bus as we drove away from Assisi.

As an important side note, WIN ’09 was originally to be held a few hundred kilometers to the south in L’Aquila, Italy near the National Scientific Laboratory at Gran Sasso. Tragically, the city was struck by a 6.3 magnitude earthquake in April of this year and is still recovering from the horrible destruction it suffered as a consequence. Planning these meetings is always a ton of work for the local committee of organizers, but it must be said that the organizers of this particular workshop have done a tremendous job at putting on a truly world-class and wonderful meeting under such difficult circumstances. Not only did they have to change the venue at the last minute, but most of the active organizers live in L’Aquila.  I believe all attendees (this one at least) were extremely grateful for the wonderful job they did with WIN 2009!

Well, I have been about the worst blogger in the world recently. Not by writing bad posts, or boring posts, or outrageous or insulting posts, but rather by writing no posts at all. It’s been another hectic month at Fermilab, at conferences and workshops, even a few days of vacation squeezed in there.

One thing definitely worth sharing here on QD is the grand finale of the Science Chicago LabFest! events which happened recently downtown at Chicago’s Millennium Park. I mentioned the LabFest events in an earlier post, but they are outdoor science fairs which have been organized by Science Chicago and have occurred in parks and at schools all over the Chicago area over the past year. A group from Fermilab has been at each event through the summer with our van full of displays and interactive demonstrations. The Millennium Park event was the final LabFest of the summer and the fourth one that I have attended.

The Fermilab tent at the Millennium Park LabFest with the Pritzker Pavillion in the background.

Kids roaming the grounds at Millennium Park LabFest with the Chicago Art Institute in the background.

Beyond the remarkable venue, however, this LabFest was special because I got to do, with another physicist from Fermilab, a 20 minute stage presentation using liquid nitrogen. Mike Cooke and I met with the master of the cryo show, Mr Freeze (a.k.a. Jerry Zimmerman from Fermilab), before the show and he was kind enough to let us borrow his stage equipment.

Jerry’s normal show runs about an hour, so it was a challenge to pick and choose the bits we would fit into 20 minutes but maintain some continuity in the material. We began by giving some idea of the basic properties of liquid nitrogen. What is it? Basically liquid air since nitrogen makes up almost 80% of the atmosphere. How cold is it? -321 degrees Fahrenheit. Yikes, not even a Chicago winter compares!  What does it look like? Pour some into a plastic ziplock bag and note that it looks like water, but is boiling at room temperature, so it can’t be water.

Next we explored the expansion that occurs as the liquid nitrogen (LN) rapidly boils into a gas.  Sealing the ziplock bag quickly leads to it ballooning until it ruptures.  Next a typical kitchen garbage bag (~13 gallons) is loaded up with 1 cup of LN and sealed with the same destructive results.  Finally, a lawn garbage bag (~45 gallons = 720 cups) is used and, upon fully inflating, is shown to barely contain 1 cup of liquid nitrogen converted into gas.  The expansion ratio is 700:1.  At this point, as a foreshadowing of things to come, Mike poured a small amount into a 20 oz. plastic bottle and sealed the cap, holding it up to the excited kids in the front rows.  They seemed to really get the point as a few began screaming that it would explode!  Fortunately, this was a fake as Mike showed them the hole he had punctured in the bottle cap before the show – but the setup was successful 🙂

Filling the special containers with liquid nitrogen for the show from supplies at Fermilab.

Mike and I rehearsing our show at the Lederman Science Center at Fermilab.

We then showed some examples of how liquid nitrogen can be used to change the properties of materials that it comes in contact with. At Fermilab, we use liquid nitrogen (and even colder liquid helium) to change some metals to become superconducting. It is these superconducting materials that are needed to produce the strong magnetic fields used to steer super high-energy protons in the accelerator.

First we used inflated balloons to show how the air inside them could be liquefied by making it cold with LN. This causes the reverse of the expansion we explored earlier, namely a ~700:1 contraction of the volume, so the balloons collapse down. Removing them from the liquid nitrogen, they slowly warm back up, crackling and twisting around like some kind of monster as they grow back to their original size. In fact, to really show the dramatic effect of contraction as the gas liquefies, we go on to pull out about a dozen large balloons we had placed before the show into a tiny dewar that they never could have fit into while fully expanded.

What about solid objects that are cooled down so much with liquid nitrogen? They don’t contract enough for the audience to see (but they certainly do contract some, as all objects do when they get cold), but their properties change in other dramatic ways. To demonstrate this we used a racquetball, a rubber glove, a small (4 inch) inflatable plastic basketball, and bananas. The racquetball goes from super bouncy to a loud crack and thud on the stage floor without much of a bounce. The soft (at room temperature) rubber glove becomes brittle to the point where the fingers can be shattered off. We set this up, of course, with Mike appearing to stick his hand into the LN dewar and me shouting that “It’s the wrong safety glove!”. He quickly pulled his hand out and shattered the fingers off revealing his safely recessed hand, much to the delight of our audience. The plastic basketball not only becomes rock hard like the racquetball, but also the air inside contracts as it liquefies, so there is no air pressure pushing out from the inside. A quick tap with the tongs and the previously rubbery, squeezable ball shatters into 1000 pieces like a light bulb.

The bananas were used to make a hammer. Mike begins to peel a banana claiming that he can use it to drive a nail into a piece of wood. I say that I don’t believe him and begin to peel my own banana which I use, at room temperature, to strike a nail. Of course, the banana breaks apart and bits of mushy banana fly around. Mike dunks his into LN to freeze the banana in a matter of moments making it super hard and successfully drives in a nail.

The view from the stage where we would be performing our show.

About time for the grand finale, don’t you think? For this, of course, we used the Cryo Cannon! A steel tub about 3 feet long and 4 inches in diameter was standing up on the concrete just off the stage to the right. We reminded the kids about the pressure built up from the expanding nitrogen when it boils as we placed a small amount into a 20 oz. soda bottle. We explained to them that we would use the release of this pressure to launch one of these small plastic basketballs into the air. “How high do you think we can launch this thing? 20 feet? 50 feet?” It was like an auction where money (or height) was no object to the purchasers – I think one kid offered 1,000 feet. Mike sealed the bottle, this time using a non-punctured cap, dropped it into the vertical metal tube, I dropped the “cannon ball” (plastic basketball) in on top, and about 15 seconds later – BOOM!, the ball was launched somewhere around 150 feet probably (about a 15 story building). There was a slight breeze from the west, so the thing floated east towards Lake Michigan as a dozen kids from the front rows tore off in chase to claim their souvenir.

Several people from the Fermilab Office of Communications were there and soon there should be an article about the event in Symmetry Magazine. Also, Susan Dahl, from the Education Office at Fermilab video recorded the cryo show, so I’ll pass those links along when they are available.

No, it has nothing to do with Chicago’s bid to host the 2016 Olympics. And no, the winner does not earn the title “World’s Greatest Athlete”. Nonetheless, the Minerva Decathlon has been a ton of fun.

We had a great turnout of 22 people and great weather for ultimate frisbee this Tuesday.

Minerva, you’ll recall, is the name of the neutrino experiment that I work on at Fermilab – a (relatively) small collaboration of about 100 people. The Decathlon was the very clever idea of one of our spokepersons as a way to get our collaborators together in a casual environment. It provides an opportunity to get to know each other a little better and relax doing something fun. I’ve also mentioned that we have a number of summer students at the undergraduate and graduate level here at the lab for the summer, so we have enough people around to make it happen.

We’ve scheduled 10 events over five weeks in June and July: five different athletic activities on Tuesday evenings and five casual physics talks/discussions on Thursdays. In both cases we get together at the Fermilab Users’ Center (that’s right, Fermilab has it’s own bar and recreation building where the best bartender in the world takes care of everyone) for a few drinks either after (for sports) or during (for talks) the event.

Me sadly attempting to defend the seemingly undefensible Thomas.

So far, we’ve played volleyball, soccer, and ultimate frisbee. In each case we’ve gotten people to come out who have never played the sport before (I mentioned it was casual) and others who participate in leagues. This past week, I was one of the former. Thomas, who I am shown attempting to defend below, appeared to be one of the latter.  “But, Dave, what’s that giant brace on your old, decrepit knee?”, you ask.  Indeed the game ended sometime in the second hour when I came down wrong and had to hobble off the field (12 year old ACL injury, so it happens all the time unfortunately).

The talks and physics discussions are designed to be just as relaxed, so everyone feels welcome to ask any and all questions. We’ve had two in the lecture series so far. The first was on the details of how we use high energy proton accelerators to make intense beams of neutrinos. The second, earning among other prizes, that for best title (title slide shown below), was about the graduate research of one of Minerva’s post docs.

“Nothing goes to Something plus Nothing…“? Okay, maybe that’s a little physics humor, but I think its hilarious. The goal of the experiment was to search for the exceedingly rare decay of the neutral kaon particle into a neutral pion particle plus two neutrinos. The extreme challenge of it (and the humor for physicists) is that none of those four particles can be directly seen! Particle physics detectors all rely on the interaction of charged particles in some detector medium. Individual charged particles actually leave very distinct tracks as they travel through a volume of gas, or a tank of liquid, or a solid scintillating material, for example. Neutral particles do none of that. The only way to detect the K -> π + ν + ν reaction is indirectly because the neutral pion will immediately decay into two photons. These two photons will interact with materials and can be “seen” by the detectors in the experiment. This was the signature that Gabe’s experiment looked for.

Display of an event in the E391 experiment where a kaon decays to three neutral pions which each decay to two photons making the six photon signatures shown.

The slide to the left, taken from his talk, shows the regions where energy is deposited in the detector for the case of three neutral pions decaying into a total of six photons (a background for the type of reaction they were searching for). You can imagine that a single pion event would only have two such deposits both consistent with being a photon.

The analysis of the E391 data set showed no such events, but the theoretical prediction for this reaction is that it should happen somewhere between 1 in 100,000,000,000 (1 in one hundred billion) and 1 in 10,000,000,000,000 (1 in ten trillion) times that a kaon decays, making it a challenging search indeed. A next generation experiment is being planned now.

Next week we play 16″ softball on Tuesday (there’s a diamond at the lab) and the talk for Thursday is “How to Explain Neutrino Physics to your Relatives” which I think is a great idea. However, I understand the father of the person leading this discussion is a fellow in the American Physical Society, so hopefully she’ll cater the discussion to a crazy ol’ Aunt or something instead!

Yesterday began the 2009 International Neutrino Summer School (INSS) being hosted at Fermilab this week and next. Its a two week immersion school with about 90 students coming from all over the world to attend.  The students are mostly graduate students working on research in the field and a few post docs who are new to neutrino physics.  There are lectures during the morning and afternoon covering the breadth of contemporary neutrino physics topics: theoretical aspects, neutrino sources and detectors, the open questions and future experiments, neutrinos in cosmology, etc.  The lecturers are the leaders in their respective subjects and have also come from all over the world to participate.  I attended such a school as a graduate student and benefited greatly from the experience.  This time around I’ve served on the local organizing committee which planned the school – oh no, does that mean I’m getting old? 🙂

Organizing committee chair Steve Brice welcoming the students to the school on the first morning.

There are also non-lecture sessions where the students are working in small groups of 3 or 4 on some rather involved theoretical and experimental problems. They’ll spend several hours each day discussing and researching the details of the question they chose and prepare 15 minute presentations on their efforts for the last day of the school.

In addition there are a set of social events planned to provide an opportunity for the students to relax as well as get to know each other a little better. They will all be colleagues for a long time in a fairly small, international field, so the connections they make here are very important. Last night we hosted a BBQ on the Fermilab site with food and drink and a few outdoor activities, volleyball, soccer, bocce. Several other such events are planned over the next two weeks including a farewell banquet on the last night.

The 2009 INSS will keep me busy the next couple of weeks, but seems to be off to a very successful start in the first two days. I’ll let you know how the rest goes!

Three of the student groups getting started discussing their chosen questions.

Opening day BBQ near the Kuhn Barn on site at Fermilab.

Man, time really can fly. Particularly during the summer. Its such a busy time and the past few weeks have been packed with meetings and work and outreach activities and parties and games and… All great things really, but in combination life can get really hectic.

I think many fields closely tied to academia, like physics, tend to experience a spike in activity during the summer. A small army of graduate students has shown up at the Lab to get started on their research. Professors suddenly have a lot more available time for research as well with teaching duties over. This sudden availability of people in the field means more professional conferences and collaboration meetings. It is an exciting and active time for sure.

You’ll notice blogging wasn’t on my list above. I’ve been bad about finding the time in this busy season, so here’s a brief tour of my life the past few weeks.

Science Chicago, LabFest! (Their exclamation point, not mine)

Although I think it deserves it. According to one quote on its website, Science Chicago is “about helping kids of all ages unleash their inner scientist. We invite Chicagoans to discover and explore the inspiring world of science in our community.” As you will see on their site, the plan is an ambitious one. For an entire year there are countless presentations, interactive exhibits, tours and learning opportunities of all kinds scheduled throughout the Chicago area. A program called LabFest is a series of outdoor summer science fairs where scientific and engineering institutions from the Chicago area set up tents full of displays and interactive learning exhibits. This summer, LabFest is visiting numerous school districts and neighborhoods around the Chicago area with several events each week until the end of August. A few Fridays ago I went along with a group from Fermilab to a LabFest event at the Johnnie Coleman Academy in Chicago.

There were hundreds and hundreds of school kids that came through that day. The last group was several kindergarten classes from a nearby school. That’s them in the pics in the bright orange shirts standing by the inclined planes we were using to study the movement of falling and rolling objects. They were all too happy to pose for my camera! I’m signed up to do several more of these events in the coming months, so I’ll let you know. But if you are in the Chicago area, check out the web sites above and come on out to a LabFest! near you.

Hyperbole safely moored in Waukeegan Harbor, halfway between Racine, WI and Chicago, IL.

Finally, the Start of Sailing Season

The next weekend (I think – see how time flies?) was one of my favorite weekends of the year – bring the sailboat down from Wisconsin to Chicago weekend! I bought a small sailboat with a friend a few years ago. We keep it in a marina in Racine, Wisconsin over the winter and sail it back and forth each Spring and Fall. Its about a 50 mile trip which takes about 10 hours on the water depending on the wind and water conditions. It was quite a bit colder on the lake than the picture below would lead you to think. On the lake we were wearing stocking caps and gloves. We usually stop at the half way point in Waukeegan, IL and spend the night. Its not strictly necessary for a 10 hour trip, but its sure a lot of fun!

Me safely moored in Waukeegan Harbor.

It sort of a funny feeling to be staying overnight about 25 miles from home. In fact, a friend drove up from the city that evening and hung out in our “hotel” for a few hours (probably took him half an hour by car). The weather has been pretty miserable the past couple of weekends, tons of rain and unseasonably cool, so I haven’t been out much since. I’m hoping July is more normal summer weather in Chicagoland and I can get out on the water a lot more than in June.

Meetings, Meetings and more Meetings

As I said above the summer is a popular time for meetings since so much of the field is free of teaching responsibilities at the universities. The annual Fermilab Users’ Meeting takes place each June, and is an opportunity for all of the groups performing research at the Laboratory to share the status of their work and their plans for the future with their peers.

Post doc Bob Bradford from MINERvA giving the status report for our experiment at the Fermilab Users' Meeting

Representatives from the Department of Energy and National Science Foundation always come as well to inform us of the activities in their departments and discuss the funding expectation for the coming year. At the end of the two day long meeting, the Director of Fermilab, Pier Oddone, addresses the User body with his vision for the future of the Lab.

And this week has been the MINERvA Collaboration Meeting. Three days of meetings and workshops where we poured over the details of the data we have been taking for the past two months with our new detector. It was a lot of fun and very exciting to have real data to be looking at. Many people on the experiment have been designing, planning and building this experiment for almost a decade and this was the first collaboration meeting with real neutrino data to look at and discuss!
(more…)

The past couple of weeks have been busy as usual. Work is always busy, of course, but the weekends have been packed as well. Last weekend was the Memorial Day holiday so I took the train down to St. Louis to visit some family. Yep, that’s right, the train. Its no secret that the inter-city train system in the US pales in comparison to its European counterpart, but fortunately Amtrak is still around serving major cities.

St. Louis Arch from my train seat

Amtrak train car en route to St. Louis

The week before, my father didn’t tell me what it was about, but he let on that he was super excited to ask me about something when he saw me. So my last Quantum Diaries post I mentioned was inspired by a 6th grader. Well, I guess this one is inspired by a 60 year old, because the question my dad could not wait to ask me, that had him practically giddy with excitement, was, “What is antimatter?” Guess what. My parents saw Angels and Demons last week!

Fortunately, I was well prepared to answer my father’s question, as I had just attended Marcela Carena’s public lecture last Thursday at Fermilab (here’s the full video stream of the event). As others have mentioned in several places, public lectures were organized around the country to coincide with the release of the film in order to answer just this question being asked by my dad and others like him.

Ramsey Auditorium at Fermilab at the start of the Angels and Demons Antimatter lecture last Thursday

The event at Fermilab was a great success with a packed Ramsey Auditorium and a fun-filled and informative lecture from Marcela. She began by welcoming the audience to the biggest antimatter factory in the world, Fermilab! which pretty much answered the first question on many people’s minds, “Is antimatter even real?”

The term ‘antimatter’ refers to otherwise normal particles, but whose various quantum properties are all reversed from their normal matter counterparts.  The most obvious and most important of these is electric charge.  So an antielectron is just like the regular electron except it has positive charge (hence, we call it the positron).  An antiquark is just like a regular quark except its charge is opposite. And a regular ol’ proton is made of three quarks which add up to positive one charge (up+up+down = 2/3Q + 2/3Q – 1/3Q = +1Q) and an antiproton is made up of the three corresonding antiquarks (antiup+antiup+antidown = -2/3Q – 2/3Q + 1/3Q = -1Q).  Its sorta just that simple. In principle, you can take this logic further. Just like a proton and electron bound together makes hydrogen, an antiproton and positron bound would make antihydrogen. 6 antiprotons, 6 antineutrons, and 6 positrons would make anticarbon, and so on. I suppose enough antiwood and antiglue could be assembled into an antichair for an antiperson to sit on. (incidentally, antihydrogen is as far as we have gotten in the science laboratory and they managed to make just 9 antihydrogen atoms each lasting a fraction of a second).

What the book and movie exploit in the story is the rather thrilling fact that when a bit of matter meets its antimatter counterpart, !PUFF!, they annihilate into a tiny burst of energy.  Here at Fermilab we are constantly creating antiprotons to push into our particle accelerators and send on a collision course with a bunch of regular protons moving in the opposite direction. When they collide, !PUFF!, a tiny burst of energy (Okay, so you can add energy to the annihilation effect if the particles are moving when they collide. Most of the energy here is actually from the protons and antiprotons tremendous velocities, 99.9999 percent of the speed of light in a vacuum or about the speed of light – 700 mph, which is why we work so hard to get them going so fast).  Einstein’s famous equation tells us that this energy E can convert into mass since E = mc^2.  This mass is the particles we see and study in our detectors.

Marcela Carena welcoming the audience to the largest antimatter factory in the world!

So what is the difference between these matter/antimatter collisions at Fermilab and the ones in the movie which are capable of releasing enough energy to destroy multiple square miles of buildings in Rome? Quantity. In the movie they use 1/4 of a gram of antimatter as a weapon. It turns out this modest enough sounding number is an incredible amount of antimatter! Perhaps the most fun fact in Marcela’s talk last week: in the entire history of Fermilab running the antiproton source for several decades, 24 hours a day, 7 days a week, we have produced only about 2 billionths of one gram of antiprotons! Instead of a huge explosion you might be able to power a light bulb for a few moments.

Another important difference between the movie and real life antimatter is containment and storage. Of the 2 billionths of a gram created over the decades at the Lab, none of it is still around. It all harmlessly collided with regular matter and !PUFF! is gone – most of it in the center of our particle detectors. But even when it didn’t, to an antiproton, the world just so happens to be made of a huge amount of very dangerous regular matter!

Which brings me to one of the really exciting open questions in particle physics research today. Where in the world did all the antimatter go? Physicists believe strongly that matter and antimatter would have been produced in symmetric, equal amounts in the earliest moments of the Universe. All of our theories and experimental results point to this conclusion. Yet here we are, safely living in a matter dominated Universe with no threat of being annihilated by stray antimatter. It could have been different. We could all be made of positively charged electrons circling around negatively charged protons. If it were that way we wouldn’t know the difference. It seems even more likely that all of the intense energy in the early moments after the Big Bang would have created matter and antimatter in equal numbers which immediately would have annihilated against itself back into intense energy – but then we wouldn’t be here today to blog about it, so we know that’s not how it went down.

Instead, something in the way the Universe works at the most basic level prefers negative electrons and positive protons (matter). Some asymmetry must exist between the opposing forms such that matter ultimately won out and was able to form the Universe we inhabit. Experiments have actually provided clues, but revealed nothing strong enough to have let matter win out totally as it seems to have done. But where is always the last place we look? Why, among the elusive neutrinos, of course.

It turns out this is the Holy Grail of modern neutrino physics research. It is possible that neutrinos violate the matter/antimatter symmetry in such a way as to explain the Universe that we live in. And the next generation of huge experiments which will send intense beams of neutrinos 100’s of miles through the Earth hope to take a peak at exactly this issue: can neutrinos explain why only one variety of matter has come to dominate our Universe and allowed us the opportunity to be here to ask the question in the first place?

Hi everyone.  This post is inspired by a letter I received recently written by a remarkable 6th grader who is working on a project about neutrinos.  He mailed his letter to the Office of Communications here at Fermilab and I was asked if I could put together a response. In his letter he asks three great questions about neutrinos and the Fermilab neutrino experiments, so I thought I would share my reply here on QD, as others might be interested.

1. How does Fermilab send beams of neutrinos up to the neutrino research lab in Minnesota?

2. How are neutrinos formed?

3. Why are neutrinos not classified as dark matter?

See, great questions, right?  Here were my thoughts…

Thank you for your letter with your three questions about the neutrino experiments being done here at Fermilab.  Indeed we do send a beam of neutrinos created here at the Laboratory in Illinois to a research laboratory about 450 miles away in northern Minnesota!

We couldn’t do this with just any particle.  Only neutrinos can travel straight through the Earth unaffected and arrive at a neutrino detector so far away.  This has to do with the way different kinds of particles interact.  There are three forces through which particles can interact (ignoring gravity since it is so weak for such tiny objects):

1.    the electromagnetic force – the force between charged particles
2.    the strong nuclear force – the force between quarks that holds protons and neutrons together
3.    the weak force – a force that acts between all particles but is much much weaker than the other two

A proton is capable of feeling the effects of all three forces – it has electric charge, is made of quarks, and feels the weak force like all particles.  The electron can feel the effects from the electromagnetic force and the weak force.  But the neutrinos can feel only the weak force since they are not charged and do not contain quarks.  This means that they can pass right through dense materials without interacting at all.  In comparison, a proton or electron would make it only a few feet or less before it gets absorbed by the surrounding material.  So we could never send a beam of electrons, for example, great distances through the Earth – they would all just interact and get absorbed in the rock and dirt.  But a beam of neutrinos will pass right through with only a very small number of them getting absorbed.

This same quality (lack of interaction with material or electric and magnetic fields) that makes the neutrino beam to Minnesota possible also makes it challenging to work with neutrinos experimentally.  To make a focused beam of charged particles like protons is relatively straightforward because you can control them directly with electric and magnetic fields.  Not so with neutrinos.

So how do we create  a neutrino beam here at Fermilab? We use the proton beam in the particle accelerator at Fermilab as a starting point.  Again, protons are easy to control.  We accelerate the protons with electric fields and guide them with magnets to collide them with a stationary, solid target.   In this case, the target is made of carbon, but other light elements can work as well, such as beryllium.  When the very energetic protons collide with the carbon nuclei in the target an interaction occurs that creates new types of particles.  The most common type is called a ‘pion’.  A pion is a combination of two different quarks (a proton is three, so a pion is just a rearrangement of the quarks that were available from the original protons in the beam and the carbon nucleus).  A very special quality of the pion particle is that is doesn’t last very long.  It travels along for about 20 billionths of a second before it spontaneously decays.

Decays?  What does that mean?  It means it converts into other particles, in this case a muon (the heavier, charged big brother of the electron) and a neutrino!  So, in summary:

protons + carbon    →    pions    →    muons + neutrinos

So, the way we create neutrinos to send to Minnesota is by using the proton beams available at Fermilab to create pions to create neutrinos.

It is important to note that the more protons you have to start with the more neutrinos you will get to do your neutrino experiments with, so a lot of effort goes into making beams with many many protons.  Since May 2005, Fermilab has delivered about 7E20 (700,000,000,000,000,000,000!!) protons onto our carbon target to create neutrinos that then go straight through the Earth’s crust to the lab in Minnesota!

Your final question, “Why are neutrinos not classified as dark matter?” is a really good question.  Technically, neutrinos are dark matter!  The term ‘dark matter’ refers to matter that does not interact with electromagnetic radiation.  It is this radiation in the form of visible light (as comes from stars) or other frequency ranges that we use to observe objects in our Universe.  The way we have ‘observed’ dark matter is by noticing the strong gravitational effects on objects we can see by some very massive object nearby that we cannot see.  These gravitational effects have been so strong that we now realize there is far more matter out in the Universe that we can’t see (dark matter) than we can.   Physicists now have evidence that 83 percent of all matter in the universe is made of dark matter.

So can neutrinos account for all the dark matter in the universe? When experimenters discovered about 10 years ago that neutrinos have mass (previously it was thought that they did not have any mass at all) people got excited thinking this may be a solution to the dark matter puzzle.  Could neutrinos be the mass that we could detect gravitationally, but not see?  We now know that, while neutrinos do have mass, and there are enormous numbers of them throughout the Universe, it is still not nearly enough mass to explain what we have seen in the astronomical observations.  Today we know that neutrinos account for less than one percent of the dark matter in the universe. That’s why people often say that neutrinos are not dark matter. But technically, they are.

So, there must be more dark matter, something other than just neutrinos, that we don’t yet know about.  And physicists are trying very hard to detect this matter directly.  They must interact very, very rarely like neutrinos, but are probably much heavier.   The direct detection of such dark matter particles will be a major and very exciting discovery in particle physics.

I hope this has answered your questions about neutrinos.  Please let me know if you have any further questions, and best of luck on your expert report!

Sincerely,
David Schmitz