Friday, May 10, 2013

Have a safe day!

Friday, May 10

3:30 p.m.

4 p.m.
Joint Experimental-Theoretical Physics Seminar - One West
Speaker: David Schmitz, University of Chicago
Title: Quasi-Elastic Scattering of Neutrinos and Anti-Neutrinos at MINERvA

Saturday, May 11

8 p.m.
Fermilab Arts Series - Auditorium
Hubbard Street 2
Tickets: $30/$15

Monday, May 13


3:30 p.m.


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Wilson Hall Cafe

Friday, May 10

- Breakfast: blueberry-stuffed French toast
- Breakfast: chorizo and egg burrito
- Cajun turkey burger
- Smart cuisine: white-fish florentine
- Enchilada-style beef and bean burrito
- Baked ham and Swiss ciabatta
- Shrimp and crab scampi
- Clam chowder
- Texas-style chili
- Assorted pizza by the slice

Wilson Hall Cafe menu
Chez Leon

Friday, May 10
- Spinach salad
- Alaskan crab legs
- Parsley potatoes
- Grilled asparagus
- Lemon panna cotta with blueberry sauce

Wednesday, May 15
- Ropa vieja (braised beef, peppers, onions)
- Yellow rice with toasted cumin
- Baked custard with rum sauce

Chez Leon menu
Call x3524 to make your reservation.


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Physics in a Nutshell

Gravity and gravitons

Legends have made a whole menagerie of mythical creatures, from centaurs to hippogryphs. The graviton is a proposed subatomic particle that causes gravity. However, since there is no experimental evidence substantiating its existence, for the moment the graviton remains mythical.

Without knowing a lot about a given topic, sometimes it's hard to separate fact from fiction. We might think the mythology of Ancient Greece to be silly with its Pegasus, mermaids and centaurs. Creatures with such a mix of properties are ridiculous, right? On the other hand, seeing the bizarre but very real platypus or sea dragon might give us pause and teach us not to be so quick to dismiss crazy-sounding reports.

In the early 1960s, physicists used the term "particle zoo" to describe the panoply of particles they had observed. With the advent of the Standard Model, scientists could predict particles that were required by the model but had not yet been discovered. The Higgs boson was one of those hypothesized particles, one that recently went from imagined to real. Another denizen of the subatomic mythical bestiary is the graviton, the force-mediating particle of gravity. While this particle is strictly outside the realm of the Standard Model, it seems like it could be more than just imaginary, given that the other three forces each have an associated quantum particle.

We know of four forces in the universe: the strong and weak nuclear forces, electromagnetism, and gravity. In the world of the super-small, the first three of these forces can be viewed as the exchange of force-mediating particles. It's a fair question to ask whether gravity also follows this pattern.

While gravity is the most familiar of all the forces, it is also the weakest. To give a sense of scale, it is 0.0000000000000
0000000000000000000001 or so times smaller than the next weakest force, the weak nuclear force. Given that particles experiencing only the weak nuclear force can penetrate five light-years of solid lead without interacting, gravity is very weak indeed.

Gravity is so weak that it is difficult to imagine ever seeing its effects in the quantum realm. Studies of gravity generally involve the human and the cosmic scales, with stars guiding planets and planets pulling people down to the ground. It takes countless particles to exert an appreciable gravitational force.

However, the success of quantum field theories to describe the other three forces, each with its own particle or particles mediating it, leads us to think that perhaps there might also be a quantum particle of gravity. This hypothetical particle is called the graviton.

Bringing us back to the idea that kicked off this Nutshell, I should caution you that there is no evidence that the graviton exists. It's merely an idea cooked up in the fertile imaginations of theoretical physicists. Still, given the nature of the gravitational force, we know what properties the graviton would have to possess. It would have to be massless to account for the infinite range of gravity and be electrically neutral. It would have to have a quantum mechanical spin of 2 to account for gravity's attractive qualities. It would have to be a fundamental particle (that is, have nothing inside it). And it would have to interact with mass as the "charge" of gravity.

Physicists have proposed ideas for graviton properties in addition to the above-listed must-haves. If there are extra dimensions in the universe, then we can reasonably put forward other ideas about gravitons, including ones that are massive and that have exotic spin states. These are theoretically credible ideas, and scientists at the LHC are looking for them. However, since we don't even know if the ordinary gravitons that would govern the orbits of the planets exist, these exotic gravitons are even sketchier ideas.

The bottom line with the graviton is that it is a perfectly reasonable idea and may well be true. However, it has never been observed. And, until it is, we don't know if it's a scientific mermaid or a sea dragon.

Don Lincoln

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Press Release

Fermilab invites neighbors, public to learn about proposed construction of neutrino project

Editor's note: A special LBNE information session for Fermilab employees and users will be held on Thursday, May 23, at noon in One West. Following a brief presentation, LBNE representatives will be available in the atrium to answer questions. Informational materials will also be on display outside One West that afternoon.

It would be the world's most ambitious neutrino experiment. And Fermilab wants everybody to know about it, especially its neighbors. Construction of the project would take place on the western portion of the laboratory site, close to Kirk and Giese roads in Batavia, and could begin as early as 2015.

The Department of Energy and Fermi National Accelerator Laboratory are inviting the local community to an informational meeting about the proposed Long-Baseline Neutrino Experiment. The meeting, which will feature illustrative posters and short presentations, will take place on Thursday, May 23, 2013, from 6:30 to 8:30 p.m. at Fermilab in the Wilson Hall atrium.

The meeting will provide neighbors and the local community with an opportunity to mingle with scientists and engineers and ask questions about the LBNE, the construction and the environmental assessment that will be prepared pursuant to the National Environmental Policy Act.

Read more

In the News

Atom's core gets pear-shaped

From Science News, May 8, 2013

Atomic nuclei come in many shapes and sizes, and scientists have now obtained precise measurements of an elusive form: pear-shaped. Studying these exotic nuclei, which are described in the May 9 Nature, could allow physicists to better understand subatomic structure and to find new particles and forces.

"It's a beautiful, clear-cut result of a very careful experiment," says Christopher Lister, a physicist at the University of Massachusetts in Lowell.

Read more

Frontier Science Result: MINERvA

Scouting the party: neutrinos and nuclei

The likelihood of a neutrino undergoing a quasi-elastic interaction for different values of the momentum transferred to the proton or neutron (Q2) compared to several theoretical models. The data agree best with a model in which the neutrino can interact with multiple protons or neutrons at a time.

Para una versión en español, haga clic aquí. Para a versão em português, clique aqui.

Neutrinos are notoriously difficult particles to study: For every 50 billion neutrinos that pass through the MINERvA detector at Fermilab, only about one will interact leaving a trace in our detector, producing particles that we can observe directly.

In spite of this, we are starting to use neutrinos to learn more about protons and neutrons and how they behave when they're together inside an atomic nucleus. We already understand a lot about the nucleus: We know that it's made of protons and neutrons, and we know the number of protons and the number of neutrons in the nucleus for every chemical element. But there is much we still don't fully understand, especially about what those protons and neutrons are doing inside the nucleus.

We can study the protons' and neutrons' behavior in the nucleus the way we might study how people act at a party. Do the party-goers mingle according to the general spirit of the party, or do they break off into pairs? We could determine the party's nature by sending in very shy folks and observing how quickly they leave and whether they leave through the same door they entered.

In a nucleus, does each proton and neutron react to just the average effect of the others, or do they occasionally pair up? One way to answer this question is to fire neutrinos at nuclei and measure the particles produced when neutrinos do interact with the nuclei of atoms in our detector. By studying those particles, we can try to infer the behavior of the protons and neutrons.

The MINERvA collaboration has done this by studying one of the simplest types of neutrino interactions: quasi-elastic scattering, in which the neutrino changes into a muon (a heavier cousin of the electron), in the process knocking some protons and neutrons out of the nucleus. We look at quasi-elastic scattering of both neutrinos and antineutrinos and study them in two ways: First, we look at the directions and energies of the muons produced in these interactions and find that the data agree better with predictions in which the protons and neutrons spend some of their time in the nucleus joined together in pairs. In this case, we'd expect that both of the particles are knocked out of the nucleus. Second, we look for these knocked-out particles directly and find an amount of energy consistent with two particles being emitted from the nucleus.

These results support the more complex model of the nucleus, with pairs of protons and neutrons continually joining up and splitting apart, and open the door for future studies of nuclear behavior using neutrinos.

Read articles submitted to the arXiv on the antineutrino and neutrino results.

—Philip Rodrigues

The energy near the neutrino interaction point in neutrino quasi-elastic events. The data points, in black, are at higher energies on average than the prediction, in red, suggesting that the neutrino really is interacting with multiple protons or neutrons, which are kicked out of the nucleus.
These physicists lead this analysis: Top row, from left: Arturo Fiorentini, CBPF; David Schmitz, U Chicago. Bottom row, from left: Laura Fields, Northwestern U; Philip Rodrigues, U Rochester.
Photo of the Day

Looking snappy

A snapping turtle takes a springtime walk. Photo: Ed Dijak, PPD

Hubbard Street 2 Dance - Fermilab Arts Series - May 11

Pet Adoption Day at Abri Credit Union in Romeoville - May 11

Barn Dance - May 12

Budker Seminar - May 13

Lecture: Big Science, Big Challenges - May 16

English country dancing Sunday afternoons at Kuhn Barn - May 19

OneNote 2010 class offered - May 22

Fermilab Family Outdoor Fair - June 9

DASTOW scheduled - June 21

Employee Health & Fitness Day volunteers needed

46th Fermilab Users Meeting registration now open

Register for Argonne-UChicago-Fermilab collaboration meeting

Changes to U.S. visa procedures

Open gym basketball Tuesday evenings

International folk dancing meets Thursday evenings in Kuhn Barn

Scottish country dancing meets Tuesday evenings in Kuhn Barn

Outdoor soccer at the Village

Fermilab lost-and-found is in Communication Center, WH GF

International folk dancing meets Thursday evenings in Kuhn Barn

Scottish country dancing meets Tuesday evenings in Kuhn Barn

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