Friday, June 7, 2013

Have a safe day!

Friday, June 7

3:30 p.m.


Monday, June 10

2:30 p.m.
Particle Astrophysics Seminar - One West
Speaker: Nathan Whitehorn, University of Wisconsin - Madison
Title: Observation of High-Energy Neutrinos with IceCube

3:30 p.m.


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Wilson Hall Cafe

Friday, June 7

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

Wilson Hall Cafe menu
Chez Leon

Friday, June 7

Wednesday, June 12
- Northern Italian lasagna
- Caesar salad
- Tiramisu

Chez Leon menu
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Physics in a Nutshell

Beautiful symmetries

While architects and artists have long known of the beauty of symmetry, as demonstrated in the breathtaking Taj Mahal, it was mathematician Emmy Noether who taught physicists to appreciate the beauty and power of symmetries in our equations.

Symmetry has several ordinary meanings. It is often taken to mean aesthetic beauty in a pleasing and regular form. It also has a technical meaning. This meaning is often geometrical in nature, as in the five-way symmetry of a starfish or how the left and right sides of a person's face are nearly identical. If you look at both a person's face and his reflection in a mirror, which swaps left and right, it's difficult to know which one is the reflection—it looks much like the original.

In contrast, if you flip a person upside down, thereby swapping feet and head, it is easy to tell the flipped version from the original. The essence of geometrical symmetry is that when you make a change, the change isn't obvious.

Emmy Noether was a brilliant early-20th-century mathematician who made some interesting discoveries about symmetries in equations. To give a simple idea of what that means, consider the sum 1+2, which, of course, equals 3. If we swap the order and write 2+1, the sum is unchanged. This equation is symmetrical under reversal of the order.

Studying far more complex symmetries, Noether was able to link mathematical symmetries with conservation laws. Conservation laws describe things that don't change. One conservation law you usually learn about in science class is the conservation of mass. If you take three buckets of sand, weigh the sand, and then dump the bucketfuls into a bigger bucket, the weight of the sand in the bigger bucket is just the sum of the weights of the sand in the three smaller buckets. The sand's mass doesn't go anywhere. (Einstein showed us that this conservation law isn't absolute, but it works well in ordinary life.)

Noether showed the following: If, in a physical equation, you replace the term for time with a different term for time—one that is offset from the first by some amount—and the altered equation makes the same prediction as the original, then energy must be conserved. That's a tricky idea, but you can think about it this way: If I define Monday as the start of the week (my "day 0") and you define Tuesday as the start of the week (your "day 0"), then we will have a one-day offset between the numbers we assign to a particular day. I'd call Wednesday "day 2" while you'd call it "day 1." If the equations don't care about this difference in day numbers and make the same predictions, then energy is conserved.

There are many other similar symmetries in nature: If it doesn't matter what location you call "position 0," then momentum is conserved. If it doesn't matter what direction you call "direction 0," then angular momentum is conserved. Noether's theorem says that every symmetry is associated with a conservation law and vice versa. The math leads to observable physical phenomena. With this observation, one of the first things a physicist will study when confronted by a new theory is its symmetries.

Don Lincoln

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In Brief

Employee performance reviews due in July

It is the time of year again to reflect on our past year's performance. The following portions of the performance review process must be completed in July:

If you have any questions about the performance review process, please e-mail Juanita Frazier, workforce relations manager, or your D/S/C HR generalist.

In the News

Skype connects students, scientists

From Pittsburgh Post-Gazette, June 6, 2013

More than 60 Peters Township High School physics students gathered around a video-capable laptop and a microphone one morning last week

The students were the first class to participate in a video conference with scientists from CERN, the European Organization for Nuclear Research and Fermilab, a particle physics laboratory in Batavia, Ill.

Read more

In the News

New telescope strategy could resolve dark-matter mystery, scientists say

From, June 4, 2013

An intriguing hint of a certain type of gamma-ray light at the center of the Milky Way might be a product of elusive dark matter—or it might not be. For the past several years, scientists have debated whether the light is really there, and what it means. Now, researchers are petitioning the management team of NASA's Fermi Gamma-Ray Space Telescope, the observatory that saw the light, to change its observing strategy to determine once and for all whether the signal really exists.

However, even if there are extra gamma-ray photons coming from the center of the galaxy, scientists are a ways from knowing whether the photons were made by dark matter.

Read more

Frontier Science Result: ArgoNeuT

The hammer of neutrino interactions

A "hammer" neutrino interaction in ArgoNeuT with back-to-back protons (p1 and p2) and one forward-going muon (μ-).

Physicists from the ArgoNeuT collaboration may be seeing some interesting new ways in which a neutrino leaves its signature. ArgoNeuT uses a detector called a liquid-argon time projection chamber, which was operated in the NuMI beamline, to collect thousands of neutrino interactions on argon. LArTPCs are very well-suited to the task of observing neutrino interactions due to their very high-quality imaging capabilities. This same detector technology will soon be used on a much larger scale by MicroBooNE, and eventually by LBNE, to further understand the behavior of neutrinos.

A single argon atom floating around in a LArTPC detector contains 40 nucleons (18 protons and 22 neutrons) within its nucleus. This nucleus presents a complicated environment for the neutrino to interact within. In the simplest interaction that can occur, an incoming neutrino knocks into a neutron in the nucleus, producing an outgoing proton and muon. Based on experiments that scatter electrons off nuclear targets, there is evidence that some nucleons can partner up, existing as a duo. Neutrinos may end up interacting with both, and not just one, of the members of the duo. This twist on the neutrino interaction can have measurable consequences that need to be accounted for in order to properly interpret experimental results and compare them against theoretical predictions.

One suggested signature of a neutrino interacting with a nucleon pair, as opposed to a lone nucleon, is two back-to-back protons emerging from the nucleus as opposed to the single proton described before. Visually this signature gives the appearance of a hammer, with the muon forming the handle and the protons forming the head. Among ArgoNeuT's data sample, several events are observed that have this telltale hammer signature, which could be the smoking gun for correlated nucleons playing a role in neutrino interactions. The back-to-back protons can be very low in energy, making them hard to detect, which is where the strengths of the LArTPC technique come into play. The excellent resolution and calorimetry of the LArTPC detector allows both protons to be identified cleanly, and the back-to-back signature is easily discerned.

ArgoNeuT's studies of these nuclear effects will help inform phenomenologists who create the tools vital to modern particle physics analysis. Theoretical models of the nuclear environment are complicated, so providing experimental data can help the model builders. These studies will also help future LArTPC experimenters know what to expect when they send the intrepid neutrino into the heart of an argon atom.

—Mitch Soderberg

Photo of the Day

University of Delhi students visit Fermilab

Last week a group of physics students from the University of Delhi visited Fermilab, taking a tour of the DZero assembly building and the MicroBooNE facility. Here they are pictured in front of the MicroBooNE time projection chamber with three of their tour guides at the far right. From right to left, the guides are: Sarah Lockwitz (PPD), Jason St. John (U. of Cincinnati) and Mike Cooke (PPD). Jennifer Raaf (PPD) and Teppei Katori (MIT), not shown, also served as tour guides. Photo: Sam Zeller, PPD

Today's New Announcements

Barn Dance - June 9

Weekly 10,000 Steps-a-Day prize winner

Fermilab Family Outdoor Fair - June 9

Heartland Blood Drive with Oberweis gift certificates - June 10, 11

Lecture: Particles, Fields and the Future - Sean Carroll - June 12

DASTOW scheduled for June 21

Children's art show - June 21

46th Fermilab Users Meeting registration now open

Learn Drupal with Fox Valley Computing Professionals

Fermilab prairie quadrat study

Volunteer opportunity - Coat Drive 2013

Bible Exploration for Lunch League begins study of prophecies

Pool now open

Swim lessons for children

Water fitness at Fermi Pool

10,000 Steps-A-Day enrollment

Ultimate Frisbee Mondays and Wednesdays

Outdoor soccer at the Village

International folk dancing moves to Wilson Hall for summer

Scottish country dancing meets Tuesday evenings in Auditorium

English country dancing at Kuhn Barn

Join the Tango Club

Raging Waves water park discount

Find new classified ads on Fermilab Today.