Friday, Sept. 27, 2013

Have a safe day!

Friday, Sept. 27

3:30 p.m.

4 p.m.
Joint Experimental-Theoretical Physics Seminar - One West
Speaker: Rick Field, University of Florida
Title: The Energy Dependence of the Underlying Event in Hadronic Collisions: Tevatron to the LHC

Monday, Sept. 30

2:30 p.m.
Particle Astrophysics Seminar - WH6W
Speaker: Tongyan Lin, University of Chicago
Title: Dark Matter and Flavor

3:30 p.m.

4 p.m.
All Experimenters' Meeting - Curia II
Special Topics: Prototype Intel Phi and NVIDIA Kepler Computing Cluster; Muon g-2 Status

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Wilson Hall Cafe

Friday, Sept. 27

- Breakfast: blueberry-stuffed French toast
- Breakfast: chorizo and egg burrito
- Teriyaki chicken breast
- Smart cuisine: white-fish florentine
- Country fried steak
- 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, Sept. 27
- Crunchy noodle salad with cabbage and peanut sauce
- Indonesian grilled swordfish
- Spiced rice
- Green beans with ginger and chili
- Sweet potato coconut cake

Wednesday, Oct. 2
- Black-bean soup with dark rum and orange zest
- Quesadillas with tomatillo salsa and salsa fresco
- Fudge pie with ancho chili

Chez Leon menu
Call x3524 to make your reservation.


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Physics in a Nutshell

Big mysteries: Ultra-high-energy cosmic rays

Cosmic rays constantly pummel the Earth, some with energies far higher than even the Large Hadron Collider can generate. The most energetic cosmic rays can have energies as much as a billion times higher than the LHC beams.

Accelerator physicists at CERN are understandably pleased with themselves for having accelerated a beam of protons to the prodigious energy of 4 trillion electronvolts. However, when interviewed for this story, the universe had a jocular response: "A trillion electronvolts? How cuteā€¦"

How is it that the universe could react so blithely? Well, it's because the universe accelerates protons to energies far higher than that all the time. These high-energy cosmic protons are called cosmic rays. Through interactions involving supernovae, white dwarfs, black holes and all sorts of denizens of the heavens, protons can be accelerated to energies thousands, millions and occasionally even billions of times higher than is possible at the LHC. These particles occasionally slam into the Earth high in the atmosphere, and we can detect the debris of the collision that makes it down to the surface.

These very high-energy cosmic rays are very rare. If you took a hypothetical picnic blanket and somehow suspended it high above the Earth, only about one cosmic ray with an energy of a few thousand times that of LHC beams will pass through the blanket per year. If you wanted to see a cosmic ray with an energy 10 million times that of the LHC, you'd have to grow your picnic blanket to be half a mile on each edge and then wait a year for the unlikely cosmic ray to pass through it. And to get the very highest-energy cosmic rays, which are about a billion times the energy of the LHC, the blanket would have to be big enough to simultaneously cover Arizona, New Mexico, Colorado and Utah to see one per year.

Studying these very high-energy cosmic rays provides insights into some of the most violent phenomena in the universe. However, scientists are still unclear on the origins of the very highest-energy protons. For instance, the universe is full of low-energy photons called the cosmic microwave background. Protons moving through space encounter these photons and, through the collisions, slow down. If you calculate the distance the proton can travel, you'll find that these very high-energy protons must, cosmically speaking, have a local origin — within 160 million light years.

Recent observations using the Auger Observatory in Argentina have suggested that perhaps the origins of ultra-high-energy cosmic rays might be active galactic nuclei, which are thought to be galaxies in which a super-massive black hole at the galaxy's center is rapidly gobbling up nearby gas clouds. However, the pointing precision of the Auger Observatory is only good to about three degrees, leaving plenty of room for ambiguity. Improvements in the number of high-energy cosmic rays observed by the Auger facility will help resolve the questions.

There are other possible explanations for very high-energy cosmic rays, from decaying dark matter to powerful electromagnetic fields in radio galaxies. The bottom line is that we don't really know where these cosmic bullets are coming from.

Understanding these energetic messengers from the heavens will shed light on the cosmos. For now, they remain one of the universe's big mysteries.

Don Lincoln

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Photo of the Day

This mushroom needs its own refrigerator shelf

This 10-inch-diameter puffball mushroom was spotted by the side of Wilson Road. Photo: Lori Limberg, BSS
In the News

The Dark Energy Camera

From WTTW11's Chicago Tonight, Sept. 25, 2013

It's the world's most powerful digital camera and it sits atop the Blanco telescope in the Andes Mountains of Chile. But it was constructed on the campus of Fermilab in far west suburban Batavia. The Dark Energy Camera officially began its work on August 31 and has already captured some amazing images of outer space. Its real mission, though, is to help scientists figure out if so-called Dark Energy is responsible for the universe's accelerating expansion.

Read more

Frontier Science Result:
Dark Energy Survey

Through a lens darkly (and strongly)

Examples of strong lensing systems imaged in the DES science verification (SV) data. Previously known strongly lensed, bluish-colored arcs are visible in the DES images of three rich galaxy clusters. Top row, from left: Bullet Cluster, RXC J2248.7-4431 and El Gordo. A nearly complete Einstein ring is visible in another cluster lensing system (bottom left), which was previously found by Fermilab scientists. Finally, two new candidate systems discovered in the DES SV data are also shown: one with a giant blue arc (bottom middle) and one with multiple blue images (bottom right).

The Dark Energy Survey collected more than 34,000 exposures during its science verification (SV) phase, from November 2012 to February 2013. It also began its first official season of observations on Aug. 31. Among the millions of astronomical objects imaged by DES so far, there are rare instances of "strong lensing" systems, where the effects of general relativity, Einstein's theory of gravity, are demonstrated in visually striking fashion.

When a foreground "lens" object is by chance very closely aligned on the sky with a much more distant background "source" object, the light from the source may be significantly deflected as it passes by the lens, due to the gravity of the lensing object's mass. This strong lensing effect leads to big distortions in the appearance of the source object: An otherwise faint and fuzzy single distant background galaxy may be transformed instead into a long bright arc, maybe into multiple blue knots or, in the rarest cases, into a so-called Einstein ring (see figure).

This wide variety in appearance of strongly lensed images is a consequence of the complexities of the lensing mass, which can range from an individual galaxy to a rich cluster of many galaxies, together with the much more massive dark matter halos in which the (luminous) galaxies reside. Studies of strong lensing systems can thus reveal to us properties of the distribution of dark matter that accompanies galaxies and galaxy clusters. Moreover, in addition to galaxy clusters, weak lensing, large-scale structure and supernovae — the four primary dark-energy probes used by DES — strong lensing may ultimately provide yet another way to study dark energy. For example, cosmological parameters, including dark energy, will affect the abundance and frequency of strong lensing systems and hence influence how many such systems we'll find in DES.

Indeed, one of the challenges of using strong lensing systems for cosmology is to find large numbers of these rare systems, but the DES is well suited for this, given both its large sky coverage and good imaging depth. Ultimately, automated methods will be employed to search for strong lensing systems within DES, but we have already found a number of good candidate systems in the DES SV data (see figure), through meticulous visual inspections of DES images by DES scientists and students, including in particular local area high-school students mentored by Fermilab scientists. As DES progresses, we expect to discover hundreds of strong lensing systems and will use them to further study and constrain the properties of dark matter and dark energy in the universe.

You can view recent images taken by the Dark Energy Survey at the new site Dark Energy Detectives.

Huan Lin

From ESH&Q

Flu vaccination information available online

Sign-up for this season's flu shot is now available online. The Fermilab Medical Office will administer flu shots on Oct. 3, 8, 10 and 15.

Read more about the Medical Office's flu vaccination administration in the Sept. 9 issue of Fermilab Today.


Today's New Announcements

SPIE digital library online trial at Fermilab

Fermilab Photo Club members exhibit application deadline - Oct. 1

Power Writing Workshop offered Oct. 24

Access 2010 classes scheduled

Interpersonal Communication Skills class scheduled for Dec. 4

Writing for Results: Email and More class offered Dec. 11

Big Move t-shirts available for purchase

NALWO "English Conversation" mornings

Accelerate to a Healthy Lifestyle

International folk dancing meets Thursday evenings in Auditorium

Indoor soccer now on Tuesdays and Thursdays

Basketball open gym on Wednesdays

Find new classified ads on Fermilab Today.