Friday, April 26, 2013

Have a safe day!

Friday, April 26

3:30 p.m.

4 p.m.
Joint Experimental-Theoretical Physics Seminar - One West
Speaker: Ryan Hooper, Lewis University
Title: The Zen of Two Z's at DZero

Monday, April 29

2:30 p.m.
Particle Astrophysics Seminar - One West
Speaker: Matt Kauer, University of Wisconsin - Madison
Title: Operation, Performance and First Results from DM-Ice17: a NaI Dark Matter Detector in the South Pole Ice

3:30 p.m.


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Wilson Hall Cafe

Friday, April 26

- Breakfast: blueberry-stuffed French toast
- Vegetarian chili
- Ye olde fish and chips
- Southern fried chicken
- Smart cuisine: seafood linguine
- Eggplant parmesan panini
- Assorted pizza by the slice
- Breakfast-for-lunch omelet bar

Wilson Hall Cafe menu
Chez Leon

Friday, April 26

Wednesday, May 1
- Jerk chicken
- Red beans and rice
- Coconut flan

Chez Leon menu
Call x3524 to make your reservation.


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Physics in a Nutshell

The weak world

Like electromagnetism and the strong force, the weak force transfers momentum by tossing an intermediate boson. However, the act of throwing or catching the boson also transforms the particles.

Of the four fundamental forces, the weak force is the most mysterious. It is the only one with no obvious role in the world we know: The strong force builds protons and nuclei, electromagnetism is responsible for nearly every macroscopic phenomenon, and gravity, though weaker than the rest, is noticeable because of our close proximity to a reasonably large planet.

The only observable phenomenon due to the weak force is the radioactivity of certain substances (not all). I sometimes wonder if this major aspect of nature might have gone unnoticed if Henri Becquerel hadn't kept his unexposed photographic film and his uranium samples in the same drawer. Early 20th-century physicists wondered why some rocks emit strange rays—it turns out that there's a new force that transforms particles so that they are no longer bound to the nucleus. Mid-20th-century physicists wondered why this force is so weak—it turns out that its intermediary force carrier, its analog of the photon in electromagnetism, is very massive and therefore rarely produced. Physicists today wonder why the weak force carrier is so massive—it may be that there's an omnipresent Higgs field binding to it, slowing it down and giving it effective mass. The particulate form of that Higgs field may have been discovered last year, at long last.

The weak force is the most eclectic of the four—it violates most of the conservation rules that the others uphold. The strong force, electromagnetism and gravity all act on antimatter the same way with the same strength as on equivalent samples of ordinary matter; the weak force does not. The same is true of mirror-flipped and time-reversed configurations; the weak force uniquely distinguishes between clockwise and counter-clockwise, between forward and backward.

In fact, interactions through the weak force change the identity of all particles involved. In previous articles, we showed how forces push and pull by exchanging an intermediary. In the case of electromagnetism, two charged particles repel by throwing a photon from one to the other, like a heavy sack thrown between two boats. For the weak force, this is either a charged W boson or a neutral Z boson. When a quark emits a W boson, however, it becomes a new type of quark. Charmed quarks turn into strange quarks, and muons become electrons. In addition to carrying the momentum of the force, the W boson takes some of the strangeness or the charmness out of one quark and into another.

In its unique role as rule-breaker, the weak force may be responsible for the matter-antimatter asymmetry in the universe. Its weakness may be hiding dark matter. The weak force seems to be tied to so many fundamental mysteries, it's amusing to think that the whole thing might have been overlooked if Victorian physicists hadn't been so curious about strangely warm rocks.

Jim Pivarski

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In the News

Rep. Bill Foster on FY 2014 Department of Energy appropriations legislation

From FYI: The AIP Bulletin of Science Policy News, April 24, 2013

An integral part of the appropriations process are requests that representatives and senators make to the appropriations committees regarding future funding legislation. These requests can take the form of "Dear Colleague" letters that are signed by many members, or a letter from an individual representative or senator.

Rep. Bill Foster (D-IL) wrote to House Energy and Water Development Appropriations Subcommittee Chairman Rodney Frelinghuysen (R-NJ) and Ranking Member Marcy Kaptur (D-OH) about FY 2014 funding levels and committee report language for the Department of Energy's Office of Science, Office of Energy Efficiency and Renewable Energy, and Office of Nuclear Energy. Committee report language, while not having the force of law, provides clear direction to federal departments and agencies regarding specific programs.

Read more

In the News

SLAC's historic 'End Station A' hosts electron beams once again

From SLAC Today, April 23, 2013

Electrons are once again streaming into SLAC's historic End Station A, setting the stage for a new user facility in the huge, concrete hall where the first evidence for quarks was discovered.

Fed by billion-particle bunches of high-energy electrons diverted from the linear accelerator supply to the Linac Coherent Light Source (LCLS), the new beamline, called the End Station Test Beam (ESTB), will initially host three types of experiments.

  • General beam physics and machine-detector interface studies for the proposed International Linear Collider and Compact Linear Collider
  • Radiation hardness tests on detector components
  • R&D for high-energy physics detectors, which will use secondary particles created when the main beam hits a target.

Read more

Frontier Science Result:
Dark Energy Survey

Supernovae light the way to dark energy

Images from the Dark Energy Camera before (left) and after (right) a supernova explosion in a galaxy about 2 billion light-years away.

The Dark Energy Survey (DES) collaboration has captured images of 176 star explosions, called supernovae, including 16 that occurred farther than 7 billion light-years away and when the universe was only about half as old as it is today. A new type of CCD detector contained in the Dark Energy Camera enabled identification of the distant supernovae, making DECam about 10 times more sensitive than other optical cameras to the long-wavelength (red and near-infrared) light coming from these very distant explosions. This improved sensitivity will allow the DES collaboration to find more supernovae from this period in the history of the universe than any other project.

Our current understanding is that the universe is made up of about 70 percent dark energy and that this dark energy is causing the universe to expand at an accelerating rate. Measuring Type 1a supernovae is a way to study dark energy. The fainter the observed explosion, the further away it is, similar to the difference in brightness between nearby and distant candles. As the light of the explosion travels to us, it is stretched by the expansion of the universe and becomes redder. By combining the measured brightness and information about how much the light is stretched, cosmologists can calculate the expansion rate of the universe.

The amount and wavelength of a supernova's light determines its age and type. Researchers use filters that divide optical light into four separate parts, with each filter allowing only certain wavelengths to pass through. We know these 16 supernovae are about 7 billion light-years away because most of the light was observed with the filter that allowed only the reddest light to pass through and be measured by the special red-sensitive detectors in the camera. Less sensitive cameras require time-consuming follow-up observations to determine the supernova age.

To search for supernovae, the DES observers take images of the same patch of sky every four to seven days. Then they subtract the images from each other and search for differences. Computers and teams of people looked at thousands of sets of DECam images to find the 176 candidate supernovae. So far five of the candidates have been followed up, and all five were confirmed to be type 1a supernovae.

The Dark Energy Survey will measure more than 3,000 type-1a supernovae in the next five years and provide new information about the mysterious nature of dark energy. For more information, see the Dark Energy Survey website.

—Brenna Flaugher

The Dark Energy Survey collaboration includes scientists, postdocs and graduate students from around the world, who worked together to build the camera, collect the images and identify the supernovae described in this result.
Video of the Day

Sunday strumming

Old-time string band Cocoa Magic warms up outside Kuhn Barn before the barn dance on Sunday, April 14. View the Fermilab Folk Club schedule to find out when you can move your feet to similar, partner-swinging music. Watch Cocoa Magic play. Video: Lynn Garren, SCD

Today's New Announcements

Rush-Copley Healthplex Open House - April 27 and 28

Engineering Group to hold seminars at Fermilab - today

Power outage in FCC2 - April 27

Changes to U.S. visa procedures - begin April 30

Permanent residence presentation by Chicago attorneys - May 1

Coed Softball League season opener - May 1

National Day of Prayer Observance - May 2

English country dancing Sunday afternoons at Kuhn Barn - May 5 and May 19

LabVIEW classes scheduled - May 10 and June 13

Hubbard Street 2 Dance - Fermilab Arts Series - May 11

Lecture: Big Science, Big Challenges - May 16

Fermilab-CERN Hadron Collider Physics Summer School open for applications

Open gym basketball Tuesday evenings

Indoor soccer

Fermilab Golf League

Indian Creek Riding Club

International folk dancing meets Thursday evenings in Kuhn Barn

Scottish country dancing meets Tuesday evenings in Kuhn Barn

Chicago Fire discount tickets

Find new classified ads on Fermilab Today.