Friday, Sept. 13, 2013

Have a safe day!

Friday, Sept. 13

3:30 p.m.

4 p.m.
Joint Experimental-Theoretical Physics Seminar - One West
Speaker: Ken Herner, Fermilab
Title: Probing the Spin/Parity of the Higgs using H→bb at DZero

8 p.m.
Fermilab Lecture Series - Auditorium
Speaker: Michael Meyer, NASA
Title: The Potential for Life on Mars: Past, Present, Future?
Tickets: $7

Monday, Sept. 16

2:30 p.m.
Particle Astrophysics Seminar - WH6W
Speaker: Ritoban Basu-Thakur, University of Illinois
Title: CDMSlite: A Search for Light WIMPs

3:30 p.m.

4 p.m.
All Experimenters' Meeting - Curia II

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a weekly calendar with links to additional information.

Ongoing and upcoming conferences at Fermilab


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Wilson Hall Cafe

Friday, Sept. 13

- Breakfast: chorizo and egg burrito
- Breakfast: blueberry-stuffed French toast
- Breakfast burger
- Seafood linguine
- Barbecue pork spareribs
- Turkey and cucumber salad wraps
- Strawberry summer salad with chicken
- Chicken noodle soup
- Texas-style chili

Wilson Hall Cafe menu
Chez Leon

Friday, Sept. 13
- Gazpacho
- Chili-glazed halibut with avocado tomatillo sauce
- Lemongrass rice
- Sauteed pea pods
- Pineapple flan

Wednesday, Sept. 18
- Southern-style barbecue ribs
- Black-eyed pea salad
- Honey cornbread muffins
- Peach cobbler

Chez Leon menu
Call x3524 to make your reservation.


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Physics in a Nutshell

Dark energy, chunky or smooth?

One of the primary questions about dark energy is whether it is the same everywhere ("smooth") or varies in density from place to place ("chunky").

The discovery of dark energy was the most surprising scientific breakthrough in my lifetime. Many physicists consider it the most baffling of nature's mysteries, and still little is known about it.

To say that it caused the textbooks to be rewritten is literally true. When I first studied cosmology, every textbook had a section on how the fate of the universe depends on the amount of matter it contains. As the universe expands, the gravitational force of all matter pulls against this expansion, slowing it down. If there is enough matter, the expansion can be reversed, pulling everything together into a big crunch. If there is too little, the universe will merely slow down as it flies apart. Dark energy is the discovery that the universe is not slowing down at all, but speeding up.

That's pretty much all we know: There's a force that more than counteracts gravity, blowing the universe apart at an ever-faster rate. Even the word "dark energy" is an empty label, since we don't really know whether it's a form of energy or not. It might not even be a thing. For instance, it may be that gravity repels, rather than attracts, on cosmic scales. There's even a term in Einstein's theory of gravity, called the cosmological constant, that might represent this large-scale repulsion.

But then again, dark energy might be a substance. This substance, often called quintessence, would have unusual properties like negative pressure. Substances can be distributed from place to place, so an observation of clumpy dark energy—more in some places than others—would teach us that it is a thing, rather than a law.

One way to search for clumps in dark energy is to map the sky with extraordinary precision. The gravitational effects of dark energy (and dark matter) leave imprints in the distributions of galaxies and the rate at which they form. These influences can be measured statistically in a sufficiently detailed map. The next generation of sky-surveying telescopes, the Dark Energy Survey, just began its five-year mission last week.

The nature of dark energy is also relevant for predicting the fate of the universe. If dark energy is a cosmological constant, a property of space, then the force it applies will get stronger as space expands—a runaway effect known as the big rip. If it is a substance like quintessence, then there are many possibilities, depending on the exact nature of the substance. Apart from just wanting to understand the world around us, learning about dark energy could have consequences in the long, long, very long term (eons).

Jim Pivarski

Want a phrase defined? Have a question? E-mail

Photo of the Day

Michael Knotek of DOE tours Fermilab and NOvA cavern

On Wednesday, DOE's Michael Knotek visited the NOvA Near-Detector Cavern at Fermilab. From left: Fermi Site Office Deputy Manager Mark Bollinger, Minos Underground Areas Coordinator Bill Lee, MINERvA scientist Debbie Harris, DOE Deputy Undersecretary of Energy for Science and Energy Michael Knotek, Fermilab Director Nigel Lockyer. Photo: Reidar Hahn
In the News

Fat gravity particle gives clues to dark energy

From Nature, Sept. 10, 2013

The Wall Street mantra "greed is good" could soon be adopted by cosmologists to explain the origins of dark energy, the mysterious entity that is speeding up the expansion of the Universe.

At a cosmology meeting last week in Cambridge, UK, attendants debated a controversial class of theories in which gravity is carried by a hypothetical 'graviton' particle that has a small, but still non-vanishing, mass. Such a particle would tend to gobble up vast amounts of energy from the fabric of space, enabling the Universe to expand at an accelerated, although not destructive, pace.

Since astronomers discovered in the late 1990s that the Universe's expansion is accelerating, researchers have struggled to explain not only the nature of the hypothetical entity—dubbed dark energy—that's causing the acceleration but also why the acceleration is so weak.

Read more

In the News

On 'The Big Bang Theory,' helping physics and fiction collide

From The New York Times, Sept. 9, 2013

It may seem improbable that a network sitcom could revolve around the lives and loves of a group of scientists at the California Institute of Technology, or Caltech. But "The Big Bang Theory," which begins its seventh season Sept. 26 on CBS, is one of the most popular comedies on television.

Part of its success might lie in the fact that one of its executive producers and script writers, Eric Kaplan, knows comedy and academia. His résumé includes not only "The Simpsons" and "The Late Show With David Letterman," but also Harvard and a Ph.D. program—never completed—at the University of California, Berkeley.

Read more

Frontier Science Result:
Theory Group

Lattice QCD at the frontiers

Global fit to experimental flavor measurements combined with Standard Model theory, known as the CKM unitarity triangle. Deviations from the CKM paradigm would manifest themselves as inconsistencies between the colored bands. The bands labeled εK +|Vcb|, |Vub|/|Vcb|, ΔMs/ΔMd , and BR(B → τν) +ΔMBs all use results from the Fermilab Lattice Collaboration. Figure courtesy of Enrico Lunghi

Precision measurements of processes that are expected to be rare in the Standard Model provide powerful probes of new physics. Conjectured new heavy particles may contribute to these processes and be observed as deviations from Standard Model expectations. For many of these quantities, numerical lattice quantum chromodynamics calculations are needed for accurate theoretical predictions, thereby maximizing the scientific impact of current and future experimental measurements.

Lattice QCD provides the only first-principles method for calculating, with controlled errors, the properties of particles containing quarks by casting the basic equations of QCD into a form amenable to high-performance computing. Since 2006, the U.S. lattice community has received essential hardware and software funding from the DOE High Energy and Nuclear Physics program offices. Fermilab has provided leadership for this project, particularly in the design and operation of dedicated high-performance parallel computers for lattice QCD.

In 2003, teraflop-scale processing power and improved computing algorithms enabled the first realistic lattice QCD calculations, including the effects of dynamical up, down and strange quarks. The methodology of lattice QCD has since been validated by comparison with a broad array of measured quantities. For example, in 2005, the Fermilab Lattice Collaboration and colleagues correctly predicted the mass of the Bc meson before it was measured by CDF.

A decade ago, the heavy-flavor factories and Tevatron Run II were beginning precision studies of charm and bottom quarks to test the Cabibbo-Kobayashi-Maskawa paradigm, which describes the weak interactions of quarks. Concurrently, the Fermilab Lattice Collaboration embarked upon an ambitious program to calculate B and D meson parameters needed to interpret the experimental heavy-flavor results as elements of the CKM matrix. These and other lattice results played an important role in establishing that the CKM paradigm describes the weak interactions of quarks to within about 10 percent. This momentous confirmation led to the share of the 2008 Nobel Prize in physics for Kobayashi and Maskawa.

To this day, the Fermilab Lattice Collaboration continues to be a leader in lattice QCD calculations to search for new quark flavor-changing interactions. We are now also expanding our physics program to provide lattice calculations needed to support future Energy and Intensity frontier experiments, focusing especially on those planned to run at Fermilab. Some examples are calculating the hadronic light-by-light contribution to the muon g-2, which is needed to solidify and improve the Standard Model prediction and interpret the upcoming measurement as a search for new physics; calculating the nucleon axial form factor, which is needed to improve determinations of neutrino interactions with protons and neutrons relevant for accelerator-based neutrino experiments such as LBNE; and improving calculations of the masses of the charm and bottom quarks and the strong coupling constant, which are needed to sharpen predictions of the different ways the Higgs can decay.

We hope that in the coming years precision measurements will definitively establish the presence of physics beyond the Standard Model, with lattice QCD calculations playing a key role.

Ruth Van de Water

The Fermilab Lattice Collaboration includes the following members of the Fermilab Theory Group. Top row, from left: Andreas Kronfeld, Paul Mackenzie. Bottom row, from left: Jim Simone, Ruth Van de Water. Not shown: Daniel Mohler and Ran Zhou.

Life on Mars - Fermilab Lecture Series - today

Annual ICW flush - through today

NALWO Annual Potluck Luncheon - Sept. 16

"Got Debt? Let's Manage It!" free webinar - Sept. 18

Artist Reception for VIEWS exhibit - Sept. 20

Second City: Happily Ever Laughter at Fermilab Arts Series - Sept. 21

Nominate a colleague for the Director's Award by Sept. 25

Power Writing Workshop offered Oct. 24

Access 2010 classes scheduled

MS Excel and Word classes offered this fall

Interpersonal Communication Skills class scheduled for Dec. 4

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

Accelerate to a Healthy Lifestyle

Abri Credit Union special offers

Butts and Guts is back

International folk dancing meets Thursday evenings in Auditorium

Outdoor soccer at the Village

Chicago Blackhawks preseason discounts

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