Thursday, Dec. 6, 2012

Have a safe day!

Thursday, Dec. 6

2:30 p.m.
Theoretical Physics Seminar - Curia II
Speaker: Myeonghun Park, CERN
Title: Collider Bounds on Dark Matter Models for Fermi Gamma-Ray Line

3:30 p.m.


Friday, Dec. 7

3:30 p.m.

4 p.m.
Joint Experimental-Theoretical Physics Seminar - One West
Speakers: Michael Begel, Brookhaven National Laboratory
Title: Recent ATLAS SUSY Results

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Wilson Hall Cafe

Thursday, Dec. 6

- Breakfast: corned-beef hash and eggs
- White chicken chili
- Monte Cristo
- Beef stroganoff
- Smart cuisine: Mediterranean-style ziti with asparagus
- Buffalo chicken tender wrap
- Assorted pizza by the slice
- Grilled- or crispy-chicken Caesar salad

Wilson Hall Cafe Menu

Chez Leon

Friday, Dec. 7
- Mushroom soup with chorizo and scallions
- Pecan-crusted beef tenderloin
- Cauliflower gratin
- Brussels sprouts with lemon and bacon
- Chocolate mousse pie

Wednesday, Dec. 12
- Shepherd's pie
- Field greens with cranberries and walnuts
- Cocoa cappuccino mousse with cookies

Chez Leon Menu
Call x3524 to make your reservation.


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From symmetry

Scientists propose new projects to unravel dark-energy secrets

Scientists have risen to the challenge to design an experiment that will make measurements of millions of galaxies to probe dark energy in new ways. Image: Sloan Digital Sky Survey

About 5 billion years ago the universe underwent a crucial transition. The gravitational tug that pulled together the matter in the universe was overwhelmed by a different, repulsive phenomenon. As a result, the universe began to expand at an accelerating rate.

Scientists have given that phenomenon a name: dark energy. However, they can say with confidence only what it does, not what it is, where it comes from or why it's pushing galaxies apart at an ever more rapid speed.

The Department of Energy recently declared the need to construct a powerful new device that scientists could use to address fundamental questions about dark energy.

Scientists have proposed two different projects to fulfill this need. The projects aim to study the three-dimensional distribution and motions of galaxies before and after the transition epoch between the matter-dominated and dark-energy-dominated eras.

"It turns out that the rate at which galaxies formed in the early universe as well as the expansion rate of the universe itself are sensitive to this stuff we call dark energy," says Fermilab physicist Josh Frieman, director of an existing dark energy experiment called the Dark Energy Survey. "So, those two things are what we're really trying to measure."

Scientists can look into the past by studying the light from distant galaxies. This will give scientists a better understanding of what role dark energy has played, Frieman says.

Scientists' main tools for studying how galaxies have been distributed over billions of years are imaging surveys and spectroscopic surveys. Imaging surveys compile a collection of images of the sky, while spectroscopic surveys go one step further, dispersing the light from certain objects within an image into individual wavelengths called a spectrum. They do this by attaching an instrument called a spectrograph to a telescope.

Scientists use imaging surveys to map out the sky and pinpoint galaxy locations. They follow these up with spectroscopic surveys. Both survey types are important because imaging surveys can accurately measure the two-dimensional positions and shapes of galaxies on the sky and spectroscopic surveys can precisely determine the three-dimensional positions.

A galaxy's spectrum contains information on its chemical composition and—more importantly to dark energy researchers—its distance from Earth. With spectroscopic surveys, scientists can construct three-dimensional maps of the sky. To do this, they have proposed two new spectroscopic surveys, one in the northern hemisphere and the other in the southern hemisphere.

Read more

Jessica Orwig

Photo of the Day

Drawing toward the high-rise

Steve Krave, TD, took this wide-angle nighttime shot of Wilson Hall.
In the News

Data teleportation: the quantum space race

From Nature, Dec. 5, 2012

Three years ago, Jian-Wei Pan brought a bit of Star Trek to the Great Wall of China. From a site near the base of the wall in the hills north of Beijing, he and his team of physicists from the University of Science and Technology of China (USTC) in Hefei aimed a laser at a detector on a rooftop 16 kilometres away, then used the quantum properties of the laser's photons to 'teleport' information across the intervening space. At the time, it was a world distance record for quantum teleportation, and a major step towards the team's ultimate aim of teleporting photons to a satellite.

If that goal is achieved, it will establish the first links of a 'quantum Internet' that harnesses the powers of subatomic physics to create a super-secure global communication network. It will confirm China's ascent in the field, from a bit-player a little more than a decade ago to a global powerhouse: in 2016, ahead of Europe and North America, China plans to launch a satellite dedicated to quantum-science experiments. It will offer physicists a new arena in which to test the foundations of quantum theory, and explore how they fit together with the general theory of relativity—Einstein's very different theory of space, time and gravity.

Read more
Result of the Week

Rare muon pairs made by chance or enhanced?

The rare decay of a Bs0 meson into two muons would be greatly enhanced by some models of new physics.

While the Standard Model allows the Bs0 meson, the particle containing a strange quark and an antibottom quark, to decay into two muons, the chance of that happening is about half that of a given lottery ticket winning the Mega Millions jackpot. This rare process is more common in theories with new physics, such as supersymmetry, where the presence of new particles can significantly enhance the Bs0 decay rate into muon pairs. The search for this decay provides an excellent window for finding any new physics that would alter the decay rate and has been a key part of the worldwide effort to search for physics beyond the Standard Model for many years. A new analysis at DZero significantly improves upon the previous DZero sensitivity to this decay and complements recent results from other collaborations.

Because this decay process is so rare and the aim of the analysis is to be sensitive to just a very few events, the analysis itself is performed "blindly," or without looking at the signal region until the entire analysis is otherwise finalized. There are two major backgrounds to the signal in this search, and the analyzers used a two-pronged approach to mitigate them. Since each major background involves more than one particle decaying in order to produce the two muons, the analyzers used information about the activity around each muon in the event to help classify it as signal or background. The analyzers also created two discriminants, one to separate the signal from each source of background, and then determined the optimal cuts on each to use as the final signal selection.

After examining the data in the signal region, the DZero analyzers find no significant excess over the background. They set a limit on the chance of a Bs0 decaying into two muons to be less than about 15 times for every billion decays, which is nearly 3½ times better than the previous DZero result. While still not sensitive enough to measure the expected Standard Model signal, the DZero constraint is the strongest limit from the Tevatron on new physics in this rare decay. The result is in agreement with the most recent results from the CDF, ATLAS, CMS and LHCb collaborations.

Mike Cooke

These physicists made major contributions to this analysis.
When a quark is produced as part of a particle collision, it turns into a spray of particles called a jet. The b-jet identification group provides tools that separate jets that originate from a bottom quark from those that originate from lighter quarks, a key element to many physics analyses at DZero.

Today's New Announcements

Clearance through customs (also streamed live) - Dec. 13

School's Out Day Camp - register by Dec. 19

Service Desk staffing hours have been extended

Give the gift that everyone can use!

C2ST screening of "A Beautiful Mind" - today

The Good Lovelies: Under the Mistletoe - Dec. 8

Barn Dance - Dec. 9

Fermilab Heartland Blood Drive - Dec. 10-11

AFS passwords to be discontinued - Dec. 11

Fermilab's Holiday Celebration - Dec. 13

Holiday stress relief massages - Dec. 20

An Honest Approach to Weight Management - register by Dec. 21

Revised Procedures for Researchers document online

Professional development courses

International Folk Dancing every Thursday through December

Indoor soccer

Employee discounts at Journey Cycle and BMX

Atrium work updates