Thursday, Dec. 19
- Breakfast: Canadian bacon, egg and cheese Texas toast
- Breakfast: Mexican omelet
- Steak soft tacos
- Smart cuisine: spinach and jack cheese enchiladas
- Beef stew in a bread bowl
- Grilled-vegetable sandwich
- Sweet and sour chicken
- Beef barley soup
- Chef's choice soup
- Assorted pizza by the slice
Wilson Hall Cafe menu
Friday, Dec. 20
- Spinach and pomegranate salad
- Lobster tail with champagne butter sauce
- Spaghetti squash with scallions
- Grilled asparagus
- Raspberry mousse with an assortment of Christmas cookies
Wednesday, Dec. 25
Chez Leon menu
Call x3524 to make your reservation.
Santa at nearly the speed of light
Editor's note: In the spirit of the holidays, we bring you this fun 1998 FermiNews article on the physics of Santa Claus' gift delivery.
About this time of year, inquisitive children of a certain age begin to question whether Santa is real. After all, Santa has a major delivery problem. There are some 2 billion children in the world expecting Christmas presents. Assuming an average of 2.5 children per household, then, Santa has to visit about 800 million homes scattered about the globe.
The distance Santa has to travel can be estimated from the following. First, while the surface area of Earth is about 1014 square meters, only about 30 percent of that is land mass, or about 0.3 x 1014 square meters. Second, we'll assume, for simplicity's sake, that the 800 million homes are equally distributed on this land mass. Dividing 0.3 x 1014 by 800 million gives 4 x 104 square meters occupied by every household (about six football fields); the square root of that is the distance between households, about 200 meters. Multiply this by the 800 million households to get the distance Santa must travel on Christmas Eve to deliver all the children's gifts: 160 million kilometers, farther than the distance from here to the sun.
Thanks to the rotation of the earth, Santa has more time than children might initially think. Standing on the International Date Line, moving from east to west and crossing different time zones, Santa has not just 10 hours to deliver his presents (from 8 p.m., when children go to bed, until 6 a.m., when they wake up), but an extra 24 hours — 34 hours in all.
Even so, Santa's task is daunting.
—Arnold Pompos and Sharon Butler
Dawn's frosty light
|A view through a frost-covered window shows the sun at dawn on a 4-degree morning. Harry Ferguson III, PPD
January wellness offerings, fitness classes and discounts
Start your new year off right with a free on-site health screening. Sign up for a Kyuki-do martial arts, Zumba Fitness, Zumba Toning or Butts & Guts class, all starting in January.
Free Wellness Offerings
Free on-site health screenings for active employees
Tuesday, Jan. 7, 7:30 a.m.-3:30 p.m.
Wilson Hall Small Dining Room
Wednesday, Jan. 8, 7:30 a.m.-3:30 p.m.
Users Center Music Room
The screening offers active employees an opportunity to have cholesterol, blood glucose, blood pressure and body composition checked. You can meet one-on-one with a health coach to review results, ask questions and discuss follow-up health and wellness resources. Registration is required to participate. Schedule your health screening appointment, and use
BuZheng Qigong and Tai Chi Easy
Mondays and Fridays, Jan. 6 - May 30, noon-1 p.m.
Wednesdays, Jan. 8 - May 28, 7-8 a.m.
Mondays and Wednesdays, Jan. 6 - Feb. 10, 5-6 p.m.
Fitness Center Gym
$60/person. Register by Dec. 30
Tuesdays, Jan. 7 - Feb. 25, 11:45 a.m -12:30 p.m.
Fitness Center Exercise Room
$50/person. Register by Dec. 31
Thursdays, Jan. 9 - Feb. 27 (no class Jan. 16), 11:45 a.m.-12:30 p.m.
Fitness Center Exercise Room
$45/person. Register by Jan. 2
Butts and Guts
Fridays, Jan. 10 - Feb. 28, 11:45 a.m.-12:30 p.m.
Fitness Center Exercise Room
$60/person. Register by Jan. 3
Tuesdays and Thursdays, 6 p.m.
Fitness Center Gym
Gym membership is required to participate. Contact O'Sheg Oshinowo for more information.
For other discount information, visit the WDRS employee discounts Web page.
AMC and Regal movie tickets
For more information, contact Jeanne Ecker in the Wellness Office at x2548 or at firstname.lastname@example.org.
Viewpoint: ups and downs in the search for dark matter
From Physics, Dec. 16, 2013
We know dark matter is out there. Astrophysical observations of gravitational effects provide evidence of its existence at all times, from the time of nucleosynthesis (a few minutes after the big bang) to the moment in which the cosmic microwave background radiation was released (300,000 years after the big bang), all the way to the present Universe. Dark matter pervades all length scales, from the universe as a whole to individual galaxies, including our Milky Way, and even to some smaller structures. The question is not, does dark matter exist? The question is, what is dark matter made of?
Chasing the neutrino to measure W boson direction
|The direction of positive (blue) and negative (red) W bosons produced in proton-antiproton collisions gives information about the underlying quark structure of these nucleons. For the best possible measurement, the momentum of the neutrinos (the fuzzy gray objects) is needed. This requires some clever techniques and a detailed understanding of the detector.
Disponible en español
The above figure may look familiar. That's because I used a very similar one for an article in September, describing a measurement of the muon asymmetry from W boson decays. The idea was to look at the direction of the positive and negative muons, from which some important details of the proton and antiproton structure can be extracted. This week the DZero experiment released a new measurement using a similar technique, though with a different particle and with a very important improvement that is worth highlighting.
The process of interest is W boson production at the Tevatron, when a quark from the proton and an antiquark from the antiproton generate a massive, charged and short-lived boson via the weak interaction. The direction of the W boson tells us how much of the proton momentum is carried by the down and up quarks, information of huge importance for many other measurements, both in particle physics (such as determining the W boson mass) and beyond (for example, in nuclear physics).
To reconstruct the W boson direction, the analyzers search for its decay into a charged lepton, in this case an electron, and a neutrino, which passes all the way through the detector without leaving any signal. The W boson direction is equal to the direction of the combined lepton-neutrino system, and so the momentum of both particles, including the undetected neutrino, is needed to make the measurement — or is it?
All is not lost! While the neutrino is not observed directly, it is conspicuous in its absence. Using the principles of conservation of momentum and energy and measuring the momenta of the other particles in the event, we can constrain the neutrino trajectory with sufficient precision to extract the W boson direction. The neutrino is like a missing piece in a jigsaw puzzle: It's only by putting all the other pieces together that the missing shape can be known.
The muon asymmetry analysis covered previously uses a different method to sidestep the issue of the missing neutrino, relying on the fact that the lepton and W boson directions are strongly correlated. However, interpreting this lepton asymmetry is reliant on certain assumptions about the decay mechanism. By using the additional detector information to infer the W boson direction directly, and also by using a different type of lepton (electron versus muon) in the W decay, this new measurement provides important and independent information about the proton structure. As an example of the benefit of this new data, using it in the final W boson mass measurements from the Tevatron could yield precision improvements of up to 15 percent.
|Hang Yin of Fermilab was the primary analyzer for this measurement.
|The DZero Monte Carlo production team is charged with the daunting task of generating up to 50 million events of simulated particle collisions per week. This is a global project, with jobs "farmed out" to computing centers all over the world. Such simulated data is vital for all measurements performed at DZero.