Friday, Nov. 1, 2013

Have a safe day!

Friday, Nov. 1

3:30 p.m.

4 p.m.
Joint Experimental-Theoretical Physics Seminar - One West
Speaker: Simon Fiorucci, Brown University
Title: First results from the LUX experiment Dark Matter Search

Saturday, Nov. 2

10:30 a.m.-4 p.m.
P5 Open Sessions - Auditorium

Sunday, Nov. 3

8 a.m.-3 p.m.
P5 Open Sessions - Auditorium

4-5:30 p.m.
P5 Town Hall Meeting - Auditorium

Monday, Nov. 4

2:30 p.m.
Particle Astrophysics Seminar - WH6W
Speaker: Sarah Andreas, Institut d'astrophysique de Paris
Title: Dark Matter in a Hidden Sector

3:30 p.m.

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

Click here for NALCAL,
a weekly calendar with links to additional information.

Ongoing and upcoming conferences at Fermilab


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Secon Level 3

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Flags at full staff

Wilson Hall Cafe

Friday, Nov. 1

- Breakfast: strawberry-stuffed French toast
- Breakfast: chorizo and egg burrito
- Texas Pete buffalo-style wings
- Smart cuisine: Beef burgundy ragout
- Tuna noodle casserole
- Honey mustard ham and Swiss panino
- Chicken fajita plate
- Cream of butternut squash
- Texas-style chili
- Assorted pizza by the slice

Wilson Hall Cafe menu
Chez Leon

Friday, Nov. 1
Menu unavailable

Wednesday, Nov. 6
- Honey mustard veggie kebobs
- Garlic quinoa
- Black forest cake

Chez Leon menu
Call x3524 to make your reservation.


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Physics in a Nutshell

Planck length, minimal length?

In this image of Max Planck, we see that the length of Planck is 1035 Planck lengths.

Read the complete column on Planck length.

We received an email from Bill G., an inquisitive reader:

"It is said that the Planck length is the smallest length possible. Is that true? If so, why?"

Readers should be warned that this article is a little more complicated than usual. Simple questions sometimes require detailed answers.

First, let's talk about what Planck length is. In 1899, German physicist Max Planck proposed a universal set of units for length, time, mass, temperature and other physical qualities. He was trying to come up with a way to define units that depended only on constants of the universe. To get an idea of why this is important, think about the difficulties associated with expressing lengths in meters versus feet. It would be even worse if we were talking to some Martian scientists and trying to compare our lengths to theirs.

A modern treatment of Planck's work begins with the speed of light c, gravitational constant G, reduced Planck constant ħ, Coulomb constant k and Boltzmann constant kB. By taking different combinations of these variables, one can find Planck units, which are truly universal. For instance, by taking √ ħG/c3 , one gets a length. This length is the Planck length, and it is 1.6 x 10-35 meters.

The beauty of the Planck units in general and the Planck length in particular is that no matter what units one chooses to make measurements, be it English, metric or Martian, everyone will determine the same Planck length. Planck himself said in his paper to the Prussian Academy of Sciences, "These necessarily retain their meaning for all times and for all civilizations, even extraterrestrial and non-human ones, and can therefore be designated as 'natural units.'"

Now that we understand what Planck length is, we can turn our attention to the question of whether it is the smallest possible length. For that, we need to turn to quantum mechanics and, specifically, a thing called the Heisenberg uncertainty principle. This general principle of the universe states that it is impossible to measure position and momentum simultaneously with infinite precision — measure one well and the other will be measured poorly.

In 1964, C. Alden Mead published a paper in which he determined the effect of gravity on a phenomenon called diffraction, which describes what happens to light when you send it through a small aperture. Because gravity is so incredibly weak compared to the force that governs the behavior of light (the electromagnetic force), its effect is completely ignored in diffraction calculations. But Mead was curious about quantifying gravity's negligible effect. When you scatter a particle of light off another particle — say an atom — the atom's gravitational attraction to the light particle causes an intrinsic uncertainty in the atom's location. Mead used the uncertainty principle and the gravitational effect of the photon to show that it is impossible to determine the position of an object to a precision smaller than the Planck length.

Read more

Don Lincoln

Want a phrase defined? Have a question? Email

Photos of the Day

Laughs and gore on 15th floor

A doorway on the 15th floor warns those who enter to beware.
WDRS' unflappable Barb Brooks take prisoners Nicole Gee and Karen Karlix-Smith back to jail.
WDRS show off their cute and corny candy corns.
The east side of the 15th floor is decked out with ghoulish spider webs, an all-seeing cat eye and not at all off-putting food. Photos: Sarah Witman
In the News

Dark matter still hiding: latest experimental sweep comes up empty

From Scientific American, Oct. 30, 2013

The world's most sensitive search for dark matter announced today that it has found—nothing. The first results from the Large Underground Xenon (LUX) detector are null, scientists say, indicating that the invisible matter thought to make up a large chunk of the universe is even more elusive than many experts thought.

Read more

Frontier Science Result: MiniBooNE

What does a neutrino see?

Neutrino-nucleon neutral-current elastic (NCE) scattering cross section (brown) and antineutrino-nucleon NCE scattering cross section (gray) as a function of the momentum transfer squared, measured by the MiniBooNE experiment.

According to lore, Albert Einstein came up with the special theory of relativity by imagining the world as seen by a beam of light. Figuring out what a neutrino sees as it traverses matter can help us understand not only the properties of neutrinos but also the structure of matter itself.

The Booster Neutrino Beamline at Fermilab produces an intense beam of neutrinos that travels to the MiniBooNE detector. When the neutrinos reach MiniBooNE they interact with the detector medium: mineral oil, made up of carbon and hydrogen. Specifically, they interact with the nucleons (protons or neutrons) and electrons that make up the carbon and hydrogen atoms. Neutrinos are known to interact only via the weak force, mediated by charged W bosons or neutral Z bosons.

One of these interaction types is Z boson-mediated neutrino-nucleon neutral-current elastic (NCE) scattering, in which an incoming neutrino scatters off a proton or neutron. This scattering mode, unique to neutrino interactions, is challenging to measure. The only previous measurement of this interaction with reasonable statistics was made by Brookhaven Lab's E734 experiment back in 1987, which saw 1,686 neutrino NCE and 1,821 antineutrino NCE candidate events.

In order to study NCE scattering, MiniBooNE looked at the scintillation light given off by the scattered proton. Data-driven methods were used to exclude other interactions mimicking the neutrino NCE scattering. In 2010, MiniBooNE reported a measurement of the neutrino-nucleon NCE scattering with a world-record sample of 94,531 events. More recently, scientists made the corresponding antineutrino-nucleon NCE scattering measurement, also with a record sample size (60,605 events). These high-statistic neutrino scattering measurements from MiniBooNE help us to understand the nuclear structure, study neutrino oscillations and even search for dark matter.

Ranjan Dharmapalan, University of Alabama

From left: Denis Perevalov (Fermilab, previously of The University of Alabama) and Ranjan Dharmapalan (The University of Alabama) worked on this MiniBooNE neutrino-nucleon neutral-current elastic scattering analysis.
Special Announcement

Change your clocks, change your batteries

The members of the Fermilab Fire Department wish to remind you to check or change the batteries in your smoke detectors and carbon monoxide detectors when turning your clocks back an hour on Sunday, Nov. 3. Smoke detectors should also be checked monthly for proper operation. Statistics show that properly working smoke detectors save lives. Contact the Fire Department at x3428 with questions.

Special Announcement

Roads B and D closed Nov. 5-8

Roads B and D in the vicinity of the Feynman Computing Center and the IARC OTE Building construction will be closed from Tuesday to Friday. Click on the map to view the detour route.

From Nov. 5-8, parts of Road B and Road D will be closed because of road improvements in front of the IARC Office Technical and Education Building and on the east side of the Feynman Computing Center.

Employees at FCC will use the FCC remote parking lot along the north side of Road B.

Employees at CDF will use the parking lot at Site 327. Access around the barricade at the far east end of Road D is allowed for CDF employees only.

Employees working in the Industrial Complex (IC and IB 1, 2, 3 and 4) will access the parking lots from Feldott Road.

See this map to view the detour route.


Today's New Announcements

Change to cafeteria hours - open at 10 a.m. - Nov. 2-3

Labwide party - Dec. 6

Deadline for Wilson Fellowship application - Nov. 1

Office of Science's Patricia Dehmer speaks at UChicago - Nov. 5

Community outreach volunteer opportunity - learn more Nov. 5

Heartland Fermilab walk-in blood drive - Nov. 5 and 6

Stars of Dance Chicago - Fermilab Arts Series - Nov. 9

CSADay 2013 training opportunities - Nov. 12

Certified Administrative Professional - Lunch and Learn - Nov. 13

Physics Slam 2013 - Fermilab Arts & Lecture Series - Nov. 15

Message regarding Windows 8.1

Donate winter wear for Fermilab Coat Exchange

Lepton flavor violation course in lecture series

Money just got cheaper

Scottish country dancing returns to Kuhn Barn Tuesday evenings

International folk dancing returns to Kuhn Barn Thursday evenings

Ringling Bros. and Barnum & Bailey discounts

Find new classified ads on Fermilab Today.