Thursday, Nov. 20, 2014

Have a safe day!

Thursday, Nov. 20

1:30 p.m.
Particle Astrophysics Seminar (NOTE DATE, TIME, LOCATION) - WH6NW
Speaker: Farinaldo Queiroz, University of California, Santa Cruz
Title: Dark Matter Complementarity

2:30 p.m.
Theoretical Physics Seminar - Curia II
Speaker: Travis Martin, TRIUMF
Title: Electroweakino Constraints from LHC8

3:30 p.m.
Director's Coffee Break - WH2XO

Friday, Nov. 21

3:30 p.m.
Director's Coffee Break - WH2XO

4 p.m.
Joint Experimental-Theoretical Physics Seminar and Fermilab Colloquium - One West
Speaker: Simona Murgia, University of California, Irvine
Title: Indirect Dark Matter Searches with Gamma Rays: Constraints and Intriguing Hints

Visit the labwide calendar to view Fermilab events

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Wilson Hall Cafe

Thursday, Nov. 20

- Breakfast: Canadian bacon, egg and cheese Texas toast
- Breakfast: Mexican omelet
- Steak soft tacos
- Pork and apple curry
- Chicken vindaloo
- Beef and cheddar wrap
- Sweet and sour chicken
- Beef barley soup
- Chef's choice soup
- Assorted pizza by the slice

Wilson Hall Cafe menu

Chez Leon

Friday, Nov. 21
- Spinach, mandarin orange and red onion salad
- Mahi mahi with avocado tomatillo salsa
- Lemongrass rice
- Sauteed pea pods
- Coconut flan

Wednesday, Nov. 26
- Cheese fondue
- Mixed greens salad
- Strawberry almond tart

Chez Leon menu
Call x3524 to make your reservation.


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From symmetry

LHCb experiment finds new particles

A new LHCb result adds two new composite particles to the quark model. Photo: CERN

[On Wednesday] the LHCb experiment at CERN's Large Hadron Collider announced the discovery of two new particles, each consisting of three quarks.

The particles, known as the Ξb'- and Ξb*-, were predicted to exist by the quark model but had never been observed. The LHCb collaboration submitted a paper reporting the finding to the journal Physical Review Letters.

Similar to the protons that the LHC accelerates and collides, these two new particles are baryons and made from three quarks bound together by the strong force.

But unlike protons — which are made of two up quarks and one down quark — the new Ξb particles both contain one beauty quark, one strange quark and one down quark. Because the b quarks are so heavy, these particles are more than six times as massive as the proton.

"We had good reason to believe that we would be able to see at least one of these two predicted particles," says Steven Blusk, an LHCb researcher and associate professor of physics at Syracuse University. "We were lucky enough to see both. It's always very exciting to discover something new."

Even though these two new particles contain the same combination of quarks, they have a different configuration of spin — which is a quantum mechanical property that describes a particle's angular momentum. This difference in spin makes Ξb*- a little heavier than Ξb' -.

Read more

Sarah Charley

Photo of the Day

Looking back: a previous praying mantis season

It's Throwback Thursday. Sept. 3, 2002: Lily Witherell, daughter of former Fermilab Director Mike Witherell and Beth Witherell, spots a praying mantis on the steps of Wilson Hall. It was her third birthday. Photo: Beth Witherell
In the News

Big bang's echo may reveal skeleton of the universe

From, Nov. 17, 2014

Scientists may soon get a look at the universe's skeleton by taking a close look at light left over from the big bang, which can be used to reveal the presence of matter like stars, galaxies, black holes and even larger structures in the otherwise empty universe. It's a lot like an X-ray revealing bones in a body, but on a cosmic scale.

X-ray machines work by shining light over an entire area and detecting how different materials react. The light passes through tissue, but is stopped by bone.

In a similar way, scientists with the international POLARBEAR collaboration want to use a diffuse light that fills every corner of the cosmos to indicate where there is matter and where there is none. POLARBEAR studies the cosmic microwave background (CMB) — the surviving light from the infant universe that is normally seen a kind of baby picture of the cosmos. Scientists estimate the universe is about 13.8 billion years old.

Read more

In the News

Milky Way's black hole may be a neutrino factory

From Discovery, Nov. 18, 2014

Less than three hours after astronomers detected the biggest burst of X-rays streaming from the black hole at the center of the Milky Way, a rarely seen, high-energy neutrino showed up in an underground detector in the South Pole.

A coincidence?

Scientists think not. The IceCube Neutrino Observatory made several more detections of the ghost-like particles a few days after the black hole, known as Sagittarius A*, flared, a newly released study shows.

Read more

Physics in a Nutshell

Heisenberg's uncertainty principle and Wi-Fi

Bandwidth, or the spreading of a radio station onto multiple, neighboring frequencies, is related to uncertainty in quantum mechanics.

When I first started teaching, I was stumped by a student who asked me if quantum mechanics affected anything in daily life. I said that the universe is fundamentally quantum mechanical and therefore it affects everything, but this didn't satisfy him. Since then, I've been noticing examples everywhere.

One surprising example is the effect of Heisenberg's uncertainty principle on Wi-Fi communication (wireless internet). Heisenberg's uncertainty principle is usually described as a limit on knowledge of a particle's position and speed: The better you know its position, the worse you know its speed. However, it is a general principle with many consequences. The most common in particle physics is that the shorter a particle's lifetime, the worse you know its mass. Both of these formulations are far removed from everyday life, though.

In everyday life, the wave nature of most particles is too small to see. The biggest exception is radio and light, which are wave-like in daily life and only particle-like (photons) in the quantum realm. In radio terminology, Heisenberg's uncertainty principle is called the bandwidth theorem, and it states that the rate at which information is carried over a radio band is proportional to the width of that band. Bandwidth is the reason that radio stations with nearly the same central frequency can sometimes be heard simultaneously: Each is broadcasting over a range of frequencies, and those ranges overlap. If you try to send shorter pulses of data at a higher rate, the range of frequencies broadens.

Although this theorem was developed in the context of Morse code over telegraph systems, it applies just as well to computer data over Wi-Fi networks. A typical Wi-Fi network transmits 54 million bits per second, or 18.5 nanoseconds per bit (zero or one). Through the bandwidth theorem, this implies a frequency spread of about 25 MHz, but the whole Wi-Fi radio dial is only 72 MHz across. In practice, only three bands can be distinguished, so only three different networks can fill the same airwaves at the same time. As the bit rate of Wi-Fi gets faster, the bandwidth gets broader, crowding the radio dial even more.

Mathematically, the Heisenberg uncertainty principle is just a special case of the bandwidth theorem, and we can see this relationship by comparing units. The lifetime of a particle can be measured in nanoseconds, just like the time for a computer to emit a zero or a one. A particle's mass, which is a form of energy, can be expressed as a frequency (for example, 1 GeV is a quarter of a trillion trillion Hz). Uncertainty in mass is therefore a frequency spread, which is to say, bandwidth.

Although it's fundamentally the same thing, the numerical scale is staggering. A computer network comprising decaying Z bosons could emit 75 million petabytes per second, and its bandwidth would be 600 trillion GHz wide.

Jim Pivarski


Today's New Announcements

Ultimate Core class sign-up due Nov. 26

NALWO winter coffee and tea

Book Fair - today

Timecards week of Nov. 17-23 due early

Fermi Society of Philosophy talk - Nov. 20

UChicago Tuition Remission Program deadline - Nov. 24

School's Day Out - Nov. 24-25

Geometric Dimensioning and Tolerancing - Dec. 1-5 (afternoon)

Excel 2010: Advanced - Dec. 3

NALWO Playgroup meets Wednesdays at 5:15 at Users Center

Scottish country dancing Tuesday evenings at Kuhn Barn

International folk dancing Thursdays at Kuhn Barn (except Thanksgiving)

Indoor soccer

Broomball open league