Thursday, Oct. 16, 2014

Have a safe day!

Thursday, Oct. 16

2:30 p.m.
Theoretical Physics Seminar - Curia II
Speaker: Seyda Ipek, University of Washington
Title: CP Violation in Pseudo-Dirac Fermion Oscillations

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

Friday, Oct. 17

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

4 p.m.
Joint Experimental-Theoretical Physics Seminar - One West
Speaker: Lisa Whitehead, University of Houston
Title: Hitting from the Baseline: Long-Baseline Neutrino Studies

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Wilson Hall Cafe

Thursday, Oct. 16

- Breakfast: Canadian bacon, egg and cheese Texas toast
- Breakfast: Corned beef hash and eggs
- Grilled chicken quesadilla
- Barbecue chicken breast
- Honey baked ham
- Italian antipasto panino
- Italian pasta bar
- Chef's choice soup
- White chicken chili
- Assorted pizza by the slice

Wilson Hall Cafe menu

Chez Leon

Friday, Oct. 17

Wednesday, Oct. 22
Vegetarian special
- Sweet potato and chickpea cakes with avocado salsa
- Sauteed lemony broccolini
- Rustic fruit tart

Chez Leon menu
Call x3524 to make your reservation.


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From symmetry

Top quark still raising questions

Why are scientists still interested in the heaviest fundamental particle nearly 20 years after its discovery? Photo: Reidar Hahn

"What happens to a quark deferred?" the poet Langston Hughes may have asked, had he been a physicist. If scientists lost interest in a particle after its discovery, much of what it could show us about the universe would remain hidden. A niche of scientists, therefore, stay dedicated to intimately understanding its properties.

Case in point: Top 2014, an annual workshop on top quark physics, recently convened in Cannes, France, to address the latest questions and scientific results surrounding the heavyweight particle discovered in 1995 (early top quark event pictured above).

Top and Higgs: a dynamic duo?
A major question addressed at the workshop, held from Sept. 29 to Oct. 3, was whether top quarks have a special connection with Higgs bosons. The two particles, weighing in at about 173 and 125 billion electronvolts, respectively, dwarf other fundamental particles (the bottom quark, for example, has a mass of about 4 billion electronvolts and a whole proton sits at just below 1 billion electronvolts).

Prevailing theory dictates that particles gain mass through interactions with the Higgs field, so why do top quarks interact so much more with the Higgs than do any other known particles?

Direct measurements of top-Higgs interactions depend on recording collisions that produce the two side-by-side. This hasn't happened yet at high enough rates to be seen; these events theoretically require higher energies than the Tevatron or even the LHC's initial run could supply. But scientists are hopeful for results from the next run at the LHC.

"We are already seeing a few tantalizing hints," says Martijn Mulders, staff scientist at CERN. "After a year of data-taking at the higher energy, we expect to see a clear signal." No one knows for sure until it happens, though, so Mulders and the rest of the top quark community are waiting anxiously.

Read more

Troy Rummler

In Brief

Medical Office offers flu vaccination this month

Sign-up for this season's flu shot is available online. The Fermilab Medical Office will administer flu shots on Oct. 29 and 30. (Flu shot appointments on Oct. 21, 22 and 23 are full.)

Read more about the Medical Office's flu vaccination administration in the Sept. 29 issue of Fermilab Today.

Photo of the Day

Habanero harvest

This habanero bounty comes from the Fermilab garden plot of Jim Simone, SCD. Photo: Georgia Schwender, OC
Special Announcement

Wilson Hall closed Oct. 18-19 for maintenance

Wilson Hall will be closed for maintenance on Saturday, Oct. 18, and Sunday, Oct. 19, and power to the building will be shut off. Please turn off all electronics before leaving on Friday.

The Fermilab site will still be open to the public from 8 a.m. to 8 p.m.

In the News

Crash course in science

From The Wall Street Journal, Oct. 12, 2014

It took almost two hours Thursday morning in stop-and-go Long Island Expressway traffic to reach Brookhaven National Laboratory. Science has never been my strong suit, but I think a comparison can be made between the daily failures of suburban traffic engineering and some of what has been accomplished at Brookhaven.

While it was unusual for me to reach speeds above 30 miles an hour for much of the trip, Brookhaven's Relativistic Heavy Ion Collider — essentially a 2.4-mile racetrack for atomic particles, and the only one in the nation — is capable of making the journey in one second. Not once, but 80,000 times traveling at 99.995 percent of the speed of light.

Imagine how fast you could get to the Hamptons.

Read more

In the News

Finding dark matter in a haze of gamma rays

From ars technica, Oct. 7, 2014

As we've recently discussed at length, dark matter is likely to be a WIMP: a weakly interacting massive particle. Weakly interacting doesn't mean no interactions, though, and there's always the chance that dark matter particles will collide with something else. Since dark matter is also the most common matter in the Universe, there's a good chance that the "something else" will be another dark matter particle. And if the collision results in the destruction of dark matter particles, it should produce a spray of things we can see, like energetic particles and photons.

Read more

In the News

What are gravitons and why can't we see them?

From io9, Oct. 9, 2014

Gravitons are tiny particles that carry the "force" of gravity. They are what brings you back down to Earth when you jump. So why have we never seen them, and why are they so impossibly complicated we need string theory to figure them out? Find out here!

Read more

Frontier Science Result: DZero

Mixing tops

This Feynman diagram shows the mixing of a b (bottom) quark into a t (top) quark. Time flows from left to right. A b enters as one of the ephemeral quarks of the "quark sea" that is the proton or antiproton. It interacts with a W boson emanating from a quark or antiquark in the other colliding particle.

In fiction, a common plot device is the police's confusion about the identity of the perpetrator of some crime. In physics, a common situation is a subatomic particle being confused about its own identity.

Mixing is a term we use to describe this kind of situation. It actually happens in a number of different situations. For example, neutrino mixing and kaon mixing are different processes at a fundamental level. But in both cases a particle changes its nature — its identity — between when it is created and decayed.

Mixing can also occur among quarks, of which there are six flavors arranged in three so-called generations. Quark mixing occurs when a quark of a given flavor makes a transition into a quark of a different flavor. This happens every time a quark interacts with a W boson — when the quark decays into a W and another quark, or perhaps when a W splits into a quark and an antiquark.

Most of the time, the two quarks have different flavors but are still within the same generation of quarks. In particular, quarks of the top flavor can become quarks of different flavors and vice versa. Quark mixing is a very common process. There is a well-established theory to describe this; it is called the Cabbibo-Kobayashi-Maskawa (CKM) matrix. Notwithstanding, there is still some possibility that the top quark could mix into some other, as yet undiscovered, particle or particles.

To gain insight into the mixing properties of this heaviest of all quarks, we study events in which only a single top was produced and subsequently decayed into a different quark type.

From earlier measurements, we know that the top quark mixes much more with the bottom quark than with the other quarks in the Standard Model. The question is, what is the absolute scale of this, and how likely is it exactly? More intriguingly, are there other quarks that are yet to be discovered that the top mixes with?

Single-top quark events are hard to find. While events with two top quarks were seen in 1995 during Tevatron Run I, observation of events with a single top took until 2009. In such a case it is very advantageous for the two Tevatron experiments to combine their results; one then effectively has twice as much data to work with.

CDF and DZero have recently combined their measurements of single-top production at the Tevatron. Explicitly allowing that there might be a new, undiscovered particle that mixes with top quarks, DZero and CDF found that a bottom quark produces a top quark through the weak interaction 104 +12/-10 percent of the time. Now, 104 percent isn't actually possible; the number must be 100 percent or less, and the only reason it came out over 100 percent is that the measurement has some margin of error. If the fact that it cannot be over 100 percent is included, bottom produces top at least 84 percent of the time, which is to say top decays into bottom pretty much all of the time.

So there isn't any evidence for a new possible particle for the top quark to decay into. The rate of the production of single top quark also matches theoretical predictions well, further supporting the idea that we have only CKM style mixing in top quarks.

Leo Bellantoni, with a little help from his friends

These physicists are the primary analysts for this result. Top row, from left: Matteo Cremonesi (INFN Pisa, Italy) and Tom Junk (Fermilab). Bottom row, from left: Christian Schwanenberger (Manchester University, England) and Reinhard Schwienhorst (Michigan State University)
Ken Herner (left) and Bo Jayatilaka have led the DZero and CDF efforts, respectively, on long-term data preservation in the Scientific Computing Division.

Today's New Announcements

Batavia Rd. asphalt work - Oct. 16-17

SharePoint for Contributors (end-user) - Oct. 17

SharePoint Designer training - Oct. 17

SharePoint for Contributors (end-user) - Oct. 17

Zumba Fitness registration due today

Main site ICW flush - Oct. 20-24

Interpersonal Communication Skills - Oct. 21

Lecture Series: Success and Failure in Engineering - Oct. 24

Muscle Toning by Bod Squad - register by Oct. 28

Excel 2010: Intermediate - Oct. 29

Managing Conflict - Nov. 5 (morning only)

Access 2010: Advanced - Nov. 12

Excel 2010: Advanced - Dec. 3

Wilson Fellowship accepting applications through Nov. 14

Featured ebook on neutrino physics

Pace Batavia Call-n-Ride service to Fermilab

International folk dancing Thursday evenings at Kuhn Barn

Scottish country dancing Tuesday evenings at Kuhn Barn

English country dancing at Kuhn Barn

Indoor soccer