Thursday, May 21, 2015
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Today's New Announcements

English country dancing at Kuhn Barn - May 24

International folk dancing Thursday evenings through June 11, cancelled May 28

Chicago Science Fest - May 28-30

Muscle Toning registration due June 2

Scottish country dancing meets Tuesday evenings at Kuhn Barn

Talk: How can scientific collaborations produce knowledge? - today

Pilates registration due May 22

LDRD preliminary proposals due May 29

Bill Kurtis presents "How the American Diet is Killing You" - June 3

Register now for LArSoft Workshop on June 3

Fermilab pool open June 9, memberships available

Managing Conflict (half-day) on June 10

Living Green! new Fermilab Library book display

Safari Online

Fermilab Board Game Guild

WalkingWorks week one winners

WalkingWorks program begins - register now

Wednesday Walkers

Pedometers available for WalkingWorks program

Swim lessons at Fermilab Pool

Adult water aerobics at Fermilab Pool

Outdoor soccer

H4 Training discount for Fermilab employees


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Special Announcement

All-hands meeting today at 10 a.m. in Ramsey Auditorium

Please attend today's all-hands meeting at 10 a.m. in Ramsey Auditorium. The talk will be streamed live.

Refreshments will be served in the Wilson Hall atrium following the meeting.

In Brief

Chicago Science Fest takes place May 28-30

Fermilab employees and users can enter a raffle for free passes to the festival.

The Illinois Science Council is throwing a three-day science extravaganza in downtown Chicago from May 28-30.

Chicago Science Fest includes a panel with Congressman Bill Foster, film screenings, an art exhibit and a full day of science talks aimed at adults, including physics talks by Fermilab's Dan Hooper, Elise Jennings and Keith Matera. More details and the full schedule are available online.

Fermilab is also raffling a number of passes to employees and users for the Friday art and film event and the Saturday talks. To enter, email Lauren Biron by the end of the day today with your name, extension and whether you would like to attend on Friday, May 29, or Saturday, May 30. Winners will be notified by Tuesday afternoon, May 26.

Photos of the Day

White trillium: three views

White trillium carpets the ground in Big Woods. Photo: Don Cossairt, ESH&Q
The life cycle of white trillium is synchronized with that of the deciduous woodland. In the Chicago area, it usually flowers between April and June. Photo: Sue Quarto, FESS
White trillium is characterized by its three white, oval petals and three sepals. The white turns pink as the flower ages. Photo: Leticia Shaddix, PPD
In the News

The data that threatened to break physics

From Nautilus, May 7, 2015

Antonio Ereditato insists that our interview be carried out through Skype with both cameras on. Just the other side of middle age, his salt-and-pepper hair frames wide open eyes and a chiseled chin. He smiles easily and his gaze captures your attention like a spotlight. An Italian accent adds extra vowels to the end of his words.

Read more

In the News

World-renowned speaker gets 'real' with Fermi audience

From Chicago Tribune, May 18, 2015

A half-hour sit-down with Temple Grandin flies by as if were five minutes. And listening to her 90-minute presentation Thursday evening at Fermi National Accelerator Laboratory passes just as quickly.

Part of the reason is because this world-renowned author on autism and animal behavior speaks fast and furious … and she peppers it all with a whole lot of funny asides.

What Grandin, diagnosed with autism as a child and unable to speak until age four, has to say is even more fascinating than how she says it. Which is why she's in such high demand as a speaker — whether it's for a conference of autism experts, educators, veterinarians or a group in the cattle industry.

It's also why Grandin, a professor of animal science at Colorado State University, sold out the 800-seat Ramsey Auditorium at Fermilab not just on Thursday, but Friday night as well.

Read more

Frontier Science Result: DZero

Measure thrice, theorize once

This shows the production of a top-antitop pair decaying in the dilepton channel. In this case the top quark decays into an antimuon, and the antitop decays into an electron.

Disponible en español

One of the very fundamental but unpredictable numbers in the Standard Model is the mass of the top quark. Like the strength of gravity, it is one of those numbers that has no explanation and yet is crucially linked to the kind of universe we live in. As Fermilab scientist Chris Quigg wrote in 1994, the year before the discovery of the top quark,

Through the uncertainty principle of quantum mechanics, top quarks and antiquarks wink in and out of an ephemeral presence in our world. Though they appear virtually, fleetingly, on borrowed time, top quarks have real effects. ... In fact, the mass of the top quark is encoded in the strengths of all the forces that rule the everyday world.

So, how do we determine this fundamental parameter? There are three basic ways, though there are many variations on these three themes.

Top quarks are mostly produced together with their corresponding antiquarks. Each decays into a W boson and a b quark, which creates a collimated spray of hadrons, called a jet. Each W can decay into either jets (usually two of them) or a lepton and neutrino. By leptons, we mean only electrons or muons. The neutrinos are undetectable. The final outcome then might be just jets (six of them), four jets with one lepton, or two jets with two leptons. So there are three different decay "channels" or "modes": the all-jets, leptons+jets and dilepton channels, respectively.

Measurements in each of the three modes present different advantages and different challenges. The dilepton channel has the advantage that it is particularly "clean," meaning that very few of the events that are selected for use in the measurement are not real top-antitop events. It has a challenge in that relatively few decay into dileptons — only about 4 percent of top-antitop pairs.

DZero has recently measured the mass of the top quark in the dilepton channel using the full Tevatron data set. There were two important variations on the theme that we chose. One was to select events so as to make the best of the small number of dilepton events available. The other was to use the jet energy calibration from the lepton+jet channel to understand the jets that are produced along with leptons in dilepton events. The result, 173.3 ± 1.6 GeV, is the most precise top quark mass measurement using the dilepton channel at the Tevatron. It is competitive with the best LHC dilepton measurements and is consistent with the average of all the top mass measurements made worldwide.

So that is one of the three ways of measuring the top mass. The other two methods also have been used at the Tevatron and the LHC. As for theorizing once, a goal of the single Theory of Everything is to provide some understanding of fundamental parameters that now have no explanation, even if they are well measured — such as the top mass. We hope one day we will arrive at such a summary of all of particle physics.

Leo Bellantoni

Huanzhao Liu, Amitabha Das, Yuriy Ilchenko and Robert Kehoe, all of Southern Methodist University, contributed to the analysis for this measurement, which is the subject of Liu's Ph.D. thesis.
The DZero collaboration relies upon many of its collaborators to carefully review analyses for scientific quality before they are released. This analysis was guided to completion by Editorial Board Chair Liza Shabalina (Physikalisches Institut, Georg-August-Universtät Göttingen, Göttingen, Germany) and the physics group conveners, Andy Jung (Fermilab), Slava Shary (CEA Irfu, Saclay, France) and Breese Quinn (University of Mississippi).