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	Friday, Feb. 15, 2013

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Calendar

Have a safe day!

Friday, Feb. 15

9 a.m.
Electric Dipole Moment Workshop - One West

3:30 p.m.
DIRECTOR'S COFFEE BREAK - 2nd Flr X-Over

4 p.m.
Joint Experimental-Theoretical Physics Seminar - One West
Speaker: Zheng-Tian Lu, Argonne National Laboratory
Title: Electric Dipole Moment Experiments with Project X

Monday, Feb. 18

THERE WILL BE NO PARTICLE ASTROPHYSICS SEMINAR THIS WEEK

3:30 p.m.
DIRECTOR'S COFFEE BREAK - 2nd Flr X-Over

THERE WILL BE NO ALL EXPERIMENTERS' MEETING THIS WEEK

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

Ongoing and upcoming conferences at Fermilab

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Take Five

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Chance of flurries
28°/14°

Extended forecast
Weather at Fermilab

Current Security Status

Secon Level 3

Current Flag Status

Flags at full staff

Wilson Hall Cafe

Friday, Feb. 15

- Breakfast: blueberry-stuffed French toast
- New England clam chowder
- Cajun turkey burger
- Enchilada-style beef and bean or bean-only burrito
- Smart cuisine: Greek fish florentine
- Baked ham and Swiss ciabatta
- Assorted pizza
- Malaysian curried chicken

Wilson Hall Cafe Menu

Chez Leon

Friday, Feb. 15
Valentine's dinner
- Spinach and strawberry salad
- Lobster tail with champagne butter sauce
- Spaghetti squash with scallions
- Roasted broccoli with red pepper butter
- Chocolate pots de crème with fresh berries

Wednesday, Feb. 20
Lunch
- Cornish hens
- Sage and onion stuffing
- Glazed baby carrots
- Pumpkin cheesecake

Chez Leon Menu
Call x3524 to make your reservation.

What's the point?

If you magnify an extended particle, it will look bigger. A point-like particle will not change in size, but the more closely you look at it, the stronger the field surrounding it.

Read the complete column on point-like particles.

The field of particle physics is full of what can be confusing dichotomies: fermion vs. boson, hadron vs. lepton, paper vs. plastic (okay, not that last one). You can add yet another to the list: extended particles vs. point-like particles.

The quarks, leptons and bosons of the Standard Model are point-like particles. Every other subatomic particle you’ve heard of is an extended particle. The most familiar are the protons and neutrons that make up the nucleus of an atom, but there are many others—pions, kaons, Lambda particles, omegas and lots more. The defining feature of these kinds of particles is that they have a reasonably measurable size (which happens to be about the size of a proton).

Now extended particles don’t have a well-defined surface like a marble does. They’re a bit more like the Earth and its atmosphere. The atmosphere of the Earth is thickest near the surface of the Earth and it gets thinner with altitude. So the exact point at which you can say that you are no longer in the Earth’s atmosphere is a bit fuzzy, but you can still safely say that the boundary between inside and outside the Earth’s atmosphere is 10 or 20 miles straight up. Independent of the exact point at which you say something is inside or outside, extended particles have a size.

Point particles are much more bizarre and are sometimes said to have zero size. This statement has raised more than one eyebrow. How can something have no size at all? And if it has mass, does the zero size mean it has infinite density? (And by the way, as you read on, you’ll see the answer to that last one is no.) You begin to see why some people are skeptical when a scientist says a particle is point-like.

Yet there is a sense in which it’s true. So how can that be?

—Don Lincoln

Want a phrase defined? Have a question? E-mail today@fnal.gov.

Photo of the Day

Accents of red

A female cardinal perches outside a Cross Gallery office window. Photo: Marty Murphy, AD

In the News

LHC's first act: Higgs found, other weird physics still at large

From Wired, Feb. 13, 2013

After a spectacular first act, the Large Hadron Collider is taking an intermission break, having shut down on Feb. 11 for two years of construction and upgrades.

The list of important things that the LHC found in its initial run can be summed up in one word: Higgs. Though scientists remain a bit coy about calling the particle they found in July 2012 the Higgs boson (more data is needed to conclusively prove this) it is something that looks like the Higgs, acts like the Higgs, and was found where the Higgs was expected. Given that this long-sought boson is all but officially discovered, it can take its place as the final piece in the puzzle of physicists' Standard Model—the established theory explaining the interactions of all known particles and forces.

While finding the Higgs has been a triumph concluding one generation of physicists' wildest dreams, scientists can rightfully said to be a little disappointed. That's because the LHC was not built just to hunt down one particular boson. It was meant to uncover a host of new subatomic particles and exotic phenomena. In this gallery, we will take a look at some of these hoped-for events and what they might have meant for science had they been found.

Frontier Science Result: MiniBooNE

Nudging the community towards measuring where all the antimatter went

This fundamental cross section shows the probability for a muon antineutrino to interact with a nucleon and produce a positively charged muon and any number of nucleons. For the first time, the MiniBooNE experiment has been able to split this measurement into a function of muon energy and scattering angle. By directly measuring the muon kinematics, these new data offer unprecedented insight into the behavior of the muon in antineutrino CCQE interactions.

Like many of the processes we study at Fermilab, neutrino interactions probe fundamental properties of the universe. The focus of the MiniBooNE experiment has been to identify whether muon-type neutrinos spontaneously change into electron-type neutrinos in one of the neutrino beams created at the lab, possibly implying an extra neutrino state. However, recent work on the interactions of the muon-type neutrinos themselves has proven compelling as well, and this new result provides a first look at a specific muon antineutrino interaction.

In 2010, MiniBooNE released the first measurement of the cross section for muon-type neutrinos to elastically interact with a neutron to produce a muon and nucleons (traditionally called a charged current quasi-elastic, or CCQE, interaction) as a function of both muon energy and production angle relative to the incoming neutrino. This is the most complete information of this process to date, and, as evidenced by the impressive number of citations it has received (more than 100!), has significantly contributed to modern understanding of intranuclear behavior.

The new data presented here provides the world's first look at how muon antineutrinos behave in similar reactions. Like the neutrino-based measurement of 2010, this antineutrino result also contributes to our knowledge of nuclear physics processes. Together, these measurements significantly advance the preparedness of the community to search for new physics with neutrinos.

In particular, these data will help us understand signal and background processes that will be observed in the coming decades in long-baseline neutrino experiments that aim to measure the ordering of the neutrino masses and a process that may well explain why our universe is almost entirely matter-dominated. The confirmation of the latter process would mean the discovery of a physical mechanism that explains the existence of our universe. These next-generation measurements will be performed by looking for subtle differences between the conversion rates of neutrinos and antineutrinos over a travel distance of hundreds to thousands of kilometers. Being able to observe such effects depends critically on understanding how neutrinos and antineutrinos interact in our detectors. This new publication from MiniBooNE provides the first details of how antineutrinos interact compared to neutrinos in a critical energy region.

—Joe Grange, University of Florida