Friday, Aug. 15, 2014

Have a safe day!

Friday, Aug. 15

9 a.m.-5 p.m.
Fermilab-CERN Hadron Collider Physics Summer Symposium

3:30 p.m.

4 p.m.
Joint Experimental-Theoretical Physics Seminar - One West
Speaker: Tom LeCompte, Argonne National Laboratory
Title: The Higgs: Past, Present and Future

8 p.m.
Fermilab Lecture Series - Auditorium
Speaker: Diandra Leslie-Pelecky
Title: The Science of Speed: Why Driving Fast is Harder Than You Think
Tickets: $7

Saturday, Aug. 16

10:40 a.m.-5:45 p.m.
Fermilab-CERN Hadron Collider Physics Summer Symposium

Monday, Aug. 18

9 a.m.-5:30 p.m.
Fermilab-CERN Hadron Collider Physics Summer Symposium


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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Wilson Hall Cafe

Friday, Aug. 15

- Breakfast: big country breakfast
- Breakfast: chorizo and egg burrito
- Backyard pulled pork burger
- Asian braised beef and vegetables
- Southern fried chicken
- Turkey and cucumber salad wraps
- Big beef or chicken burrito
- Shrimp gazpacho
- Texas-style chili
- Assorted pizza by the slice

Wilson Hall Cafe menu

Chez Leon

Friday, Aug. 15
- Wild mushroom tart
- Porcini-crusted filet
- Boursin creamed spinach
- Roasted new potatoes
- Double-caramel turtle cake

Wednesday, Aug. 20
- Grilled vegetable lasagna
- Red cabbage and spinach salad
- Ricotta cheesecake with fresh berry topping

Chez Leon menu
Call x3524 to make your reservation.


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NOvA near detector complete

A PPD technician installs the last avalanche photodiode, better known as an APD, on the NOvA near detector. Photo: Ting Miao, PPD

On Tuesday, Aug. 12, the NOvA collaboration finished instrumenting the final block of the NOvA near detector, with all electronics turned on. This marks the conclusion of roughly six months of instrumentation work on the detector.

Located 350 feet underground on the Fermilab site, the 330-ton NOvA near detector is filled with liquid scintillator. When a neutrino interacts in the liquid scintillator, the detector's electronics will convey the interaction's signal, allowing scientists to measure interactions of the elusive particle.

Physics in a Nutshell

What is a WIMP?

Physicists — especially particle physicists — have a habit of choosing colorful names for their various topics of studies. MACHOs and WIMPs are two terms commonly used in dark matter studies. Today's column tells us what a WIMP is.

Read the full article on WIMPs

If you want to understand dark matter, you need to understand terms such as MACHO and WIMP. It's enough to recall one of those 1970s comic book advertisements for Charles Atlas' body building program (well, for those of us of a certain age anyway).

To understand the term WIMP, we need to go back to the idea of dark matter and why we think it exists. The easiest-to-understand evidence for the existence of dark matter involves spinning galaxies. As early as the 1930s, scientists combined measurements of the rotational speed of galaxies with Newton's theory of gravity and determined that something was awry. The galaxies were spinning so fast that they could not be held together by the gravitational force of the observed matter and should have torn themselves apart. After decades of studies, scientists have determined that the most probable explanation is that there exists another form of matter that we now call dark matter. It is generally imagined that dark matter is essentially a diffuse gas of massive subatomic particles.

Astronomical evidence has allowed us to determine a fairly specific list of properties for dark matter, if it exists. Because this matter neither emits nor absorbs light, it neither is charged nor contains charge within it. This is why we call it dark. It is also stable. We know this because galaxies persist for billions of years. It does not interact via the strong force, as we see no evidence of cosmic rays (made of protons) interacting with it. And because this matter causes galaxies to rotate quickly, we know it both contains mass and participates in the gravitational force.

That last point is crucial. There are four known forces: the strong and weak nuclear forces, electromagnetism and gravity. We know that dark matter does not experience the strong or electromagnetic forces. We know it does experience gravity. We don't know about the weak force.

So let's think about that for a bit. While the weak force is ... well, weak ... gravity is incredibly weak, about a trillion trillion trillion times weaker than the weak force. We have never measured the force due to gravity between two subatomic particles (and we probably never will). So if gravity is the only force that dark matter feels, we will likely never detect it, nor will we ever make it any conceivable particle accelerator.

So how is it that Fermilab (and others) have a vibrant research program looking for dark matter? Is it all wishful thinking?

Read more

Don Lincoln

Want a phrase defined? Have a question? Email

In the News

Using antineutrinos to monitor nuclear reactors

From Physics World, Aug. 12, 2014

A new system that uses an antineutrino detector to monitor a nuclear reactor for the production of weapons material has been proposed by an international team of physicists. A detector parked close to the facility could fully assess the state of the reactor core by detecting the antineutrinos it emits. However, the researchers admit that current detectors are not up to the job and additional research and development will be needed before their method is viable.

Read more

In the News

The smallest possible scale in the universe

From Medium, Aug. 12, 2014

Good ideas start with a question. Great ideas start with a question that comes back to you. One such question that has haunted scientists and philosophers for thousands of years is whether there is a smallest unit of length, a shortest distance below which we cannot resolve structures. Can we forever look closer and ever closer into space, time, and matter? Or is there a fundamental limit, and if so, what is it, and what is it that dictates its nature?

Read more

Frontier Science Result:
Theory Group

Hidden interactions of quarks

The hypothetical Z' boson could be produced in proton-proton collisions. It would then decay into quark-antiquark pairs.

You've likely heard that there are four elementary forces (or interactions) in nature. With the 2012 discovery of the Higgs particle, we can now talk of a fifth force. Let's call it the Higgs force.

All five forces are understood as being mediated by some particles generically called bosons. These are the photon (mediator of electromagnetism), the graviton (mediator of gravity), the gluon (mediator of the strong force), the W and Z bosons (mediators of the weak force), and the Higgs boson. The Higgs force, like the weak and strong forces, acts only at very short distances, and its effects on macroscopic objects cannot be detected.

Quarks, the building blocks of most things around (and within) us, experience all five elementary forces. One of the questions explored by particle physics is whether there might be additional forces acting on quarks. A hypothetical force of this kind can be mediated by a particle called the Z' (read "Z prime") boson, which is hidden for now, presumably because of its short lifetime and large mass. The experiments at the Large Hadron Collider are searching for Z' bosons of mass up to a few thousand GeV; 1 GeV is slightly more than the proton mass.

There is, however, another way for the Z' boson to hide: If its interaction with quarks is feeble, then it is difficult to produce and detect in experiments. For example, if a Z' particle has a mass of only a few GeV and an interaction strength a few times smaller than that of the photon, then low-energy experiments do not yet have sufficient intensity to produce it, and direct searches at the LHC are hampered by large backgrounds.

Fermilab theorists have recently derived a new upper limit on the strength of the Z' force. This arises from self-consistency conditions within theories that include a Z' boson, in combination with collider searches for other particles, called vector-like fermions. Nevertheless, plenty of room for Z' bosons remains to be explored in experiments.

A related intriguing possibility is that Z' bosons interact not only with quarks but also with the mysterious dark matter that dominates the mass of the universe. In that case, the scattering of protons on nuclei may produce a beam of dark matter. The protons from the Main Injector, currently Fermilab's highest-energy accelerator, could produce such dark matter beams, while neutrino detectors on the Fermilab site (NOvA, MINOS and the future LBNF) may then probe the presence of dark matter particles.

The searches for the Z' particle demonstrate the synergy between experiments at the energy and intensity frontiers in conjunction with theoretical constraints.

Bogdan Dobrescu

Postdocs Claudia Frugiuele and Felix Yu, from the Fermilab Theoretical Physics Department, are experts in physics beyond the Standard Model.
Photo of the Day

Fermilab in full bloom

Vibrant colors surround Wilson Hall on a summer day. Photo: Laura Wimmers Paterno

Today's New Announcements

Cafeteria will be open on Saturday, Aug. 16

Fermilab Lecture Series presents The Science of Speed - today

FermiPoint extended outage Aug. 15-18

FermiWorks update Aug. 16-17

Deadline for the UChicago tuition remission program - Aug. 18

Call for applications: URA Visiting Scholars Program - apply by Aug. 25

Walk 2 Run offers two time slots in August

Zumba Toning and Zumba Fitness registration

International folk dancing Thursday evenings at Ramsey through August

Scottish country dancing Tuesday evenings at Ramsey through August

English country dancing at Kuhn Barn

Fermilab Tango Club

Outdoor soccer

Find new classified ads on Fermilab Today.