Friday, May 2, 2014

Have a safe day!

Friday, May 2

9:30 a.m.-5 p.m.
New Perspectives on Dark Matter - Curia II
Registration is free

3:30 p.m.

4 p.m.
Joint Experimental-Theoretical Physics Seminar - One West
Speaker: Maxim Pospelov, Perimeter Institute and University of Victoria
Title: Broadening the Search for New Physics at Intensity Frontier Experiments

Monday, May 5

2 p.m.
Particle Astrophysics Seminar - Curia II
Speaker: Marc Postman, Space Telescope Science Institute
Title: Latest Results from the Cluster Lensing and Supernovae Survey with Hubble (CLASH)

3:30 p.m.

4 p.m.
All Experimenters' Meeting - Curia II

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Wilson Hall Cafe

Friday, May 2

- Breakfast: French bistro breakfast
- Breakfast: chorizo and egg burrito
- Grilled chicken quesadilla
- Smart cuisine: herb and lemon fish
- Vegetarian eggplant lasagna
- Cuban panino
- Breakfast-for-lunch omelet bar
- New England clam chowder
- Texas-style chili
- Assorted pizza by the slice

Wilson Hall Cafe menu
Chez Leon

Friday, May 2

Wednesday, May 7
- Potato cod cakes with dijon tartar sauce
- Kale salad
- Lemon pound cake with blueberry sauce

Chez Leon menu
Call x3524 to make your reservation.


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Physics in a Nutshell

The twin paradox

The twin paradox is a classic seeming conundrum of Einstein's theory of special relativity. Today's column explains why it is important that the word "seeming" is added. In reality, there is no paradox.

Read the full column on the twin paradox

In my last column, I discussed the fact that time passes slower for clocks that are moving at high velocity, and I showed that the Fermilab MINOS beamline proves that the predictions of relativity are right.

However, one must be very careful. The "relativity" in the theory's name comes from the absolute core premise of Einstein's idea, which is that nothing is absolute. If you are standing on a train platform and a train whizzes by, you would say that a person on the train is moving. On the other hand, a person sitting on the train would say that he is stationary and that you are moving. Relativity says that both of you are right. Who is moving and who is stationary is just a matter of perspective, and the laws of physics must work equally well for both people.

But this raises a conundrum when applied to the question of moving clocks. How can moving clocks tick more slowly than stationary ones if the question of who is moving is a matter of opinion? If I can say you are moving and your clock is slow, and if you can say I am moving and my clock is slow, something is inconsistent.

This longstanding question about special relativity is called the twin paradox. Suppose one in a set of twins sets off in a spaceship, travels to a distant star and then returns. On both legs of the trip, he accelerates to high velocity and then coasts for most of the journey. According to the "moving clocks tick slower" premise, the twin who stays on Earth will have experienced one duration, while the traveling twin will have experienced another, slower duration. The spacefaring twin will return to Earth younger than his homebody brother.

"But wait," says the traveling twin, "according to my definition, I was just sitting there on my stationary spaceship while the Earth zoomed away from me and then zoomed back. By all rights, Earth twin should be younger!"

Read more

Don Lincoln

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Photo of the Day

U.S.-Japan collaboration in high-energy physics

On April 25 in Tokyo, DOE Associate Director for High-Energy Physics Jim Siegrist (seated, left) and KEK Executive Director Yasuhiro Okada (seated, right) signed an agreement on the U.S.-Japan collaboration in high-energy physics. The agreement as it relates to Fermilab covers advanced accelerator technology, including for a linear collider, and the development of advanced technology for neutrino experiments with high-power beams. Photo: KEK
Special Announcement

Wilson Street entrance closed starting May 5

The Wilson Street entrance to the Fermilab site will be closed for construction starting May 5. It is scheduled to reopen on Monday, May 19, weather permitting. Truck deliveries and employees will be rerouted to the Pine Street entrance.

In the News

Forget the Higgs, neutrinos may be the key to breaking the Standard Model

From ars technica, April 30, 2014

​Some physicists are surprised that two relatively recent discoveries in their field have captured so much widespread attention: cosmic inflation, the ballooning expansion of the baby universe, and the Higgs boson, which endows other particles with mass. These are heady and interesting concepts, but, in one sense, what's new about them is downright boring.

These discoveries suggest that so far, our prevailing theories governing large and small — the Big Bang and the Standard Model of subatomic particles and forces — are accurate, good to go. But both cosmic inflation and the Higgs boson fall short of unifying these phenomena and explaining the deepest cosmic questions. "The Standard Model, as it stands, has no good explanation for why the Universe has anything in it at all," says Mark Messier, physics professor at Indiana University and spokesman for an under-construction particle detector.

Read more

Frontier Science Result: ArgoNeuT

Catching (anti)neutrinos in a liquid-argon detector

The angular distribution with respect to the incoming (anti)neutrino beam of the outgoing muon in the charged-current interaction. GENIE and NUWRO are simulated-neutrino-event generators.

The ArgoNeuT experiment has measured the first antineutrino differential cross sections in a liquid-argon time projection chamber, or LArTPC.

Neutrinos share some properties with quarks, the particles that constitute the familiar proton and neutron. Like quarks, neutrinos come in three types. Also like quarks, neutrinos can oscillate, or change from one of their three types into another.

That's about where the resemblance ends. Neutrino masses are many orders of magnitude smaller than the quark masses. Although they oscillate among themselves, they do so with entirely different parameters than do quarks. And while every quark has an antiquark partner, neutrinos may or may not be their own antiparticles.

Before we stampede to the grand unified theory that explains all these bizarre observations, we need to do the most pedestrian thing: We must carefully characterize neutrino interactions in our liquid-argon detectors.

When a neutrino or antineutrino interacts with a liquid-argon nucleus, it produces secondary particles, such as a muon.

Some crucial properties of these antineutrino interactions can be characterized by measuring the properties of the outgoing muon. These are called charged-current inclusive interactions. The ArgoNeuT detector — the first LArTPC to record neutrino data in the United States — offers a very high-resolution view into the nature of these particle interactions.

The 170-liter detector took data from 2009-10 in the NuMI beam. The MINOS near detector, located behind ArgoNeuT, measures the charge and momentum of muons from ArgoNeuT's (anti)neutrino interactions.

During ArgoNeuT's data collection, a short one-month run in neutrino beam mode was followed by a longer run in antineutrino beam mode. ArgoNeuT released the results of the charged-current cross section in neutrino beam mode two years ago. New results from the antineutrino beam mode — which contains both neutrino and antineutrino sources — show agreement with simulations and no surprises in the distributions of the angle and momentum of the outgoing muon.

There is little data on the rates of these interactions in argon and even less on specific properties of the outgoing particles that arise from them. The LArTPC technology will be used in future long- and short-baseline experiments at Fermilab, and the measurements reported here lay the foundation for automated reconstruction techniques using the LArSoft software package. Such techniques will be important to these programs. ArgoNeuT's neutrinos are at roughly the same energy that will be studied in future long-baseline neutrino experiments, so this result can already help shape preparations for similar analyses on those experiments.

LArTPCs, with measurements like this one, are rewarding the investment placed in them by the U.S. high-energy physics community.

Eric Church, Yale University, and Tingjun Yang, Fermilab

Eric Church (left) of Yale University and Tingjun Yang of Fermilab conducted this analysis.

English country dancing - May 4 and with live music on May 18

Wilson Street entrance closed starting May 5

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