Friday, Jan. 7, 2011

Have a safe day!

Friday, Jan. 7
3:30 p.m.
4 p.m.
Joint Experimental-Theoretical Physics Seminar - One West
Speaker: Dan Amidei, University of Michigan
Title: Evidence for a Mass Dependent Forward-Backward Asymmetry in Top Quark Pair Production at CDF

Monday, Jan. 10
2:30 p.m.
Particle Astrophysics Seminar - One West
Speaker: Daniele Spier Moreira Alves, Stanford University
Title: What We May Learn About Dark Matter and the Milky Way Halo Profile with Directional Detection
3:30 p.m.
4 p.m.
All Experimenters' Meeting - Curia II
Special Topics: High-Power Laser Lab in MP8; Developing a New Test Beam Facility in MCenter

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Wilson Hall Cafe

Friday, Dec. 10

- Breakfast: Chorizo burrito
- Italian vegetable soup
- Teriyaki chicken
- Southern-fried chicken
- Mediterranean baked tilapia
- Eggplant parmesan panini
- Assorted sliced pizza
- Assorted sub sandwich

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Chez Leon

Wednesday, Jan. 12
- Spicy black bean & sausage calzone
- Confetti corn salad
- Pineapple flan

Thursday, Jan. 13

- Closed

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Call x3524 to make your reservation.


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Fermilab researcher Cristian Peña receives Fulbright award

MINERvA researcher Cristian Peña, in front of the MINERvA experiment. Photo: Reidar Hahn.

Cristian Peña, a research scholar on MINERvA from Santa Maria University in Valparaiso, Chile, has received the prestigious Fulbright scholarship for international studies.

The Fulbright scholarship is intended to increase mutual understanding between individuals in the United States and those from other countries. Each year, it is awarded to 1,800 foreign students for graduate study in the United States.

“I’m really excited,” Peña said. “I thought the possibilities were low, so I was surprised. The Fulbright will help a lot in my intention to go to graduate school here.”

Peña, who completed the Chilean equivalent of a master’s degree in electrical engineering in January 2009, already had an extensive amount of international research experience when he applied for the scholarship. While a student in Chile, he worked for Thomas Jefferson National Accelerator Facility, creating simulations to help researchers detect faint signals in the Two Photon Exchange experiment.

In August, Peña had the opportunity to bring his simulation-creating experience to Fermilab. He is one of the first two students from Santa Maria University ever to work at Fermilab. Peña currently studies how the MINERvA detector analyzes subatomic particles known as pions under the direction of Fermilab scientist Jorge Morfin. Peña also works on creating software to increase the efficiency with which MINERvA data is recorded and accessed. With this software now implemented, files that used to take 90 minutes to read now take only 15 seconds.

“He immediately jumped into challenging work,” Morfin said. “You have to be very clever to work on these problems. He’s a bright person, and I’m happy to see he’s doing so well.”

Peña is currently applying to Ph.D. programs. He hopes to attend a university with a strong presence at MINERvA.

William Brooks, a professor at Santa Maria University who works on MINERvA, said that Peña would have a significant head start compared to most graduate students if he stays with the cutting-edge experiment.

“I have a great deal of confidence that Cristian will be a big success in graduate school and quickly demonstrate leadership in the field,” Brooks said.

- Sara Reardon

Photo of the Day

New employees - Dec. 6

Mukti Ranjan Jana, APC; Tanja Waltrip, PPD; Sergey Mironov, AD. Photo: Cindy Arnold

In the News

Fermi's Large Area Telescope sees surprising flares in Crab Nebula

From, Jan. 6, 2011

Menlo Park, Calif. — The Crab Nebula, one of our best-known and most stable neighbors in the winter sky, is shocking scientists with a propensity for fireworks—gamma-ray flares set off by the most energetic particles ever traced to a specific astronomical object. The discovery, reported today by scientists working with two orbiting telescopes, is leading researchers to rethink their ideas of how cosmic particles are accelerated.

"We were dumbfounded," said Roger Blandford, who directs the Kavli Institute for Particle Astrophysics and Cosmology, jointly located at the Department of Energy's SLAC National Accelerator Laboratory and Stanford University. "It's an emblematic object," he said; also known as M1, the Crab Nebula was the first astronomical object catalogued in 1771 by Charles Messier. "It's a big deal historically, and we're making an amazing discovery about it."

Blandford was part of a KIPAC team led by scientists Rolf Buehler and Stefan Funk that used observations from the Large Area Telescope, one of two primary instruments aboard NASA's Fermi Gamma-ray Space Telescope, to confirm one flare and discover another. Their report was posted online today in Science Express alongside a report from the Italian orbiting telescope Astro-rivelatore Gamma a Immagini LEggero, or AGILE, which also detected gamma-ray flares in the Crab Nebula.

Read more

In the News

At South Pole, world's most extreme scientific construction project

From, Jan. 5, 2011

IceCube, the world's largest observatory ever built to detect the elusive sub-atomic particles called neutrinos, has just been completed in the crystal clear ice at the South Pole. Trillions of neutrinos stream through the human body at any given moment, but they rarely interact with regular matter, and researchers want to know more about them. The observatory provides an innovative means to investigate the sources and properties of neutrinos, which originate in some of the most spectacular phenomena in the universe.

Over a multi-year construction period, IceCube scientists melted 86 holes -- each 1.5-miles deep -- in the polar ice cap and inserted strings of light sensors into each hole. The water in each of the holes refroze, locking in an array of 5,160 light sensors, all connected to surface computers near the National Science Foundation's Amundsen-Scott South Pole Station. "We started drilling the holes with hot water in the ice at the geographic South Pole in 2003 and now, after seven years of work in bone-chilling temperatures, we have completed our ice-bound observatory, the world's first large-scale neutrino telescope," said Doug Cowen, an IceCube scientist and both a professor of physics and professor of astronomy and astrophysics at Penn State University, one of the leading institutions in the IceCube collaboration. "This telescope is large enough to hold about 1,000 football stadiums as large as the one at Penn State -- or a very close-packed arrangement of all the humans now living on Earth," Cowen said.

Read more

Special Result of the Week

CDF finds evidence for top quark production asymmetry

photo of the day
The figures show the number of top events as a function of delta rapidity. The blue shape is that of the background, the green is the Standard Model prediction for top, and the points are our data. The plot on the left contains events in which the ttbar mass is less than 450 GeV/c2 and is very symmetric. The plot on the right is for a ttbar mass of greater than 450 GeV/c2 and illustrates the discrepancy between expected and observed.

A new analysis that will be presented at a Wine and Cheese lecture at Fermilab today points to an asymmetry in top quark production. This analysis raises the asymmetry of forward and backward top quark production found in a 2008 analysis to a ~3 sigma level.

In nature, symmetry is seen as pleasing and balanced designs, such as the intricate pattern on a tortoise shell or the structure of a snowflake.

In elementary particle physics, symmetry is fundamental to the theories we use to describe the world in which we live. A discrepancy in the symmetry predicted by theories of the Standard Model can point to new types of physics, an anomaly in the data or that the current theories need revision.

CDF researchers have measured the symmetry of how top quarks emerge from collisions, forward or backward, and how they decay. This analysis was performed for the first time in 2006 at CDF. CDF and DZero both published their inclusive analysis of this asymmetry in 2008. These highly cited white papers already pointed to an anomaly that has generated much interest in the theoretical community. This latest result takes the 2008 publications a step further, by adding more data, and looking at the dependence on the mass of the system. It is this dependence that is most discrepant with the Standard Model.

Fermilab’s Tevatron produces collisions that create top quark and anti-top-quark pairs via the strong force. Simple theoretical calculations predict that the Tevatron detectors should observe symmetric distributions of both top and antitop quarks. However, more detailed calculations suggest that these oppositely charged particles should have a slight preference as to how they emerge from the collisions.

The origins of this symmetry are subtle, but CDF has the sensitivity to be able to observe the 6 percent imbalance, which is predicted by the Standard Model. This result shows that nature prefers an imbalance that is even larger than predicted.

It is important to determine whether the top quark we are observing behaves the way we expect this Standard Model object to act. There are a number of Beyond-the-Standard-Model theories such as Z’ (pronounced Z-prime) and large extra dimensions that predicts much higher asymmetries. By measuring this asymmetry in top quark production, CDF physicists can compare it to theoretical expectations and probe for potentially undiscovered new physics.

Utilizing 5.3 inverse femtobarns of data, CDF measured the top forward backward asymmetry and observed significant asymmetries when studying the production and the production as related to the pairs' center of mass energy, t-tbar.

When considering the pairs’ mass, the asymmetry is dependent on both the mass and the direction of the production. Scientists expect that the same number of top quarks and antitop quarks would be produced along the beam line, but CDF saw that more tops were produced along the proton direction of the beam and fewer tops produced along the antiproton direction of the beam. This effect is magnified when one looks at the mass dependence of the top-antitop system.

For Mttbar > 450 GeV/c2 the asymmetry is measured to be 48 ± 11 percent, three standard deviations from Standard Model expectation (9 ± 1 percent). Some theories suggest that such a mass dependence could be evidence of a massive new particle just out of reach at the Tevatron’s collision energy.

The LHC, a machine with significantly higher energy, cannot easily study this phenomenon, since the LHC does not make protons and antiprotons collide. However a new particle would still be observable in energy spectrum at the LHC. If the result at CDF truly is a sign of new physics, it may be that both machines will be required to understand its nature.

This result may provide the first important clue that there is new physics beyond the Standard Model. There may still be other interesting results as scientists from both Fermilab experiments continue to analyze the Tevatron's now nearly 10 inverse femtobarns of sample data.

-- Rob Roser, CDF co-spokesperson

photo of the day
First row from left: Dan Amidei, Myron Campbell and Andrew Eppig; University of Michigan. Second row from left: David Mietlicki, Glenn Strycker, Alexei Varganov and Tom Wright; University of Michigan. Third row from left: Robin Erbacher and Tom Schwarz, University of California, Davis; and Joey Huston, Michigan State University.

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