Friday, March 20, 2015
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Today's New Announcements

Nominations for Employee Advisory Group due April 17

URA Thesis Award competition deadline - today

FermiPoint (including FermiDash), MyPoint, downtime - March 23 and 24

Muscle Toning Class registration due March 24

URA Visiting Scholars Program deadline delayed to March 30

2015 URA Alvin Tollestrup Award application deadline - April 1

2014 FSA deadline is April 30

Interpersonal Communication Skills course - May 20

Mac OS X security patches

SharePoint online training videos available for on-site users

Monday Golf League

Fermilab Golf League 2015 season is just around the corner

International folk dancing Thursday evenings at Kuhn Barn

Indoor soccer

Changarro restaurant offers Fermilab employee discount

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Expanding the cosmic search

The South Pole Telescope scans the skies during a South Pole winter. Photo: Jason Gallicchio, University of Chicago

Down at the South Pole, where temperatures drop below negative 100 degrees Fahrenheit and darkness blankets the land for six months at a time, the South Pole Telescope (SPT) searches the skies for answers to the mysteries of our universe.

This mighty scavenger is about to get a major upgrade — a new camera that will help scientists further understand neutrinos, the ghost-like particles without electric charge that rarely interact with matter.

The 10-meter SPT is the largest telescope ever to make its way to the South Pole. It stands atop a two-mile thick plateau of ice, mapping the cosmic microwave background (CMB), the light left over from the big bang. Astrophysicists use these observations to understand the composition and evolution of the universe, all the way back to the first fraction of a second after the big bang, when scientists believe the universe quickly expanded during a period called inflation.

One of the goals of the SPT is to determine the masses of the neutrinos, which were produced in great abundance soon after the big bang. Though nearly massless, because neutrinos exist in huge numbers, they contribute to the total mass of the universe and affect its expansion. By mapping out the mass density of the universe through measurements of CMB lensing, the bending of light caused by immense objects such as large galaxies, astrophysicists are trying to determine the masses of these elusive particles.

To conduct these extremely precise measurements, scientists are installing a bigger, more sensitive camera on the telescope. This new camera, SPT-3G, will be four times heavier and have a factor of about 10 more detectors than the current camera. Its higher level of sensitivity will allow researchers to make extremely precise measurements of the CMB that will hopefully make it possible to cosmologically detect neutrino mass.

"In the next several years, we should be able to get to the sensitivity level where we can measure the number of neutrinos and derive their mass, which will tell us how they contribute to the overall density of the universe," explained Bradford Benson, the head of the CMB Group at Fermilab. "This measurement will also enable even more sensitive constraints on inflation and has the potential to measure the energy scale of the associated physics that caused it."

SPT-3G is being completed by a collaboration of scientists spanning the DOE national laboratories, including Fermilab and Argonne, and universities including the University of Chicago and University of California, Berkeley. The national laboratories provide the resources needed for the bigger camera and larger detector array while the universities bring years of expertise in CMB research.

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Diana Kwon

A wafer of detectors for the SPT-3G camera undergoes inspection at Fermilab. Photo: Bradford Benson, University of Chicago and Fermilab
Photo of the Day

In miniature

Former intern Alyssa Miller took this photo of the Fermilab site model displayed on the 15th floor of Wilson Hall. Photo: Alyssa Miller
In the News

Surprising gamma ray signal in satellite galaxy could come from WIMPs

From ars technica, March 18, 2015

Like moons orbiting a planet, there are smaller bodies circling the Milky Way. Known as dwarf galaxies, they can be dim enough to escape detection—it's not known how many there are in total, and new dwarfs are still being detected. One such dwarf galaxy was discovered within the last few weeks using data from the Dark Energy Survey, an experiment that scans the southern sky in order to learn about the accelerating expansion of the Universe (the experiment's name comes from the mysterious dark energy that causes that acceleration).

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Frontier Science Result: MINERvA

The MINERvA test beam program: trust but verify

This plot shows the energy deposited in the MINERVA test beam detector divided by the incoming kinetic energy of the pion as a function of the kinetic energy of the pion.

Para una versión en español, haga clic aquí.

All particle physics experiments rely on computer simulations of their detectors to make measurements, but neutrino experiments struggle to test these simulations using particles that are created from the neutrino beam itself.

Neutrino interactions often produce charged particles such as muons or electrons, and they knock one or more protons or neutrons out of the nucleus. Neutrino interactions also produce quark-antiquark pairs called pions (see earlier MINERvA results from February, August and January). Each of these different particles gives us a view inside the nucleus, but to make these precise measurements, MINERvA needs to understand what these particles do once they exit the nucleus and enter the rest of the detector.

We could simply trust a computer package (called Geant4) that simulates particle interactions, but to be rigorous, we verify that package. To do this we use a well-calibrated low-energy beam of pions, protons, muons and electrons from the Fermilab Test Beam Facility and a scaled-down version of the full MINERvA detector that is made of planes of scintillator, lead and steel. This smaller detector, which can be configured to replicate the downstream third of the neutrino detector, uses the same materials, electronics and calibration strategy.

We took data for six weeks in the summer of 2010 using the scaled-down detector and have been poring over this data ever since to measure many different aspects of the way the detector performs.

With these data we were able to address, for one, how the kinetic energy of a pion entering our detector is translated into an energy measurement. When we use a popular Geant4 model for low-energy pions interacting in the simulated detector, the prediction is a good, though not perfect, description of the data. The experiment was designed to test the simulation, and the systematic uncertainties are small enough that we can assign a small uncertainty on how well Geant4 predicts the pion's energy.

We also used the test beam data to measure details about the scintillator material itself to improve the model of the detector geometry and electronics. We also improved how we calibrate both the test beam and the neutrino detector.

We have continually fed back all of these improvements into the neutrino analysis since the test beam program started. This has been a benefit to other programs too. For example, the low-energy beamline design and hardware is now being used in MCenter for the LArIAT experiment.

The results have been recommended for publication in Nuclear Instruments and Methods A. MINERvA has also started a second round of higher-energy test beam measurements to match the new higher-energy neutrino beam to understand still more about the way this detector performs.

Rik Gran, University of Minnesota – Duluth

Josh Devan of the College of William and Mary in 2010 helps assemble the low-energy test beam run detector.
Pictured here is part of the test beam crew. From left: Anne Norrick (College of William and Mary), Rob Fine (University of Rochester), Carrie McGivern (University of Pittsburgh), Leo Bellantoni, (Fermilab, front), Dan Ruterbories (University of Rochester, in red), Aaron Bercellie (University of Rochester), Manuel Alejandro Ramirez (University of Guanajuato), Geoff Savage (Fermilab).
In the News

Probing dark energy with the Large Synoptic Survey Telescope

From iSGTW, March 18, 2015

If you wear or have ever worn glasses, you know what it means to finally see with clarity. The Large Synoptic Survey Telescope (LSST) — currently under construction on Cerro Pachon near Vicuña,Chile — will give humanity a new set of 'glasses' to peer into the universe.

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