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	Monday, Aug. 10, 2015

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The short-baseline detectives and the mysterious case of the sterile neutrino

The Fermilab Short-Baseline Neutrino program will use three detectors: SBND, MicroBooNE (shown here) and ICARUS. Photo: Reidar Hahn

In 1995, physicists working on the Liquid Scintillator Neutrino Detector, or LSND, at Los Alamos National Laboratory stumbled upon some curious results.

The experiment, whose goal was to investigate oscillations between the three different flavors of the elusive neutrino, saw evidence that there might be at least one additional flavor of neutrino lurking just out of reach. In 2002, an experiment at Fermilab called MiniBooNE started collecting data to explore this anomaly, but the results were inconclusive: some data seemed to refute the possibility of a fourth neutrino, but other data seemed to indicate particle interactions that couldn't be explained with conventional three-neutrino models. The possibility of a mysterious, fourth neutrino remained alive.

"It's a question that's been first lingering with the anomalies from LSND and then MiniBooNE," said Bonnie Fleming, co-spokesperson of a new neutrino experiment at Fermilab called MicroBooNE. "There's now a worldwide campaign to address whether these short-baseline oscillations and hints from other experiments are indicating new physics."

Scientists from Fermilab and more than 45 institutions around the world have teamed up to design a program to catch this hypothetical neutrino in the act. The program, called the Short-Baseline Neutrino (SBN) program, makes use of a trio of detectors positioned along one of Fermilab's neutrino beams. Although there are other reactor and source-based experiments in the world that actively seek a fourth neutrino, also called a sterile neutrino, SBN is the only program that uses a particle accelerator to produce neutrinos and multiple neutrino detectors for this search.

"No one else is doing an experiment like this," said Peter Wilson, coordinator for the SBN program. "There are no other experiments on this energy scale using the concept of a near detector and a far detector."

Determining whether there are more than three neutrino flavors would affect how scientists interpret data from experiments like the planned Deep Underground Neutrino Experiment, which is expected to make transformative discoveries about neutrinos, and perhaps other aspects of the universe, in the future. Solving the mystery of the anomalies seen at LSND and MiniBooNE, however, will not be easy. Because the sterile neutrino would not interact through the weak nuclear force as the other three do (hence the name "sterile"), detecting this particle would be like chasing the shadow of a ghost.

—Ali Sundermier

In Brief

Your visit to the Fermilab library is long overdue

Although we are in a digital era, many people still associate the library with only print resources. However, the Fermilab Library provides sitewide online access to hundreds of journals and other materials and can help you access these both on site and from around the world.

If you want access to something new or different or have problems accessing something, Fermilab's librarians are happy to help. The library can send you PDFs of journal articles and more at no cost to you and with a turnaround time of only 24 hours. You can eliminate the inconvenience and hassle of ordering and paying for resources yourself. Perhaps the biggest benefit is having a fast, accurate and personalized service provided by professionals who are both knowledgeable and passionate about helping others.

Stop by the "Ask Me about Library Services" booth in the Wilson Hall atrium from Aug. 10-14 between 11:30 a.m. and 1:30 p.m. to ask questions and learn more about the Fermilab Library.

In the News

Theories of everything, mapped

From Quanta Magazine, Aug. 3, 2015

"Ever since the dawn of civilization," Stephen Hawking wrote in his international bestseller A Brief History of Time, "people have not been content to see events as unconnected and inexplicable. They have craved an understanding of the underlying order in the world."

In the quest for a unified, coherent description of all of nature — a "theory of everything" — physicists have unearthed the taproots linking ever more disparate phenomena. With the law of universal gravitation, Isaac Newton wedded the fall of an apple to the orbits of the planets. Albert Einstein, in his theory of relativity, wove space and time into a single fabric, and showed how apples and planets fall along the fabric's curves. And today, all known elementary particles plug neatly into a mathematical structure called the Standard Model. But our physical theories remain riddled with disunions, holes and inconsistencies. These are the deep questions that must be answered in pursuit of the theory of everything.

Tip of the Week: Sustainability

So long, Styrofoam

Styrofoam does not biodegrade. Fermilab is taking steps to reduce Styrofoam use at the laboratory. Photo: hermitsmoores

Picture Main Ring Road lined with Styrofoam cups. Now think of Styrofoam cups circling Main Ring Road 17 times. That is 68 miles of Styrofoam cups! And it is how many cups have been used by Fermilab since 2010 — 1,188,000 of them. It may surprise you to learn that that total does not include cups from the cafeteria. This many cups were ordered through the Stockroom by employees.

As a small step in greening Fermilab, the laboratory's Sustainability Committee and FESS' Logistics and Property Control Group have decided to eliminate Styrofoam (correctly known as polystyrene foam) cups available in the stockroom. They will be replaced by paper cups that contain 10 percent post-consumer recycled content from recycled office paper. The paper cups cost three times as much as their polystyrene equivalent, but the price is only about four cents more per cup: Polystyrene cups are about two cents each, while each paper cup is about six cents.

While the per-paper-cup cost is low, we recognize that it is nevertheless an increase in price. Our hope is that this change will encourage people to think twice about using disposable, single-use cups in the first place. Even New York City has banned single-use polystyrene foam as of July 1.

Polystyrene is made of benzene and styrene, toxic substances that are suspected carcinogens and neurotoxins. It does not biodegrade: The cup will dissolve in about 500 years, but the chemicals will remain in the ecosystem. In the United States, about 25 billion cups are thrown away each year, and that's only the polystyrene found in cups, not other packaging or food containers. Polystyrene consumes more than 25 percent of landfill space. It is not recyclable by municipalities.

Unfortunately, we cannot control or eliminate all uses of polystyrene at Fermilab. But Fermilab's Logistics and Property Control collects clean number 6 white packaging foam at Wilson Hall, Feynman Computing Center and the Cross Gallery for recycling at the Dart facility in Aurora. They will also do special pickups if you have a large quantity to dispose of. Packaging peanuts are also collected at Warehouse 2 to be reused by the Shipping Department.

We all should do our part to decrease our use of disposable, single-use items such as Styrofoam coffee cups. Be Earth-friendly and bring your own mug from home to be used not only in your office but also at meetings or events. If you purchase coffee with your own mug at the cafeteria, you will even receive a discount! And while you're at it, check out the stockroom's other greener options, which carry an "SA" in the Stockroom number. You can also search for "environmentally friendly" in the description.

Sometimes the greener choice costs more in the short term, but in the long term, the benefits to society outweigh the short-term price.

—Katie Kosirog

Photos of the Day

American lotus

American lotus by the Main Ring are in bloom. Photos: Rich Motill, TD

In the News

Solving a long-standing atomic mass difference puzzle paves way to the neutrino mass

From Institut Laue-Langevin, Aug. 4, 2015

How heavy are neutrinos? To find out, radioactive decays are studied in which they are emitted. An essential ingredient is the decay energy which corresponds to the mass difference between the mother and daughter nuclei. It must be known with highest precision. A team of scientists now succeeded to resolve a severe discrepancy of the decay energy for the artificial holmium (Ho) isotope with mass number 163. It decays by electron capture to the stable dysprosium-163 (163Dy) and appears well suited to measure the neutrino mass. The team prepared pure samples of 163Ho and 163Dy and directly measured their mass difference with high accuracy using the Penning-trap mass spectrometer SHIPTRAP.