Do neutrinos and antineutrinos behave differently?

December 12, 2008 | 3:49 am

Stretch out your hand, and a trillion neutrinos cross it within three seconds. Yet very little is known about these invisible particles, despite enormous progress in the field of neutrino physics over the last two decades. Scientists now know that neutrinos have mass and that they can morph from one type into another–a process called neutrino oscillation or neutrino mixing. But numerous questions remain.

This Thursday, the MiniBooNE collaboration at the Department of Energy’s Fermi National Accelerator Laboratory released a preliminary result that sheds more light on neutrino oscillations. This is the collaboration’s first result with antineutrinos, the antiparticles of neutrinos.

The MiniBooNE experiment uses 1280 photomultiplier tubes to detect neutrinos interacting in a tank of mineral oil.

Three types of neutrinos have been observed so far: electron neutrino, muon neutrino, and tau neutrino. The MiniBooNE experiment explores the question of whether muon neutrinos morph into electron neutrinos. In the 1990s, the Liquid Scintillator Neutrino Detector at Los Alamos National Laboratory seemed to have observed such a signal for antineutrinos.

But the LSND neutrino observation did not fit in with neutrino oscillations measured at other experiments. One possible explanation: the existence of a fourth type of neutrino.

Scientists specifically designed the MiniBooNE experiment to resolve the LSND dilemma. In April 2007, the MiniBooNE collaboration announced its first results obtained with neutrinos. The experiment could not confirm the LSND result.

But that wasn’t the end of the story. Instead, MiniBooNE found an excess of electron neutrinos emerging from its primary beam of muon neutrinos at neutrino energies lower than what would be expected under a simple two-neutrino mixing interpretation of LSND data. (symmetry published an article on this puzzling observation.)

The 2007 result opened up the door for new questions. Is the low energy excess observed by MiniBooNE in neutrino mode due to some misestimated background? Is it due to some new physics? Can it be related to the LSND anomaly observed for antineutrinos? After all, there might be a difference between the oscillation of antineutrinos and that of neutrinos…

Georgia Karagiori

While theorists have been pondering possibilities, the MiniBooNE experiment has been busy collecting new data with a predominantly antineutrino beam. This, however, takes a lot longer. In the antineutrino mode, data are acquired five times slower than in the neutrino mode as antineutrinos interact differently with ordinary matter than neutrinos.

“It’s much harder to accumulate enough statistics with antineutrinos. That’s why we started our experiment in neutrino mode. Because of its setup, LSND didn’t have the neutrino option,” said Steve Brice, spokesperson for the MiniBooNE collaboration.

On Thursday, Georgia Karagiorgi, MIT, the lead graduate student on the antineutrino oscillation analysis, presented the first results from a blind analysis of MiniBooNE antineutrino data. The sparse data, which have large statistical uncertainties associated with them, show no excess of antineutrino events. In fact, the electron antineutrino signal candidates found in the data are in agreement with the underlying background prediction, even in the low-energy region.

Given the large low-energy excess observed in the MiniBooNE neutrino data in 2007, the lack of a corresponding excess in the antineutrino data is quite intriguing.

MiniBooNE photomultiplier tubes

“One can make different hypotheses to explain the excess observed in the MiniBooNE neutrino mode,” Brice said. “Some predicted an excess for our antineutrino data as well, some not.”

With regard to the LSND signal, the lack of statistical power of the MiniBooNE antineutrino result precludes any strong conclusions. The best fit includes nearly all of the LSND-allowed parameter space as well as the null hypothesis.

The single largest improvement that MiniBooNE can make to produce a more conclusive result is to gather more antineutrino data. The experiment is scheduled to run well into 2009. This will increase its antineutrino data sample by 50 percent.

Kurt Riesselmann

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Rare isotope facility to be built at Michigan State University

December 11, 2008 | 10:29 pm

Conceptual drawing showing a possible plan for the proposed facility. All concepts are subject to final approval by the DOE. Image provided by the National Superconducting Cyclotron Laboratory.

The Facility for Rare Isotope Beams (FRIB) will be constructed at Michigan State University according to a press release from the US Department of Energy. The facility will create beams of short-lived nuclear isotopes that are not commonly found in either nature or existing nuclear experiments. These isotopes will be used to study a diverse range of nuclear physics topics from the structure of the nucleus and the nature of the strong force, to understanding the evolution of stars and the origin of elements in astrophysical processes, to tests of the fundamental symmetries of nature. Rare isotopes also have application in medical research and nuclear stockpile stewardship.

Two remaining candidates had been competing to host FRIB, Michigan State and the University of Chicago/Argonne National Laboratory. The DOE made the decision based on evaluation against Merit Review criteria.

The facility will take approximately a decade to design and construct at a cost of about $550 million. It will be a DOE User Facility which means that it will be available for use by researchers from the United States and internationally.

A detailed scientific rationale for the process can be read in a 2006 report by the National Academy of Sciences: report (PDF).

A facility like FRIB was recommended as a high priority in a 1996 report by the joint DOE/National Science Foundation Nuclear Science Advisory Committee (NSAC) and the 2007 NSAC report concluded the facility is vital to the US nuclear science program.

Michigan State University has a press release with more information.

David Harris

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Another record! Tevatron accelerator surpasses expectations repeatedly

December 11, 2008 | 9:53 am

When Mary Convery moved to the Accelerator Division about one and a half years ago, people told her that with major upgrades finished there wasn’t much to do but to keep the nearly three-decades-old Tevatron particle accelerator running smoothly.

“‘There are no more home runs to get,’ I was told,” says Convery, Fermi National Accelerator Laboratory deputy run coordinator. “Yet, we keep continuing to make improvements.”

In the past five years at the Tevatron, the luminosity–the number of collisions per second–has increased sixfold. In the last six weeks alone, overall luminosity has improved 10 percent, generating more than a dozen luminosity records, sometimes multiple records in one week. Since October, the Tevatron has had nine of the top ten stores in its history.

The Tevatron consistently tops past integrated luminosity records even without increasing the number of protons and antiprotons injected into the accelerator ring.

The higher the luminosity, the better the chance for discovery–including sighting the Higgs boson, theorized to impart mass to other particles. Higher luminosity increases the probability of collisions producing a discovery of new physics, that discovery coming sooner and the precision at which scientists can study the Standard Model.

The Tevatron is on track to beat the FY 2009 estimated maximum weekly integrated luminosity by 20 to 25 percent. Earlier this month, the machine showed its stamina with a run of 15 uninterrupted stores. Achieving a run of more than six stores without interruption is considered good.

Read the rest of this entry »

Tona Kunz

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Steven Chu is choice for next Secretary of Energy

December 10, 2008 | 5:53 pm

Lawrence Berkeley National Laboratory Director Steven Chu will be Barack Obama’s nominee for Secretary of Energy according to reports in CNN and Reuters today. He will be one of the most scientifically qualified people to hold the position of Secretary of Energy.

Chu shared the Nobel Prize in Physics in 1997 “for development of methods to cool and trap atoms with laser light.” He was at Stanford University at the time but then moved to Berkeley to become director of LBNL. His research interests moved to include biophysics and he became a strong and vocal supporter of climate and energy research.

It will be interesting to see if he can pass on the messages in the lecture “What Our Next President Needs to Know” held at LBNL in October 2008. (Video below.)

Chu gave a presentation at a symposium in his honor at LBNL in August 2008 about his work on laser trapping and cooling, single molecule biophysics, and energy science:

David Harris

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Accelerator physicists show future collider compatibility

December 10, 2008 | 2:00 pm

As fractions of the beam are extracted in short bursts, or pings, the amount of current in the Main Injector extraction magnet, represented by the green line, spikes while the amount of beam in the Main Injector, represented by the red line, drops.

By temporarily altering the way the Main Injector releases beam, the Fermilab Accelerator Division has shown that physicists can use it to test machinery built for future accelerators.

The recently demonstrated mode of transferring beam out of the Main Injector imitates the way future colliders, such as the International Linear Collider, would function.

“We can provide users with beam that has the characteristics they want,” says Fermilab engineer Peter Prieto, who helped reconfigure the Main Injector slow extraction regulator.

Rather than releasing beam in one of the usual methods–all at once or draining in a slow spill over a period of one to four seconds–division scientists released beam in short spurts, or pings, that took a matter of milliseconds to fire.

“We have very good control,” says Fermilab physicist Erik Ramberg. “We can make the beam bursts five milliseconds or three milliseconds or one millisecond.”

Fermilab has used the technique before on beam extracted from the Tevatron. Members of the Accelerator Division began adapting the technique to the Main Injector about a year ago. 

When a power outage shut down the Tevatron on Nov. 5, 2008, they took the opportunity to test the ping method without the risk of interfering with the Tevatron’s operation. They announced the results at the Linear Collider Workshop last month.

To release the beam in pings, Fermilab operators needed to adjust the tune of the machine. When proton beams circulate around the Main Injector, they oscillate in waves. The height of those waves is determined by the magnets in the Main Injector.

When operators want just a portion of the protons to exit the Main Injector, they change the tune of the injector so that some of the protons will waver enough to be directed out of the ring. To kick out beam in bursts, engineers added carefully measured jolts of energy to the magnets at specific intervals.

Operators hope to continue perfecting the technique before attempting to use it while the Tevatron is running.

“This was proof of a principle,” Prieto says. “We proved we could ping the beam out.”

This story first appeared in Fermilab Today.

Kathryn Grim

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Lights, camera, render

December 9, 2008 | 6:08 pm

  

Scientists at the KIPAC Computational Physics Department simulate the birth of a galaxy. The red plumes represent ionized hydrogen gas that condenses into bright white glowing stars. (Image courtesy of the Ralf Kaehler.)

A red plume of hydrogen gas streams in three dimensions across a movie screen that almost spans the width of a dark conference room. Within the plume a brilliant white spot forms. The spot expands and quickly explodes into an orange and red cloud. Soon this cloud dissipates and a new bright dot grows elsewhere on the screen. In less than a minute, the movie has told the story of a young galaxy forming.

Three-dimensional movies of galactic birth are just some of the stunning visuals at the Schwob Computing and Information Center, a resource at the Kavli Institute for Particle Astrophysics and Cosmology’s Computational Physics Department. The center allows scientists and visitors at SLAC National Accelerator Laboratory to visualize the physics of the evolving universe.

“The idea is to understand how the universe works,” says KIPAC computational department member Ralf Kaehler, who produces the astrophysics videos. “These are visualizations of simulation data that follow the laws of physics, not some imaginary models as are often used in science TV shows or documentaries.”

Scientists in the department, which is led by SLAC and Stanford Associate Professor of Physics Tom Abel, simulate astrophysical events such as the birth of galaxies and the formation of the first stars in the universe. Each simulation is packed with data at an extremely high resolution. Matthew Turk, a physicist in Abel’s group, describes this level of detail as equivalent to watching flu viruses within a volume the size of the earth. Data with such large scale and fine detail can be difficult to analyze in static, flat pictures.

“Without creative and useful visualization techniques, we could never mine that data for useful information,” Turk says. Physicists in Abel’s group produce animations of their data with a combination of pre-existing visualization software and new computer programs that Kaehler writes from scratch. They then watch their simulations unfold on a high-definition screen more than 13 feet wide and seven feet tall. Behind the screen, two digital projectors shine images separately for the left and right eye, to produce the three-dimensional picture.

The astrophysicists can rotate the three-dimensional models and watch the movie from different perspectives to extract more information from the simulations. They can also highlight specific events in the simulation by changing the colors associated with the data. “We have a lot of sessions where we just sit in front of the screen and look at the data interactively,” Kaehler says.

But the movie screen isn’t used only for data analysis. Abel’s group also participates in outreach programs for groups outside SLAC. “It’s much easier to communicate what’s going on at KIPAC to non-experts who aren’t into all the equations and details by showing these colorful animations,” Kaehler says.

Visitors ranging from elementary school students to former Secretary of State George Schultz have sat in this physics cinema, donned 3-D glasses and watched astrophysics movies. In their demonstrations, the physicists mix KIPAC’s simulations with recent pictures snapped by ground and space telescopes to tell the story of the universe’s development.

Randy Melen, Tofigh Azemoon, Yemi Adesanya and Ralf Kaehler in front of SLAC's Supercomputing '08 display in November. (Photo courtesy of Alf Wachsmann.)

To expand the center’s visualization tools, Kaehler says the group plans to construct a wall-size computer screen that comprises 15 individual monitors, tiled in a five-by-three display. The Scientific Computing and Computer Services department presented an example of these tiled monitors last month at the International Conference for High Performance Computing, Networking, Storage and Analysis in Austin, Texas. (See “Supercomputing ’08.”) Physicists will be able to observe an even deeper level of detail in their simulations with this screen because it will display static pictures at a resolution of 6000 by 6000 pixels-a resolution 15 times greater than high-definition TV.

By Michael Torrice, symmetry intern

This story first appeared in SLAC Today.

Guest author

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Physics license plates

December 9, 2008 | 7:19 am

Regular readers of symmetry will have seen our collection of physics license plates but we are always looking to expand it. The latest print issue features a couple of extra plates we’ve added to the gallery: QUARKS, FYZYKZ, and SU3SU2U1.

See the whole collection here, and send us a photo of your physics license plate with a short text about what inspired you to get it, what kinds of reactions you get, or even just what it means (if it is obscure!) You can send your submissions to mail@symmetrymagazine.org.

Here are a couple of images from the gallery.

I have Illinois license plate PHYSICS on my 2005 Toyota Camry. I believe that it cannot get more physics than that! The story is simple, unlike Tom Nash’s (Oct/Nov 07). I work at Fermilab and I used to have a Toyota pickup truck with 900 GEV plates (the TeV ring energy at that time). When I traded my truck in for a Camry, I had to get new plates because Illinois does not allow truck plates on cars. I applied for PHYSICS as my first choice and, much to my surprise, I got it.

Jym Clendenin, a retired SLAC physicist, acquired his plates about 15 years ago when he was commissioning the SLC polarized electron source. E MINUS stands for electrons and their negative electric charge. Clendenin was in charge of the SLAC linac electron injector until his recent retirement. Common comment received: “That’s a really poor grade!”

I’ve had the custom license plate SOLITON for 30 years. I transfer it from one car to the next. In many ways a car behaves like a soliton: It is a wave localized in a certain region of space, it keeps its shape when traveling, and it interacts with other solitons (cars) emerging unchanged, most times, perhaps with only a small phase shift.

It’s a lot of fun and a great conversation starter using aspects of my work as a physicist on license plates. Friends are quick to spot whenever a new one goes on the car, and invariably ask what it means. For some I provide a brief explanation, but for my weekly hiking group there is ample time to also give some background about the significance of the research. Those not familiar with Los Alamos National Laboratory are pleasantly surprised to learn that there is basic research going on in addition to work on nuclear weapons. I try to come up with a new license plate every year. I am proudest of the very first one: NUCLEON, because it contains my first name. On the other hand, one wag suggested it was an invitation to nuke Leon.

David Harris

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Flat Children visit labs by mail

December 8, 2008 | 8:34 am

Flat Johnny. Image courtesy of Sarah Demers

At the Large Hadron Collider’s ATLAS control room in Geneva, Swizerland, SLAC National Accelerator Laboratory postdoctoral researcher Sarah Demers meets travelers from all over the world. Her most recent visitor is made of paper and arrived by mail.

Hand-drawn by 8-year-old Johnny, a relative of Demer’s, “Flat Johnny” took a tour of ATLAS and the town of Dresden with her. She chronicled their travels in a series of pictures.

The real Johnny mailed his paper namesake as part of a classroom activity inspired by the book Flat Stanley. In the story, a young boy named Stanley is flattened by a falling bulletin board, and realizes that he can now travel the world by mail. Flat Stanley has his picture taken in various exotic and beautiful locations, and with the people he meets there. The Flat Stanley Project has grown to include thousands of participants, and teaches children letter writing as they send their own “flat” selves to other students, people in locations they’d like to visit, or famous figures. Clint Eastwood appeared with his daughter’s “Flat Stanley” at the Academy Awards, and California Gov. Arnold Schwarzenegger brought his son’s “flat self” on The Tonight Show. Recipients take photos with the flat people and send them back to the students.

Along with photos, Demers sent postcards from France and Switzerland back to Johnny and his class. “I don’t know how much the kids know about CERN. I didn’t delve into the physics too much,” she said. “I told [Johnny] one of the things I like most about my job is that I get to work with people from all over the world.” Demers will continue to work at ATLAS for a few years. She is looking at tau leptons, and works on the trigger for the ATLAS detector with the SLAC group at CERN.

Flat Maya admires the LHC tunnel with traveling companion Travis Brooks. Photo courtesy of Travis Brooks

A Flat Stanley visited the SLAC Klystron Gallery a few years ago with Web consultant Kevin Munday and his wife, Kelly Daley. Their flat traveling companions, often drawn by one of their 26 nieces and nephews, have also visited ITER in France. “With the SLAC visit, I remember that we wanted to get the photo in the world’s longest building,” said Munday, who does contract work for SLAC. “It’s a great way to get kids excited about physics.”

Johnny isn’t the only Flat Child who’s visited CERN.  Travis Brooks, who runs the SPIRES databases at SLAC,  took Flat Maya to the lab last year; she’s the 2D version of his niece, who lives in Atlanta and was 8 at the time.  Here they are posing in the Large Hadron Collider’s 15-mile-long circular tunnel. You can follow their adventures in these photos posted on flickr. 

Brooks and his wife seem to be an epicenter of Flat Tourism.  They had a visit from Flat Maya the previous year, too, and took her climbing in Yosemite, tied by a shoestring to a climbing harness. And before that came Flat Wyatt, sent by his cousin’s son. Unfortunately he arrived at a dull time, Brooks says: “Flat Wyatt mostly lounged around the house.”

An earlier version of this story first appeared in SLAC Today.

Calla Cofield

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Celebrating BaBar

December 5, 2008 | 4:32 pm

The BaBar experiment at SLAC National Accelerator Laboratory stopped data collection earlier this year, but fantastic results will continue to come from the data for years to come. More than 300 BaBar scientists from around the world came to celebrate the end of data collection at a symposium held at Stanford University, home of SLAC.

symmetry writer Calla Cofield went to the symposium to speak with some of the scientists about their experiences with BaBar. See that video above.

You can read more about one of the major BaBar results released in 2008, the discovery of the bottom-most bottomonium, in the current print issue of symmetry. You can also read Calla’s interview with the elusive eta sub b particle.

David Harris

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LHC to restart in 2009

December 5, 2008 | 11:58 am

The CERN Press Office issued a release this morning announcing that the Large Hadron Collider will restart in 2009. The news comes after this week’s CERN Council Meeting. The current schedule estimates that CERN will reinstall the final magnet by the end of March 2009, with the LHC cold and ready for power tests by the end of June 2009. Read the full press release and report here.

Elizabeth Clements

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