A joint Fermilab/SLAC publication

dimensionsofparticlephysics

october 2010

issue 5

volume 7

symmetry

On the cover and inside coverPhysics, architecture and nature intersect at the Garden of Cosmic Speculation in Scotland, created by noted architect and designer Charles Jencks (see Gallery, page 34). As our cover shows, it’s also a place where creative people from physics and the arts intersect. From left: Rolf Heuer, director general of the European particle physics laboratory, CERN; Peter Higgs, theoretical physicist and co-inventor of the Higgs boson; and Charles Jencks.Photos: maverickphotoagency.com

02 Editorial: Muons, the Next Discovery Particles?Particle physicists are used to using electrons, positrons, protons, and anti-protons as their primary collision particles. Might the muon have a role in the future?

03 Commentary: Doug SarnoWhen I began my professional life as a civil engineer, I thought that I would spend my career building bridges. As it turned out, that’s what I’m doing—only the bridges that I help build are very different from those I studied in engineering school.

04 Signal to BackgroundSumo, slippers, and science; softball crosses the pond; space weather outlook: fl aring; icebreakers for physicists; mirror fi nish with marbles; license plates and letters.

08 symmetrybreakingA summary of recent stories published online in symmetry breaking, www.symmetrymagazine.org/blog/oct2010

10 When Muons CollideA new type of particle collider known as a muon collider—considered a wild idea a decade ago—is winning over skeptics as scientists fi nd solutions to the machine’s many technological challenges.

16 To Catch a SupernovaSome exploding stars release bursts of oddball neu-trinos. Scientists with the Long Baseline Neutrino Experiment are eager to catch those neutrinos and milk them for discoveries. But they must weigh the benefi ts of doing that against the risk that nothing will happen—no supernova, no neutrino burst—during the experiment’s 50-year lifetime.

24 Community + LaboratoryFermilab has joined up with local residents to think about the best ways for the lab to serve not only science, but also the surrounding area.

30 Day in the Life: Peter KasperFor birders like Fermilab accelerator physicist Peter Kasper, it all comes down to that moment: Focus your binoculars, steady your hands, and look, hard, until you fi nd that glimpse of feathers, a spark of recognition.

34 Gallery: Charles JencksThe Garden of Cosmic Speculation has become a focal point for Charles Jencks’ exploration of nature’s fundamental building blocks, the process of discovery, and modern scientifi c achievements. The garden challenges society’s ideas of how one experiences nature and what a garden looks like.

symmetryA joint Fermilab/SLAC publication

volume 7 | issue 5 | october 2010

38 Accelerator Apps: HydrogelsHydrogel bandages do not dry and stick to a wound the way gauze does. They act more like the body’s own tissue. “They can work as a pseudo-blister, cre-ating an ideal environment for burn wounds to heal,” says dermatologist Kyomi Mihara.

C3 Logbook: First Tevatron CollisionAt 3:10 a.m. on October 13, 1985, scientists with the Collider Detector at Fermilab experiment informed the main control room that they had observed the Tevatron collider’s fi rst antiproton-proton collision. The collision’s center-of-mass energy of 1.6 TeV was three times higher than the previous world record.

C4 Explain it in 60 Seconds: The Big BangThe big bang refers to the start of the rapid expan-sion of our universe, discovered by Edwin Hubble in the 1920s. His observations of faraway galaxies showed the distances between them are growing as time rolls on.

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from the editor

symmetry

SymmetryPO Box 500MS 206Batavia Illinois 60510USA

630 840 3351 telephone630 840 8780 faxmail@symmetrymagazine.org

For subscription services go to www.symmetrymagazine.org

symmetry (ISSN 1931-8367) is published six times per year by Fermi National Accelerator Laboratory and SLAC National Accelerator Laboratory, funded by the US Department of Energy Offi ce of Science. (c) 2010 symmetry All rights reserved

Editor-in-ChiefDavid Harris650 926 8580

Deputy EditorGlennda Chui

Managing EditorKurt Riesselmann

Senior EditorTona Kunz

Staff WritersElizabeth ClementsCalla Cofi eldKathryn GrimKelen TuttleRhianna Wisniewski

InternsLeah HeslaCatherine MeyersSara ReardonLauren RuganiLori Ann White Daisy Yuhas

PublisherJudy Jackson, FNAL

Contributing EditorsRoberta Antolini, LNGSPeter Barratt, STFCRomeo Bassoli, INFNKandice Carter, JLabLynn Yarris, LBNLJames Gillies, CERNSilvia Giromini, LNFYouhei Morita, KEKTim Meyer, TRIUMFPerrine Royole-Degieux, IN2P3Yuri Ryabov, IHEP ProtvinoYves Sacquin, CEA-SaclayKendra Snyder, BNLBoris Starchenko, JINRMaury Tigner, LEPPUte Wilhelmsen, DESYTongzhou Xu, IHEP BeijingGabby Zegers, NIKHEF

Print Design and ProductionSandbox StudioChicago, Illinois

Art DirectorMichael Branigan

Designers/IllustratorsAaron GrantAndrea Stember

Web Design and ProductionXeno MediaOakbrook Terrace, Illinois

Web ArchitectKevin Munday

Web DesignKaren AcklinJustin Dauer Alex Tarasiewicz

Web ProgrammerMike Acklin

Photographic ServicesFermilab Visual Media Services

Muons: the next discovery particles?

Electrons, positrons, protons, antiprotons: These particles have formed the basis for much of the particle physics research and many of the discov-eries of the past hundred years. Will there be other particles that play a similar role in the future?

Muons are very much like electrons, but 200 times more massive. They don’t have any constit-uent parts so they create clean collisions. Their higher mass means they don’t give off as much energy as X-rays when they are guided along curved paths. They are a tool that can be used to explore fundamental physics with high preci-sion and at the high energies needed to study the next generation of particles beyond the Standard

Model of physics. They are also extremely sen-sitive, in measurable ways, to the effects of currently unknown physics, mostly due to their higher mass.

There’s just one problem. They only live for about two thou-sandths of a second. That means they are diffi cult to create in suffi ciently large quan-tities that survive long enough to use as the

precision tools they could be.Fortunately, nature has a loophole described by

Einstein’s special theory of relativity. When parti-cles are moving with high energy at nearly the speed of light, they have signifi cantly longer life-times. Muons created 15 kilometers above the surface of the Earth can be detected at ground level because of this effect. Otherwise, they would travel less than one kilometer before decaying.

With these extended lifetimes, muons can be created, accelerated, stored, and either studied by themselves or slammed into targets—or each other. When they do fi nally decay, they give rise to a supply of muon neutrinos, which are useful for other studies. Getting to this point, however, will be extremely technically challenging.

The research, design, and engineering needed to make muon accelerators and colliders have for a long time been thought too diffi cult to even attempt. But some physicists have rethought the problem in light of more sophisticated accelerator technologies and now think a muon collider is quite feasible.

It will still be a long road to a working muon collider, but the effort will create other kinds of particle physics machines and experiments along the way. A muon collider might be the technol-ogy needed to explore the new world of particles that physicists expect the Large Hadron Collider to reveal. Perhaps in 50 years we will look back at the history of particle physics and the list of key discovery particles will include that heftier, short-lived cousin of the electron, the muon.David Harris, Editor-in-chief

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commentary: doug sarno

Why science labsshould engage their neighborsWhen I began my professional life as a civil engi-neer, I thought that I would spend my career building bridges. As it turned out, that’s what I’m doing—only the bridges that I help build are very different from those I studied in engineer-ing school.

For over 20 years, I have put aside my technical skills and devoted my attention to the “soft” side of decision-making—developing ways to bring vastly different people together to fi nd consensus on complex and controversial topics. One of my clients recently asked, “If this is the ‘soft’ side of science, then why is it so hard?” The truth is that it is not hard at all, but it does require a sin-cere and sustained effort in order to succeed. It is an effort that few organizations ever put forth.

For the past six years, Fermilab has been making that effort, and it has paid off in dramatic fashion (See article, page 27). Over that period, Fermilab has conducted three community advisory boards, a series of employee focus groups and an employee advisory board. First, in 2004, Fermilab established the Fermilab Task Force on Public Participation. The result was an insightful and achievable set of recommendations for effec-tively involving the local community in planning and decision-making at the laboratory. These recommendations were instrumental in helping Fermilab manage its fi rst-ever environmental release of small concentrations of tritium beyond the laboratory borders. Next came the Citizens Task Force for the International Linear Collider. The detailed and thoughtful report from the task force showed the degree to which the public can understand and support basic science research.

Today, Fermilab has an active community advisory board to help chart the future of the laboratory and its potential impacts on the com-munity, as well as an Employee Advisory Group to help improve communication and create a positive workplace for all Fermilab employees. Like their predecessors, these boards are tack-ling real issues and achieving real results for the betterment of the lab and the achievement of its science mission.

Why do these boards work? At their core, they are a forum to create broad-based under-standing and conduct in-depth dialogue around issues that matter. By inviting all key viewpoints to the table, we all learn from and about each other. We work through challenging issues before they become crises and positions harden. As people fi nd that their voices are heard, they

also establish owner-ship in the decisions that are made.

Are the conditions at Fermilab unique? Not at all. I have con-vened and managed dozens of boards on a wide variety of diffi -cult issues for many organizations and in diverse communities. The results are always the same. Where there is a sincere commit-ment to engaging stakeholders and the creation of a solid process with diverse stakeholders, people almost always fi nd common ground. As a result, decisions that could easily bog down in personal, organiza-tional, and legal confl icts instead are achieved with broad understanding, agreement, and enthu-siasm for the future. Now more than ever, the success of basic science research needs this level of common understanding and enthusiasm.

Building bridges to all our stakeholders—communities, workers, scientists, funders, agencies—is one construction project we cannot afford to ignore.

Doug Sarno is Principal of Forum Facilitation Group in Arlington, Virginia. He can be reached at doug@forumfg.com

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Members of the Fermilab Community Advisory Board discuss how changes at the laboratory are likely to affect the surrounding communities.

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signal to background

Sumo, slippers, and science; softball crosses the pond; space weather

outlook: fl aring; icebreakers for physicists; mirror fi nish with marbles; license

plates and letters.

Treading lightly in TokyoIt was my fi rst morning in Tokyo. Carrying a camera, an offering of saké, and a note in Japanese that I hoped explained why I was there, I stepped into the sumo training hall to watch the day’s practice.

Even with my limited knowl-edge of the language, I under-stood immediately that I had done something wrong. A short, thin man sprinted toward me, waving his arms and exclaiming in protest.

He motioned toward my feet. My cheeks burned. I real-ized I had committed the sin of dosoku—wearing my street shoes inside.

In Japan, people remove their shoes and sometimes change into slippers before entering homes, temples, traditional

restaurants and, apparently, sumo training halls. I was sur-prised to discover later that this list also includes certain areas of physics laboratories.

At Japan’s high-energy phys-ics laboratory KEK, employees and visitors change into rubber sandals before entering the con-trol room for the B-factory accel-erator, KEKB. Kyoto University staff members ask people who go near their accelerators to wear bright yellow clogs.

Kazuo Abe of Tokyo’s Institute for the Physics and Mathematics of the Universe explained in an e-mail that only a small number of laboratories enforce the tradition, which most Japanese learn in elementary school. “They do so more out of a respect for the custom than to keep the place clean,” he wrote. “We mostly go along

without arguing.” Youhei Morita of KEK

explained the practice this way: “Traditional Japanese regard [outdoor shoes] as carrying the impurity of the outside world, and it becomes almost our sec-ond nature to take them off at the entrance.”

Perhaps it’s a good metaphor for scientists, who seek the truth uncolored by the expecta-tions of the world around them.Kathryn Grim

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Hit it over the AlpsEvery summer weekend, several dozen CERN physicists gather to enjoy a beloved American tra-dition: They play for the Quarks and the Leptons in an interna-tional softball league.

The games are hosted by the US Marines at a site just north of Geneva, with a view of the Swiss Alps over the center-fi eld fence.

Playing the Marines is “like jocks versus nerds, and we tend to give them a run for their money,” says Jim Degenhardt, a postdoc from the University of Pennsylvania working on the ATLAS experiment. “Unfor-tunately, the jocks usually win, but we all have fun.”

Americans who grew up playing baseball or softball are in the minority on the two CERN teams. Some of the European players, particularly the English, had never seen a baseball bat before arriving at CERN, but by the end of the summer they can hit a baseball at least as com-fortably as they hit a cricket ball. The teams have a strong tra-dition of coaching anyone with the desire to learn, yet remain avidly competitive.

Their competition includes teams of employees from international companies and organizations like Merrill Lynch, Caterpillar, and the United Nations.

The Quarks and the Leptons are part of the CERN softball club, which fi elds more women in this co-ed league—and, incidentally, more talented women—

than any other club. It was also the fi rst ball club in the world to have a page on the World Wide Web, beating out any team from Major League Baseball. (Of course it had a leg up, since the Web was invented at CERN.)

Vicki Moeller, an ATLAS col-laborator from the University of Cambridge, says, “Sipping A&W [root beer] between innings, looking out on Geneva and the lake from our fi eld, and hitting a game-winning two-run double in the bottom of the ninth is a great way to spend a Sunday afternoon.”Zach Marshall

Armenia detects space weather On Mount Aragats, the highest point in the Armenian landscape, atop a volcano ribboned with glaciers, lava-born fi ssures, and medieval fortifi cations, an early 20th century observatory is lead-ing Armenian physics in new, 21st century directions.

After the fall of the Soviet Union, Armenian researchers realized they could not afford to maintain their observatories and develop large detectors for competitive research in high-energy physics.

Taking advantage of the airy altitude of their observatories, they began investigating new avenues of research.

“We found our niche in the relatively new science of space weather,” explains Ashot Chilingarian, director

of the Yerevan Physics Institute. “You don’t need a huge detector to make excellent physics. Instead, you need a small detec-tor in the appropriate place.”

Research into solar flares and geomagnetic storms is increasingly valuable as the world depends more on satellite technologies. Solar fl ares, for example, can knock out an entire satellite or power grid.

The ground-based detectors designed and fabricated by Armenian scientists, each no wider than a meter, complement space-based systems that forecast space weather. They record millions of particles produced in cosmic ray showers from the sun.

The success of these detectors has contributed to their dispersal around the globe. Armenia leads the Space Environmental Viewing and Analysis Network, or SEVAN, and has crafted SEVAN detectors for Croatia, Bulgaria, India, and Slovakia. This network can provide reliable 24-hour fore-casting and advanced solar storm warnings, crucial to sophisticated technologies that protect astronauts and your next door neighbor’s GPS.

Another detector program studies the multiplication and acceleration of electrons in thun-der clouds, which can affect air travel. This little-understood phe-nomenon has been puzzling scientists since the 1990s.Daisy Yuhas

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signal to background

Riding the waves in search of cosmic raysAs physics lab environments go, one could do worse than sharing the expanse of the Atlantic Ocean or the animal-dotted ice shelves of Antarctica with 20 pancake-cooking, dart-playing Swedish sailors.

Such was the setting for three University of Wisconsin

undergraduates who took weeks-long turns aboard the Oden icebreaker last winter as it travelled from Sweden to Antarctica, carrying a small particle detector.

The young scientists moni-tored the detector’s response to particle showers that arise when low-energy cosmic rays hit the atmosphere. The intensities of these secondary particles vary as you travel from the equator to the poles. Measuring those variations along the ship’s north-south track will help calibrate IceTop, an array of cosmic-ray detectors in Antarctica that’s part of the IceCube neutrino observatory.

While taking data, the stu-dents also had to calibrate their stomachs.

“When we were on the Oden, the fi rst thing they said was that we could rock up to 45 degrees. I thought, ‘That is insane,’” says Samantha Jakel, then at UW-Rock County. Soon, though, she found she was able to roll with the pitches.

Jakel got up close to killer whales and Adélie penguins. “The penguins are adorable and I think they know it,” Jakel says. Indifferent seals stayed put even as, only yards away, the 13,000-ton vessel broke the ice where they squatted.

“Icebergs were all around, anywhere from the size of your kitchen table to things bigger than anything I’ve ever seen,” says Kyle Jero, a physics major at UW-River Falls.

As short-term denizens of a Swedish ship, the students joined the crew in observances of pea soup-and-pancakes Thursdays and in ping-pong matches between work shifts.

“It was perfect,” says Drew Anderson, also at UW-River Falls. “The crew was fun. We got all the data we were looking for. It really couldn’t have gone much better.” Leah Hesla

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His car is plus a minusI worked for Jym Clendenin at SLAC from 1993-2000 before leaving for a position in my native Texas. I always liked his license plates (see “A Bumper Crop of Physics Plates,” Aug 08). For the past six years I have been working at my own company, Saxet Surface Science, on DOE-funded photocathode research targeted to sources of spin-polarized electrons for accelerators (some in collaboration with Jym before he retired.) Last year I took the opportunity to grab “E Minus” plates for my vehicle, picture attached.Gregory Mulhollan, Austin, Texas

The new wave of linear lightsourcesI enjoyed your fi ne article on synchrotron lightsources in the February issue of symmetry. Synchrotron lightsources are indeed useful in a wide variety of applications. However, I would like to point out that not all lightsources are synchrotron-based, which may be inferred from the phrase in the article that begins: “Lightsources are circular particle accelerators…”

Several current and planned lightsources are powered by linear accelerators, such as SLAC National Accelerator Lab’s X-ray lightsource, known as the LCLS, and Jefferson Lab’s Free-Electron Laser. The Jefferson Lab FEL is primarily an infrared lightsource, but it also produces prodigious amounts of terahertz light and will soon also produce ultraviolet laser light. The LCLS and the Jefferson Lab FELare each the most powerful lightsources in their class, far outshining older synchrotron lightsources that produce the same wavelengths of laser light. In addition, Jefferson Lab’s FEL is built with energy-recovering linear accelerator technology, making its operation highly effi cient. The LCLS recently became the world’s fi rst X-ray laser at 1.5 Angstrom with brightness far exceeding any source in this wavelength range and is being applied to a variety of groundbreaking scientifi c measurements. Indeed, the next generation of lightsource user facilities will be based on these developments.George R. Neil, Thomas Jefferson National Accelerator Facility

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High-tech marbles and bubblegum Fermilab scientists are using what look like dime-store toys to polish specialized accelera-tor cavities, each of which costs about as much as a brand-new Maserati.

Think someone’s lost their marbles? Think again.

These superconducting cavities, designed for next-gen-eration accelerators, are made of pure niobium, which is very soft and vulnerable to damage from any scratch or bump during the manufacturing process.

“It’s like polishing bubblegum,” says Fermilab’s Lance Cooley, who researches superconduct-ing radio-frequency materials like the niobium used to make these cavities.

Yet a smooth fi nish is vital, because it allows electrons to fl ow freely and accelerate to nearly the speed of light. So the hunt is on to fi nd the best, cheapest polishing method.

One possible answer: tum-bling marbles.

Tumbling is used in industry to remove rough spots from the surfaces of metals. Labs that work with superconducting cavi-ties, such as Germany’s DESY and Japan’s KEK, have also started to explore the technique. Here’s how it works: Place a combination of water and pol-ishing materials inside the superconducting cavity and put it in a special device that spins it around like a Tilt-A-Whirl ride. The materials whoosh around until the inner surface has a mir-ror-smooth fi nish.

The marbles used for polish-ing are not toys. Scientists use only marbles made of fi ne por-celain—pure aluminum oxide—

to prevent contamination of the cavity’s inner surface.

Charlie Cooper and his col-leagues at Fermilab also are testing other tumbling materials including cork, dried corncobs, walnut wood chips, ceramics, and plastics. At the moment, the tumble-polish process is like a recipe that many have tried but no one has perfected, in part because rigorous testing has yet to be performed.

“We know what works but we don’t know why, and we want to fi nd out so we can optimize it,” Cooper says. “We’re taking an art and fi nding the science.”Daisy Yuhas

symmetrybreaking

Highlights from our blog

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Heroes of the Tevatron: electrical tape and ingenuitySeptember 29, 2010

When the need to mend a small piece of Fermilab’s Tevatron threatened to shut down the entire machine for more than a week, a repair team found an unexpected use for electrical tape: keeping the world’s larg-est proton-antiproton collider running.

Fermilab considers extending Tevatron run by three yearsSeptember 21, 2010

The director of Fermilab announced that the laboratory would extend the run of its fl ag-ship particle accelerator by three years, provided that it could secure additional resources and minimize the effect that con-tinuing to run the Tevatron would have on other experiments.

LHC experiment observes potentially new and interesting effectSeptember 21, 2010

In the aftermath of particle collisions at the Large Hadron Collider, members of the CMS collaboration observed effects that bore some resemblance to those observed at the RHIC facility at Brookhaven National Laboratory, where scientists have created quark gluon plasma.

DUSEL planning on trackSeptember 13, 2010

At the fi rst meeting of potential users of the proposed Deep Underground Science and Engineering Laboratory, partici-pants and funding agencies expressed satisfaction with the progress of the design for the laboratory and its experiments. If approved, construction and experiment installation could begin in 2014 and continue for seven years.

Using art to under-stand particle physicsSeptember 10, 2010

Chicago’s Chuck Przybyl chal-lenged a handful of artists to interpret the principles and practices of particle physics in their favored media. The result was Hard Science, an exhibit that recently concluded at the Chicago Art Department.

Autos to acceleratorsSeptember 8, 2010

Manufacturing jobs in Michigan have decreased fairly steadily over the past 10 years. But in Lansing, a town haunted by the remains of fallen automobile plants, companies are hiring workers to put their car-manu-facturing skills toward building particle accelerators.

Move over Britney, Lady Gaga’s in physics nowSeptember 2, 2010

For years, the Britney Spears Guide to Semiconductor Physics has been floating around the Web intriguing, amusing, educating, troubling, and infuriating people. Going one better, pop star Lady Gaga is now immortalized in the name of a published physics paper.

First African School of Physics empowers studentsAugust 30, 2010

Sixty-fi ve students from around the globe–including more than 50 from 17 African countries–came together in Stellenbosch, South Africa, this month for the fi rst African School of Fundamental Physics and its Applications. They left with more information than they could process, new friends and con-nections, and ideas on how to pursue a particle-physics career.

LHC lawsuit dis-missed by US courtAugust 26, 2010

An appellate judge has dis-missed the lawsuit Walter Wagner brought against the US government to prevent the start-up of the Large Hadron Collider. According to the deci-sion, Wagner failed to show a “credible threat of harm” and brought a case against the wrong party, as the US govern-ment does not control operation of the LHC.

Read the full text of these stories and more at www.symmetrymagazine.org/blog/oct2010

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The Particle Physics SongAugust 26, 2010

This week CERN posted a video of the CERN choir performing “The Particle Physics Song,” an ode to the Higgs boson to be sung to the tune of “The Hippopotamus Song” by British comedians Michael Flanders and Donald Swann. British psy-chologist Danuta Orlowska submitted the song to a CERN publication, and the choir tried it in a performance in the CERN Control Center on Feb. 3.

The strange case of solar fl ares and radioactive elementsAugust 23, 2010

The rate of decay of radioactive material is supposed to be con-stant. But the decay of some elements sitting quietly in labo-ratories on Earth seems to have been infl uenced by activities inside the sun, 93 million miles away. If this apparent relation-ship between fl ares and decay rates proves true, it could lead to a method of predicting solar fl ares, which could help pre-vent damage to satellites and electric grids, as well as save the lives of astronauts in space.

Dark energy studies top astronomy and astrophysics prioritiesAugust 13, 2010

A National Research Council committee ranked dark energy and dark matter studies among those of highest importance in “New Worlds, New Horizons in Astronomy and Astrophysics,” a decadal study of astronomy and astrophysics priorities.

COUPP bubble chamber goes deep in search for dark matterAugust 12, 2010

This month physicists are deploying a 4-kilogram bubble chamber more than a mile underground at SNOLab in Ontario, Canada, to search for dark matter particles. Scientists predict the theoretical particles will leave bubbles in their tracks when passing through the liquid in the chamber.

Snippets of science: Berkeley Lab’s Video GlossaryAugust 9, 2010

For those of you who are fans of symmetry ’s “Explain it in 60 Seconds,” Lawrence Berkeley National Laboratory has its own version: the Video Glossary, made up of about 70 clips in which scientists defi ne a variety of terms from “Standard Model” to “extremophile.”

Particle night fever in ParisAugust 6, 2010

Organizers of a physics confer-ence convinced 2000 Parisians and tourists to spend an entire summer night talking about physics at “Nuit des particules”–Particle Night. The trick? Find a magic venue, invite fascinating speakers and well-known art-ists, explore the frontier between science and cinema, and adver-tise, advertise, advertise.

Aluminum foil to the rescue at SLAC’s X-ray laserAugust 3, 2010

MacGyver-like physicists are using aluminum foil to modify pulses of light from an X-ray laser at the Linac Coherent Light Source at SLAC National Accelerator Laboratory. The use of this novel piece of technology aims to make the world’s briefest X-ray pulses even briefer.

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A new type of particle collider known as a muon collider—considered a wild idea a decade ago —is winning over skeptics as scientists fi nd solutions to the machine’s many technological challenges. By Leah Hesla

AB SOR B E R

MAG N ET

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MAG N ETTARG ET

M UON S

When Fermilab physicist Steve Geer agreed to per-form a calculation as part of a muon collider task force 10 years ago, he imagined he would show that the collider’s technical challenges were too diffi cult to be solved and move on to other matters. But as he delved further into the problem, he realized that the obsta-cles he had envisioned could in principle be overcome.

“I started as a skeptic,” he says. “But the more I studied it, I realized it might be a solvable problem.”

A muon collider—a machine that currently exists only in computer simulation—is a relative newcomer to the world of particle accelerators. At the moment, the reception from the particle physics community to this fi rst-of-its-kind particle smasher is “polite,” says Fermilab physicist Alan Bross.

Politeness will suffi ce for now: research and development on the machine are gearing up thanks to funding from the US Department of Energy. In August, a DOE review panel supported the launch of the Muon Accelerator Program, or MAP, an inter-national initiative led by Fermilab. Scientists hope the program will receive about $15 million per year over seven years to examine the collider’s feasibility and cost effectiveness.

Mutable muonsAs with any new high-energy physics project, the muon collider has its share of skeptics who voice doubts about its projected R&D timeline or its cans of engineering worms. But Bross, a member of the MAP management council, assures the physics com-munity that “we’re not raving lunatics.”

Muons—heavy cousins of the electron—have trag-ically short lifetimes: they decay after about two millionths of a second. Yet these blink-and-you-miss-them muons may help particle scientists fi nd answers to some of the universe’s most nagging questions.

Accelerator scientists are accustomed to arranging collisions between electrons or protons. Since these particles don’t decay, they can travel around a circular accelerator for days or weeks. Muons, in contrast, don’t leave much time for acceleration and manip-ulation. Still, it’s an obstacle scientists believe they can overcome.

“It’s doable,” says Vladimir Shiltsev, director of Fermilab’s Accelerator Physics Center.

A muon collider would accelerate two beams of muons in opposite directions around a 6-kilometer-circumference underground ring. Those beams would collide head-on at close to the speed of light. Scientists would mine the collision aftermath to look for dark matter, supersymmetric particles, signs of extra spatial dimensions, and other subatomic phenomena.

Getting to the point where a muon-muon collision is in principle achievable means being able to pro-duce and manipulate a beam of muons, and that’s no small challenge.

Avoiding a subatomic messThe Large Hadron Collider in Europe, which started operations in 2009, is a proton-proton collider with a circumference of 27 kilometers. Scientists think of the LHC as a universal particle physics discovery machine. It scans a wide range of energies to look for the elusive Higgs boson and other particles, the way a birdwatcher would walk through a forest and look for a particular bird. But once he’s located the bird in a treetop and wants to get a close look, the naked eye won’t cut it. He’ll want a pair of binoculars to better study the bird’s plumage and behavior.

A muon collider would be a particle physicist’s set of binoculars. It would zoom in on a narrow region of energy to uncover the physics phenomena that the LHC can’t reveal on its own. It would provide a clear, unobstructed view of the subatomic world.

“The beauty of a muon collider is that the collision events are clean,” says Shiltsev.

Clean events arise because muons are indivisible. Unlike protons, which contain quarks and gluons, muons have no component parts. Two colliding pro-tons are like two high-velocity bags of trash meeting in mid-air: the pieces of garbage inside the bags, not the two bags themselves, are doing the colliding. The diffi culty then lies in sorting through the mess each collision creates and tracing which bottle cap triggered the trajectory of which candy wrapper.

With muons, there is no garbage. Being a muon

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is uncomplicated. When two colliding muons have opposite charges—one positive, one negative—they annihilate, and all their energy goes into making new matter. In contrast, when the LHC accelerates protons, it’s really the quarks and gluons inside the protons that are colliding, and each component carries only a fraction of the total proton energy.

“The actual collisions you see at the LHC in gen-eral have something like a tenth of the energy” of the full proton-proton collision, says Bob Palmer of Brookhaven National Laboratory, who has led pre-vious incarnations of the muon collider collaboration.

Muons vs. electronsThe muon collider faces some competition. The fam-iliar electron, another collision candidate, is also indivisible and produces clean collisions as well. But the lightweight electron is harder to accelerate along a curved path than heavier particles, such as muons and protons. An electron, whose mass is 1/200th that of a muon, easily radiates its energy away when it fol-lows the curve of a circular accelerator at high speed.

A muon would better retain its energy, even as it zooms around a 6-kilometer circle thousands of times at close to the speed of light. Those multiple trips around the track would allow muons to reach high collision energies, higher than those of quark-quark and quark-gluon collisions produced at the LHC.

Scientists can overcome the electron’s radiation problem by designing electron colliders that are straight and tens of kilometers long. Right now, the physics community contemplates two possible options. One is the International Linear Collider, a pro-posed 30-kilometer-long electron-positron collider. In 2012, scientists and engineers will deliver the detailed drawings and plans for the ILC. Although the ILC option is the furthest along in R&D, its cost, estimated at $15 billion to $20 billion, gives scientists and would-be funders pause.

The other option is CERN’s Compact Linear Collider, which would be about 15 to 20 kilometers longer than the ILC. Scientists hope that CLIC can reach much higher energies than the ILC by using a different acceleration technology. It will be another

year or so before scientists will have fi gured out whether the CLIC concept is feasible. But the length of the proposed machine—about 50 kilometers—could make CLIC extremely expensive.

Which one of these three collider designs will be nominated as the LHC’s precision counterpart depends in great part on the discoveries that the LHC will make in the next several years. They will determine how high a collision energy an electron or muon collider must achieve.

Particles live at different energy scales, measured in TeV, or Tera-electronvolts. Thanks to Fermilab’s Tevatron collider and generations of particle accel-erators before it, scientists know which particles live at which energies—up to a certain energy level. Beyond that point, the energy realm is unexplored territory, and scientists think there is a bonanza of particles waiting to be unearthed.

Results from the LHC, a machine that could reveal particles as heavy as a few TeV, will tell scientists where to go digging. Right now, they’re wondering whether the LHC’s most interesting discoveries will be at less than half a TeV.

“If the answer is ‘yes,’ then the International Linear Collider is the way to go,” Shiltsev says. “If the answer is ‘no,’ then there will be a choice between CLIC and the muon collider.”

CLIC could reach energies of up to 3 TeV. Scientists developing the muon collider are aiming for energies up to 4 TeV, about the energy of the most powerful quark-quark collisions at the LHC.

Higher energies typically lead to higher costs. But the compact size of a circular muon collider has the potential to be cheaper than the ILC or CLIC.

“The muon collider is quite tiny for the same energy as the LHC,” Palmer says. “It would easily fi t on the Fermilab site. It would even fi t on the Brookhaven site.”

The challengeTo make the muon collider a real contender as the next particle collider, scientists will have to show that the machine can attain a good deal of some-thing called luminosity.

Making a muon beamScientists create large numbers of muons by steering an intense proton beam into a target made of a dense liquid such as mercury. A set of magnets gets the resulting muons moving in the right direction. The challenge is to corral the muons into dense beams. Physicists are developing a technique known as ionization cooling. It tames muons by sending them through a series of magnets and absorbers fi lled with gas. The gas slows the muons and absorbs their energy while the magnetic fi elds confi ne the muons and narrow the beam. Acceleration devices then pro-pel the muons forward. This process is repeated many times until the muon beam is almost laser-like.

Slow beam Slow beamAccelerate forward Accelerate forward

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Luminosity is a measure of how many collision events your machine can produce per second. To increase the chances of seeing interesting events, colliders must have as much luminosity as possible. To achieve that, you need lots of particles traveling through your accelerator, and you need them to be contained in compact, dense packets, called bunches.

Loose bunches of particles cannot effectively collide. It would be similar to throwing two handfuls of rice at each other from far away and hoping a few grains hit each other.

Wrangling ephemeral muons to form tight bunches and speed around a ring is tougher than herding cats. To create those bunches, particles have to be cor-ralled, or cooled, as the process is called in physics. For the muon collider, successful cooling is the single greatest engineering challenge facing scientists, and they will have to draw on bold ingenuity to get it done.

In nature, muons come to us from cosmic rays. For a muon accelerator, scientists would create muons by smashing protons into a dense liquid such as mercury. Muons born from these human-made collisions are an unruly bunch, fl ying every which-way with every which-energy.

“It’s been described as a pumpkin-sized beam,” Geer says. “You can’t put that immediately into an accelerator.”

Two experiments—MuCool at Fermilab and the Muon Ionization Cooling Experiment at the Rutherford-Appleton Laboratory in Oxfordshire,

England—are dedicated to advancing techniques for muon cooling.

The aim is to shrink a pumpkin-sized beam into a millionth of its volume in two millionths of a second, well before the muons decay into electrons and neutrinos.

“We do beam cooling all the time with beams of other particles,” Geer says. “But the present tech-niques take far longer than a couple of microseconds. We need a new technique that takes a very short period of time.”

One of the techniques under consideration looks particularly promising: ionization cooling. It tames muons by sending them through a series of magnets and containers fi lled with liquid hydrogen, for example. As the muons repeatedly collide with the hydrogen, it absorbs the muons’ frenetic energy while the magnetic fi elds confi ne the particles and narrow the beam. Acceleration devices then propel the compressed beam of muons forward. This pro-cess is repeated until the muon beam is almost laser-like, ready for injection into the main accelerator.

Although cooling is only one of the big hurdles scientists face, the muon collider community is rather optimistic that it can overcome all engineer-ing challenges.

“We are right on the cusp of knowing how to solve the problems that we’ve been talking about for so long,” Palmer says. “And now, we’re getting to the point where we see how the thing is actually possible.”

Proposed particle collidersParticle physicists are considering three types of particle colliders for reach-ing higher collision energies. Their relative sizes are shown at right, with the Large Hadron Collider for compar-ison. A 4-TeV muon collider would be only a couple of kilometers in diam-eter and fi t on the Fermilab site, but it still faces many engineering chal-lenges. The well-advanced design of the International Linear Collider, which would make electrons and positrons collide at 0.5 TeV, calls for a 30-kilometer-long machine. Also under consideration is a 3-TeV electron-positron collider known as the Compact Linear Collider, or CLIC. If technically feasible, it would be about 50 kilo-meters long. In comparison, the Large Hadron Collider in operation at the European laboratory CERN has a cir-cumference of 27 kilometers and is more than eight kilometers in diameter.

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First stage: Project XTaking into consideration the decades it takes to plan and build a large particle accelerator, high-energy physicists hope to keep pace with the LHC and choose between an electron and muon collider in the next several years.

“One of the enormous potential strengths of the muon collider is that you can imagine a stageable program,” says Geer. “You can start Project X here at Fermilab, build a muon facility, build a neutrino factory, and you end up with a muon collider. There’s a rich array of possibilities.”

Project X is a proposed high-intensity proton accelerator at Fermilab. Its main purpose is to provide an intense proton beam for a number of kaon, muon, neutrino, and nuclear physics experiments. Ultimately, the Project X accelerator could serve as the front end of a muon collider and deliver an abundance of protons, the raw material for producing muons.

The next stage would be a muon facility that cools and accelerates the muons produced by Project X. This would allow for the construction of a neu-trino factory, an official component of the Muon Accelerator Program. In a neutrino factory, an intense beam of muons would circle in a storage ring until the particles decay into electrons and neutrinos, ghost-like particles that might explain the evolution of the early universe and the abundance of matter over antimatter.

“On the way to building a muon collider, we will

have a great opportunity to build a neutrino factory,” says Bross.

As its name indicates, a neutrino factory would provide physicists with a plentiful supply of the hard-to-catch neutrinos.

“Each muon creates two neutrinos for science,” says British physicist Ken Long, chair of the International Design Study for the Neutrino Factory. “The muon collider and neutrino factory are a mar-riage made in heaven.”

The last stage would be the construction of the muon collider ring, which would send two beams of muons in opposite directions and make them collide. It would be built while earlier stages of the accelerator complex were already providing the physics commu-nity with scientifi c programs that could be continued with or without the collider itself.

This staged approach to the muon collider—a machine that seemed an unlikely possibility only 10 years ago—is now an idea that physicists and funding agencies deem worth investigating.

At the moment, the muon collider may still be trailing the electron colliders in R&D efforts. But if scientists succeed, it will be “one heck of a machine, which is why the idea hasn’t died in the forty-plus years it’s been around,” says Shiltsev.

“At some moment years away, we hope to be at the level where we can, with a light heart, say that we believe we can build this muon collider,” he says. “It will be a superb machine for high-energy particle physics.”

Expansion of the Fermilab accelerator complex: conceptual layout

Project XAccelerate protons to 8 GeV using superconducting radio-frequency (SRF) cavities. Protons would be used for low-energy experiments and sent into the existing Main Injector to create high-intensity neutrino beams.

Compressor ringReduce size of beam before it hits target.

Muon production targetSmash protons into target material, generating muons with energies of about 200 MeV.

Muon capture and coolingCapture, bunch, and cool muons to create a tight beam.

Initial muon accelerationIn a dozen turns, accelerate muons to 20 GeV. These muons could power a neutrino factory.

Recirculating linear acceleratorIn a number of turns, accelerate muons up to 2 TeV using SRF cavities.

Muon colliderBring positively and negatively charged muons into collision at two locations 100 meters underground.

For an animated version of this graphic, visit www.fnal.gov/muoncollider/animation.html

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TO CATCHA SUPERNOVA

New 3-D simulations of Supernova 1987A show rings of material leaving the star at 62 million miles per hour. Observations of 1987A were the fi rst to confi rm that core-collapse super-novae emit neutrinos. Image: European Southern Observatory/ L. Calçada

BY CALLA COFIELD

TO CATCH A SUPERNOVA

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SOME EXPLODING STARS RELEASE BURSTS OF ODDBALL NEUTRINOS. SCIENTISTS WITH THE LONG BASELINE NEUTRINO EXPERIMENT ARE EAGER TO CATCH THOSE NEUTRINOS AND MILK THEM FOR DISCOVERIES. BUT THEY MUST WEIGH THE BENEFITS OF DOING THAT AGAINST THE RISK THAT NOTHING WILL HAPPEN—NO SUPERNOVA, NO NEUTRINO BURST—DURING THE EXPERIMENT’S 50-YEAR LIFETIME.

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IN THE WEE HOURS OF THE MORNING ON MARCH 7, 1987, BOB SVOBODA WAS COMBING THROUGH DATA, LOOKING FOR THE ANSWER TO A QUESTION ABOUT ONE OF THE MOST EXOTIC EVENTS IN OUR UNIVERSE.Normally, such an answer reveals itself gradually over time; but this night was different. Around 2 a.m. he picked up the phone and started waking his colleagues.

Svoboda was a postdoctoral researcher at the University of California, Irvine working on the Irvine-Michigan-Brookhaven, or IMB, nucleon detector and neutrino observatory. IMB was set up to detect proton decay, but the apparatus doubled as a neutrino detector. Neutrinos are perhaps best known as the subatomic particles that rarely interact with other forms of matter; the steady fl ow of them produced by the sun passes through the Earth like a parade of ghosts. Out of those many trillions of trillions of neutrinos, IMB collected about two a day.

But on one fateful night, researchers had reason to think this number had abruptly increased.

On February 23 the International Astronomical Union’s Central Bureau for Astronomical Telegrams had reported a star explosion—a supernova—just outside the Milky Way galaxy. Telescopes quickly turned to watch the star’s violent death in the Southern Hemisphere. It was the fi rst supernova in 383 years that could be seen with the naked eye. Dubbed 1987A because it was the fi rst supernova of that year, this was a core-collapse supernova,

Bob Svoboda is a physicist at the University of California, Davis, co-spokesperson for the Long Baseline Neutrino Experiment, and supernova neutrino hunter.Photo: Bradley Plummer, SLAC

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Top: Framed on Bob Svoboda’s office wall is an actual IMB data chart from February 23, 1987. A spike in the neutrino count is clearly visible at the moment that IMB captured supernova neutrinos from 1987A.

Bottom: Combined optical images from the Hubble Space Telescope and X-ray images from the Chandra X-ray Observatory illuminate the remnants of 1987A. Image: (X-ray) NASA/CXC/PSU/S. Park and D. Burrows.; (Optical) NASA/STScI/CfA/P. Challis

meaning its massive outer shell, weighing nearly 10 times the mass of the sun, had come crashing down onto the star’s burnt-out core. The impact of the collapse would release a mind-boggling amount of energy, and at the time some models of supernovae predicted that this energy might convert into neutrinos. The only way to know for sure was to directly observe neutrinos coming from a supernova burst.

Svoboda and the UC Irvine group were the fi rst IMB collaborators to respond to the news. They requested data from the detector site, an old Morton salt mine outside Cleveland, Ohio. When it fi nally arrived by FedEx, the group spent four days in the lab, barely sleeping, combing the data from February 23 onward for a sign of a neutrino spike. They found nothing.

Their hopes rose when they got a tip that the Large Scintillation Detector in Italy had picked up a neutrino signal. But again they found nothing (and, in fact, no one was ever able to confi rm the LSDfi ndings). This was a bitter disappointment, consid-ering that supernovae go off in the Milky Way, on average, only once every 50 years, and the last recorded supernova visible from Earth was in 1604. IMB seemed to have missed a once-in-a-life-time event.

Svoboda’s wife suggested they try to relieve the disappointment out on the ocean; March is peak whale-watching season in California. It was there that Svoboda realized that he and the team had not looked at a period of time when one of the detector’s power supplies had failed. The analysis software automatically skipped over such periods, so to see it, one would have to alter the software. When the boat docked he hurried back to the lab.

Svoboda was working on the software when he got word that the Kamiokande neutrino detector in Japan had detected a burst precisely during the power supply failure time. With the altered software he immediately ran the data from the correct time, and saw what he’d been hoping for.

“I didn’t even have to analyze it,” said Svoboda. “It was obvious we had a neutrino burst.”

At 2:35 a.m. on February 23, eight neutrinos had collided with the detector in a matter of six seconds.

The team once again assumed a schedule of barely sleeping, rushing to get their observations ready for publication. To ensure that the work would be published simultaneously with that of their colleagues at Kamiokande II, they had a messenger fl y from California to New York and hand deliver the draft.

A total of 24 neutrinos had been collected—eight by IMB, 11 by Kamiokande II in Japan, and fi ve by the Baksan Neutrino Observatory in Russia. The news of the supernova was on the cover of most major newspapers, and a cover story in Time magazine mentioned the neutrino search.

The neutrino data shook astrophysics and rippled through the larger physics community. Any theoretical model of supernovae that didn’t take into account neutrino emission had to be scrapped. For astrophysicists studying supernovae, the neutrino data was a revelatory shaft of light. In the 23 years since its publication, hundreds of papers have been written about those 24 particles.

If two dozen supernova neutrinos could do that, imagine what tens of thou-sands could do.

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THE NEXT DETECTORA lot has changed since 1987. Astronomical tele-grams go out over email, and large data sets travel almost instantly over the Internet. Svoboda is now a physics professor at the University of California, Davis, a leader in the fi eld of neutrino physics, and co-spokesperson for the Long Baseline Neutrino Experiment, or LBNE, which would be one of the most ambitious neutrino experiments ever undertaken.

The plan is to build a neutrino detector with ten times the neutrino-sensitive material of any that exists today, and install it in the proposed Deep Underground Science and Engineering Laboratory, DUSEL, which would be the deepest science facility in the world. LBNE would collect and study neutrinos from a beam generated at Fermilab, which, when built, would pack in more neutrinos per square inch than any neutrino beam before, allowing an unprec-edented rate of data collection.

Besides being one of the most elusive particles in the universe, neutrinos are also one of the most abundant, and our understanding of neutrinos is a critical part of our understanding of the universe as a whole. Many of LBNE’s scientifi c goals will address basic questions about neutrinos, such as those surrounding their masses. Via this advanced study of neutrinos, the collaboration will also take a crack at other major questions in modern physics, including the fundamental relationship between quarks and leptons (and hints at a grand theory of unifi cation) and CP violation (how did matter survive after the big bang?). It may also look for relic neutrinos left over from the many core-collapse supernovae that have been going off in the universe

almost constantly since the beginning of star and galaxy formation. Now LBNE is approaching a critical moment: deciding what kind of detector

it should build. Three basic designs exist, although LBNE will have the opportu-nity to add its own details. Groups of LBNE scientists around the country are evaluating how each design could benefi t the areas they wish to study.

One of those scientifi c areas, much to Svoboda’s delight, is supernova neutrino physics. A team of researchers led by Kate Scholberg of Duke University is conducting simulations to determine the best design for catching supernova neutrinos and fi gure out how to wring the most information out of them.

“Right now we’re trying to reduce that vast landscape of possibilities into something that’s very concrete,” says Svoboda. “It’s a combination of what science we would like to do and what we can afford.”

The next time a core-collapse supernova goes off in our galaxy, LBNE and other major neutrino detectors around the world stand to collect hundreds of thousands of neutrinos. But physicists want more than a neutrino headcount. They’re after detailed readings on the energies of neutrinos, and that requires special equipment capable of receiving short, strong bursts of particles, the ability to glean a great deal of information from them, and the computing power and data storage capacity to record it all. And that will cost money.

The LBNE construction budget is not yet fi nalized, but will land above $1 billion. The 300 or so LBNE collaborators plan to present their scientifi c report, including a rough budget estimate, to major funding agencies in December—one step in the lengthy process of getting construction approval. Svoboda and

Only about one in 1016 neutrinos will interact with a neutrino detector such as LBNE. The proposed DUSEL facility will protect detectors from cosmic rays and other stray particles that could obscure the faint neutrino signal. Image: Sandbox Studio

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DEEP UNDERGROUND SCIENCE & ENGINEERING LABORATORYDUSEL

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his LBNE co-spokesperson Milind Diwan, a researcher at Brookhaven National Laboratory, will include supernova neutrino burst capabilities in their pitch in December. Many of the requirements are already built into the LBNE plan because they enable other science goals of the machine, and Diwan says ultimately the fi nancial investment for catching supernova neutrino bursts is relatively modest. Right now, he says, “it looks like the collaboration would like do that. That’s not such a big deal.”

The monetary investment may be small, but LBNE has a serious risk to con-sider: there is no guarantee that a supernova will go off within the lifetime of the experiment and send neutrinos fl ying into the specially equipped detector.

An estimated 20 supernovae go off in our galaxy every 1000 years (or about one every 50 years), but there is no mechanism driving this estimate or formula for predicting when the next one might occur. What’s more, only one type of supernova—a core-collapse—generates such large bursts of neutrinos, and that burst must occur within the Milky Way; otherwise only a handful of neutrinos would reach detectors on Earth. To make the investment worth the risk, the data set would have to be something very special.

A TREASURE CHEST OF DATAIn 1987 scientists weren’t even sure if supernovae emitted neutrinos. Now these neutrinos may unlock mysteries in particle physics, astrophysics, and nuclear physics.

A neutrino carries a certain amount of information about the event that pro-duced it. Through the study of solar neutrinos, scientists have deduced a great deal about the inner workings of our sun, including exactly what kind of nuclear processes keep it burning. Supernova neutrinos hold the promise of

To get an idea of what scientists are up against when studying supernova neutrinos, imagine that a piece of string connects each neutrino to its point of origin. As the particle heads out into space, we can follow the string to see where the neutrino came from and where it has been. Because neutrinos from the sun don’t interact with other matter or with each other, their strings are straight, smooth, and easy to follow.

But supernova neutrinos are another story, because they do interact with each other. When two neutrinos interact, or “couple,” their strings tangle together. Each neutrino goes on to couple with a series of other neutrinos, until the imaginary strings of all 1058 neutrinos twist and knot into a mess that would make untangling Christmas lights seem like a walk in the park.

And it gets more complicated. These interactions fundamentally alter the way a neutrino changes fl avor, or transforms from one of the three basic neutrino types into another, which normally takes place independently.

Simulating the behavior of the nice neat neutrinos coming from the sun is what’s called a linear problem; the behavior changes in a simple, predictable way. But the path of a super-nova neutrino is a non-linear problem, meaning small changes in the environment can cause drastic, complicated changes in the behavior of the subject. “That’s sort of the legacy of non-linear systems,” says George Fuller of the University of California, San Diego, “They’re squirrely.”

THE DOUBLE LIVES OF NEUTRINOS

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A TREASURE CHEST OF DATA

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carrying similar information about what goes on inside an exploding star. Those explosions are thought to produce all the heavy elements in our universe—elements crucial for life as we know it—but major uncertainties surround this theory. Learning about the processes taking place inside a supernova might settle some of the debate. This information will most certainly increase scientists’ understanding of those intense nuclear reactions and feed into the study of nuclear physics, which has applications in energy research.

This multidisciplinary appeal is one of the central reasons that Diwan thinks funding agencies will get behind the necessary upgrades to the LBNE.

“Anytime some science is of interest to multiple disciplines there is something interesting going on there,” Diwan says. “We really need to understand why and how this thing works, because nobody has a complete picture.”

For years after 1987A shook up the study of supernovae, scientists have tried to create a picture of what is going on inside these dying stars, and what life there might be like for neutrinos. In the late 1980s George Fuller was a graduate student in neutrino physics, and saw the fi eld suddenly receive the attention not only of the public, but of both particle physicists and astrophysicists. The result, he says, were a lot of projections about supernova neutrinos that were “just plain wrong.”

Fuller drifted away from the fi eld for a few years, but returned as a popula-tion of specialized supernova neutrino physicists began to emerge. He was there at the turn of the 21st century when he and his colleagues began to suspect that something very peculiar was happening to supernova neutrinos. And when computer technology fi nally caught up with theory and supernova neutrino computer models were created, Fuller saw the fi rst shocking results.

Neutrinos, it turns out, lead double lives. The neutrinos we know on Earth–those that come from the sun, from radioactive material in the Earth, or from cosmic ray collisions in the upper atmosphere–are ghostly, anti-social individ-uals. Most of them pass right though our bodies, cars, buildings, and indeed through the center of the Earth without interacting with other matter. That’s why a detector like LBNE can record only about one in 1016 (ten thousand trillion!) neutrinos. This is a characteristic no other subatomic particle exhibits to such an extreme degree.

So imagine physicists’ surprise when they began to realize that if neutrinos are packed together tightly enough, they become social, interactive party animals.

This unusual behavior can only take place in an extreme environment—the inside of a supernova is currently the only one we know of, and may be the only one we are ever able to detect. The models of core-collapse supernovae show that when the outer layers of the dying star come crashing down, 99 percent of that energy turns into neutrinos. If the sun provides a shower of neutrinos and a man-made neutrino beam is a neutrino fi re hose, then a supernova burst is a veritable neutrino tsunami. The force of the collapse packs the particles together so tightly that for a moment there are more neutrinos per cubic inch than electrons. In that intensely crowded environment, the neutrinos no longer act like their typical selves. They begin to scatter off each other, touching and colliding much as other forms of matter do.

This scattering induces another odd behavior: neutrino coupling, in which the neutrinos don’t just collide, but become linked. After two coupled neutrinos part ways, they may each couple with another neutrino, connecting all four of them. As the coupling continues, the entire body of 1058 neutrinos becomes connected.

When neutrino fl avor changing, or the spontaneous switching of identities from one of the three types of neutrino to another, is taken into account, coupling

New supernova simulations reveal “con-vective blobs” that emerge from the star’s core as it explodes. The energy deposited by the neutrinos as they course out of the core drive these blobs. This particular supernova has the potential energy of 25 trillion trillion nuclear weapons.Image: A. Burrows and J. Nordhaus, Princeton; H. Childs, UC Davis

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increases to such a degree that large clumps of neutrinos may all change fl avor together, rather than randomly, as individuals. But is there a connection between the fl avor-changing behavior of neutrinos and their peculiar coupling? What can this tell us about neutrino physics, or about other events that release neutrinos?

“We don’t know all the answers right now, and we don’t have predictions for the supernova neutrino signal that are set in stone,” says Alexander Friedland, a supernova neutrino physicist at Los Alamos National Laboratory in New Mexico. “I predict in the next couple of years there will be a lot more interesting results found, and we’ll gain a more defi nite picture of supernova neutrinos. But right now we have this wonderful Wild West period of discovery.”

The unique journey that neutrinos take on their way from a supernova to Earth may deeply impact LBNE. (See illustration, page 21) In order to deduce what happened at the neutrinos’ source, scientists must be able to untangle the neutrinos’ paths and understand how scattering and coupling may have altered these particles. Supernova neutrino physicists like Friedland, Scholberg, and Fuller, along with colleagues including Huaiyu Duan, now a professor of physics at the University of New Mexico, will guide LBNE in this regard. Fuller and his group at the University of California, San Diego have accomplished one major step in this process by untangling the path of a single supernova neutrino. Although there is more work to be done to refi ne their results, their computer models can now tell LBNE physicists what to expect from supernova neutrinos, and how to be better prepared to catch them.

LOOKING FORWARDSvoboda thinks the fi eld is ready for a new set of data from hundreds of thou-sands of supernova neutrinos, and that LBNE is the best machine to gather it. Talking to Svoboda about the possibility of catching a supernova blast is like talking to a kid anticipating Christmas. His enthusiasm for the subject, for the possibilities this data might hold and for the chance to follow up on the discovery that started it all, is infectious. Diwan doesn’t have the personal connection thatSvoboda has to supernova neutrinos, but he arrives at the same conclusion: the impact that the last batch of supernova neutrinos had on the physics com-munity was deep and long lasting, and the benefi ts of preparing LBNE to catch another batch are, he says, “crystal clear.”

To maximize the chance of doing that, scientists plan on running the LBNEdetector for at least 50 years. But that will be a policy decision, up for re-evalu-ation every ten years or so.

Over the course of those decades, LBNE will operate two separate detectors, with at least one of them running at any given moment. Friedland expresses a deep anxiety of his fi eld when he says it would be too bad if LBNE never saw a core-collapse supernova go off in the Milky Way, “but it would be a tragedy if one went off while LBNE wasn’t prepared.”

His sentiment rings true for the small community of supernova neutrino scientists around the world, who love the fi eld they study but will always run the risk of never seeing another real data set in their lifetimes.

Fuller, who is working with Scholberg on her detector analysis, is hungry for data, and aware that the rarity of supernovae poses a signifi cant challenge to getting it.

“A funding agency will never give us a stand-alone supernova neutrino detector,” he says. “And we accept that this machine should have a day job, so to speak.” LBNE will essentially moonlight as a supernova neutrino detector, leading a double life not unlike those of the neutrinos Fuller hopes it will catch.

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Thomas Van Cleave brings multiple perspectives to the group as a county board member and a resident of a neighborhood across the road from Fermilab.Photos: Reidar Hahn, Fermilab

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BY TONA

KU N Z

COM M U N ITY+

LABORATORY

Fermilab has joined up with local residents to think

about the best ways for the lab to serve not only science,

but also the surrounding area.

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planning a project a decade ago, Fermilab told its neighbors they might want to prepare for a little construction noise. In retrospect, that wasn’t the greatest decision, even though the project took place entirely within the lab-oratory’s boundaries.

For one thing, the heads-up to local residents didn’t come until the laboratory had already signed contracts to blast thousands of tons of rock and dirt into the air for a tunnel to house a neutrino detector.

For another, Fermilab had announced that the blasting would sound to neighbors “like distant thunder.” Actually, in certain weather conditions it sounded like a semi-truck driving through their living rooms. Blasts rattled windows and had neighbors fearing for the safety of their homes’ foundations.

Although, ultimately, homes suffered no damage and the blasting eventually ended, the experience had shaken Fermilab’s credibility and good com-munity relations.

Former project manager and Fermilab Associate Director for Research Greg Bock remembers, “When we fi nally met with the neighbors it was a good inter-action, but it was a little late in the game.”

The laboratory doesn’t plan to make that mis-take again.

In 2004, Fermilab convened a task force of local residents to advise on how they’d like to interact with the laboratory when issues arise that affect both the community and Fermilab. Neighbors said they wanted an earlier heads-up on large projects and a much closer working relationship with the laboratory on a wide range of community-related

issues. Fermilab listened. The laboratory asked friends and former foes from

more than half a dozen nearby towns to join task forces to review plans for future projects, make recommendations for laboratory planning and deci-sion-making, and serve as community liaisons. By mid-2010, Fermilab’s third task force was just warming up.

“I’m all for lack of confl ict”Late one evening in June, Bock once again found himself explaining a possible on-site tunnel digto neighbors. Only this time construction wouldn’t start for three to four years and neighbors would have ample opportunity to weigh in on the process.

“And we think we will really benefi t from that,” Bock said.

The 24 advisory board members around the table ranged in age from late teens to retirees and captured the multi-ethnic nature of the area, as well as the mix of blue- and white-collar workers, stay-at-home parents, educators, and local offi cials. They offered the viewpoints of not-in-my-backyard activists, small-town politicians, retirees, young professionals, educators, environmentalists, and business owners.

In the years since Fermilab has embraced public participation, these local task forces have vigorously debated a wide range of issues and allowed Fermilab to incorporate community perspectives into planning and operations.

“I’m all for lack of confl ict,” said Elaine McCluskey, grinning as the group peppered her with a list of questions she should prepare to address. She’s proj-ect manager for the Long Baseline Neutrino Experiment. The LBNE project will require a new tunnel whose construction will take place even closer to an adjacent neighborhood than the previous tunnel. It will also require new buildings visible from

WH E N

> Fermilab physicist Rob Plunkett explains safety precautions planned for an upgrade of the neutrino beam that runs from Fermilab to the NOνA experiment in Minnesota.

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adjacent neighborhoods.The idea behind the community task forces is to

hear and address hard-hitting questions and concerns now, while change is physically and fi nancially possi-ble, rather than waiting until neighbors fill the letter-to-the-editor sections of newspapers and light up the Fermilab switchboard with irate calls.

“Decisions that get made in the conceptual phase will affect how things move along,” says task force facilitator Doug Sarno.

Using a short on-site tunnel, LBNE will shoot a beam of harmless neutrino particles through the earth for a distance of more than 1000 kilometers to the world’s largest particle detectors, likely housed in a proposed underground laboratory in Lead, South Dakota. The project will assure Fermilab’s place asa world leader in neutrino research and is the fi rst of several construction projects the laboratory plans for the next decade. The task force will learn about and contribute to all of these projects in their early planning phases and provide ongoing feedback during design and construction.

Involving neighbors in project planning early in the design phase was a recommendation of the fi rst pub-lic participation group six years ago. Deciding exactly when and how the task force and the laboratory should share that information with the wider commu-nity remains an ongoing debate, with everyone agreeing to err on the side of sooner rather than later.

“Timing is critical,” says task force member Joe Suchecki. “If you wait too late, residents feel left out.” He pointed to an instance in which managers of an area forest preserve brought completed design plans before residents for comment. “The residents said ‘Well, why are we here if this isn’t going to change?’” Suchecki recalls.

In return for giving up evenings with their families, the task force members gain the rare opportunity for meaningful participation in “Big Science.” They gain a voice in a scientifi c enterprise that is an eco-nomic engine for the Illinois area, a key element in US competitiveness, and a partner in the global search for knowledge of the fundamental physics of the universe.

Some members joined the task force not knowing

a quark from a quack, but wanting to make sure development fi ts with community standards. Others love science and saw a chance to learn more about a rapidly changing fi eld of physics. Some were drawn by the economic impact of the laboratory, or by the need to protect their property values. Still others toured the laboratory as children and wanted to make sure it maintains a sustainable path.

They all have questions: Why do you have to do this here? How will your plans affect my quality of life? Why is this a good investment for US taxpayers?

And they want facts to back up those answers. A response from a scientist that Fermilab had weighed costs for different tunneling methods to min-imize construction length and noise brought nods of approval. But it also brought the comment that the public would want to see the facts and fi gures that went into that decision, not just hear the fi nal choice.

The discussion highlighted a new attitude toward science. Gone are the Cold War days when the public deferred to scientists’ views and plans without signifi cant scrutiny. Today they wanted to peer into the process and judge for themselves the value of everything from particle-physics construction plans to climate-change studies.

Task force member Tim Klaus brought home the point while discussing the group’s tour of the lab’s MINOS experiment tunnel, which illustrates the type of construction LBNE will require on the Fermilab site.

“When you were talking about making sure the water goes back into the tunnel and not into the groundwater, the fi rst thing that popped into my head is: ‘That is probably what BP said.’ So just be prepared for people to not take you at face value and to want transparency,” he said.

“To lie dormant for three to four years would be wrong”Municipalities often create community task forces to solicit input for school and park developments, and government zoning changes require early oversight on myriad projects. Similarly, in the rarefi ed world of large high-energy-physics laboratories, public participation is gaining ground.

Switzerland-based CERN holds informational

>Left: An overview of Fermilab’s accelerator complex shows the routes taken by an existing neutrino beam to the NOνA experiment in Minnesota (orange) and by a proposed neutrino beam to the LBNE experiment in South Dakota (blue). Right: Board members visit the NuMI tunnel, where neutrinos rush through, unnoticed, on their way to Minnesota.

meetings with French and Swiss elected offi cials and townspeople who live along its 27-kilometer accelerator ring.

When Japan’s KEK laboratory had to tear down a forest to construct a new physics research campus, it invited residents to join in planting replacement trees. Japan also started a campaign to establish a science culture in Tsukuba, the town nearest the laboratory, in part to increase the cosmopolitan nature of the area to attract foreign physicists.

In Germany, preparation for the TESLA project at DESY entailed communicating with neighbors in 15 communities about six years in advance of the expected formal project approval. A TESLA research campus would have occupied the center of Ellerhoop, and the small town’s residents were wary. But through strong communication, they grew to embrace the plan, and were disappointed when the TESLA project was scrapped in 2003 for a different project, the European X-ray Laser Project XFEL. The quick shift left DESY staff with little time to consult with XFELneighbors. The result was pickets and protests.

However, all those efforts involved specifi c projects or experiments that would extend beyond laboratory boundaries and thus require cooperation or oversight from local governments. Fermilab’s future plans fi t within the laboratory’s boundaries and within state and local regulations, yet the laboratory still solicits community input.

Fermilab also wants to hear from task force mem-bers about more than brick-and-mortar concerns. Task force members look at the big-picture question of the appropriate role for the United States in international high-energy physics and at Fermilab’s role as the nation’s only national laboratory devoted entirely to that fi eld. Such science-policy questions affect the daily lives of those living near the labora-tory in ways that they and scientists are working to understand.

“We are really seeking advice on how to proceed so that each aspect will be successful for the lab and everyone around it,” Sarno says.

Fermilab hopes to avoid the kind of disconnect

that occurs when laboratories focus only on one-way outreach and try to deduce the temperament of the community from limited comments by science-minded attendees at open houses and science education events. Scientists and non-scientists tend to view the world through different prisms of experience, just as parents and non-parents do, or country and city dwellers.

When scientists told the Fermilab task force during a July meeting that they thought the community was well aware of the science Fermilab does and the fact that it has a vibrant portfolio of research plans, they were met with a resounding “No” from members.

“The overriding impression I get from people is that they think the lab is almost closed,” said task force member Mike Herlihy. “To lie dormant for three to four years would be wrong. You need to communicate that there is interest in the lab and its science, that there are plenty of things to discover, and that the lab is viable.” That will make all future conversations easier, he added.

Later, a fl urry of horizontal head shaking followed a physicist’s comment that neighbors could wait for answers to questions about LBNE, as they had with an earlier Fermilab neutrino experiment, until publi-cation of the required environmental documentation for the project.

Through the lens of bureaucratic procedure and vetted research, physicists see these documentsas offering the most accurate answers. Until all the data is in, earlier answers would be speculative and, at worst, wrong.

But through the lens of a non-scientist who watched the Katrina and BP emergency responses on TV, waiting seems suspicious; they want to be part of watching the answers evolve.

“As a resident I would not want to wait for that environmental assessment and then be like ‘Oh my god’,” said Herlihy, whose role as a city councilman has exposed him to residents complaining about a lack of government transparency and foresight.

This time, Fermilab won’t be keeping the neigh-bors waiting.

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> Above: Board members Mollie Millen, a county plan commissioner, and John Fildes, a Batavia resident, discuss community views of Fermilab’s science. Right: The board gets briefed on proposed future experiments.

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day in the life: peter kasper

For birders, it all comes down to that moment. Focus your binoculars, steady your hands, and look, hard, until you fi nd that glimpse of feathers, a spark of recognition.

“Do you see it?”Peter Kasper points over the fi eld and across,

to where the caps of Queen Anne’s Lace dance in the breeze and a discerning eye can just make out a slight brown blob—a Henslow’s Sparrow, an uncommon bird in the state of Illinois.

Fermi National Accelerator Laboratory is home to more than 280 species of birds, including several endangered species, and a way station for unusual migrants.

Accelerator physicist Peter Kasper monitors the site avidly. He has been birding since the fourth grade, when he saved up pocket money for bin-oculars and one of the fi rst bird books ever written for his home country, Australia. While he joins in far-fl ung expeditions across continents with fellow birders and physicists, it’s Fermilab that he prowls with binoculars every week. He knows the birds that come and go like old neighbors or friends.

“In the early years, it was really an exploration,” Kasper says. “Now I know this site like the back of my hand.”

When Kasper joined the Accelerator Division at Fermilab in 1986, he encountered 6800 acres of land that were rich in potential for birding discoveries.

The laboratory has been a haven for naturalists and ecologists since at least the 1970s, when Professor Robert Betz of Northeastern Illinois University began leading a project to restore Fermilab’s prairie land. Volunteers, including lab and local park district staffers and nature enthu-siasts on and off site, formed the Ecological Land Management Committee to promote the restora-tion of the lab’s tall-grass prairie. Later its scope expanded to embrace Fermilab’s woodlands, savannah, and other ecosystems.

“Fermilab has one of the more diverse ranges of habitats—and therefore impressive species richness—of any of the preserves within DuPage and Kane counties,” says Diann Bilderback, for-mer president of the DuPage County Birders Club.

The committee has worked with the lab’s Roads and Grounds Department, which imple-ments its land-management suggestions, to turn the site into a showcase for native plants and a sanctuary for wildlife.

Dave Spleha, who has accompanied Kasper for more than a decade, says, “A lot of Fermilab is closed to the general public. It’s more untouched than local forest reserves.” As a result, he says, the areas that are open for birding “let you see birds that are hard to fi nd anywhere else in the local counties.”

As one of only seven National Environmental Research Parks established by the Department

WORKING IN A BIRDER’S PARADISE BY DAISY YUHAS

Ospreys soar, egrets stalk fi sh, and pelicans fl oat in Fermilab’s natural areas. Pelicans, whose migration route t