dimensions volume 05 of symmetryA joint Fermilab/SLAC publication

issue 05

november 08 volume 05 | issue 05 | november 08

On the cover In the last few months of the BaBar experiment at SLAC National Accelerator Laboratory, scientists pulled one last trick out of their bag and produced a new particle— the bottom-most bottomonium. In doing so, the 500-member symmetryA joint Fermilab/SLAC publication collaboration proved as agile as its cartoon namesake.

Highlights from our blog, www.symmetrymagazine.org/breaking/

Crunch time for Joint First gamma-ray-only Large Hadron Collider’s Computing in a grid Dark Energy Mission pulsar observation ATLAS in Second Life or a cloud October 14, 2008: Last October 16, 2008: About October 22, 2008: A dedi- October 24, 2008: With month’s surprise cancella- three times a second, a cated LHC fan has recre- two relatively new models tion of the competition 10,000-year-old stellar ated the ATLAS experiment of computing floating about, to develop the Joint Dark corpse sweeps a beam of from the LHC in Second many commentators have Energy Mission left gamma-rays toward Earth. Life. This is done in the spirit been discussing the pros researchers stunned. Now This object, known as a of fan art, but I can tell you and cons of each, as if it the former competitors have pulsar, is the first one known from having been in the were a face-off with only less than two months to to “blink” only in gamma ATLAS cavern while it was one likely to be the victor come together and redefine rays, giving scientists new being built that this does a in a fight for dominance. what the mission should insights into how stars work. very good job of the look A new analysis argues that accomplish. and feel of the real detector. the two technologies are complementary. contents

02 Editorial: Starting up the Large Hadron Collider The Large Hadron Collider successfully circulated beams for the first time in September. That wonderful achievement moves the LHC toward first collisions and physics results, but other labs are still working hard in friendly competition.

03 Commentary: Kate McAlpine “I think rap is a good way to communicate. Rhyme has always helped embed words in my mind; hopefully science rap can help cement ideas in the minds of students and other interested people.”

04 Signal to Background Giving a hoot about restoration; open access to galaxies; ask a Nobel laureate; a collider inspires comic artists; Google commemorates the LHC first beam; eclipse chaser; letters.

08 BaBar and the Very Tiny Particle In which the 500 members of the BaBar experiment buy enough time for one last adventure: capturing the bottom-most bottomonium.

14 The Dark Universe Debate Who will be the first to prove the existence of dark and dark energy? A particle physicist and an astrophysicist go head to head.

20 Where Old Physics Stuff Goes to Live The Fermilab boneyard is no burial ground; it’s a place where unwanted parts find new homes and lives. They’re matched with scientists who can put them to good use, donated to local schools and parks, or sold for recycling.

28 Q&A With eta sub b symmetry’s Calla Cofield scores an exclusive interview with the particle…the ground state…the artist eta sub b, who recently emerged into the public spotlight after 30 years in hiding.

32 Essay: Robin Hanson “Today’s LHC forecasts are no easier to score than the typical horoscope.”

C3 Logbook: LHC Startup On September 10, 2008, scientists at the European laboratory CERN attempted for the first time to send a beam of particles around a new , the Large Hadron Collider.

C4 Explain it in 60 Seconds: Quench A magnet quench is a dramatic yet fairly routine event within a particle accelerator. In the case of a large superconducting magnet, such a quench generates as much force as an exploding stick of dynamite. from the editor

failed, causing a magnet to quench and helium Starting coolant to leak. Although this is a setback, to be up the sure, there is nothing too surprising about an incident like this. Essentially all particle acceler- Large ators have suffered similar problems in the Hadron startup process. The LHC is a machine of unprecedented complexity, and no scientist ever Collider expected to just throw a switch and have the On September 10, machine operate. LHC engineers and scientists physicists and physics will repair this fault, start the machine up again, enthusiasts around probably deal with a number of other minor the world watched problems, and then, some time next year, see expectantly as CERN attempted to circulate first collisions. At that time, the science begins particle beams in the Large Hadron Collider for and theorists’ predictions will be under the the first time. Those of us watching from the microscope (see page 32). United States stayed up late and tried to get Meanwhile, there is a world of particle physics one of the precious Web connections to the going on outside the LHC. Over the summer, streaming broadcast of the event. the BaBar collaboration at SLAC released some

Photo: Reidar Hahn, Fermilab In less than one hour—thereby winning LHC outstanding results. Physicists had been looking Project Leader Lyn Evans a bet—the first beam for the lowest-energy state of bottomonium, had made it, sector by sector, all the way around a particle with bottom and anti-bottom quarks, the 27-km tunnel and back to the starting point. for 30 years and finally nabbed it (see page 8). Never had two dots appearing on a computer The “eta sub b” might not have the name recog- screen so excited so many people. (See the log- nition of the Higgs boson, but the story of book in this issue of symmetry.) Later that finding it well illustrates just what it takes to morning, a beam was circulated in the opposite make a discovery in particle physics. direction and the first beam injection for the The answers to our scientific questions LHC was complete, more smoothly and rapidly won’t come only from energy-frontier machines. than most people expected. The successful Astrophysicists are good-naturedly racing to first beams are a testament to the immense beat particle physicists to the discovery of dark effort of a worldwide collaboration of scientists, matter and an understanding of the dark uni- engineers, and support staff. The whole team verse (see page 14). For those physicists trying deserves the flood of congratulations they to be the first to discoveries, the pressure is on received. while the LHC gets back on its feet. But they As symmetry readers are probably aware, had better hurry: The LHC will be up and running the LHC suffered an interruption to the smooth in no time. startup when a faulty electrical connection David Harris, Editor-in-chief

Symmetry Editor-in-Chief Publishers Print Design and Production PO Box 500 David Harris Rob Brown, SLAC Sandbox Studio MS 206 650 926 8580 Judy Jackson, FNAL Chicago, Illinois Batavia Illinois 60510 Deputy Editor Art Director/Designer USA Contributing Editors Glennda Chui Roberta Antolini, LNGS Michael Branigan 630 840 3351 telephone Managing Editor Peter Barratt, STFC Design Assistant 630 840 8780 fax Kurt Riesselmann Romeo Bassoli, INFN Jared Scott www.symmetrymagazine.org Stefano Bianco, LNF [email protected] Senior Editor Illustrator Tona Kunz Kandice Carter, JLab Aaron Grant (c) 2008 symmetry All rights Lynn Yarris, LBNL reserved Staff Writers James Gillies, CERN Web Design and Production Elizabeth Clements Xeno Media symmetry (ISSN 1931-8367) Silvia Giromini, LNF Kelen Tuttle Youhei Morita, KEK Hinsdale, Illinois is published 6 times per Rhianna Wisniewski year by Fermi National Tim Meyer, TRIUMF Web Architect Accelerator Laboratory and Copy Editor Perrine Royole-Degieux, IN2P3 Kevin Munday symmetry | volume 05 issue november 08 SLAC National Accelerator Melinda Lee Yuri Ryabov, IHEP Protvino Web Design Laboratory, funded by the Interns Yves Sacquin, CEA-Saclay Karen Acklin US Department of Energy Calla Cofield Kendra Snyder, BNL Boris Starchenko, JINR Web Programmer Office of Science. Kathryn Grim Mike Acklin Jennifer Lee Johnson Maury Tigner, LEPP Michael Torrice Ute Wilhelmsen, DESY Photographic Services Tongzhou Xu, IHEP Beijing Fermilab Visual Media symmetry Gabby Zegers, NIKHEF Services

2 commentary: kate mcalpine

in the universe that had been commissioned by Rapping NASA. It was also picked up by the press and physics has had tens of thousands of views on YouTube. Jonathan and I both hope to see more sci- A good portion of the ence rap. Maybe it’s just a flash in the pan, or public is curious about maybe this will become another way to get the what is going on in word out about scientific ideas and research. particle physics right One of the challenges in communication and now, and we have an outreach is that it’s often undervalued. Funding ever-longer list of ways can seem hard to justify because already-limited for them to find out— budgets are intended to support research. The from lab newsletters US LHC bloggers aren’t paid for the thought and to personal blogs, popular-level magazines, and time they put into posts. Volunteers often guide plain-language Web sites. public lab tours, and physicists involved in outreach CERN TV has been experimenting with work usually do it on their own time. YouTube since last October, and in late July, my This is part of the beauty of enthusiasm. colleagues and I put particles to music in the Nevertheless, it would be nice if scientists who “Large Hadron Rap,” a slightly goofy project aimed write about their work on blogs or craft articles at educating people about CERN’s Large for an outreach Web site could see those efforts

Photo courtesy of Kate McAlpine Hadron Collider on the French-Swiss border (to valued on an equal footing with the hours they the extent that this is possible in five minutes!) spend coding software, for instance. I think rap is a good way to communicate. It would be nice if we didn’t have to decide Rhyme has always helped embed words in my between hiring an intern to create a public Web mind; hopefully science rap can help cement site and spending that money directly on an ideas in the minds of students and other inter- experiment. But without the Web site, informa- ested people. “Nerdcore” has been on the Web tion about the experiment just wouldn’t be as for a while, fusing “nerdy” from the cultures of readily available to members of the general pub- video games and hard science with the “hardcore” lic, and this would be a greater loss than some of rock and hip-hop. scientists realize. This was not my first science rap; in 2007 I On the other hand, most major laboratories do enlisted fellow interns to perform in “N3UROCH!P,” hire professional communicators and outreach based on the work of two physicists in Tel Aviv coordinators. I’m glad to see that at CERN, at who imprinted rudimentary memories on neurons. least, even the individual experiments are begin- Colleagues, bosses, and friends have been any- ning to hire people who can make their outreach where from baffled to amused at my physics-rap pages more readable and aesthetically pleasing. efforts, but overall I’ve had a lot of help and support. Communication is vital for a field that requires At CERN, Katie Yurkewicz, whose position as large investments of public money. To keep this US LHC communicator I borrowed while she interesting and valuable research funded, we need was on maternity leave, also lent me her camera scientifically aware citizens and politicians. We to film the dancing. James Gillies, head of the need to keep putting information out at a level press office, helped convince the ATLAS secre- that people without specialized training can tariat to let us film in the cavern. Fellow science understand, appreciate, and maybe even dance to. communicators were a bit dubious about dancing at first, but they made it fun with their “experi- Science communicator Kate McAlpine writes about the Large Hadron Collider’s ATLAS experiment for ATLAS e-News. Her mental” moves. Will Barras, a linguistics student nom de rap is alpinekat. at the University of Edinburgh, made the “90s party rap” backing track and mixed my voice. The rap’s surprising popularity started with Adam Yurkewicz posting it on the US LHC blog, where a reporter for The New York Times saw symmetry | volume 05 issue november 08 it and ran a story. Other newspapers and radio stations began picking it up, blogs spread the word, and it garnered millions of hits, along with translations into a number of languages. Two weeks after the “Large Hadron Rap” went online, Jonathan Chase, a science commu- nication student in Wales, posted “Astrobiology 2008—Infotainment,” a rap about the study of life

3 signal to background

Giving a hoot about restoration; open access to galaxies; ask a Nobel laureate; a collider inspires comic artists; Google commemorates the LHC first beam; eclipse chaser; letters.

Home sweet Barn owls stand about a high-quality habitat and the Lifted out of a travel carrier, foot tall. Pepper-like black spots abundance of open grassland,” the owl screeched and bit its and brown freckles dust their Thompson says. “It is one of handler’s leather glove. tan bodies, and white down cov- the longest contiguous pieces The bird was returning to ers their flat, round faces. Their of grassland in the state. We its historic home—and helping pink beaks form sharp Vs below also chose it for Fermilab’s com- to save its species. intelligent black eyes. mitment to ecological health.” Barn owls are endangered The first owl struggled as it With much of its research in Illinois, pushed to the brink by was taken out of its carrier. It machinery in underground tun- pesticides, more tightly sealed flipped upside down and spread nels, the lab is a haven for doz- barns, and the replacement its foot-long wings, flashing its ens of wildlife species and is one of farms by shops and homes. white underside. It screamed of six National Environmental Less than one-tenth of one like a Velociraptor from the movie Research Parks located on percent of the state’s natural Jurassic Park. The second owl Department of Energy sites. prairie remains. was no happier, clacking its beak Thompson plans to release But the restoration of more in protest. more barn owls onto Fermilab than 1200 acres of prairie at One at a time, Thompson property each year; the red barn Fermi National Accelerator carried the owls up a 20-foot is big enough to house a num- Laboratory is giving Illinois its ladder to a box mounted high ber of the birds. Next time, he best shot at keeping and on the inside of the barn wall. says, they’ll wear satellite trans- breeding the owls, says county There they would stay, peering mitters so researchers can track ecologist Dan Thompson. through a screen at the world their movements. Scientists have introduced two outside, until accustomed to the Kathryn Grim year-old males, both born in sights and smells of the lab captivity, to an old red barn on grounds. the lab grounds. “We chose Fermilab for the symmetry | volume 05 issue november 08

Photos: Reidar Hahn, Fermilab

4 signs offering to answer phys- ics questions. Even in a city of people too busy for impromptu sidewalk conversations, the sight was too tempting to resist. “They sat down and asked about the big bang and black holes,” Lederman says. “They were good questions. People were very curious.” Soon about 20 people formed a line down the block. They asked Lederman about the strong force, time and space, fusion, and even time travel. Some asked follow-up questions to get a clearer understanding, while others just seemed thrilled at the chance to meet a Nobel Sloan Survey shares universities, volunteers have Prize winner. starry snapshots been classifying millions of gal- Lederman said he was In the old days, astronomers axies seen in Sloan images. impressed that most people who wanted to use a powerful Making all this data public asked about physics; there telescope had to buy plane “just makes a lot of scientific were no off-the-wall questions. tickets and cross their fingers sense,” says Michael Strauss, The native New Yorker said the weather would cooperate. deputy project scientist for he’d gladly do it again. Image: Sloan Digital Sky Survey “You would apply for time,” Sloan. “There was far more sci- The idea stemmed from says Brian Yanny, a scientist ence than we could do ourselves discussions in late May at the in Fermilab’s experimental anyway.” World Science Festival in New astrophysics group, “and if you The Sloan Web site has got- York about bringing science were lucky you would get ten more than 467 million hits to the streets. Lederman and three to six nights a year.” since 2001. In 2008, it has aver- a film crew set up shop under Astronomers still use tele- aged 10 million hits per month, a few hand-drawn “Ask a Nobel scopes the old-fashioned way. 1.6 million of which are requests Prize-winning physicist” signs But today, all you need to access for data. More than half of in front of a hotel on 34th Street, a decade’s worth of images and the more than 2000 published within view of the Empire State information about the stars is an papers based on data from the building. Internet connection. Fermilab, survey were written by research- Lederman shared the 1988 which handles data for the Sloan ers not directly involved in it. Nobel Prize in Physics for his Digital Sky Survey, makes that Two other projects, the Two contributions to neutrino phys- data available through the Web Micron All Sky Survey and the ics. He is well-known for his to scientists and armchair UK Infrared Deep Sky Survey, book The God Particle and for astronomers alike. are following the Sloan model his outreach and education Sloan surveyed more than a by making all their data publicly efforts. His street-corner debut quarter of the sky using an imag- available. was filmed by ScienCentral ing camera—basically a giant “One of the things we’re in conjunction with the World digital camera attached to the proud of at SDSS is that we Science Festival, and can be back of a 2.5-meter telescope have been the inspiration for viewed in two parts on YouTube. in New Mexico. It also measured the next generation of projects,” Rhianna Wisniewski Image: YouTube the distances to the brightest Strauss says. “One of the les- symmetry | volume 05 issue november 08 one million galaxies in its field sons is: You don’t have to keep of view. your cards close to your chest.” On the survey’s Web site, Kathryn Grim www.sdss.org, you can comb through images looking for Street-corner physics undiscovered comets or new Leon Lederman, a 1988 Nobel classes of stars, or simply find a laureate and Fermilab physicist, cool background image for your plopped a folding table and computer screen. In a related two chairs on a busy New York project called Galaxy Zoo, cre- City street corner and sat ated by researchers at three under colorful hand-scrawled

5 signal to background

Linear Collider came to sell LHC controllers posted in the their own doujinshi promoting accelerator’s electronic log- the project. book a special version of the One, called The Scientist’s Google logo (see bottom Viewpoint, featured physicists’ image), which had appeared reviews of science fiction novels. on the company’s Web site “The scientists have made that day. It’s one of a series of serious explanations, not just logos Google has designed criticizing them as impossible for its search page to cele- or ridiculous things,” Fujino says. brate holidays, historic events, “I think this makes our publica- and other occasions. For more tion very attractive.” The ILC on the LHC first beam, see supporters expected to sell the logbook on the inside back about 20 copies but wound up cover of this issue. selling 150: “I am surprised to Glennda Chui see a lot of people interested in accelerator and fundamental Life’s one eclipse physics,” Fujino said. after another A second publication was On the wall outside Cherrill titled Kasokuki de Go! or Let’s Spencer’s office, a scientific go with the accelerator! It used poster describes a prototype comics, essays, and other for- for a new type of accelerator mats to analyze the personali- magnet; a card thanks her for Image courtesy of Keisuke Mori, ILC Fan Club 2008 Fan Mori, ILC Image courtesy of Keisuke Boosting a collider ties of ILC scientists, based on donating her long hair to make one comic at a time their responses to a question- a wig for an ailing girl; and Comiket—short for Comic naire. “We can feel the sense a scribbled note points to Market—is the world’s largest of closeness to the scientists a spot on a map southeast of comic convention. Held in this way,” Shino Kojima, one Novosibirsk, Russia. It reads, Tokyo, it draws more than half of the founders of the ILC fan “This is where Cherrill will a million people from all over club, says. be on 1st August, 2008 at ~17h the world to buy and sell dou- In both cases, the fans were Siberian time.” jinshi—self-published manga happy just to recover the costs Above it is a photo she shot, and graphic novels. Some of of printing their books. “The from that out-of-the-way spot, of these artists and writers have deadline for the next Comiket a total solar eclipse. become so famous that people is this coming Wednesday, and It’s one of dozens Spencer wait in line for three hours to we are going to prepare the has taken since 1983, when her buy their work. application,” Fujino says. “We will first eclipse, on the island of Getting a ticket to exhibit be here on December 30th if Java in Indonesia, gave her at Comiket isn’t easy, either; we can get the tickets again.” a new focus for planning vaca- sometimes there are six appli- Rika Takahashi tions. Eclipse-chasing has cants for every slot. taken her to Hawaii, Zambia, “I was pretty surprised to get A special recognition Australia, and Libya. She saw a table,” says Masao Fujino, a On Sept. 10, scientists at the the sun wink out from a ship on student at the University of European laboratory CERN the Caribbean and waited in Tokyo Graduate School for Law sent the first beam of protons an English drizzle for the clouds and Politics. He and other fans around the Large Hadron to part—which they finally did, of the proposed International Collider. Forty-six minutes later, for 10 seconds. Image courtesy of the LHC Remote Operations Center at Fermilab symmetry | volume 05 issue november 08

6 “I like to travel,” she says, “and It’s no surprise, then, to hear dimmed, casting an eerie twi- it was an excuse to go to all that she started taking her light over the land, “The animals these places. I choose my total daughter to eclipses at the age thought it was time to go to bed. eclipses based on where they of three. Sierra is now 14, The baboons started chatter- are, and whether I’d like to Spencer says, and “probably ing. They sleep in trees, and they visit that place, and whether holds some sort of record for started arguing about who I’ve been there before.” how young she is and how many gets to sleep where.” As the magnet engineer for total eclipses she’s seen.” Spencer is already planning SLAC National Accelerator The experience is incredi- her next eclipse in July 2009, Photos courtesy of Cherrill Spencer Laboratory, Spencer designs ble, she says, and not just for which she’ll watch with 1600 and follows them the eclipse itself. other people from a cruise ship through construction and mea- In Zambia, her group camped near Iwo Jima. surement. She also puts in along the Zambezi River and With six minutes and 39 sec- many hours as a volunteer for drove three hours at about 10 onds of totality, she says, “This programs that encourage mph—“along the worst road is going to be the longest one in girls and women to take up in the world,” she adds—to our remaining lifetimes.” scientific careers. a national park. When the sun Glennda Chui symmetry | volume 05 issue november 08 letters

More physics license plates

I did not respond in time for the license plate issue, but I do have a good one from an old photo taken while on leave at Caltech in the ’70s. The car (right) belonged to Murray Gell-Mann, Nobel Laureate in Physics. I don't know if he still has it. Gene Sprouse, American Physical Society

I liked the plates shown in the current issue, but I think my Virginia plate is more original—FYZYKZ! Greg Hood, Tidewater Community College, Virginia Beach, VA

I liked your cover showing physics-related license plates. The Maryland plates that I have had for several decades say QUARK. They have initiated many interesting conversations about science, literature, and cheese. Bruce Barnett, Johns Hopkins University

I got this plate when I moved to Brookhaven National Laboratory to work in the theory division. I chose a plate with the gauge group SU(3) x SU(2) x U(1), the mathematical structure that underlies the theory of particle physics. A passerby once asked me if I was a law- yer; he had interpreted the plate as “Sue three, sue two, you won.” Scott Willenbrock, University of Illinois, Urbana-Champaign

To view more physics-related license plates and to submit your own photos and stories, please go to www.symmetrymagazine.org/licenseplates/

7 Postdoctoral researcher Veronique Ziegler is one of five analysts who pulled a new particle out of a deep pool of BaBar data.

Photo-illustration: Sandbox Studio 8 Symmetry | Volume 05 | Issue 05 | November 08 05 | November Issue 05 | Volume | Symmetry

9 the cartoon elephant, captured the It would mean facing international competition, tight Kingimaginations Babar, of millions of children. Despite his lumbering deadlines, and intense peer review—a real test of the size he could walk upright, run, jump, dance the conga, and skills BaBar had shaped and polished over the years. The even do yoga. elephant would have to learn to dance. But King Babar had the advantage of cartoon-hood, where anything is possible. His namesake, an experiment Matter domination known as BaBar at SLAC National Accelerator Laboratory, It had taken five years to build the BaBar . did not. Twenty-five feet tall and just as wide, weighing around With 500 collaborators from 10 countries and 74 insti- 1200 tons, it required more than 100 people per shift to tutions, BaBar had the potential to be as clumsy as any keep it running and to gather and process the resulting real elephant. Yet in nine years of data taking, the experi- data. The detector rested in a cavernous cement hall, ment produced more than 350 published papers and where it received beams of and their made major contributions to our understanding of how counterparts, . The fast-moving beams swung matter escaped annihilation after the big bang and formed around a 1.4-mile circular track before they entered the the world we see today. BaBar had matured into an ele- detector and collided, giving rise to sprays of new particles. phant of great agility and skill. BaBar earned the title of B-factory because it produced Then the storm struck. hundreds of millions of particles known as B mesons for In December 2007, BaBar scientists were preparing scientists to study. It generated both regular B mesons and for a final year of data collection when they got the their antimatter counterparts, known as B-bar mesons; news: Rather than increasing the budget for high-energy hence the acronym B and B Bar, or BaBar. physics for FY08 as expected, Congress cut it by nearly Matter and antimatter are like the black-and-white Spy $100 million. US Department of Energy laboratories vs. Spy cartoons: Whenever they get together they annihi- across the country, including SLAC, were forced to cut late. This volatile relationship poses a troubling question: back experiments and, more painfully, jobs. BaBar had If equal amounts of matter and antimatter were created been scheduled to run for nine more months; now it would after the big bang, as scientists believe, why didn’t they close down almost immediately. annihilate each other? How did enough matter survive Not two days after the budget crisis hit, BaBar manage- to form everything we see? ment and spokesperson Hassan Jawahery finished BaBar’s observations of B mesons support the theory a proposal asking the DOE to keep the experiment run- that explains how matter came to dominate. This , ning long enough to pursue one more avenue of great known as CP violation, means that the laws of physics are scientific interest. slightly different for matter than for antimatter. It fits the pre-

10 dictions of the , a theory held in high regard pool of data at the energy level required to produce ηb. because of its beauty and, thus far, its accuracy in describ- Perhaps Belle was also close to nabbing the particle. ing the building blocks of the universe. Although the experi- BaBar set a goal of getting its results published in time ment was a success, the results did not completely account for the International Conference on High Energy Physics, for the dominance of regular matter in our universe, and or ICHEP, in late July. That left six months to complete there are still many questions left to be answered. a process that can sometimes take years. B mesons are not the only interesting things that come As the collaboration switched gears, Silke Nelson, one out of - collisions. Meet the bottomonia: of five physicists on the analysis team, was laboring a whole family of particles that each contain both a bottom, under her own deadline. Her second child was due a few or b, quark and an anti-b quark. A treasure chest of informa- weeks before ICHEP. While many members of the col- tion about the particle physics world, the bottomonium laboration would contribute to the particle’s discovery, particles would take scientists down a yet-untraveled path. and other analysis teams would pursue it from different The proposal BaBar management put together angles, Nelson and four other analysts—fellow postdoc would focus the collaboration’s efforts on certain members Veronique Ziegler, SLAC staff scientists Philippe Grenier of the family. At the top of the to-do list was finding a and Peter Kim, and PhD student Chris West—would be particle called ηb (pronounced eta sub bee), the lowest- the ones to dip into the deep pool of data and, with luck, energy member of the bottomonium family. The missing pull out the tiny bottomonium. piece of a larger puzzle and the subject of multiple theories, This particular analysis team, like most, was a mix of

ηb had thus far eluded scientists. Its discovery would not senior experts and younger scientists—postdocs and gradu- only help complete the bottomonium family portrait, but add ate students—eager to get their hands on raw data, and to the understanding of the strong force that holds sub- willing to put in long hours to make sense of it. Jonathan atomic particles together. “We saw that this was a chance Dorfan, the former SLAC director who helped found BaBar, to do something new,” says Jawahery, tapping the table says this practice gives “young tigers” a chance to directly for emphasis. “A chance to do new physics.” participate in the data evaluation with oversight from more The US Department of Energy granted BaBar an extra experienced scientists. three months to switch course and collect more data. Data analysis is a complex process. The BaBar detector does not simply illuminate single particles. It collects Racing against time the entire splatter of particles and light that comes out of BaBar wasn’t alone on this treasure hunt. The Belle electron-positron collisions. Scientists sift this tangled B-factory experiment at the KEK laboratory in Japan had nest of data for particular events or signals. To further also produced strong results, and had collected a small complicate things, bottomonia cannot be seen directly. Finding them is akin to identifying a car that just raced the Indy 500 by looking for the tread marks it left on the track. In this case, the tire track is a photon released as one of

the more energetic bottomonia, Upsilon 3S, decays into ηb. What has stumped scientists is how to pick out this partic- ular photon from millions that look similar. “You might be searching for a rare event that happens once in a million other events,” says Owen Long, BaBar’s new physics coordinator. “Sometimes the event is not rare, but we’re trying to measure it extremely precisely. We have to understand exactly how our detector responds to certain types of particles and events. This is why some measure-

ments can take years.” BaBar had only a few months. 08 05 | November Issue 05 | Volume | Symmetry A grueling analysis Early in the life of the experiment, collaborators had been placed in Analysis Working Groups based on areas of expertise. The AWGs are the moving parts of the elephant’s body, working together to achieve a larger function. Today’s 13 AWGs have names like “charmless quasi two-body b-decays” and “hadronic particle spectra.” Each consists of 30 to 40 members and oversees a number of smaller analysis teams, offering them feedback, sugges- tions, and sometimes criticism.

11 Each analysis team also has its own three-member collaboration’s analyses have been floating around for years, review committee, and can seek guidance from the entire waiting for new developments to push them forward. collaboration through BaBar’s private section on Some need to develop, some await new data, and some Hypernews, an online discussion board. “People get back may quietly die. to you so fast,” Ziegler says, as West nods in agreement. Once a paper makes it through the review committee “Whatever problem you’re having, no matter what it is, and the AWG, other members of the collaboration have there’s someone out there who has encountered it before.” two weeks to comment on it. The experiment’s publication For four hectic months the analysis group pored over board also invites 13 to 15 institutions to review the paper. the incoming data, looking for signs that the tiny ηb particle In most cases, about half will comply, but the ηb analysis had appeared where theory predicted it would be. Nelson’s drew comments from all 15. Grenier shakes his head belly grew larger, members dropped other projects they and says, “That almost never happens.” An exceptionally were working on, and the small-group structure became high percentage of collaboration members reviewed the even more important as the deadline approached. paper as well. “Since this was a very important analysis, “By the end we were meeting every day,” Grenier says. many people wanted to read it,” Dorfan says, “to make “We would discuss what each person had done in the last sure it was accurate.” 24 hours and what they would do over the next 24 hours.” With ICHEP rapidly approaching, BaBar’s publication The review committee insisted that the analysis team board reduced the usual two-week window for review blind its study, protecting the results from bias. As Dorfan to just two days. A few reviewers worked non-stop to pelt explains, “It’s not that anyone is deliberately changing any- the analysts with questions and critiques, polishing the thing, but if you expect an answer then you might give more paper into a form everyone could endorse. Only then did attention to one area and less attention to another.” the publication board declare it signed by the collaboration. As the final analysis program ran, the analysts paced up In the lingo of particle physics, the results had now been and down the hall. It took two hours for the program to blessed. search through millions of data points, tally all the photons The group immediately submitted the paper to Physical that looked like companions of ηb, and stack them into a Review Letters, where it was accepted on July 15—two graph. When the run ended and the group unblinded the weeks before ICHEP. analysis, lifting the veil from the results, they saw a small yet significant bump. It proclaimed, like scratchings on a high New beginnings school desk: ηb was here. During a follow-up interview, Grenier breathed a deep sigh. He looked forward to a week’s vacation at home in η The real grunt work starts France after presenting the b results at ICHEP. One week later the group poses for a photograph after Jawahery arrived in Maryland in time for his child to announcing its results. Nelson looks refreshed as she begin school, passing the title of spokesperson to rests her hands on her swollen belly and shines a wide François Le Diberder on October 1. At the same time, smile. Ziegler turns her petite frame just a little while Sören Prell, who as physics coordinator had overseen the West faces his broad shoulders front and center, and the many analyses going on at BaBar, handed off that job to group talks about running the final program. Two differ- Long. Although the machine has shut down, analysts will ent computers ran the program simultaneously to cross keep digging through the data for at least a decade, check the results. “I wanted to run it on my computer at searching for more discoveries. the same time, but it crashed!” says West, getting laughs Three days after the paper was submitted, Nelson and from the group. “I was hoping mine would finish before her husband welcomed their son into the world. Discussing yours,” Ziegler says to Grenier, “but then you called and her quick return to work, one of her colleagues mentioned said it was done.” Dorfan recalls walking into his office that the infant was present at a particle physics seminar ear- building and seeing one of the AWG members walking lier that week. “They’re starting them younger and younger,” out. “I asked if they had just unblinded the analysis, and another joked. he said, ‘Yes.’” Dorfan says he didn’t have to ask what the Nelson and Ziegler will soon be looking for permanent results were; it was obvious from the big smile on the positions at laboratories or universities, and West may analyst’s face. seek a postdoctoral position somewhere. Ziegler says she That celebration didn’t last long, Ziegler says: “After that might see what the ATLAS experiment at the Large is when the real grunt work starts.” Hadron Collider in Geneva has to offer. Wherever they go, Like other physics collaborations, BaBar reviews its own these three, like other young BaBar scientists, will bring results before submitting them for publication and scrutiny with them lessons about how to make a large collaboration by the wider scientific community. “The BaBar peer review function quickly and efficiently—dance lessons for future process is very thorough,” Grenier says. “It’s very tough and elephants. very long. Sometimes it can take weeks.” Here BaBar’s size can be its greatest strength and its One month after his first appearance, the reclusive particle known greatest weakness. The intense review by so many as eta sub b (ηb) granted an exclusive interview to our reporter. members of the collaboration ensures that BaBar con- See page 28. sistently produces strong results. But obtaining the approval of so many scientists takes time, and differing opinions can halt an analysis in its tracks. Some of the

12 Symmetry | Volume 05 | Issue 05 | November 08 05 | November Issue 05 | Volume | Symmetry

BaBar physicists catch up with their favorite cartoon elephant. Clockwise from left: Peter Kim of the eta sub b analysis team; Steve Sekula, who helped write the proposal that set BaBar on a new course; Owen Long, the current BaBar physics coordinator; and Chris West of the analysis team. 13 The dark universe debate 14 Who will be the first to prove the existence of dark matter and dark energy? A particle physicist and an astrophysicist go head to head. By Kathryn Grim symmetry | volume 05 issue november 08

Particle physicist Joe Lykken, Fermilab; astrophysicist Rocky Kolb; and University of Chicago astrophysicist Michael Turner, who served as moderator of the debate.

Photos: Reidar Hahn, Fermilab Photo-illustration: Sandbox Studio

15 The way Joe Lykken sees it, every modern scientist has accelerators. The question is: Who’s going to get there first? moments of jealousy when pondering the endless oppor- Lykken and University of Chicago astrophysicist tunities open to researchers of yore. How easy it must Rocky Kolb playfully duked it out over their fields’ sibling have been to come up with discoveries in the days before rivalry Sept. 24 in “The Dark Side of the Universe,” a people knew what atoms were, or how gravity worked. public discussion of dark matter and dark energy. It’s easy to think “they had all these great things just Lykken argued that particle physicists will be the first lying around to discover, and it’s not like that anymore,” to find evidence of dark matter and dark energy, using the Fermilab particle physicist said. particle accelerators and detectors buried in mines or polar But that’s not true, he said: The more scientists learn, the ice caps. Kolb said astrophysicists would be first with more they realize that “the whole universe is up for grabs.” the help of satellites, telescopes, and those same under- Researchers understand only the four percent of the ground detectors. universe made up of atoms, compared to the 96 percent They spoke to a crowd of almost 400 at the Smithsonian that they think is composed of dark matter and dark energy. Museum of Natural History in Washington, DC. Michael Scientists have found evidence of dark matter and dark Turner, an astrophysicist at the University of Chicago who energy, but no one knows what they are. coined the term “dark energy,” moderated. Scientists from multiple disciplines are taking up the “The stuff we’re talking about tonight really, really dazzles,” search—looking for these exotic entities in space, waiting Turner said. “But why should the taxpayer invest in this? for them underground, and trying to create them in particle Why should the man or woman on the street be interested

16 in answers to these questions about the dark side?” dicted “superpartner” particles, the neutralino, is a leading Lykken responded by pointing out that quantum candidate for the dark matter thought to have existed mechanics—the study of the interaction of particles at since the very early, high-energy days of the universe, the smallest level—seemed at first to be a purely intellec- where it helped matter cluster together to form galaxies. tual exercise with no practical application. But it led to “Supersymmetry has explained both how the sub- the invention of electronics, including the computer. And atomic world holds together and how the galaxies and the seemingly egg-headed pursuit of playing with the cosmos hold together,” Lykken said. “It’s this inner-space, connection between magnetism and electricity led to the outer-space connection.” technology that runs today’s power plants. “I see,” Turner mused. “So you weren’t interested in [dark matter]. But once you saw it was important, you remem- United by a search in the dark bered that you predicted it.” Scientists first found evidence of dark matter in 1935. They “Well,” Lykken said, cheering on his particle physics theorized that clusters of dark matter formed the back- colleagues, “it turns out we also predicted dark energy.” bones of galaxies, holding them together as planets and Particle physicists had called it “vacuum energy” and stars formed. Albert Einstein had called it the “cosmological constant,” About a decade ago, scientists discovered that an and they all shared the basic idea that empty space isn’t opposite force was pushing the universe apart, causing empty at all. it to expand at an accelerating rate. “We can tell there’s something there,” Lykken said, The search for an understanding of dark matter and “because when we smash particles together, they seem to dark energy has given a common goal to scientists who get knocked around a little bit by the vacuum of space.” once operated independently, Lykken admitted. “Until recently,” Lykken said, ribbing Kolb, “particle Shining light on dark matter physicists considered astronomers like Rocky to be Particle physicists hope to find dark matter in one of two insomniacs who stayed up all night taking pictures we ways: either by producing it in a particle accelerator or by didn’t care about.” identifying it with ultra-sensitive underground detectors as But then, Lykken said, particle physicists realized that it passes through the Earth. Many believe the reason par- their theory of supersymmetry predicted the existence ticle accelerators have not yet found dark matter is that it of something similar to the dark matter astrophysicists would take a substantial amount of energy to make it—a were seeking. Supersymmetry holds that every known level of energy the newly minted Large Hadron Collider at particle has a corresponding particle that behaves in the border of Switzerland and France could produce. a different way. This theory would help fill in the missing “My guess is that the LHC is going to find something pieces of how the building blocks of matter and forces of that’s really going to shake our fundamental knowledge nature work to create objects. The lightest of these pre- of physics,” said Lykken, who is working with the LHC’s symmetry | volume 05 issue november 08

Photos: Reidar Hahn, Fermilab Photo-illustration: Sandbox Studio Background image: Bubble Chamber “Strange Event” algorithm, Jared Tarbell 2004 17 Compact Solenoid experiment. ing a long time ago, compared to how fast it expanded more Asked whether scientists will discover dark matter recently. within the next three years, Lykken said yes, the LHC will They found their basis of comparison by looking at far- produce dark matter by that time. away objects in space: supernovae, or exploding stars. Kolb shot back, “We will first discover it with astronomy— These explosions always put out the same amount of light. within two and a half years.” Measuring how faint these supernovae are as seen from Two clues have led astronomers to suspect the exis- Earth, scientists can tell exactly how far away they are. tence of dark matter, Kolb said. Because light takes time to travel to the Earth, the First, when they measured the masses of the stars distant supernovae also allow scientists to look back and planets that make up galaxies, they discovered that in time. When scientists look at objects that are far away, the gravity of those atom-built objects alone was not they actually see how they looked in the past. “So as great enough to hold the galaxies together. Something I look out here in the audience, people in the back seem they couldn’t see must contribute mass—and hence a younger to me,” Kolb joked. gravitational pull—as well. Astronomers had expected the expansion of the uni- Second, they could see distortions of light in space, verse to slow over time, since gravity would pull things normally caused by large masses, in places that seemed back in. To their surprise, they discovered that the expan- empty. They called this invisible presence dark matter. sion was speeding up; the supernovae were moving “You’re sure [dark matter] is there?” Turner asked. away from us at a faster and faster clip. It seemed some “I would bet your life,” Kolb replied. other force was pushing these objects—and everything else in the universe—apart. Detecting dark energy While Turner believes this is best explained by the The researchers weren’t as confident of success in the hunt repulsive gravity of dark energy, he said there could be for dark energy, a mysterious form of energy that would some other explanation for these surprising observa- push the universe to expand at faster and faster rates. Both tions. “Hit me with your craziest idea,” he said to Lykken said the best possible development could be proving that, and Kolb. “Really, really crazy. Paris Hilton kind of crazy.” contrary to Turner’s prediction, dark energy does not exist. Kolb said dark energy could be “the ether of the 21st This would give them a blank check to start over with new century.” Early theorists thought this hypothetical sub- theories. stance filled the universe and allowed light to travel “Just for the record, it was a Tuesday in 1964 when through what would otherwise be empty space. After find- I made a mistake,” Turner cracked. “I just want the record ing the speed of light to be the same in different direc- to show that there was a time I made a mistake. It’s not tions of space, experimenters refuted the ether concept. impossible.” “We think [dark energy] is there, but perhaps dark Astronomers came up with idea of dark energy after energy isn’t there and there’s something even odder they measured the rate at which the universe was expand- going on, even more surprising,” Kolb said. “One possibility

Photos: Reidar Hahn, Fermilab Photo-illustration: Sandbox Studio Background image: NASA and STScI 18 that I’ve worked on is that the universe is so inhomo- One hundred years ago, Kolb said, astronomers believed geneous that somehow, in some unknown way, this the Milky Way galaxy made up the entire universe: “I think changes the expansion of the universe and makes us 100 years from now we will understand the fact that what think there’s dark energy. So if this idea is correct, the we today call the universe will just be another small part of way we’ve been doing the basic equations of cosmology something we might call a multiverse or megaverse.” since 1922 would be changed. Turner turned to Lykken. “Will we have found intelligent “I’m the only person who thinks this, by the way,” he life on Earth?” he asked. added, to laughter from the audience. “I think the history of particle physics is finding out Lykken said the idea of dark energy might be explained there’s a new force of nature,” Lykken said, “new kinds of by a flaw in our understanding of gravity. matter we didn’t suspect were there. So I think 100 years “One reason is we may be doing gravity in the wrong from now it’s very likely we’ll have found at least one new number of dimensions,” he said. String theorists predict force of nature.” the existence of at least six dimensions in addition to the Lykken also predicted we would finally get a handle four space-time dimensions we perceive. on how gravity works. “If this doesn’t get you interested in science,” he said, Coming soon “then I give up.” Turner prompted his colleagues to predict where science would be a century from now. symmetry | volume 05 issue november 08

19 Where old physics stuff goes to live

20 Photography by Reidar Hahn

By Jennifer Lee Johnson symmetry | volume 05 issue november 08

The Fermilab boneyard is no burial ground; it’s a place where unwanted parts find new homes and lives. They’re matched with scientists who can put them to good use, donated to local schools and parks, or sold for recycling.

21 Hidden from view by old willow trees, the cast-off tools of high-energy physics are strewn across 11 acres: rejected cables, tables with missing limbs, and computers that couldn’t keep pace. Swallows nest in rusty magnet frames, raccoons pillage through buckets of bolts, and coyote pups hide from the wind under a metal plate painted with the American flag. Many laboratories and universities lack the space to store old equipment and scrap, so Fermi National Accelerator Laboratory takes it in. “I just hate to see stuff get melted down when it doesn’t have to be,” Todd Wagner says. “Sooner or later, somebody is going to come out here and Todd Wagner in the Fermilab boneyard need it. There’s enough talent at this lab here that we can find a use for anything.” Wagner oversees the Fermilab boneyard—a recycling center for experi- mental components that might otherwise end up in a landfill. Scientists adapt these pieces for other experiments—some for short terms, others per- manently. Sometimes, to his dismay, Wagner can’t find a good home for a part and must recycle it for a new life in consumer goods. “The name of the yard—boneyard—is misleading,” Wagner says. “You hear ‘bone’ in the title and you think it’s where stuff comes to die. I like to think the opposite—that it’s where items get reborn.”

22 23

symmetry | volume 05 | issue 05 | november 08 Playing matchmaker The goods on display range from giant copper coils and van-sized chunks of particle detectors to small pieces of equipment Wagner rescues by hand during his weekly tour of the lab. Back at the yard, he sorts scraps into bins of copper, aluminum, brass, steel, and iron. Discards from other US labora- tories—and even from foreign countries—come in by rail. Before setting aside materials to sell to private industry, Wagner checks to make sure they are free of radioactive contamination caused by the particle beam. “Everything gets surveyed twice so there’s no chance of any activity,” he says, sweeping the wand of a Geiger counter over a piece of metal. Once he knows what he has, he can match a displaced item with a sci- entist or contractor who needs it. “They’ll say, ‘Do you have any steel drums?’ or ‘Do you have a rivet so-and-so size?’ and I’ll go and get it for them,” Wagner says. Sometimes scientists want to pick their own parts. Physicists with the neutrino experiment SciBooNE scoured the bone- yard to find a dozen 9-by-10-foot steel plates from a calorimeter last used at Fermilab in the early 1980s. Scientists with the NOνA neutrino experiment recently claimed three stainless steel drums. Other discards find new lives outside of physics, where old sections of tunnel become tornado shelters and steel scaffolding has been crafted into a staircase. Parking medians in a local park used to be wooden power poles, designed by Fermilab’s founding director Robert Wilson in the shape of the Greek letter π.

24 25

symmetry | volume 05 | issue 05 | november 08 26 Strolling through history Walking through the boneyard provides a glimpse into the evolution of particle physics. There are bins of circuit boards pushed aside by smaller, faster models and a 61-year-old synchrocyclotron magnet that might never turn on again. The magnet, conceived by Enrico Fermi following his work on the Manhattan Project, once drew crowds to its former home at the University of Chicago. In the early 1950s it pushed particles to the highest energy in the world, 450 MeV. Now a flower sprouts at its base, looking as out of place as a mouse at the foot of an elephant. “That magnet got a lot of use,” Wagner says. “I bet it could get even more at an art museum.” What Fermilab can’t reuse or donate to local schools and parks is sold to scrap contractors, raising more than $1.5 million since 2001. Fermilab also collects and sells about 200,000 pounds of electronic waste each year, including discards from nearby Argonne National Laboratory. This earned the lab a US Department of Energy environmental award in 2006. “Some of this scrap will become a toy or a car part,” Wagner says. “If it came back, I wouldn’t recognize it.” As Wagner walks through the yard, he tidies up random pieces of cable blown by the wind. “It all counts,” he says, tossing the cable into a giant bin. “It doesn’t go to a landfill. That’s the good thing.” symmetry | volume 05 issue november 08

27 Q&A: eta sub b

symmetry’s Calla Cofield scored an exclusive interview with the particle…the ground state…the artist “eta sub b,” who signs his name ηb. One month after eta sub b’s stunning entrance into the public spotlight via the BaBar experiment (see story, p. 28), this in-depth interview reveals eta sub b’s struggle to shine next to his brother Upsilon 1S; his upbeat attitude despite a life surrounded by static; and a look at just how well our reporters prepare for interviews. Photos: Bradley Plummer

28 symmetry: So eta…can I call you eta? s: That’s gonna be a tough sell. What are

ηb: Well, I wouldn’t want to get confused with you working on right now? one of the other etas. The “sub b” is really the ηb: Well, at the moment, I’m focusing on my most unique part of my name. appearance in the big bang. That’s really the core of my work, but maybe it’s time I branch out, try s: I think you’re the only eta people will be something new. talking about for a while.

ηb: You flatter me. s: I’m sorry, what exactly is it that you do? ηb: Did you even research this interview? s: Don’t be flattered. Most people still have no idea who you are. s: What was I supposed to do? There’s no

ηb: Getting back to your question… Wikipedia entry about you yet. ηb: Are you kidding me? There’s an entry about s: You’ve been in hiding for 30 years. Why Eliphalet Trask and there’s not even one about me?! reveal yourself now?

ηb: I stayed out of the spotlight for personal rea- s: Who the heck is Eliphalet Trask? sons. There was a lot of noise surrounding me. ηb: Just a completely un-noteworthy lieutenant I knew who I was supposed to be, but I had to sift governor of Massachusetts in the mid-1800s! through a lot of static to really find myself. What more do people want from me?! I’ve got mystery! I’ve got glamour! I could be crucial s: Now that you’re out, the ladies want to in understanding quantum chromodynamics!! know if you’re still single.

ηb: Really? s: Take it easy. ηb: Ugh…I’m sorry. Could you not write that s: No, not really. I freaked out?

ηb: Well, I’m a singlet. s: I am a professional journalist and I s: Cute. So you’re not dating anyone? report the truth. Let’s move on. Have you

ηb: I don’t think you understand…that means been hitting the gym a lot? I have only one spin state. Other particles might ηb: I’m a particle. be happy to give two, three spins. But I stick to my guns. s: I guess people can’t see you anyway.

ηb: It’s the subatomic thing. s: You know you’re not getting any younger. s: It’s my permanent state. It’s what defines me. s: By the way, how long until you decay?

ηb: That’s none of your business. s: Afraid of long-term commitment? Sooo George Clooney. Where are you living? s: If you don’t want to talk about it I can η : The insides of stars, mostly. always go ask the theorists. b symmetry | volume 05 issue november 08 ηb: Look, I’m no charged …

29 Q&A: eta sub b

s: Hey, who is? s: Actually, I’d like to talk about your par-

ηb: But I’m around a lot longer than…well… ticle status. -25 some other particles…I mean, one times 10 ηb: I was told that would not be discussed here. seconds hardly seems worth the effort. s: You aren’t technically a new particle.

s: Woah! Mr. Big Talk over here! ηb: I don’t have to explain my art to you. ηb: Hey, I’m not judging anybody. s: This is physics.

s: Let’s get back to you coming out. ηb: What are you? A shrink?! ηb: Um, could you say being detected instead? s: I minored in psychology.

s: I’m a professional journalist and I report ηb: Really? Well…I have wanted to get this off my the truth. To be totally honest, you weren’t chest. See, I’m not a new particle. I’m just an energy exactly trying to stay hidden, were you? state in a family of particles that has already made

ηb: You’re right; I was overshadowed. My brother a name for itself. I’m the smallest one in my family Upsilon sub b 1S emitted a lot of photons—pho- in an already absurdly small realm! tons very similar to mine. It was hard for people to see the light I was giving off next to his. s: Wait, maybe it was cosmetology…

ηb: I stayed hidden for 30 years trying to, you s: Of your four Upsilon brothers he’s the know, build the suspense. But outside of particle one most like you. physics no one seems to care.

ηb: In reality we’re not that much alike. I know we’ve got similar energy values, but we’re as dif- s: No, it was comp lit. But hey, you’re right. ferent as eta sub c and Upsilon sub c. Most people don’t care.

ηb: I really don’t like you. s: Or John and Paul.

ηb: The particles? s: I’m a professional psychologist and I report the truth. By the way, did you know s: No, the Beatles. Here’s how I see it: they’re still in the process of confirming Upsilon 1S is like Paul. He’s got three that it was you they found in their detector? states: Beatles, Wings, and Heather Mills. And if it’s not you, what else could it be You’re like John. Just one state. but the particle known as Higgs boson?!

ηb: Actually, I think people would argue that John And people care about her! Ironic, huh? Lennon had some really distinct phases. ηb: Do you think I could run with “might be Higgs” for a while? s: Hey, if I spin you backwards does it say “Paul is dead”? s: No. But you should think about getting

ηb: No, you still get zero. a clever nickname. ηb: I was thinking of “The Disco Particle.” s: That blows my mind, man.

ηb: Look, Upsilon might be a higher energy state s: Yes! I’d read that book. than me, but in the end we’re all high energy, right? We’re all subatomic particles.

30 symmetry | volume 05 issue november 08

31 essay: robin hanson

Yes, some have made qualitative LHC fore- LHC forecasts: better casts, such as these: than horoscopes? Brian Greene: The LHC could provide evi- dence for more than three dimensions of space. My horoscope today Nima Arkani-Hamed: “They will find the says, “Focus on the Higgs particle. There’s also a pretty fair chance small stuff.” Now, such that they might observe some of the particles advice does have con- that make up the mysterious dark matter.” tent. It predicts that Sir Chris Llewellyn-Smith: “A Higgs boson when readers interpret will be found (95% probability), and (with 60% its words in the usual probability) supersymmetry.” way as a guide to These LHC forecasts are not without con- action, those who do tent, but as in the case of most horoscopes, what they think it scoring them may require lots of interpretation; recommends will, on in many plausible scenarios the accuracy of average, feel they such forecasts could be unclear. got more of what they Clearer forecasts would be phrased in terms wanted than those of new particle mass, spin, charge, decay rates, who ignored it. etc. And the academic literature does contain Even so, astrologers sure don’t make it easy papers with more precise indications of what the for us to test their claims. If they wanted to LHC might see. But different papers predict dif- make it easier, they would do what forecasters ferent things, and prominent physicists have not in weather, sports, and business do: issue fore- picked particular papers to endorse. Yes, the casts in a clear, standardized form. A horoscope space of possible new particle properties is very is like a weather forecast that says, “Some rain large, and each paper may only (with some prob- likely nearby, soon.” It’s much easier to evaluate ability) exclude some regions of this large space;

Photo courtesy of Robin Hanson a forecast that a particular rain gauge has a but we have ways to score such forecasts. 15% percent chance of collecting more than an The bottom line is that to score physicists for inch of rain during the next calendar day. LHC forecast accuracy, we must either attempt When multiple forecasters each make many the enormous task of averaging over forecasts such forecasts on overlapping topics, we can from thousands of diverse academic papers, or use standard scoring rules to evaluate their we must apply great judgment to interpret a few relative accuracy. Such scores are a standard high-profile quotes. Today’s LHC forecasts are way to evaluate forecasts in weather, sports, no easier to score than the typical horoscope. and business, and to evaluate students on tests. Yes, physicists eventually will form a consensus Which bring us to the issue of forecasts related on what if any supersymmetry or Higgs-like pro- to the Large Hadron Collider. cess best explains the LHC data, and yes, that Physicists are rightly proud that their theories consensus will allow precise, scoreable forecasts usually support scoreable forecasts. While in of particle phenomena. But geez—the LHC costs private a physicist might suggest, “Something more than $10 billion of public money. Shouldn’t like this should work,” for a critical audience he we expect big-shot physicists who hope to crow or she will try to calculate probability distributions to the public about LHC vindication to express over yet-to-be-observed parameters. In contrast their predictions in a more scoreable form? We to horoscopes, physics forecasts are commonly don’t accept less from weather, business, or clear enough to be scored against other forecasts. sport forecasters; why accept less from physicists? Physicists are also proud of the LHC and its public image. The odds are good that within the Robin Hanson, an associate professor of economics at George Mason University, is a pioneer in the field of prediction markets, next few years the public will see news articles also known as information markets or idea futures. in which big-shot theorists crow that some new LHC result has vindicated their approach to par- symmetry | volume 05 issue november 08 ticle physics, and implicitly vindicated physicists in general for having supported that approach against skeptics who questioned their judgments on funding, etc. In this context it is worth noticing: There are today no public predictions about LHC results by high-profile physicists that are stated precisely enough to be clearly scored for accuracy.

32 logbook: LHC startup

scientists at the European laboratory CERN On September 10, 2008, attempted for the first time to send a beam of particles around a new particle accelerator, the Large Hadron Collider. The machine has a cir- cumference of 27 kilometers and uses thousands of magnets to steer particles around the ring. At 10:25 a.m., Swiss time, the LHC team used remote controls to remove the last collimator that blocked one of the LHC’s two beam pipes. One minute later, accelerator experts sent a beam of pro- tons clockwise into the pipe at an energy of 450 billion . Traveling at close to the speed of light, the protons completed their first turn around the ring. The CERN Control Centre documented the historic event in this electronic logbook. A beam screen near the injection point recorded the beam’s passage right after its injection and after its first round trip (two orange dots in the center left graph). Beam position monitors throughout the ring reported the vertical and horizontal positions of the beam (center right graph). A few minutes later, after making some adjustments, the LHC team injected another proton beam that traveled around the ring twice. Four and a half hours later, the team succeeded in sending a beam of protons around the LHC’s second beam pipe in the opposite direction. Kurt Riesselmann Image courtesy of the LHC Remote Operations Center at Fermilab explain it in 60 seconds

is a dramatic yet fairly routine event within A magnet quench a particle accelerator. It occurs when one of the superconducting magnets that steer and focus the particle beams warms above a critical temperature, bringing operations to an abrupt halt. A quench often starts when stray particles from the beam enter a magnet’s coils, producing an initial burst of heat. Within a fraction of a second, parts of the superconducting wire in the magnet lose their ability to conduct electricity without resistance, generating more heat that quickly spreads throughout the entire magnet. The coolant surrounding the magnet begins to boil. In the case of a large superconducting magnet, which can be several meters long and carry currents of 10,000 amps or more, the quench creates a loud roar as the coolant—liquid helium with a temperature close to absolute zero—turns into gas and vents through pressure relief valves, like steam escaping a tea kettle. Such a quench generates as much force as an exploding stick of dynamite. A magnet usually withstands this force and is operational again in a few hours after cooling back down. If repair is required, it takes valuable time to warm up, fix, and then cool down the magnet—days or weeks in which no particle beams can be circulated, and no science can be done. Tom Peterson, Fermilab

Symmetry A joint Fermilab/SLAC publication PO Box 500 MS 206 Batavia Illinois 60510 symmetryUSA