Dimensions of Particle Physics a Joint Fermilab/SLAC Publication

Home , Melissa Franklin, Patricia Burchat

dimensions volume 04 of particle physics symmetryA joint Fermilab/SLAC publication

issue 01

jan/feb 07 On the Cover Babar the elephant made its debut in a 1931 children’s book by Jean de Brunhoff. BaBar the particle detector has been collecting data at Stanford Linear Accelerator Center since 1999, studying the tell-tale signs of the quantum world. One type of rare quantum process that the BaBar collaboration is studying is called the “penguin.”

Photos: Reidar Hahn, Fermilab symmetryA joint Fermilab/SLAC publication

volume 04 | issue 01 | jan/feb 07

2 Editorial: 8 BaBar’s Window on 30 Deconstruction: Budget Progress the Weak Force CMS Assembly The proposed US budget has prom- The BaBar B-factory experiment at Moving and assembling a particle ising developments for the particle Stanford Linear Accelerator Center detector underground is a delicate physics community but physicists looks to double its data in a mere operation, especially when the detec- need to do what they can to support two years as it hunts for hints of tor weighs more than 12,000 tons. their interests. spectacular new physics and guide future experiments. 32 Essay: 3 Commentary: Reality—Better than Fiction Prioritizing US Particle Physics 14 Evolution of a Collider A literature student, excited by physics A roadmap produced by the US parti- As physicists and engineers devise but turned off by how it was taught, cle physics community sets a direc- ways to make the International took to inventing her own theories of tion for how the research community Linear Collider perform better at a the universe. Then a university course can answer its most pressing scien- lower cost, the design evolves, showed her that reality is more inter- tific questions in particle physics over sometimes with tweaks, but other esting than anything she could invent. the next five years. times with major reconfigurations. ibc Logbook: 4 Signal to Background 20 And They Lived in Physics Single Top Production Delicate detector surgery; walking in Bliss Forever After… In 1985, physicists were wondering the dark; dark matter song; flying When physicists marry physicists, the whether particle colliders could dis- across Antarctica to catch particles; beginning may be a “big bang,” but cover new, heavier generations of big bang re-enactment; letters. issues of life, love, and family gravitate quarks. Twenty years later, the calcu- toward the universal. lation applies to the production of single top quarks at the Tevatron. 28 Day in the Life: Stanford Guest House bc Explain it in 60 Seconds: Guest houses are common among Simulations particle physics labs. But in many Simulations are used in physics to ways, the Stanford Guest House, sit- explore many “What if?” scenarios. In uated on the grounds of Stanford particle physics, they are used for Linear Accelerator Center, is different. application from designing new types of accelerators and detectors to evaluating the final analysis of data.

Office of Science U.S. Department of Energy from the editor Budget progress The Fiscal Year 2008 budget request has just been released by the President of the United States. At the roughest cut of the figures, the FY08 high- energy physics program within the Department of Energy gets a 12% increase over the enacted FY06 budget level. (Comparisons with FY07 are not meaningful as Congress had not yet passed a budget at the time we went to print.) The FY08 increase takes the place of a similar request in FY07. Given that there had not been much budgetary growth for particle physics in recent years, any increase is welcome at this time, and these requests are a positive sign. Not all members of the particle physics community will see the FY08 budget request as good news since money would be shifted from one research program to another and some research efforts would see delays. This process is a stark reminder for all scientists about how money is allocated and who decides how money is spent in the United States: the people, through their elected representatives.

Photo: Fred Ullrich, Fermilab Photo: Fred Scientists are beholden to the people who provide their funding. That’s how it should be. As a result, scientists’ proposals will only be enacted if they are consistent with a government’s priorities. The particle physics community has conducted a few prioritization analyses of their own, including the P5 report mentioned in Abe Seiden’s commentary (page 3). Those analyses are meant to provide advice and guidance, and the FY08 request reflects some of the priorities established by the particle physics community. In particular, R&D for the International Linear Collider would receive $60 million. With this item being one of the highest established priorities in particle physics, the strategic work by the community begins to pay off. In the reality of the current US budget climate, there are further steps the physics community should take. It should continue to present its achievements, prove that it is using its funds wisely, and ask to launch new research initiatives when the budgetary circumstances are right. Pushing too hard too soon will only attract a “No” for an answer, the last thing research-driven physicists would like to hear. Right now, the priority for physicists is to do what they can to ensure the US Congress passes a budget that satisfies their needs. David Harris, Editor-in-chief

Symmetry Editor-in-Chief Publishers Print Design and Production PO Box 500 David Harris Neil Calder, SLAC Sandbox Studio MS 206 650 926 8580 Judy Jackson, FNAL Chicago, Illinois Batavia Illinois 60510 USA Executive Editor Contributing Editors Art Director Mike Perricone Roberta Antolini, LNGS Michael Branigan 630 840 3351 telephone Peter Barratt, PPARC 630 840 8780 fax Managing Editor Stefano Bianco, LNF Designers www.symmetrymagazine.org Kurt Riesselmann Reid Edwards, LBNL Aaron Grant Anilou Price [email protected] Catherine Foster, ANL Staff Writers Tara Kennedy Elizabeth Clements James Gillies, CERN (c) 2006 symmetry All rights Silvia Giromini, LNF reserved Brad Plummer Web Design and Production Heather Rock Woods Jacky Hutchinson, RAL Xeno Media symmetry (ISSN 1931-8367) Siri Steiner Youhei Morita, KEK Hinsdale, Illinois is published 10 times per year Kelen Tuttle Marcello Pavan, TRIUMF by Fermi National Accelerator Mona Rowe, BNL Web Architect Laboratory and Stanford Interns Perrine Royole-Degieux, IN2P3 Kevin Munday 07 symmetry | volume 04 issue 01 jan/feb Linear Accelerator Center, Rachel Courtland Yuri Ryabov, IHEP Protvino D.A. Venton Yves Sacquin, CEA-Saclay Web Design funded by the US Department Karen Acklin of Energy Office of Science. Jennifer Yauck Boris Starchenko, JINR Maury Tigner, LEPP Alex Tarasiewicz Jacques Visser, NIKHEF Web Programmer Linda Ware, JLab Mike Acklin Ute Wilhelmsen, DESY Tongzhou Xu, IHEP Beijing Photographic Services Fermilab Visual Media symmetry Services

commentary: abe seiden

A program to understand dark matter, com- The plementary to work in astrophysics, seeks to Particle study its particle nature directly in the laboratory. However, dark energy can only be studied (at Physics our present level of understanding) through astro- Roadmap nomical observations; therefore, projects typically involve interagency collaborations with the astron- In October 2006, the omy programs at NSF or NASA. Particle Physics For major construction and R&D over the rest Project Prioritization of this decade, P5 set these three priorities: Panel (P5) provided a new roadmap for a broad research at the energy frontier, including the full and very exciting science agenda in particle LHC program and R&D for the ILC; a near-term physics research. The roadmap’s destinations program in dark matter and dark energy, as Photo: Monica Lee are among the most intriguing questions in sci- well as measurement of the small neutrino-mixing ence: the origins of mass and the search for the angle; and construction of the NOνA neutrino- Higgs boson; extra dimensions; dark matter oscillation experiment, along with related modest and dark energy; unification of the known forces Fermilab accelerator complex improvements. and possible new forces; the three families of The dark matter and dark energy program matter, from the massive top quark to the near- includes the 25 kg Cryogenic Dark Matter massless neutrino; and CP violation, the key Search (CDMS), the Dark Energy Survey (DES), to the imbalance between matter and antimatter and finalizing a cost and schedule plan for two in the universe. dark energy projects: The Large Synoptic Survey The P5 plan recommends construction and Telescope, in collaboration with the NSF; and R&D toward major projects for the next five SNAP, one of three options for a dark energy years, within an international context, and within space mission. DOE should work with NASA budget guidance from the US Department of to determine the best space mission. Energy (DOE) and the National Science Neutrino efforts include the Daya Bay (China) Foundation (NSF). There are recommended reactor neutrino experiment, along with R&D for review dates for projects anticipated to be ready a Deep Underground Science and Engineering for construction early in the next decade. Along Lab (DUSEL), R&D for a large dark matter with ongoing projects, and projects with con- detector, and a neutrinoless double-beta decay struction nearing completion, these recommen- experiment to be located at DUSEL. dations form the new roadmap. P5 advocated a review toward the end of this P5 is a subpanel of the High Energy Physics decade for a number of projects, many of which Advisory Panel, chartered jointly by DOE and could start construction soon thereafter. ILC pro- NSF. HEPAP endorsed the P5 plan in October gress will be reviewed, including a possible US 2006. The P5 panel received important input bid to host the ILC. The LHC upgrade construc- from specialized assessment panels in individual tion is required to raise LHC luminosity tenfold. physics areas, and from the report of the DUSEL, including the large dark matter and neu- Committee on Elementary Particle Physics in trinoless double-beta decay experiments that it the 21st Century (EPP2010), Revealing the could host, will be reviewed. The two large dark Hidden Nature of Space and Time: Charting the energy experiments will need to be revisited. The Course for Elementary Particle Physics. The status of flavor physics, and the importance of P5 recommendations converge on these major further new charged lepton or quark flavor exper- scientific opportunities: the energy frontier of iments, will also be monitored. The best direc- the Large Hadron Collider and the proposed tions for further neutrino physics experiments International Linear Collider; the nature of dark would be based on the physics results over the matter and dark energy; neutrinos; and precision next five to ten years. measurements with charged leptons or quarks. With appropriate reviews, new discoveries, symmetry | volume 04 | issue 01 | jan/feb 07 symmetry | volume 04 issue 01 jan/feb There is enormous potential for across-the- adaptations to budget constraints, and progress frontier discovery projects at the LHC and on interagency and international collaboration, ILC, with the LHC addressing the full spectrum projects on the P5 roadmap are poised to make of science questions from the nature of mass, significant discoveries in the years ahead. to dark matter and dark energy, unification, and CP violation. Neutrino science investigations Abraham Seiden is the chair of the P5 subpanel and a physi- would encompass neutrinoless double-beta cist at the University of California, Santa Cruz. Find link to full P5 report online at www.symmetrymagazine.org decay, reactor and accelerator neutrino oscillation experiments, and neutrinos from space.

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Delicate detector surgery; walking in the dark; dark matter song; flying across Antarctica to catch particles; big bang re-enactment; letters.

Engineering big lovingly tied, bundled, and org- narrow slots angled at 60 upgrades anized the thousands of cables degrees. The lift fit alongside How do you renovate a delicate, that blocked the way to the the front end of the detector

Photo: David Harris irreplaceable detector? Very muon identification system. with only inches to spare, sand- carefully. To access the outermost wiched between the beam pipe During the last four months layer of the detector where that pierces the center of the of 2006, the BaBar collaboration the muon system resides, the detector and the opened door. at SLAC successfully replaced mechanical operations crew The new muon detectors come a prematurely aging muon iden- used thousands of crane lifts on one-inch-thick, 12-feet-long tification system. Creative and to remove several layers and flexible sheets. Standing on the solid engineering played a big many tons of steel, including lift’s platform, crews used the role in upgrading a detector that critical pieces where the sup- built-in angled tray to help hold wasn’t meant to be taken apart. port arms for the calorimeter the long, delicate sheets in Jim Krebs, BaBar’s chief detector attach. Protecting position for insertion. engineer for mechanical oper- the calorimeter was one of the When everything was put ations, spent five years on the toughest engineering chal- back together and the detector project. “We had to figure out lenges, and required suspend- doors closed again, many peo- 07 symmetry | volume 04 issue 01 jan/feb how to take everything apart.” ing 44,000 pounds, about half ple let out sighs of relief. In August, crews opened the its weight. The support scheme Opening the detector required doors that protect the three- performed flawlessly. taking a calculated risk because story-tall detector, exposing five Early engineering efforts not all of the earthquake protec- layers of detection instrumenta- went into building a special lift tion could stay in place. Now, tion and a nervous system of to tackle the difficult job of pull- the refurbished detector is tak- wires and cables. Graduate stu- ing out the old muon detectors ing data again. dents disconnected and then and feeding the new ones into Heather Rock Woods

Walking in the dark? “favorite” for some physicists, got Dark Matter Rap I have been attending hundreds only 46 votes. The moral of this, I first heard of dark matter at of talks by particle physicists for me, is that unlike the early a Moriond Conference in 1987. who look for a very specific 90s, when we knew what we A guy named David Spergel experimental signature that is were looking for—the top quark had the idea that if dark matter predicted by a very specific that had to be there—now we was weakly interacting massive theory extending the Standard are walking in the dark. particles (WIMPs) they would Model. However, I was curious Something must exist to be captured gravitationally by how much faith my colleagues play the role of the Higgs, but the sun and cool it enough to have that what they’re looking we can only try to guess right explain why Ray Davis only for can be real. So I asked them now. None of our guesses can observed 1/3 of the expected in an informal poll. be taken very seriously. What number of neutrinos. I think The chances of certain dis- will guide our theories will be he named them “Cosmions”, but coveries looked very low to me, experimental data. At this point, WIMP sounded much better. and it seems that the voters it makes all the sense to search My PhD thesis was a big agree. The Standard Model for the “unknown” in our data. germanium detector designed Higgs received 90 votes and for The good thing is that whatever to look for a type of nuclear many voters was a second tick- is to be found next, it will be reaction called double-beta mark. (Voters could check multi- very exciting; even more so than decay but it turned out we ple answers.) Other potential the top quark was. could also look for WIMPs. I discoveries received far fewer Georgios Choudalakis, spent about a month driving to votes. Supersymmetry, a great MIT/Fermilab and from the Gotthard Tunnel in Switzerland where we could reduce the background noise What kind of physics do you enough to detect dark matter expect to be discovered at LHC? if it was made of heavy neu- 100 trinos. Daniel Reusser continued after I left and in 1989 pub- 80 lished a paper that showed 60 that dark matter could not be made of neutrinos unless they 40 had a mass of more than about 20 1 TeV, far higher than what is now known to be the case. For a long time, I thought dark matter was just some- Answers Votes thing that was cooked up to 1 Standard Model Higgs 90 explain the solar neutrino problem and galactic rotation 2 SUSY 46 curves. It was not until I heard

3 Extra dimensions 18 David Weinberg’s Dark Matter Rap that I understood what a 4 Compositeness 18 long and important history dark (excited quarks, leptons, gauge bosons) matter has had in astronomy. I actually learned much of what 5 Leptoquarks 5 I know by reading the papers

6 New strong dynamics 18 mentioned in Weinberg’s song. (technicolor) I also learned about astrono- mers who care more about 7 Other, that is not included 20 in this list but has been “How much? Do we need it? proposed. Where is it?” than what dark matter actually is.

8 Other, that would surprise 82 07 symmetry | volume 04 issue 01 jan/feb everyone. Peter Fisher, MIT

9 I expect no new physics 34 Read the text of the Dark Matter Rap and listen to an mp3 recording on the symmetry website.

Answers were taken through the [email protected] mailing list, which reaches graduate students, postdocs, and professors. Each person was able to vote for more than one choice. Voter’s IP addresses were recorded to prevent them from voting for the same item twice.

signal to background

just as important!” said Smoot, grinning ear to ear. Smoot mounted the tall ladder ordinarily used by band director Robert Calonico and delivered a short course in how the universe was created. “Now, I gotta tell you what the big bang is, so you guys can do this before the sun goes down… We’re going to simulate a really smooth, hot, dense, early universe and spread out, and we’re Photo: ANITA collaboration Photo: ANITA going to form structure—galax- ies, stars, planets, and every- ANITA takes flight which included both radio thing else,” he explained. “Let’s A one-time visitor to SLAC, the waves and visible light. go for it. Go Bears! Go band!” Antarctic Impulsive Transient Brad Plummer A marching band simulate Antenna (ANITA), recently took the big bang? Mellophonist to the frigid skies over Berkeley Band re- Jason Lo spoke for the band: Antarctica on a mission look- enacts the big bang “We can do this!” ing for evidence of cosmic-ray The world, by some accounts, Smoot continued with the neutrinos. was created in seven days. Not cosmological choreography. On December 14, 2006, sci- to try and top that, but a univer- “There’s a brass section out entists tethered the 20-foot- sity band managed to re-enact there called tubas. They make tall probe to a high-altitude the big bang in a period of a real spectacular spiral galaxy, helium balloon and released it less than an hour. a really big one like our own into the atmosphere. ANITA The band was recruited by galaxy, or like Andromeda. You circled the south polar conti- University of California, guys get to be near the middle, nent three and a half times at Berkeley, astrophysicist George but you get to orient, and get an altitude of more than Smoot for a “creation” role in to rotate with a twist up. You’re 100,000 feet—three times as the Nobel Prize ceremony in like the centerpiece of all this. high as a passenger jet. The Stockholm, Sweden, at which he Go tubas!” probe’s array of antennae was was presented the Nobel Prize A member of the Swedish tuned to scan for the radio in Physics for findings confirm- television crew filming this signals that are produced ing the big bang theory. Back in event said he had one question when cosmic-ray neutrinos November, Smoot asked the before the band began its ren- strike the Antarctic ice below. Berkeley band for help in filming dition of the big bang. “What ANITA landed nearly 1100 a video to be shown during starts the big bang?” he asked. miles from the original launch the Nobel festivities on Sunday, Simple, said Smoot. “Drums!” site on January 19, 2007, after December 10, 2006. Jeffery Kahn, University of 35 days aloft—the second “Professor Smoot came up California, Berkeley longest duration for a scien- to the band and asked if later A video of the performance can be seen tific balloon flight in history. that week, when we practiced online at http://tinyurl.com/yhe23j

Before traveling to at Memorial Stadium, we could Illustration: Sandbox Studio Antarctica, ANITA first got its do a formation like the uni- bearings during calibration verse forming. He wanted the tests at SLAC. In early June band to form up a blob and 2006, a team of collaborators re-enact the big bang. That’s tuned the antennas with a what he asked,” marveled 07 symmetry | volume 04 issue 01 jan/feb series of experiments con- Hanadi Shatara, the band’s ducted in End Station A using public relations director. a 10-ton block of ice to simu- Not long after, Smoot late the Antarctic environment. addressed the members of the Researchers then blasted the band, assembled in a modified ice with pulses of electrons, blob midfield at Memorial producing a cascade of radia- Stadium. “It’s a little more com- tion called Cˇ erenkov radiation, plicated than ‘Go Bears,’ but it’s

Letters

Dorm life I found it fitting that the picture from Fermilab in the article about dorm life (Oct/Nov 2006) came from an ultimate frisbee game. In the summer of 2000, I came to the Fermilab dorms as an undergraduate from Bucknell University to work on MiniBooNE and I ended up working on my ultimate frisbee game every single afternoon. We had a huge group of players all thanks to the organizing and advertising done by Melanie Novak, also from Bucknell. We had tons of fun and even challenged Argonne National Laboratory to a friendly inter-laboratory tournament. I am very glad to see that the ultimate games have continued at Fermilab. Jeremy Urban, Cornell University

I am writing concerning your article in the October/November issue about dormitories and guest houses at labs everywhere. I realized that I have stayed in such accommodations at 11 different insti- tutes: IHEP Protvino, Moscow Radiotechnical Institute, Manhe Siegbahn Laboratory (Stockholm), DESY, CERN, Brookhaven, Jefferson Lab, Fermilab, ANL, TRUIMF, and KEK. I wonder how my list compares with those of other frequent travelers? Peter Lucas, Fermilab

Make some noise for whispers I love the “Whispers of dark matter” article (symmetry, Dec 2006). The metaphor of listening for vibrations is wonderful, and the illustrations guide you through our magical world of dark matter with their lucidity. Ben Kilminster, Ohio State University

A present for the future During the majority of my 57 years of existence, I’ve waited with the anticipation of a child on Christmas Eve for the truly exciting discoveries that have been and continue to be made. Whether from deep space, quantum mechanics, or particle physics, they remain important towards expanding our understanding of not only who we are, but what we are. Twenty years ago, at the age of 6, my daughter was shown a cyclotron housed in the University of Rochester, NY, where we lived. She was taught how to pronounce the word, given a basic explana- tion of what it did and has never forgotten the moment. I am up to date with the news that Fermilab releases on its Web site and find it absolutely incredible! In view of what’s being discovered, I believe it is vital that scientists be sufficiently funded in order to continue exploring these fundamental building blocks. I wish I were young enough to see the outcome of these fantastic experiments and I hope the government and private sector keep up the funding so perhaps my daughter may. Thanks for the great write-ups. Michael Giambra, Reno, NV

Corrections Our article on lightning at Fermilab (symmetry, Oct/Nov 2006 issue, p. 4) incorrectly gave an energy value. Cloud-to-ground lightning bolts typically cross a voltage of 100 million volts. The insulating vacuum of the ILC test cryogenic vessel (symmetry, Oct/Nov 2006 issue, p. 26) typically has a pressure of only 10-5 to 10-7 torr to avoid heat leaks. 07 symmetry | volume 04 issue 01 jan/feb

Letters can be submitted via [email protected]

Photo: Reidar Hahn, Fermilab BaBar’s This violation. iscalledcharge-parity asymmetry (CP) it doesnotactequally onmatterandantimatter—unlike theotherforces. rate thantheantimatter versions.That meanstheweak forceislopsided: different slightly a at decay matter of made ones the that determined force, itwouldholdtogether forever.” of MIT. Steve Sekula BaBar collaborator “Left onitsown without the weak quark to form a (or pairs: onemadeofmatter, onemadeofantimatter. abottom Each contains samplebytheendof2008. ble itsowndata antimatter partners,positrons.The BaBarteamexpects tomorethandou their and electrons together slamming by them of pairs billion a almost a called ticle The par toolfor exploring experiments’ theweakforceisaheavy primary The are seizingtheiruniqueopportunitiestodecipherthem. of theuniverse.The weakforcestillholdssecrets, andBaBarBelle force’s sometimes-odd behavior, andopengatewaystothebigmysteries stretch, theexperiments theweak areracingtolearnevenmoreabout their firsteightyearsofoperation.Nowenteringthefinaltwo-yearhome in discoveries landmark made have They Japan. in KEK at Belle and inCalifornia LinearAcceleratorCenter(SLAC) ments—BaBar atStanford detectors work, and indicate the age of ancient skeletons and tools. radioactive decays that diagnose disease and treat cancer, make your smoke heat the Earth’s core. It’s also tremendously useful. The weak force drives ourlives,drivingthenuclearreactionsthatpowersunand sustains the weakforce. The sunisshining;theEarthwarminsteadoficy. Life isgood,thanksto By HeatherRock Woods hints ofspectacularnewphysics. a meretwoyearsasithuntsfor Center looks to double its data in at StanfordLinearAccelerator TheBaBar weak force the window on Because theweakforceexists, “The Providing awindowontheweakforcearetwo“ One ofthefourknownforcesthatshapeuniverse,weakforce b ) quark, the second heaviest quark. The B B playground meson is a playground or laboratory fortheweakforce,” mesonisaplaygroundorlaboratory says B meson. The meson. B meson. B

B -factory experiment experiment -factory factories together have manufactured manufactured have together factories B mesonsdofallapart.Physicists have b quark partners with a lighter B mesonsareproducedin

B factory” experi factory”

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symmetry | volume 04 | issue 01 | jan/feb 07 Photos: David Harris

Physicists already knew CP violation existed when BaBar got underway, Top photos: Technicians work and they knew that this phenomenon must contribute to the dominance of on reconnecting elements of the BaBar detector after a matter over antimatter in the universe. The B factories confirmed that all CP major upgrade. Bottom photo: violation we see in nature comes from the weak force—but they also found Babar rests in the PEP-II that it’s not enough to explain the amount of matter in the universe today. storage ring tunnel, his name- sake detector behind the The mismatch between experimental results and the actual universe high- wall in the background. lights the incompleteness of the prevailing theory of how nature works, known as the Standard Model. Something more is at play, and BaBar and Belle have a shot at saying who the players are. “The matter-antimatter imbalance remains one of the top mysteries of the universe. The weak force appears not to be the thing that solves it for us. Whatever causes the imbalance, the effects are subtle,” says Sekula.

Precision The two pillars of the BaBar program are to deeply understand the realm where the weak force and quarks interact, and to use that precise understanding to search for rare and new kinds of physics. BaBar Spokesperson Hassan Jawahery, professor at the University of Maryland, says, “We’re embarking to a new world, and we need to know

10 high-energy realm. high-energy the in look to where into insight keen providing are and can they cles, Butwhilethe atCERN. (LHC) that willbeachieved atnewmachines liketheLargeHadronCollider new particles.BaBarandBelleoperateatafractionoftheenergyreach see newformsofphysics,whether supersymmetry, extra dimensions,or force. theweak raredecayswouldexplainmere existence more about ofcertain and to increase the chances of seeing extremely rare events. Indeed, the inalltypesofmeasurements toreduceuncertainties both amounts ofdata to compare it with.” the old world very well so when we see something new, we have something that physicists still need to search. professor Patricia Burchat. Tightening the constraints reduces the territory future must be consistent with what we’ve observed,” says Stanford physics we reveal no inconsistencies with the Standard Model, every theory in the will still bequeath something substantial. nificantly reducetheuncertainty, cansolvethisquandary. which willincreasethenumberofallpenguin decaysandsig more data, still hasplentyofroomtorevealthecontributionsnewphysics. Only Modelpredictionsbut in thattypeofpenguindecayisclosetoStandard seen asymmetry of detector.Theamount the in observed decays meson billion one roughly the in far so times 1200 only detected have they appreciable,” saysJawahery. something newiscomingin, itmaychange inawaythat’s theasymmetry Model,aclearindicationofnew physics. dicted bytheStandard differentcase, theexperiments ratesofdecaysthanpre would observe that couldchange theamountofmatter-antimatterasymmetry. Inthat particle, oranotherkindoftheorizedparticle. tual particlescouldbethemuch-sought Higgsparticle,asupersymmetric print. unmistakable an leaves it concrete, wet in walking cat a like But, directly. observed never is particle virtual a that quickly so repaid be to has energy the However, space. of vacuum the from energy borrow temporarily to them more massivethantheoriginal almost instantly. place where “virtual” particles pop into existence and then disappear again is a decay that requires the weak force but also contains a “virtual loop”—a more commonthanothers. falls apartinoneofhundredsdifferent ways,someofwhich aremuch B betweenmeasures theamountofasymmetry about the existence of new kinds of physics. Deviations from what’s expected in the Standard Model would tell physicists Hunting penguins Rome. INFN says thepastphysicsanalysiscoordinatorforBaBar, Riccardo Faccini of before?’” come has that data the all with consistent seeing I’m what ‘Is meson lives about a trillionth of a second after being created and then then and created being after second a of trillionth a about lives meson findanewparticle,oneofthequestionswillbe, “If physicistsattheLHC What the vast collecting on depends years two next the in success BaBar’s “The Even if the chance to herald the new doesn’t materialize, the manytypesofpenguindecays,including onetype BaBar hasobserved if because nice them makes which rare, very are decays “Penguin If newparticlesdoenterpenguinloops,theywillintroduceinteractions Physicists areinhotpursuitofthesepenguindecaysbecausethevir Even thoughitsoundsimpossible,thesevirtualparticlescanbemuch One of the rare processes is called a “penguin” (see sidebar next page). It To search forsurprises,a B factories will leave a legacy ofprecisionmeasurements.Evenif factorieswillleavealegacy B factories find will be vital tofuture experiments thathopeto factoriesfindwillbevital B B factory usesitstypicalmodusoperandi:it factory B factories can’t directly observe newparti factoriescan’tdirectlyobserve mesons.Quantummechanics allows B andanti- 11 B decays.Each B factories B

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symmetry | volume 04 | issue 01 | jan/feb 07 The origin of penguins at Harvard. One evening, she, I, and Serge went Told by John Ellis: to a pub, and she and I started a game of darts. We made a bet that if I lost I had to put the word “Mary K. [Gaillard], Dimitri [Nanopoulos], and I first penguin into my next paper. She actually left the got interested in what are now called penguin darts game before the end, and was replaced by diagrams while we were studying CP violation in Serge, who beat me. Nevertheless, I felt obligated the Standard Model in 1976… The penguin name to carry out the conditions of the bet. came in 1977, as follows. For some time, it was not clear to me how to In the spring of 1977, Mike Chanowitz, Mary K. get the word into this b quark paper that we and I wrote a paper on GUTs [Grand Unified were writing at the time…. Later…I had a sud- Theories] predicting the b quark mass before it den flash that the famous diagrams look like was found. When it was found a few weeks later, penguins. So we put the name into our paper, Mary K., Dimitri, Serge Rudaz and I immediately and the rest, as they say, is history.” started working on its phenomenology. That summer, there was a student at CERN, John Ellis in Mikhail Shifman’s “ITEP Lectures in Particle Melissa Franklin, who is now an experimentalist Physics and Field Theory”, hep-ph/9510397

Antibottom Antistrange Quark Quark W-Boson

Antitop Antitop Quark Quark

Gluon

Strange Antistrange Quark Quark

More than a B factory BaBar physicists have multiple sources of urgency for the final two years, because this may be the last chance to make certain kinds of measurements. Although the LHC will have a b-quark experiment (LHCb), the exist- ing B factories can do certain measurements that will be difficult or impos- sible in future experiments. BaBar and Belle also serve as excellent factories for other particles, especially charm mesons (containing a charm, or c, quark) and tau particles (the heaviest relative of the electron). In fact, physicists are using the plethora of tau particles to look for new physics in a completely different way. They are currently seeking tau decays that end without producing a tau neutrino—find- ing such decays would be iron-clad proof that something new is going on. It might also help unravel the mystery of how neutrinos change from one kind to another. “The detector is so multipurpose that we can make a wide range of measurements that touch on a wide array of topics,” says Princeton professor Jim Olsen, physics analysis coordinator for BaBar. “We’re learning things that will change textbooks.”

12 Photos: David Harris

Much more to come Top photos: The BaBar control room is staffed 24 hours per day Both B factories are continually pushing their limits in the quest for greater with collaboration members from luminosities, or number of events they produce. around the world visiting to take At SLAC, the PEP-II accelerator, which provides the electron and posi- shifts overseeing operation and data collection. Bottom photo: tron beams for the BaBar experiment, has already exceeded its original Babar visited the BaBar experi- goal for luminosity by a factor of four. The BaBar collaboration and the mental hall during upgrades to PEP-II team recently made a number of major upgrades to the detector the detector. and the accelerator to further increase luminosity by a dramatic 70 percent, and to make the detector even more sensitive. The final experimental stretch will run from January 2007 through September 2008. symmetry | volume 04 | issue 01 | jan/feb 07 symmetry | volume 04 issue 01 jan/feb “We have at least 100 kinds of measurements to do in the next two years,” says Olsen. He expects around 150 analyses to be published in this time. “The amount of physics coming out of BaBar is huge.” Long after the last event flings its offspring through the BaBar detector, physicists in the 600-person international collaboration will be quarrying their mountains of data in a quest to solve the mysteries of the weak force and more.

13 Evolution of a Collider by Elizabeth Clements, ILC Global Design Effort As physicists and engineers devise ways to make the International Linear Collider perform better at a lower cost, the design evolves, sometimes with tweaks but at other times with major reconfigurations.

Photos: Reidar Hahn, Fermilab 14 15

symmetry | volume 04 | issue 01 | jan/feb 07 “Optimizing cost without compromising the physics performance is the goal of the reference design.”—Barry Barish

Designing the International Linear Collider is an accelerators that would each extend approxi- evolutionary process. The ILC would be a next- mately 15 kilometers, this reconfiguration makes generation machine that smashes together elec- it possible to fit many of the large technical sys- trons and their opposites, positrons, to unlock tems of the ILC in one central complex. The main some of the deepest mysteries about the universe. motivation, however, for the modification: slash But aside from the new science, the ILC enters the construction cost of the ILC by eliminating new territory in terms of planning and designing a circular 6.7 kilometer tunnel and associated for the particle-physics community. facilities, resulting in a savings of 39 percent for The Global Design Effort (GDE) for the ILC is the damping rings. an international team of physicists and engineers “Optimizing cost without compromising the that continuously evaluates the project’s ever- physics performance is the goal of the reference progressing design. The design team’s goal is design,” says GDE director Barry Barish. “Our a machine that produces optimal physics with design has evolved through an orderly change good value for money. control process that carefully considered the In December 2005, the GDE produced a potential risks for each modification and sought Baseline Configuration Document. Intended to input from the larger physics community. Further give the scientific community a first glimpse of cost optimizations will continue to be made in the what the ILC would look like, this baseline design next engineering phase of the project, but for outlined the physics parameters and overall now, changes like the damping ring reconfigura- schematic of the machine. The GDE completed tion allow us to propose a more financially this baseline document as a first attempt—a responsible machine.” launching pad—to put down on paper a design that will continue to be refined. The evolution In 2006, the GDE began stage two of ILC The idea of placing two damping rings in one tun- planning: the Reference Design Report. Publicly nel is an old idea. In fact, physicists have toyed released in February 2007, this more detailed with the idea of a central damping ring complex conceptual report specifies all hardware compo- since the project’s first conception. Having the nents in enough detail to assess performance majority of large technical components on one and prepare a preliminary value estimate. laboratory’s site makes maintenance much easier In developing a value estimate, members of the and limits the disturbance to surrounding neigh- GDE asked themselves: How can the baseline borhoods during construction. “Just the time that design be modified to optimize the costs without you save by not having to drive 15 kilometers every dramatically compromising the physics capabilities time you need to fix something in the damping of the machine? Such exercises resulted in a rings makes the central campus better,” says series of changes—some quite large—to the base- Peter Tenenbaum, who helped with the recon- line design. figuration as a GDE member from Stanford Linear Accelerator Center. “Think about it. You A big change could spend an entire shift driving back and In October 2006, one significant modification forth just to replace one part.” completely reconfigured the footprint of the Until recently physicists required two positron machine, combining the electron and positron damping rings to counter an “electron cloud damping rings in one tunnel and relocating effect”—a building up of electrons inside the beam them to the center of the machine, surrounding pipe that interfere with the oppositely charged the detectors. With the exception of the linear positrons, destroying the beam density that is

“Further costoptimizationswillcontinue of techniques forcombatingtheelectroncloud, damping ringR&Dstudiesproducedanumber After crowd. a be would three tunnel, one in the problem.While tworingscansitcomfortably required twopositrondampingringstocounter physicists that ILC the from desired physics the producing to threat a such posed cloud This collisions. precise producing for essential different requireaprecise stepsofeach cycle intheILConly0.2seconds.Theone cycle takes to the final collision of electrons and positrons, From the production of the first particle bunches Configuration challenges beam transportsystem. rings, resultinginacomplete overhaultothe sit inthecentralcomplex, next tothedamping positron- andelectron-injectorsystemsnowalso than remainingateitherendofthelinacs,both systems.Rather thebeamdelivery meters above 10 sits that wide meters 4.5 and cumference cir in kilometers 6.7 tunnel one in other each the electronringandpositronontopof configuration (seediagram,next page)places it.” ignore can’t we that cost in reduction substantial a such has it but risks, reasonable cost.There maybesometechnical that issafe enoughtoworkbutnowhasamore that we got from R&D and made a configuration results at “We looked Institute. Cockcroft the dampingringsgroupAndyWolski of of theGDE worked, butitwasexpensive,” saystheleader electron ringinthesametunnel. the remainingsinglepositronringand ILC physicists,thenext naturalstepwastoput eliminate onepositronringtocutcosts.For the could they that confident became physicists Without threateningphysicsresults,thenew “We knewthatwecouldbuildamachine that phase of theproject.” to bemadein thenext engineering -

1 7 one out, the others will know. We need to work work know. Weto will need others the out, one age rings will talk to each other. When you take bunches,” Wolski says.“The bunches in thestor has never been done before with long trains of ing theextraction process. ofthebeamdur stability lenges formaintaining positrons arrivetorefillit. This presents chal positron ringwillbepartiallyemptybefore new the electronbeamishalfwaydownlinac, Because thepositronbeamisnotcreateduntil times. right the precisely at rings damping machine, both beams must be extracted from the lide at the interaction point in the center of the new configuration. coordination, introducing timing challenges for the back down to the level of the transport lines. lines. transport the of level the to down back electrons and positrons the bring to escalator beam a requiring linacs, main the above meters 10 sit rings damping The rings. damping the GDE. the for group (RTML) Linac Main to Ring the of leader beam,” the Tenenbaum, says destroying co- a without line straight a almost in B point to A transfer line, because it just has to get from point entire tunnel. “It is actually easy to have a long without eating into the savings of eliminating an either direction to the beginning of the linacs, damping ring and transport them 15 kilometers in of the electrons and positrons after they exit the the beam transfer lines: preserve the beam quality fer lines to the new configuration. The main job for of introducing two 15-kilometer-long beam trans rings R&D.” place, which iswhythisapriorityfordamping right the in stay they that sure make to hard “It is an unusual thing to do to the beam, and it In order for the electrons and positrons to col The trickiest part involves entering and exiting The also GDE had to consider the implications —Barry Barish

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symmetry | volume 04 | issue 01 | jan/feb 07 Electrons Positrons 5-Gev Linac Undulator 5-Gev Linac DR DR

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Even though the beam escalators have a slow, the damping rings while we are still building Electronsgradual slope, asking particles to move vertically is the rest of the machine,” says Ewan Paterson, Positrons not simple. “It is incredibly fussy, but it can be of Stanford Linear Accelerator Center. done,” Tenenbaum says. “It is just a geometric 5-Gev Linac challenge and requires a lot of thought and effort.”UndulatorChange control5-Gev process Linac To fit the new long transfer lines into the new Knowing that the baseline design for the ILC DRconfiguration, they will be in the ceiling of the would continue to evolve, the GDE implemented DR main linac to allow room for all of the other com- a Change Control Board in December 2005 to ponents that must go in the same tunnel. review all proposed changes. Chaired by KEK’s Tenenbaum compared the size of the tunnel to a Nobu Toge, eight additional physicists from typical plane on a trans-Atlantic flight. “Watch different laboratories around the world with dif- people struggle with their bags in the overhead ferent areas of expertise make up the board. bins on a plane,” he says. “That is what it will “We are not external reviewers; we are from be like to work on the transfer lines. It is always within the GDE to help our colleagues decide. harder to work above your head.” The CCB’s job, however, is to try its best to One of the benefits of having the damping ensure that our design decisions are reasonable rings and injectors sit 10 meters above the rest of and that they survive the relevant experts’ scru- the machine is thatMain they will Linac be able to operate tiny,” Toge says. “If a proposal offers a healthy Main Linac independently of the main linacs and interaction working solution with a feasible design, the CCB regions. Ample shielding between the damping approves the change. If not, the CCB signals a rings and the main linacs makes it safe to have warning sign and disapproves the change.” 6ERSION electrons and positrons circling above and physi- Serving as a set of fine-grain eyes, the Change cists working in the beam delivery area below, Control Board conducts a review to evaluate the yielding more potential cost savings. “You can save benefits and potential hazards of implementing a lot of commissioning time because we can test each change request. “When you are looking at

Electrons Positron source Detectors Electron source Positrons Undulator

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18 Electrons Positrons 5-Gev Linac Undulator 5-Gev Linac DR DR

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the big picture, it’s good to have many eyes,” review panel, the relocation of the damping rings Electrons PositronsToge says. to a central campus offered extra benefits for Because the damping rings reconfiguration commissioning, operations, and sharing facilities. had an impact on almost every system in the Confident in the overall design for the machine, 5-Gev Linac Undulator 5-Gev Linac ILC—a huge task to consider when reviewing the GDE still has some questions about details the proposed change—the GDE called for rein- of the central campus. “With the competence of DR forcementsDR and enlisted Paterson to help. As the people we have, these are things that we the designated “Integration Scientist” for the can solve,” Toge says. GDE, Paterson focuses on the interfaces and The nuances of the new configuration will con- interactions between systems in the ILC, mak- tinue to be defined through R&D activities and ing it very appropriate for him to oversee the eventually in the ILC Technical Engineering damping rings reconfiguration process. From Design Report. With the change process running civil construction to beam delivery, Paterson smoothly, ILC physicists are confident that they coordinated all of the different systems affected can continue to improve the design while lowering in the change request and presented the costs as they take the ILC through the next engi- change request as one neat package for the neering design phase and closer to its exploration CCB to review. “We asked ourselves, in our of the universe’s foundations. Main Linac Main Linacdesire to save, are we overlooking something?” Paterson says. “You can’t just blindly go ahead.”

Putting it all together 6ERSION After a series of reviews, the CCB and GDE Executive Committee strongly supported the change request. While the cost-savings alone made the reconfiguration appealing to the

In the new ILC design, electrons are generated, accelerated Electrons Positron source Detectors Electron source Positrons to 5 GeV, and injected into the electron damping ring (blue oval). After the particles circle the ring 10,000 times, the ring Undulator spits out a compact beam thinner than a human hair, which then travels along a transport line all the way to the beginning of the main electron linac.

Then the electron beam is accelerated along the main linac toward the central region. The electrons pass through an “undulator”, which causes them to emit light, and are accelerated further toward the collision point.

The light generated by the undulator hits a titanium alloy target, which leads to the emission of positrons. The positrons are accelerated, sent into their own damping ring (orange oval), and made into compact bunches. Then they travel to the start of the main positron linac. From there, they are accelerated to collide with electrons coming from the opposite direction.

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19 Photo: Reidar Hahn, Fermilab 20 And they lived in physics bliss forever after… When physicists marry physicists, the beginning may be a ‘big bang,’ but issues of life, love, and family gravitate toward the universal. By Mike Perricone

In a physics lab class during his sophomore year are envisioning their future with the singular clear at Indiana University, Jason Rieger made a big optimism of a young married couple. impression on his lab partner. “All our friends have real jobs at this point,” Leah “He blew something up,” says Leah Welty, who says. “We hope that with our PhDs, we’ll be able has been Leah Welty-Rieger since Friday, August to catch up. Our goal is that once we’re 30, all 13, 2004, when she and Jason were married in her those things should be even.” home town of Joliet, Illinois. Randomly assigned as lab partners, they Making things work became self-described “best friends” for a year Particle physicists might spend much of their and a half before actually dating. On a trip to professional lives in a phantasmagorical quantum New York City three years later, when both were realm, but their personal lives are usually rooted graduate students in particle physics at Indiana firmly in the everyday world of house and home, University, they walked to the midpoint of the children and family, bills and benefits, dreams Brooklyn Bridge, where Jason proposed and Leah and realities. When physicists marry physicists, accepted. their issues still run the conventional gamut, “We had stopped at a jewelry store in whether they live in America, Europe, or Asia. Manhattan to pick out a ring,” Leah recalls. “But The logistics for dual-physicist couples, how- we had it mailed home to save money on the ever, often adds a flavor of complexity. “Which tax, so then we had to find another ring. Then town shall we live in?” can become “Which country when we called everyone in the family to give shall we live in?” and “Who picks up the kids them the news, nobody was home.” The news, of while I’m at work in the city?” can transform into course, spread eventually, with the ceremony “Who picks up the kids while I’m at a conference and celebration taking place a year later on the in Japan?” grounds of a rented mansion in Joliet. Tuula Maki and Mikko Voutilainen are phys- Leah and Jason have now settled into life as ics graduate students from Finland. They are graduate students at Fermilab, commuting 40 working on their PhD research at Fermilab and miles from an apartment on the near-west side have begun a marital journey similar to that of of Chicago. Both are researching the physics of Leah and Jason. Tuula is from Tampere, and the bottom quark as members of the DZero Mikko is from Joensuu; they met as students at detector collaboration, sharing the same office the Helsinki University of Technology. “It’s the space, and working to finish their PhD theses. MIT of Finland,” Tuula says. They “got along very They “don’t buy a lot of extra stuff” on their well” for two years before they started dating, symmetry | volume 04 | issue 01 | jan/feb 07 symmetry | volume 04 issue 01 jan/feb grad student stipends, Jason says—except for Mikko says, and they became engaged three running shoes. Both are marathon runners, and years later. they just completed their second Chicago mara- Tuula and Mikko were both board members thon; both finished in less than four hours for the for the Guild of Physics, a student organization first time. They want to have children (Leah, an at Helsinki, and Tuula just wound up a term as only child herself, wants more than one), and they head of the Graduate Students’ Association at

21 Patrizia Azzi and Nicola Bacchetta (from left): Patrizia in the CDF control room during her Fermilab tenure; Patrizia and Nicola with their first son, Marco; their wedding in 1993 in Verona. The reception was held in the medieval Castelvecchio.

Left photo: Reidar Hahn. Other photos courtesy of Patrizia Azzi and Nicola Bacchetta.

Fermilab. “I like to have a role in the field, to stay at Fermilab. Maria was born after they had help improve student life,” Tuula says. They live moved from Fermilab back to Padova, but a in a furnished apartment on the east side of month later Nicola moved to CERN to work on the Fermilab site, in the area called The Village, CMS. And so they moved to Geneva, Switzerland, where they are happy to be close to work without where Patrizia also joined CMS following the worrying about furniture, cars, and commuting. completion of her maternity leave. When they finish their PhDs some time in With three young children and two full-time 2007, both Tuula, now at CDF, and Mikko, now at physicists now in Geneva, the domestic equations DZero, anticipate postdoctoral positions at were unlikely to balance. Marco and Lorenzo CERN, where the Large Hadron Collider will be were enrolled in an English-speaking school, so starting operations. “I think it should be pretty they wouldn’t have to learn a third language easy to find positions for both of us,” Mikko (French). Childcare for baby Maria took a bit more says. “In particle physics, you stay near the big creativity and, eventually, luck also lent a hand. accelerators, and there should be plenty of “After a lot of searching,” Patrizia says, “we experimental groups…We do know some scien- finally found amaman-du-jour , that is a lady that tists with careers in two different cities, who meet keeps the baby at her house for the day. We on weekends, although we wouldn’t like that.” like her a lot and we are very happy. She lives five As for possibly raising a family: “We haven’t minutes from CERN and she speaks Spanish been thinking about that yet,” Tuula says. Mikko and French, so it was easier for me to communi- adds that he would like to better understand how cate in the beginning. I did not speak any French. physics couples who have been married for sev- The other great thing is that a teacher from the eral years solve problems such as conflicting job Fermilab [day care center], Patina Waterstreet, offers, and how they manage to raise children with who we already knew very well, decided to come both parents working as physicists. live with us as an au-pair for one year—or more?— after her graduation. I’m sure you can imagine Juggling children and careers that life with three kids and two parents working Patrizia Azzi and Nicola Bacchetta, both physi- full-time can be crazy. Now Patina is just part of cists, have mastered these issues. They have the family.” dealt with raising three children while building careers in physics. Today, they both work on Meeting away from home the Compact Muon Solenoid (CMS) experiment Patrizia and Nicola are both from northern Italy; at CERN, with permanent positions at Italy’s Patrizia from Desenzano del Garda and Nicola Istituto Nazionale di Fisica Nucleare in Padova. from Venice. Both attended the University of Patrizia says she and Nicola did not give a lot Padova, but not concurrently. They both worked of consideration to the issues of work and travel on the Collider Detector at Fermilab for more that double in complexity when both spouses than 14 years. They met in 1991, on the day of are members of a thoroughly international field. Patrizia’s traumatic arrival at Fermilab. “No, we really did not think very much about it,” “I had a bad experience at Immigration because Patrizia says. “Otherwise we would have never I needed to stay for four months, but my boss did done it!” not tell me I had only a three month visa waiver,” In what might be compared to the timing of Patrizia recalls. “My English was very bad. In the a precision experiment, Patrizia and Nicola had end, moved by my tears, Immigration let me in children Marco (May 5, 1999), Lorenzo (May 8, after having me pay 90 dollars for a visa at the air- 2001) and Maria (May 9, 2005). “That is not a port. I was tired and nerve-wrecked, when another typo,” Patrizia says. Marco and Lorenzo were born friend took me to the apartment in Country Ridge, in Naperville, Illinois, late in the couple’s 14-year behind the Family Foods supermarket, that

22 symmetry | volume 04 | issue 01 | jan/feb 07 symmetry | volume 04 issue 01 jan/feb

23 Tuula Maki and Mikko Voutilainen (from left): Tuula and Mikko, both out- doors types, spent part of their honey- moon hiking in the Grand Canyon; they have an apartment in The Village on the Fermilab site; a soft rain was falling on their wedding day, in Kuva, Finland.

Center photo: Fred Ullrich, Fermilab. Others are courtesy of Tuula Maki and Mikko Voutilainen.

24 Padova University was renting. That evening It might be the only wedding in the world in Nicola was also there. And he was not particularly which one of the most famous graduate-level understanding of the situation, telling me I should physics textbooks played a role. “In ancient India, have known better. Oh well…” boys traditionally went to a boarding school, But all went well enough. They were married then returned home to seek a bride,” explains in November 1993 in Verona. The reception, Pushpa. “The wedding ceremony includes a rit- thanks to Patrizia’s father being a former officer ual in which the groom needs to show off his in the Italian Army, was held at the Officers’ scholarship. Chandra showed up with Jackson’s Club in the medieval Castelvecchio. Classical Electrodynamics in hand.” “It has always worked out in the end,” Patrizia says. “Clearly we are very lucky in having kids Moving abroad that are very good, sweet, and healthy. The basic Pushpa and Chandra defended their PhD theses rule was always to stay together, no matter on the same day in Bangalore. They moved to where, instead of having a parent away most of the Netherlands for a few years, then settled as the time. My kids have changed many houses— postdocs in Durham, North Carolina, with and they remember them all—but I think they Pushpa at Duke University and Chandra work- can feel ‘at home,’ wherever home is. They seem ing in nuclear physics at the University of North to be nice and happy kids, so we must have done Carolina-Chapel Hill. Chandra recalls that they something right.” decided not to begin raising a family until finish- Pushpa and Chandra Bhat have been mar- ing grad school and settling-in somewhere. ried for 26 years. Pushpa, of the DZero and Their son, Shreyas, was born in Durham in 1986. CMS experiments, and Chandra, of Fermilab’s That day, Pushpa’s mother arrived and stayed Accelerator Division, are both from India. Pushpa for about seven months to help the new family. is from a family of white-collar professionals Pushpa had wanted to work at Fermilab in the city of Bangalore, while Chandra is from since she first became smitten with the knowl- a family of farmers in the western mountain edge of particle physics and big accelerators. region near the Arabian Sea and the coast city Chandra waited for the right time to change his of Goa. They met while attending graduate field to accelerator physics and he joined school at Bangalore University in the late 1970s; Fermilab’s Antiproton Department in 1988. As in fact, when Chandra showed up for an inter- a member of the high-energy physics group view at the university, he first was quizzed by at Duke University, Pushpa had worked on Pushpa, the top-ranked student and university Fermilab experiments since 1985, and joined gold medalist, before he met with a professor. Fermilab in 1989. Wanting the best for their son Their connection was immediate. They co- was paramount in accepting a position at authored the first paper that each published, Fermilab. In the following years, they stayed at in 1978. “Then, love blossomed,” Chandra says, Fermilab instead of seeking academic positions. “and we got married in 1980.” Pushpa emphasizes “We are both workaholics and have worked symmetry | volume 04 | issue 01 | jan/feb 07 symmetry | volume 04 issue 01 jan/feb that while the marriage was not an arranged non-stop for, oh, however many decades,” Pushpa one, it was very much a traditional South Indian says. “We made the decision to stay at Fermilab wedding. “We were married on May 7th in and not try to go to a university because if one of Bangalore,” she says. “About 1500 people attend- us traveled on a regular basis we thought it would ed the wedding. The ceremonies took place be hard on the family and especially for our son. over five or six days.” So, we have mainly traveled to conferences/

25 Pushpa and Chandra Bhat (from left): their wedding in Bangalore had 1500 guests and extended more than five days; their son, Shreyas, is about to enter graduate school on a physics career path; Pushpa first worked on Fermilab experiments in 1985, and Chandra joined the lab in 1988.

Left two photos courtesy of Chandra Bhat. Right photo: Reider Hahn, Fermilab.

26 Leah Welty-Rieger and Jason Rieger (from left): both are experienced marathon- ers, including the Chicago Marathon; their wedding took place at a mansion (rented) in Joliet, Illinois; both are working on the DZero experiment at Fermilab.

Left two photos courtesy of Leah Welty-Rieger and Jason Rieger. Right photo: Reidar Hahn, Fermilab.

meetings a few times a year and mostly dragged with the intellectual and emotional development along the other two. These have been great of the children,” she says. “Neither parent should experiences for our son. He has traveled with us miss those various wonderful phases with their to many conferences all over the world and children. Even if you have to pull a late night, you attended our talks. He used to ask questions had better go to that concert or show or soccer publicly after our talks, always interesting and game. Most of all, it is important that both partners sometimes tough ones.” realize that the careers and ambitions of each Chandra adds, “Shreyas enjoyed it all thor- person are equally important. Then, it is possible oughly and hardly complained. By 14, he went to to support the other and lend a helping hand.” the Illinois Mathematics and Science Academy Pushpa says that it is important for each [a boarding school] and had to live there. I would partner to be valued equally. “The times are very say the whole experience was great and quite different from when we started our careers,” smooth.” Shreyas is now a senior at the University she says. “Physicist couples are now encouraged of Chicago and is applying to graduate schools, to strive for the best bargain for both of them envisioning a career in physics. in employment.” And when they both have their careers, she adds, “It is important to share Words of advice responsibilities and household duties.” With their son making his way in the world, and Chandra offers an example. “I cook for us most the perspective gained from looking back upon of the time, and she cooks for us sometimes,” he a marriage of achievement and longevity, says. “And, in fact, when she has to cook, we go Pushpa and Chandra are willing to offer insight out to eat.” to younger couples beginning the same path– This, of course, is an example of how it can offering only because they have been asked. be done. Chandra emphasizes their mutual respect. “Since both of us understand quite a bit of each other’s issues and problems,” he says, “we solved them as they occurred. We respect each other’s priorities and care for each other’s suc- cesses, as any couple would.” They also respect each other’s differences. “I am quite a practical person,” Chandra says. “Pushpa is an optimist of the highest order. I have never known anyone more optimistic and hopeful and caring than she is. She is a highly imaginative and creative person too. She, of course, thinks, she could have done more, but being the optimist she is, she thinks that the best is yet to come. Generally our approaches to solving problems are different symmetry | volume 04 | issue 01 | jan/feb 07 symmetry | volume 04 issue 01 jan/feb but the desired effects are the same. It has worked out quite well.” For her part, Pushpa stresses the importance of each partner being a valued and active parent. “Fathers can be soccer dads while also helping

27 day in the life: stanford guest house

are common among particle physics labs, and Guest houses the Stanford Linear Accelerator Center is no exception. But in many ways, the Stanford Guest House, situated on the grounds of SLAC, is different. Elizabeth Clements, director of ILC communi- cation for the Americas, travels to SLAC and other labs several times a year. She says that compared to other places she’s stayed, the Stanford Guest House is more like a hotel. “It’s one of my favorite places to go. I’ve actually turned down staying with friends in the Bay Area over staying at the guest house,” Clements says. “It’s just so comfortable, clean, and convenient. Plus the view from the exer- cise room is amazing. I have a whole routine when I stay there.” According to General Manager Jonathan Faulkner, SLAC collaborators are the main business at the Guest House. However, visitors often com- ment on the wide range of people they meet in the common areas. The unique institutional relationship between Stanford University and SLAC makes the 112-room guest house a crossroads for visitors of all types of Stanford affiliation—from guests of the Medical School to Stanford alumni, parents of current Stanford students, and SLAC users and collaborators.

Text: Brad Plummer Photos: Brad Plummer, Sandbox Studio, and Diana Rogers, SLAC.

28 symmetry | volume 04 | issue 01 | jan/feb 07 symmetry | volume 04 issue 01 jan/feb

29 deconstruction: CMS assembly

(CMS) detector is one of the two The Compact Muon Solenoid general purpose particle detectors being constructed at CERN’s Large Hadron Collider (LHC) outside Geneva, Switzerland. The conceptual design of CMS started taking shape 16 years ago with physicists trying to work out how to build such a large detector and install it underground. Building on his previous experience with the installation of the L3 detector at the Large Electron Positron (LEP) collider, the CMS technical coordinator Alain Hervé decided that building large objects on the surface and transferring them completed to the underground area was the clear way to go. This modular concept also minimizes the time required to access, uncable, dismount, remount, recable, and recommission detector subsystems during shutdown periods.

30 1 The basic modular design of CMS was finalized in the summer of 1992. The design incorporated 15 large elements that could each be built on the surface and lowered 100 meters underground by a gantry crane, albeit one that could lift 2500 tons via four enormous cable bundles. Over the past few years these pieces have been assembled at CERN from elements built by physicists, engineers, and technicians at the 155 institutions of the CMS collaboration. All pieces undergo detailed tests before they are lowered underground.

2 Following extensive tests of the gantry crane, the first pieces to be lowered into the cavern were the two Hadronic Forward calo- rimeters, or “HFs”. These 300-ton objects are made from steel em- bedded with quartz fibers that emit Cˇ erenkov light when particles pass through them faster than light can. The light produced provides an estimation of the energy of particles traveling through the HFs.

3 The first of six endcap disks (three on each side of the CMS detector) was lowered into the cavern in November 2006. This solid steel disk forms part of the magnet return yoke and is equipped on both sides with muon detectors. It is around 16 meters in diameter, about a half- meter thick, and weighs about 400 tons.

4 The green superstructure at- tached to the disk will house electronics for a part of the detector that registers muons (heavy relatives of the electron). Moving the superstructure is an exciting task: during the ten-hour journey underground the clearance between the disks and the shaft walls is just 20 centimeters!

The remaining endcap disks and 07 symmetry | volume 04 issue 01 jan/feb the five barrel “rings” (weighing up to 2000 tons) will all be lowered by the middle of 2007, shortly fol- lowed by the lowering, installation, and commissioning of the inner detectors to be ready for the LHC startup.

Text: Dave Barney, CERN Photo: CERN

31 essay: emily ewins

astrophysics without demanding the mathemati- cal background required of most science classes. In my course, lecturer Stone Brusca provided qualitative explanations of numerical calculations involved in quantum mechanics, general relativity, and special relativity. He combined these with Web pages featuring incredible images of earth- scapes and outer-spatial phenomena, impressive demonstrations (including an unforgettable epi- sode involving a professor sandwiched between two beds of nails), and numerous visual analogies Photo courtesy of Emily Ewins to ensure that all brain types and learning styles were able to grok the complex ideas presented. Bridging the fissure between left- and right-brain Reality: Better than processes, the multimethod technique used in Fiction this course brings an understanding of the cos- Like many Americans, my taste for the sciences mos into the grasp of any interested person. was soured at a young age. I recall lugging This newfound knowledge challenged me to around heavy, impersonal textbooks full of con- reevaluate my spiritual constructs and provided fusing diagrams and bizarre word problems. the foundation for a richer appreciation of the I was frustrated by the rigidity of the left-brain complexity of our universe. I am now proud to call dominant disciplines and emerged from high myself an utter and complete “Cosmos” nerd. school with great animosity towards the subject Easily distracted by images of virtual particle as a whole. From the course material presented eruptions, I am fascinated by the possibilities I learned that 17th century revolutionaries had of intricate phase entanglements, and have night reshaped primitive notions of an Earth-centric frights about matter-antimatter annihilation universe and cracked the governing codes of occurring in my room. I am a dork, and I love it! nature. Neither quantum mechanics nor general For the first time in my academic career I have relativity had been introduced as anything other become completely consumed by a subject… than far-fetched, ungraspable notions reserved ironically, one that I had long rejected from years for supercomputing brains like Albert Einstein’s. of negative exposure. My teachers taught classical physics as the After fifteen weeks of rampant dendrite ultimate doctrine, but I refused to accept it as the development, we wrapped up our semester by concluding step in scientific progress. Despite addressing the last of seven backbone conclu- my opposition, my instructors dogmatically sions: the the anthropic principle, to introduce the insisted that Newton’s laws and descriptions theory of evolutionary cosmology. After years of of the universe were as close to a complete soul-searching for bizarre speculations about the understanding as I would get. I was able to ade- nature of our universe, I finally discovered that quately regurgitate that information on com- empirical, scientific “truths” really are stranger mand, but my rebellious nature would not allow than fiction. I would never have reached such an me to personally accept such a definitive end of astounding conclusion on my own. advancement in any subject matter. So, inspired I have recently been inspired by a Serbian by the adventurous tales of historical radicals, proverb that means infinitely more to me now than I rejected physical laws as universal and took it it ever could have prior to studying the cosmos. upon myself to develop a unique, alternative “Be humble, for you are made of earth. Be noble, perception of my physical surroundings. for you are made of stars.” This guidance effec- Up through the spring semester of 2006, I tively summarizes the paradoxical duality I now created intricate theories about the nature of face in feeling so small and insignificant in the reality; the more far-fetched, I thought, the better. universe, and simultaneously so priveleged to be I truly believed that our universe was freely inter- part of an existence that developed with such 07 symmetry | volume 04 issue 01 jan/feb pretable and that empirical data was no more finely-tuned precision. convincing than my own mental constructs. This Emily Ewins notion came crashing down during the preview Emily Ewins is a student of International Studies and French lecture for a course that would ultimately change language at Humboldt State University in Arcata, California. my perspective on the universe. More information about the “Cosmos” course can be found at “Cosmos” is an intense, upper-division general- http://www.humboldt.edu/~cosmos/. education physics course. It allows non-science majors to appreciate the glory of cosmology and

32 logbook: single top production Document courtesy of Scott Willenbrock

ten years before scientists at Fermilab discovered the top quark, Scott Willenbrock was a graduate In 1985, student at the University of Texas at Austin. He and Duane Dicus were wondering how likely it would be for a particle collider such as the Fermilab Tevatron to produce a single heavy quark. Willenbrock remembers that the eureka moment came when he was sitting in a UTexas shuttle bus on his way home. There he realized that a subatomic process called “W-gluon fusion” could lead to a single heavy quark. To outline the calculation, Willenbrock made this to-do list and included the remark, “Could even be t quark!” “Back then we were thinking about a hypothetical fourth generation of quarks [labeled U,D in the list],” says Willenbrock, now a professor at the University of Illinois at Urbana-Champaign. “Physicists had no idea how heavy the [third-generation] top was, and we didn’t know whether this calculation would be relevant to the top.” In 1995, the CDF and DZero experiments at Fermilab observed top quarks for the first time, produced in pairs via the strong nuclear force. The particle was so heavy that scientists began to search for single top quark production as well. In December 2006, about twenty-one years after Dicus and Willenbrock published their predictions, the DZero collaboration reported the first evidence for single top production at the Tevatron. Kurt Riesselmann explain it in 60 seconds

are used in physics to explore Simulations many “what if?” scenarios. In particle physics, they are used from designing new types of accelerators and detectors to evaluating the final analysis of data. Physicists use simulations to build and test virtual equipment to save the time and money required to test multiple real prototype machines. By running the virtual machines many times with various input data, scientists can better understand how the real machine would work when built, and then optimize it for best performance. Without these simulations, particle physics experiments would be harder to construct. Simulations are also used to understand how signals of new physics phenomena could be detected with an experiment. Software programs create a virtual set of particles according to a specific theore-tical model and let them interact with a simulated particle detector. By analyz- ing how the virtual detector responds, physicists begin to understand the different signatures of new types of physics. Vice versa, if physicists encounter a strange signal in their real experiment, they can use simulations to explore a variety of possible explanations by simply varying the theoretical input. Without simulations, physicists would have trouble interpreting the signals they see in a detector. Norman Graf, Stanford Linear Accelerator Center

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