dimensionsof particle physicssymmetry

A joint Fermilab/SLAC publication

volume 04

issue 01

jan/feb 07

On the CoverBabar 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 quan-tum process that the BaBar collabor-ation is studying is called the “penguin.”

Photos: Reidar Hahn, Fermilab

Office of ScienceU.S. Department of Energy

volume 04 | issue 01 | jan/feb 07

2 Editorial: Budget ProgressThe proposed US budget has prom-ising developments for the particle physics community but physicists need to do what they can to support their interests.

3 Commentary: Prioritizing US Particle PhysicsA roadmap produced by the US parti-cle physics community sets a direc-tion for how the research community can answer its most pressing scien-tific questions in particle physics over the next five years.

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

8 BaBar’s Window on the Weak ForceThe BaBar B-factory experiment at Stanford Linear Accelerator Center looks to double its data in a mere two years as it hunts for hints of spectacular new physics and guide future experiments.

14 Evolution of a ColliderAs physicists and engineers devise ways to make the International Linear Collider perform better at a lower cost, the design evolves, sometimes with tweaks, but other times with major reconfigurations.

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.

28 Day in the Life: Stanford Guest HouseGuest houses are common among particle physics labs. But in many ways, the Stanford Guest House, sit-uated on the grounds of Stanford Linear Accelerator Center, is different.

30 Deconstruction: CMS AssemblyMoving and assembling a particle detector underground is a delicate operation, especially when the detec-tor weighs more than 12,000 tons.

32 Essay: Reality—Better than FictionA literature student, excited by physics but turned off by how it was taught, took to inventing her own theories of the universe. Then a university course showed her that reality is more inter-esting than anything she could invent.

ibc Logbook: Single Top ProductionIn 1985, physicists were wondering whether particle colliders could dis-cover new, heavier generations of quarks. Twenty years later, the calcu-lation applies to the production of single top quarks at the Tevatron.

bc Explain it in 60 Seconds: SimulationsSimulations are used in physics to explore many “What if?” scenarios. In particle physics, they are used for application from designing new types of accelerators and detectors to evaluating the final analysis of data.

symmetryA joint Fermilab/SLAC publication

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Budget progressThe 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.

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 bud-get that satisfies their needs.David Harris, Editor-in-chief

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SymmetryPO Box 500MS 206Batavia Illinois 60510USA

630 840 3351 telephone630 840 8780 faxwww.symmetrymagazine.orgmail@symmetrymagazine.org

(c) 2006 symmetry All rights reserved

symmetry (ISSN 1931-8367) is published 10 times per year by Fermi National Accelerator Laboratory and Stanford Linear Accelerator Center, funded by the US Department of Energy Office of Science.

Editor-in-ChiefDavid Harris650 926 8580

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commentary: abe seiden

The Particle Physics RoadmapIn October 2006, the Particle Physics Project Prioritization

Panel (P5) provided a new roadmap for a broad and very exciting science agenda in particle physics research. The roadmap’s destinations are among the most intriguing questions in sci-ence: the origins of mass and the search for the Higgs boson; extra dimensions; dark matter and dark energy; unification of the known forces and possible new forces; the three families of matter, from the massive top quark to the near-massless neutrino; and CP violation, the key to the imbalance between matter and antimatter in the universe.

The P5 plan recommends construction and R&D toward major projects for the next five years, within an international context, and within budget guidance from the US Department of Energy (DOE) and the National Science Foundation (NSF). There are recommended review dates for projects anticipated to be ready for construction early in the next decade. Along with ongoing projects, and projects with con-struction nearing completion, these recommen-dations form the new roadmap.

P5 is a subpanel of the High Energy Physics Advisory Panel, chartered jointly by DOE and NSF. HEPAP endorsed the P5 plan in October 2006. The P5 panel received important input from specialized assessment panels in individual physics areas, and from the report of the Committee on Elementary Particle Physics in the 21st Century (EPP2010), Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics. The P5 recommendations converge on these major scientific opportunities: the energy frontier of the Large Hadron Collider and the proposed International Linear Collider; the nature of dark matter and dark energy; neutrinos; and precision measurements with charged leptons or quarks.

There is enormous potential for across-the-frontier discovery projects at the LHC and ILC, with the LHC addressing the full spectrum of science questions from the nature of mass, to dark matter and dark energy, unification, and CP violation. Neutrino science investigations would encompass neutrinoless double-beta decay, reactor and accelerator neutrino oscilla-tion experiments, and neutrinos from space.

A program to understand dark matter, com-plementary to work in astrophysics, seeks to study its particle nature directly in the laboratory. However, dark energy can only be studied (at our present level of understanding) through astro-nomical observations; therefore, projects typically involve interagency collaborations with the astron-omy programs at NSF or NASA.

For major construction and R&D over the rest of this decade, P5 set these three priorities: research at the energy frontier, including the full LHC program and R&D for the ILC; a near-term program in dark matter and dark energy, as well as measurement of the small neutrino-mixing angle; and construction of the NOνA neutrino-oscillation experiment, along with related modest Fermilab accelerator complex improvements.

The dark matter and dark energy program includes the 25 kg Cryogenic Dark Matter Search (CDMS), the Dark Energy Survey (DES), and finalizing a cost and schedule plan for two dark energy projects: The Large Synoptic Survey Telescope, in collaboration with the NSF; and SNAP, one of three options for a dark energy space mission. DOE should work with NASA to determine the best space mission.

Neutrino efforts include the Daya Bay (China) reactor neutrino experiment, along with R&D for a Deep Underground Science and Engineering Lab (DUSEL), R&D for a large dark matter detector, and a neutrinoless double-beta decay experiment to be located at DUSEL.

P5 advocated a review toward the end of this decade for a number of projects, many of which could start construction soon thereafter. ILC pro-gress will be reviewed, including a possible US bid to host the ILC. The LHC upgrade construc-tion is required to raise LHC luminosity tenfold. DUSEL, including the large dark matter and neu-trinoless double-beta decay experiments that it could host, will be reviewed. The two large dark energy experiments will need to be revisited. The status of flavor physics, and the importance of further new charged lepton or quark flavor exper-iments, will also be monitored. The best direc-tions for further neutrino physics experiments would be based on the physics results over the next five to ten years.

With appropriate reviews, new discoveries, adaptations to budget constraints, and progress on interagency and international collaboration, projects on the P5 roadmap are poised to make significant discoveries in the years ahead.

Abraham Seiden is the chair of the P5 subpanel and a physi-cist at the University of California, Santa Cruz. Find link to full P5 report online at www.symmetrymagazine.org

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signal to background

Delicate detector surgery; walking in the dark; dark matter song; flying across

Antarctica to catch particles; big bang re-enactment; letters.

Engineering big upgradesHow do you renovate a delicate, irreplaceable detector? Very carefully.

During the last four months of 2006, the BaBar collaboration at SLAC successfully replaced a prematurely aging muon iden-tification system. Creative and solid engineering played a big role in upgrading a detector that wasn’t meant to be taken apart.

Jim Krebs, BaBar’s chief engineer for mechanical oper-ations, spent five years on the project. “We had to figure out how to take everything apart.”

In August, crews opened the doors that protect the three-story-tall detector, exposing five layers of detection instrumenta-tion and a nervous system of wires and cables. Graduate stu-dents disconnected and then

lovingly tied, bundled, and org-anized the thousands of cables that blocked the way to the muon identification system.

To access the outermost layer of the detector where the muon system resides, the mechanical operations crew used thousands of crane lifts to remove several layers and many tons of steel, including critical pieces where the sup-port arms for the calorimeter detector attach. Protecting the calorimeter was one of the toughest engineering chal-lenges, and required suspend-ing 44,000 pounds, about half its weight. The support scheme performed flawlessly.

Early engineering efforts went into building a special lift to tackle the difficult job of pull-ing out the old muon detectors and feeding the new ones into

narrow slots angled at 60 degrees. The lift fit alongside the front end of the detector with only inches to spare, sand-wiched between the beam pipe that pierces the center of the detector and the opened door. The new muon detectors come on one-inch-thick, 12-feet-long flexible sheets. Standing on the lift’s platform, crews used the built-in angled tray to help hold the long, delicate sheets in position for insertion.

When everything was put back together and the detector doors closed again, many peo-ple let out sighs of relief. Opening the detector required taking a calculated risk because not all of the earthquake protec-tion could stay in place. Now, the refurbished detector is tak-ing data again.Heather Rock Woods

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Walking in the dark?I have been attending hundreds of talks by particle physicists who look for a very specific experimental signature that is predicted by a very specific theory extending the Standard Model. However, I was curious how much faith my colleagues have that what they’re looking for can be real. So I asked them in an informal poll.

The chances of certain dis-coveries looked very low to me, and it seems that the voters agree. The Standard Model Higgs received 90 votes and for many voters was a second tick-mark. (Voters could check multi-ple answers.) Other potential discoveries received far fewer votes. Supersymmetry, a great

“favorite” for some physicists, got only 46 votes. The moral of this, for me, is that unlike the early 90s, when we knew what we were looking for—the top quark that had to be there—now we are walking in the dark.

Something must exist to play the role of the Higgs, but we can only try to guess right now. None of our guesses can be taken very seriously. What will guide our theories will be experimental data. At this point, it makes all the sense to search for the “unknown” in our data. The good thing is that whatever is to be found next, it will be very exciting; even more so than the top quark was.Georgios Choudalakis, MIT/Fermilab

Dark Matter RapI first heard of dark matter at a Moriond Conference in 1987. A guy named David Spergel had the idea that if dark matter was weakly interacting massive particles (WIMPs) they would be captured gravitationally by the sun and cool it enough to explain why Ray Davis only observed 1/3 of the expected number of neutrinos. I think he named them “Cosmions”, but WIMP sounded much better.

My PhD thesis was a big germanium detector designed to look for a type of nuclear reaction called double-beta decay but it turned out we could also look for WIMPs. I spent about a month driving to and from the Gotthard Tunnel in Switzerland where we could reduce the background noise enough to detect dark matter if it was made of heavy neu-trinos. Daniel Reusser contin-ued after I left and in 1989 pub-lished a paper that showed that dark matter could not be made of neutrinos unless they had a mass of more than about 1 TeV, far higher than what is now known to be the case.

For a long time, I thought dark matter was just some-thing that was cooked up to explain the solar neutrino problem and galactic rotation curves. It was not until I heard David Weinberg’s Dark Matter Rap that I understood what a long and important history dark matter has had in astronomy. I actually learned much of what I know by reading the papers mentioned in Weinberg’s song. I also learned about astrono-mers who care more about “How much? Do we need it? Where is it?” than what dark matter actually is.Peter Fisher, MIT

Read the text of the Dark Matter Rap and listen to an mp3 recording on the symmetry website.

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What kind of physics do you expect to be discovered at LHC?

Answers Votes

Standard Model Higgs

SUSY

Extra dimensions

Compositeness (excited quarks, leptons,gauge bosons)

Leptoquarks

New strong dynamics (technicolor)

Other, that is not includedin this list but has beenproposed.

Other, that would surpriseeveryone.

I expect no new physics

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Answers were taken through the fnalgrads@fnal.gov 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.

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signal to background

ANITA takes flightA one-time visitor to SLAC, the Antarctic Impulsive Transient Antenna (ANITA), recently took to the frigid skies over Antarctica on a mission look-ing for evidence of cosmic-ray neutrinos.

On December 14, 2006, sci-entists tethered the 20-foot-tall probe to a high-altitude helium balloon and released it into the atmosphere. ANITA circled the south polar conti-nent three and a half times at an altitude of more than 100,000 feet—three times as high as a passenger jet. The probe’s array of antennae was tuned to scan for the radio signals that are produced when cosmic-ray neutrinos strike the Antarctic ice below. ANITA landed nearly 1100 miles from the original launch site on January 19, 2007, after 35 days aloft—the second longest duration for a scien-tific balloon flight in history.

Before traveling to Antarctica, ANITA first got its bearings during calibration tests at SLAC. In early June 2006, a team of collaborators tuned the antennas with a series of experiments con-ducted in End Station A using a 10-ton block of ice to simu-late the Antarctic environment. Researchers then blasted the ice with pulses of electrons, producing a cascade of radia-tion called Cerenkov radiation,

which included both radio waves and visible light.Brad Plummer

Berkeley Band re- enacts the big bangThe world, by some accounts, was created in seven days. Not to try and top that, but a univer-sity band managed to re-enact the big bang in a period of less than an hour.

The band was recruited by University of California, Berkeley, astrophysicist George Smoot for a “creation” role in the Nobel Prize ceremony in Stockholm, Sweden, at which he was presented the Nobel Prize in Physics for findings confirm-ing the big bang theory. Back in November, Smoot asked the Berkeley band for help in filming a video to be shown during the Nobel festivities on Sunday, December 10, 2006.

“Professor Smoot came up to the band and asked if later that week, when we practiced at Memorial Stadium, we could do a formation like the uni-verse forming. He wanted the band to form up a blob and re-enact the big bang. That’s what he asked,” marveled Hanadi Shatara, the band’s public relations director.

Not long after, Smoot addressed the members of the band, assembled in a modified blob midfield at Memorial Stadium. “It’s a little more com-plicated than ‘Go Bears,’ but it’s

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 uni-verse and spread out, and we’re going to form structure—galax-ies, stars, planets, and every-thing else,” he explained. “Let’s go for it. Go Bears! Go band!”

A marching band simulate the big bang? Mellophonist Jason Lo spoke for the band: “We can do this!”

Smoot continued with the cosmological choreography. “There’s a brass section out there called tubas. They make a real spectacular spiral galaxy, a really big one like our own galaxy, or like Andromeda. You guys get to be near the middle, but you get to orient, and get to rotate with a twist up. You’re like the centerpiece of all this. Go tubas!”

A member of the Swedish television crew filming this event said he had one question before the band began its ren-dition of the big bang. “What starts the big bang?” he asked.

Simple, said Smoot. “Drums!”Jeffery Kahn, University of California, Berkeley

A video of the performance can be seen online at http://tinyurl.com/yhe23j

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Letters

Dorm lifeI 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 whispersI 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 futureDuring 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 under-standing 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

CorrectionsOur 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.

Letters can be submitted via letters@symmetrymagazine.org

�Photo: Reidar Hahn, Fermilab

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The sun is shining; the Earth is warm instead of icy. Life is good, thanks to the weak force.

One of the four known forces that shape the universe, the weak force sustains our lives, driving the nuclear reactions that power the sun and heat the Earth’s core. It’s also tremendously useful. The weak force drives radioactive decays that diagnose disease and treat cancer, make your smoke detectors work, and indicate the age of ancient skeletons and tools.

Providing a window on the weak force are the two “B factory” experi-ments—BaBar at Stanford Linear Accelerator Center (SLAC) in California and Belle at KEK in Japan. They have made landmark discoveries in their first eight years of operation. Now entering the final two-year home stretch, the experiments are racing to learn even more about the weak force’s sometimes-odd behavior, and open gateways to the big mysteries of the universe. The weak force still holds secrets, and BaBar and Belle are seizing their unique opportunities to decipher them.

The B playgroundThe experiments’ primary tool for exploring the weak force is a heavy par-ticle called a B meson. The B factories together have manufactured almost a billion pairs of them by slamming together electrons and their antimatter partners, positrons. The BaBar team expects to more than dou-ble its own data sample by the end of 2008. B mesons are produced in pairs: one made of matter, one made of antimatter. Each contains a bottom (or b) quark, the second heaviest quark. The b quark partners with a lighter quark to form a B meson.

“The B meson is a playground or laboratory for the weak force,” says BaBar collaborator Steve Sekula of MIT. “Left on its own without the weak force, it would hold together forever.”

Because the weak force exists, B mesons do fall apart. Physicists have determined that the ones made of matter decay at a slightly different rate than the antimatter versions. That means the weak force is lopsided: it does not act equally on matter and antimatter—unlike the other forces. This asymmetry is called charge-parity (CP) violation.

BaBar’s window on the weak forceThe BaBar B-factory experiment at Stanford Linear Accelerator Center looks to double its data in a mere two years as it hunts for hints of spectacular new physics.By Heather Rock Woods

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Physicists already knew CP violation existed when BaBar got underway, and they knew that this phenomenon must contribute to the dominance of matter over antimatter in the universe. The B factories confirmed that all CP violation we see in nature comes from the weak force—but they also found that it’s not enough to explain the amount of matter in the universe today. The mismatch between experimental results and the actual universe high-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.

PrecisionThe two pillars of the BaBar program are to deeply understand the realm where the weak force and quarks interact, and to use that precise under-standing 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

Top photos: Technicians work on reconnecting elements of the BaBar detector after a major upgrade. Bottom photo: Babar rests in the PEP-II storage ring tunnel, his name-sake detector behind the wall in the background.

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the old world very well so when we see something new, we have something to compare it with.”

BaBar’s success in the next two years depends on collecting vast amounts of data both to reduce uncertainties in all types of measurements and to increase the chances of seeing extremely rare events. Indeed, the mere existence of certain rare decays would explain more about the weak force.

What the B factories find will be vital to future experiments that hope to see new forms of physics, whether supersymmetry, extra dimensions, or new particles. BaBar and Belle operate at a fraction of the energy reach that will be achieved at new machines like the Large Hadron Collider (LHC) at CERN. But while the B factories can’t directly observe new parti-cles, they can and are providing keen insight into where to look in the high-energy realm.

“If physicists at the LHC find a new particle, one of the questions will be, ‘Is what I’m seeing consistent with all the data that has come before?’” says the past physics analysis coordinator for BaBar, Riccardo Faccini of INFN Rome.

Hunting penguinsDeviations from what’s expected in the Standard Model would tell physicists about the existence of new kinds of physics.

To search for surprises, a B factory uses its typical modus operandi: it measures the amount of asymmetry between B and anti-B decays. Each B meson lives about a trillionth of a second after being created and then falls apart in one of hundreds of different ways, some of which are much more common than others.

One of the rare processes is called a “penguin” (see sidebar next page). It is a decay that requires the weak force but also contains a “virtual loop”—a place where “virtual” particles pop into existence and then disappear again almost instantly.

Even though it sounds impossible, these virtual particles can be much more massive than the original B mesons. Quantum mechanics allows them to temporarily borrow energy from the vacuum of space. However, the energy has to be repaid so quickly that a virtual particle is never observed directly. But, like a cat walking in wet concrete, it leaves an unmistakable print.

Physicists are in hot pursuit of these penguin decays because the vir-tual particles could be the much-sought Higgs particle, a supersymmetric particle, or another kind of theorized particle.

If new particles do enter penguin loops, they will introduce interactions that could change the amount of matter-antimatter asymmetry. In that case, the experiments would observe different rates of decays than pre-dicted by the Standard Model, a clear indication of new physics.

“Penguin decays are very rare, which makes them nice because if something new is coming in, it may change the asymmetry in a way that’s appreciable,” says Jawahery.

BaBar has observed many types of penguin decays, including one type they have detected only 1200 times so far in the roughly one billion B meson decays observed in the detector. The amount of asymmetry seen in that type of penguin decay is close to Standard Model predictions but still has plenty of room to reveal the contributions of new physics. Only more data, which will increase the number of all penguin decays and sig-nificantly reduce the uncertainty, can solve this quandary.

Even if the chance to herald the new doesn’t materialize, the B factories will still bequeath something substantial.

“The B factories will leave a legacy of precision measurements. Even if we reveal no inconsistencies with the Standard Model, every theory in the future must be consistent with what we’ve observed,” says Stanford physics professor Patricia Burchat. Tightening the constraints reduces the territory that physicists still need to search.

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More than a B factoryBaBar physicists have multiple sources of urgency for the final two years, because this may be the last chance to make certain kinds of measure-ments. 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, espe-cially 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 mea-surements 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.”

AntibottomQuark

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The origin of penguinsTold by John Ellis:

“Mary K. [Gaillard], Dimitri [Nanopoulos], and I first got interested in what are now called penguin diagrams while we were studying CP violation in the Standard Model in 1976… The penguin name came in 1977, as follows.

In the spring of 1977, Mike Chanowitz, Mary K. and I wrote a paper on GUTs [Grand Unified Theories] predicting the b quark mass before it was found. When it was found a few weeks later, Mary K., Dimitri, Serge Rudaz and I immediately started working on its phenomenology.

That summer, there was a student at CERN, Melissa Franklin, who is now an experimentalist

at Harvard. One evening, she, I, and Serge went 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 penguin into my next paper. She actually left the darts game before the end, and was replaced by Serge, who beat me. Nevertheless, I felt obligated to carry out the conditions of the bet.

For some time, it was not clear to me how to get the word into this b quark paper that we were writing at the time…. Later…I had a sud-den flash that the famous diagrams look like penguins. So we put the name into our paper, and the rest, as they say, is history.”

John Ellis in Mikhail Shifman’s “ITEP Lectures in Particle Physics and Field Theory”, hep-ph/9510397

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Top photos: The BaBar control room is staffed 24 hours per day with collaboration members from around the world visiting to take shifts overseeing operation and data collection. Bottom photo: Babar visited the BaBar experi-mental hall during upgrades to the detector.

Much more to comeBoth B factories are continually pushing their limits in the quest for greater luminosities, or number of events they produce.

At SLAC, the PEP-II accelerator, which provides the electron and posi-tron beams for the BaBar experiment, has already exceeded its original goal for luminosity by a factor of four. The BaBar collaboration and the PEP-II team recently made a number of major upgrades to the detector and the accelerator to further increase luminosity by a dramatic 70 per-cent, and to make the detector even more sensitive. The final experimental stretch will run from January 2007 through September 2008.

“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.

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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 1�

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Designing the International Linear Collider is an evolutionary process. The ILC would be a next-generation machine that smashes together elec-trons and their opposites, positrons, to unlock some of the deepest mysteries about the universe. But aside from the new science, the ILC enters new territory in terms of planning and designing for the particle-physics community.

The Global Design Effort (GDE) for the ILC is an international team of physicists and engineers that continuously evaluates the project’s ever-progressing design. The design team’s goal is a machine that produces optimal physics with good value for money.

In December 2005, the GDE produced a Baseline Configuration Document. Intended to give the scientific community a first glimpse of what the ILC would look like, this baseline design outlined the physics parameters and overall schematic of the machine. The GDE completed this baseline document as a first attempt—a launching pad—to put down on paper a design that will continue to be refined.

In 2006, the GDE began stage two of ILC planning: the Reference Design Report. Publicly released in February 2007, this more detailed conceptual report specifies all hardware compo-nents in enough detail to assess performance and prepare a preliminary value estimate.

In developing a value estimate, members of the GDE asked themselves: How can the baseline design be modified to optimize the costs without dramatically compromising the physics capabilities of the machine? Such exercises resulted in a series of changes—some quite large—to the base-line design.

A big changeIn October 2006, one significant modification completely reconfigured the footprint of the machine, combining the electron and positron damping rings in one tunnel and relocating them to the center of the machine, surrounding the detectors. With the exception of the linear

accelerators that would each extend approxi-mately 15 kilometers, this reconfiguration makes it possible to fit many of the large technical sys-tems of the ILC in one central complex. The main motivation, however, for the modification: slash the construction cost of the ILC by eliminating a circular 6.7 kilometer tunnel and associated facilities, resulting in a savings of 39 percent for the damping rings.

“Optimizing cost without compromising the physics performance is the goal of the reference design,” says GDE director Barry Barish. “Our design has evolved through an orderly change control process that carefully considered the potential risks for each modification and sought input from the larger physics community. Further cost optimizations will continue to be made in the next engineering phase of the project, but for now, changes like the damping ring reconfigura-tion allow us to propose a more financially responsible machine.”

The evolutionThe idea of placing two damping rings in one tun-nel is an old idea. In fact, physicists have toyed with the idea of a central damping ring complex since the project’s first conception. Having the majority of large technical components on one laboratory’s site makes maintenance much easier and limits the disturbance to surrounding neigh-borhoods during construction. “Just the time that you save by not having to drive 15 kilometers every time you need to fix something in the damping rings makes the central campus better,” says Peter Tenenbaum, who helped with the recon-figuration as a GDE member from Stanford Linear Accelerator Center. “Think about it. You could spend an entire shift driving back and forth just to replace one part.”

Until recently physicists required two positron damping rings to counter an “electron cloud effect”—a building up of electrons inside the beam pipe that interfere with the oppositely charged positrons, destroying the beam density that is

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“Optimizing cost without compromising the physics performance is the goal of the reference design.”—Barry Barish

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“Further cost optimizations will continue to be made in the next engineering phase of the project.”—Barry Barish

essential for producing precise collisions. This cloud posed such a threat to producing the physics desired from the ILC that physicists required two positron damping rings to counter the problem. While two rings can sit comfortably in one tunnel, three would be a crowd. After damping ring R&D studies produced a number of techniques for combating the electron cloud, physicists became confident that they could eliminate one positron ring to cut costs. For the ILC physicists, the next natural step was to put the remaining single positron ring and the single electron ring in the same tunnel.

“We knew that we could build a machine that worked, but it was expensive,” says the leader of the GDE damping rings group Andy Wolski of the Cockcroft Institute. “We looked at results that we got from R&D and made a configuration that is safe enough to work but now has a more reasonable cost. There may be some technical risks, but it has such a substantial reduction in cost that we can’t ignore it.”

Without threatening physics results, the new configuration (see diagram, next page) places the electron ring and the positron ring on top of each other in one tunnel 6.7 kilometers in cir-cumference and 4.5 meters wide that sits 10 meters above the beam delivery systems. Rather than remaining at either end of the linacs, both positron- and electron-injector systems now also sit in the central complex, next to the damping rings, resulting in a complete overhaul to the beam transport system.

Configuration challengesFrom the production of the first particle bunches to the final collision of electrons and positrons, one cycle in the ILC takes only 0.2 seconds. The different steps of each cycle require a precise

coordination, introducing timing challenges for the new configuration.

In order for the electrons and positrons to col-lide at the interaction point in the center of the machine, both beams must be extracted from the damping rings at precisely the right times. Because the positron beam is not created until the electron beam is halfway down the linac, the positron ring will be partially empty before new positrons arrive to refill it. This presents chal-lenges for maintaining stability of the beam dur-ing the extraction process.

“It is an unusual thing to do to the beam, and it has never been done before with long trains of bunches,” Wolski says. “The bunches in the stor-age rings will talk to each other. When you take one out, the others will know. We need to work hard to make sure that they stay in the right place, which is why this is a priority for damping rings R&D.”

The GDE also had to consider the implications of introducing two 15-kilometer-long beam trans-fer lines to the new configuration. The main job for the beam transfer lines: preserve the beam quality of the electrons and positrons after they exit the damping ring and transport them 15 kilometers in either direction to the beginning of the linacs, without eating into the savings of eliminating an entire tunnel. “It is actually easy to have a long transfer line, because it just has to get from point A to point B in almost a straight line without destroying the beam,” says Tenenbaum, a co-leader of the Ring to Main Linac (RTML) group for the GDE.

The trickiest part involves entering and exiting the damping rings. The damping rings sit 10 meters above the main linacs, requiring a beam escalator to bring the positrons and electrons back down to the level of the transport lines.

Electrons Positrons

Damping RingsMain Linac Main Linac

UndulatorDetectors Electron sourcePositron source

DR DR5-Gev LinacUndulator5-Gev Linac

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Electrons Positrons

Electrons Positrons

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5-Gev LinacUndulator5-Gev Linac

Even though the beam escalators have a slow, gradual slope, asking particles to move vertically is not simple. “It is incredibly fussy, but it can be done,” Tenenbaum says. “It is just a geometric challenge and requires a lot of thought and effort.”

To fit the new long transfer lines into the new configuration, they will be in the ceiling of the main linac to allow room for all of the other com-ponents that must go in the same tunnel. Tenenbaum compared the size of the tunnel to a typical plane on a trans-Atlantic flight. “Watch people struggle with their bags in the overhead bins on a plane,” he says. “That is what it will be like to work on the transfer lines. It is always harder to work above your head.”

One of the benefits of having the damping rings and injectors sit 10 meters above the rest of the machine is that they will be able to operate independently of the main linacs and interaction regions. Ample shielding between the damping rings and the main linacs makes it safe to have electrons and positrons circling above and physi-cists working in the beam delivery area below, yielding more potential cost savings. “You can save a lot of commissioning time because we can test

the damping rings while we are still building the rest of the machine,” says Ewan Paterson, of Stanford Linear Accelerator Center.

Change control processKnowing that the baseline design for the ILC would continue to evolve, the GDE implemented a Change Control Board in December 2005 to review all proposed changes. Chaired by KEK’s Nobu Toge, eight additional physicists from different laboratories around the world with dif-ferent areas of expertise make up the board. “We are not external reviewers; we are from within the GDE to help our colleagues decide. The CCB’s job, however, is to try its best to ensure that our design decisions are reasonable and that they survive the relevant experts’ scru-tiny,” Toge says. “If a proposal offers a healthy working solution with a feasible design, the CCB approves the change. If not, the CCB signals a warning sign and disapproves the change.”

Serving as a set of fine-grain eyes, the Change Control Board conducts a review to evaluate the benefits and potential hazards of implementing each change request. “When you are looking at

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In the new ILC design, electrons are generated, accelerated to 5 GeV, and injected into the electron damping ring (blue oval). After the particles circle the ring 10,000 times, the ring 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 acceler-ated 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.

the big picture, it’s good to have many eyes,” Toge says.

Because the damping rings reconfiguration had an impact on almost every system in the ILC—a huge task to consider when reviewing the proposed change—the GDE called for rein-forcements and enlisted Paterson to help. As the designated “Integration Scientist” for the GDE, Paterson focuses on the interfaces and interactions between systems in the ILC, mak-ing it very appropriate for him to oversee the damping rings reconfiguration process. From civil construction to beam delivery, Paterson coordinated all of the different systems affected in the change request and presented the change request as one neat package for the CCB to review. “We asked ourselves, in our desire to save, are we overlooking something?” Paterson says. “You can’t just blindly go ahead.”

Putting it all togetherAfter 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

review panel, the relocation of the damping rings to a central campus offered extra benefits for commissioning, operations, and sharing facilities. Confident in the overall design for the machine, the GDE still has some questions about details of the central campus. “With the competence of the people we have, these are things that we can solve,” Toge says.

The nuances of the new configuration will con-tinue to be defined through R&D activities and eventually in the ILC Technical Engineering Design Report. With the change process running smoothly, ILC physicists are confident that they can continue to improve the design while lowering costs as they take the ILC through the next engi-neering design phase and closer to its exploration of the universe’s foundations.

Electrons Positrons

Damping RingsMain Linac Main Linac

UndulatorDetectors Electron sourcePositron source

DR DR5-Gev LinacUndulator5-Gev Linac

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Photo: Reidar Hahn, Fermilab �0

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In a physics lab class during his sophomore year at Indiana University, Jason Rieger made a big impression on his lab partner.

“He blew something up,” says Leah Welty, who has been Leah Welty-Rieger since Friday, August 13, 2004, when she and Jason were married in her home town of Joliet, Illinois.

Randomly assigned as lab partners, they became self-described “best friends” for a year and a half before actually dating. On a trip to New York City three years later, when both were graduate students in particle physics at Indiana University, they walked to the midpoint of the Brooklyn Bridge, where Jason proposed and Leah accepted.

“We had stopped at a jewelry store in Manhattan to pick out a ring,” Leah recalls. “But we had it mailed home to save money on the tax, so then we had to find another ring. Then when we called everyone in the family to give them the news, nobody was home.” The news, of course, spread eventually, with the ceremony and celebration taking place a year later on the grounds of a rented mansion in Joliet.

Leah and Jason have now settled into life as graduate students at Fermilab, commuting 40 miles from an apartment on the near-west side of Chicago. Both are researching the physics of the bottom quark as members of the DZero detector collaboration, sharing the same office space, and working to finish their PhD theses.

They “don’t buy a lot of extra stuff” on their grad student stipends, Jason says—except for running shoes. Both are marathon runners, and they just completed their second Chicago mara-thon; both finished in less than four hours for the first time. They want to have children (Leah, an only child herself, wants more than one), and they

are envisioning their future with the singular clear optimism of a young married couple.

“All our friends have real jobs at this point,” Leah says. “We hope that with our PhDs, we’ll be able to catch up. Our goal is that once we’re 30, all those things should be even.”

Making things workParticle physicists might spend much of their professional lives in a phantasmagorical quantum realm, but their personal lives are usually rooted firmly in the everyday world of house and home, children and family, bills and benefits, dreams and realities. When physicists marry physicists, their issues still run the conventional gamut, whether they live in America, Europe, or Asia.

The logistics for dual-physicist couples, how-ever, often adds a flavor of complexity. “Which town shall we live in?” can become “Which country shall we live in?” and “Who picks up the kids while I’m at work in the city?” can transform into “Who picks up the kids while I’m at a conference in Japan?”

Tuula Maki and Mikko Voutilainen are phys-ics graduate students from Finland. They are working on their PhD research at Fermilab and have begun a marital journey similar to that of Leah and Jason. Tuula is from Tampere, and Mikko is from Joensuu; they met as students at the Helsinki University of Technology. “It’s the MIT of Finland,” Tuula says. They “got along very well” for two years before they started dating, Mikko says, and they became engaged three years later.

Tuula and Mikko were both board members for the Guild of Physics, a student organization at Helsinki, and Tuula just wound up a term as head of the Graduate Students’ Association at

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

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Fermilab. “I like to have a role in the field, to help improve student life,” Tuula says. They live in a furnished apartment on the east side of the Fermilab site, in the area called The Village, where they are happy to be close to work without worrying about furniture, cars, and commuting.

When they finish their PhDs some time in 2007, both Tuula, now at CDF, and Mikko, now at DZero, anticipate postdoctoral positions at CERN, where the Large Hadron Collider will be starting operations. “I think it should be pretty easy to find positions for both of us,” Mikko says. “In particle physics, you stay near the big accelerators, and there should be plenty of experimental groups…We do know some scien-tists with careers in two different cities, who meet on weekends, although we wouldn’t like that.”

As for possibly raising a family: “We haven’t been thinking about that yet,” Tuula says. Mikko adds that he would like to better understand how physics couples who have been married for sev-eral years solve problems such as conflicting job offers, and how they manage to raise children with both parents working as physicists.

Juggling children and careersPatrizia Azzi and Nicola Bacchetta, both physi-cists, have mastered these issues. They have dealt with raising three children while building careers in physics. Today, they both work on the Compact Muon Solenoid (CMS) experiment at CERN, with permanent positions at Italy’s Istituto Nazionale di Fisica Nucleare in Padova. Patrizia says she and Nicola did not give a lot of consideration to the issues of work and travel that double in complexity when both spouses are members of a thoroughly international field. “No, we really did not think very much about it,” Patrizia says. “Otherwise we would have never done it!”

In what might be compared to the timing of a precision experiment, Patrizia and Nicola had children Marco (May 5, 1999), Lorenzo (May 8, 2001) and Maria (May 9, 2005). “That is not a typo,” Patrizia says. Marco and Lorenzo were born in Naperville, Illinois, late in the couple’s 14-year

stay at Fermilab. Maria was born after they had moved from Fermilab back to Padova, but a month later Nicola moved to CERN to work on CMS. And so they moved to Geneva, Switzerland, where Patrizia also joined CMS following the completion of her maternity leave.

With three young children and two full-time physicists now in Geneva, the domestic equations were unlikely to balance. Marco and Lorenzo were enrolled in an English-speaking school, so they wouldn’t have to learn a third language (French). Childcare for baby Maria took a bit more creativity and, eventually, luck also lent a hand.

“After a lot of searching,” Patrizia says, “we finally found a maman-du-jour, that is a lady that keeps the baby at her house for the day. We like her a lot and we are very happy. She lives five minutes from CERN and she speaks Spanish and French, so it was easier for me to communi-cate in the beginning. I did not speak any French. The other great thing is that a teacher from the Fermilab [day care center], Patina Waterstreet, who we already knew very well, decided to come live with us as an au-pair for one year—or more?—after her graduation. I’m sure you can imagine that life with three kids and two parents working full-time can be crazy. Now Patina is just part of the family.”

Meeting away from homePatrizia and Nicola are both from northern Italy; Patrizia from Desenzano del Garda and Nicola from Venice. Both attended the University of Padova, but not concurrently. They both worked on the Collider Detector at Fermilab for more than 14 years. They met in 1991, on the day of Patrizia’s traumatic arrival at Fermilab.

“I had a bad experience at Immigration because I needed to stay for four months, but my boss did not tell me I had only a three month visa waiver,” Patrizia recalls. “My English was very bad. In the end, moved by my tears, Immigration let me in after having me pay 90 dollars for a visa at the air-port. I was tired and nerve-wrecked, when another friend took me to the apartment in Country Ridge, behind the Family Foods supermarket, that

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 re-ception was held in the medieval Castelvecchio.

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

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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.

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Padova University was renting. That evening Nicola was also there. And he was not particularly understanding of the situation, telling me I should have known better. Oh well…”

But all went well enough. They were married in November 1993 in Verona. The reception, thanks to Patrizia’s father being a former officer in the Italian Army, was held at the Officers’ Club in the medieval Castelvecchio.

“It has always worked out in the end,” Patrizia says. “Clearly we are very lucky in having kids that are very good, sweet, and healthy. The basic rule was always to stay together, no matter where, instead of having a parent away most of the time. My kids have changed many houses—and they remember them all—but I think they can feel ‘at home,’ wherever home is. They seem to be nice and happy kids, so we must have done something right.”

Pushpa and Chandra Bhat have been mar-ried for 26 years. Pushpa, of the DZero and CMS experiments, and Chandra, of Fermilab’s Accelerator Division, are both from India. Pushpa is from a family of white-collar professionals in the city of Bangalore, while Chandra is from a family of farmers in the western mountain region near the Arabian Sea and the coast city of Goa. They met while attending graduate school at Bangalore University in the late 1970s; in fact, when Chandra showed up for an inter-view at the university, he first was quizzed by Pushpa, the top-ranked student and university gold medalist, before he met with a professor.

Their connection was immediate. They co-authored the first paper that each published, in 1978. “Then, love blossomed,” Chandra says, “and we got married in 1980.” Pushpa emphasizes that while the marriage was not an arranged one, it was very much a traditional South Indian wedding. “We were married on May 7th in Bangalore,” she says. “About 1500 people attend-ed the wedding. The ceremonies took place over five or six days.”

It might be the only wedding in the world in which one of the most famous graduate-level physics textbooks played a role. “In ancient India, boys traditionally went to a boarding school, then returned home to seek a bride,” explains Pushpa. “The wedding ceremony includes a rit-ual in which the groom needs to show off his scholarship. Chandra showed up with Jackson’s Classical Electrodynamics in hand.”

Moving abroadPushpa and Chandra defended their PhD theses on the same day in Bangalore. They moved to the Netherlands for a few years, then settled as postdocs in Durham, North Carolina, with Pushpa at Duke University and Chandra work-ing in nuclear physics at the University of North Carolina-Chapel Hill. Chandra recalls that they decided not to begin raising a family until finish-ing grad school and settling-in somewhere. Their son, Shreyas, was born in Durham in 1986. That day, Pushpa’s mother arrived and stayed for about seven months to help the new family.

Pushpa had wanted to work at Fermilab since she first became smitten with the knowl-edge of particle physics and big accelerators. Chandra waited for the right time to change his field to accelerator physics and he joined Fermilab’s Antiproton Department in 1988. As a member of the high-energy physics group at Duke University, Pushpa had worked on Fermilab experiments since 1985, and joined Fermilab in 1989. Wanting the best for their son was paramount in accepting a position at Fermilab. In the following years, they stayed at Fermilab instead of seeking academic positions.

“We are both workaholics and have worked non-stop for, oh, however many decades,” Pushpa says. “We made the decision to stay at Fermilab and not try to go to a university because if one of us traveled on a regular basis we thought it would be hard on the family and especially for our son. So, we have mainly traveled to conferences/

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.

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meetings a few times a year and mostly dragged along the other two. These have been great experiences for our son. He has traveled with us to many conferences all over the world and attended our talks. He used to ask questions publicly after our talks, always interesting and sometimes tough ones.”

Chandra adds, “Shreyas enjoyed it all thor-oughly and hardly complained. By 14, he went to the Illinois Mathematics and Science Academy [a boarding school] and had to live there. I would say the whole experience was great and quite smooth.” Shreyas is now a senior at the University of Chicago and is applying to graduate schools, envisioning a career in physics.

Words of adviceWith their son making his way in the world, and the perspective gained from looking back upon a marriage of achievement and longevity, Pushpa and Chandra are willing to offer insight to younger couples beginning the same path–offering only because they have been asked.

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 per-son 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 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

with the intellectual and emotional development of the children,” she says. “Neither parent should miss those various wonderful phases with their children. Even if you have to pull a late night, you had better go to that concert or show or soccer game. Most of all, it is important that both partners realize that the careers and ambitions of each person are equally important. Then, it is possible to support the other and lend a helping hand.”

Pushpa says that it is important for each partner to be valued equally. “The times are very different from when we started our careers,” she says. “Physicist couples are now encouraged to strive for the best bargain for both of them in employment.” And when they both have their careers, she adds, “It is important to share responsibilities and household duties.”

Chandra offers an example. “I cook for us most of the time, and she cooks for us sometimes,” he says. “And, in fact, when she has to cook, we go out to eat.”

This, of course, is an example of how it can be done.

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.

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day in the life: stanford guest house

Guest houses are common among particle physics labs, and 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 PlummerPhotos: Brad Plummer, Sandbox Studio, and Diana Rogers, SLAC.

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deconstruction: CMS assembly

The Compact Muon Solenoid (CMS) detector is one of the two general purpose particle detectors

being constructed at CERN’s Large Hadron Collider (LHC) outside Geneva, Switzerland. The con-ceptual 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.

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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 low-ered 100 meters underground by a gantry crane, albeit one that could lift 2500 tons via four enor-mous cable bundles. Over the past few years these pieces have been assembled at CERN from elements built by physicists, engi-neers, and technicians at the 155 institutions of the CMS collabo-ration. All pieces undergo de-tailed tests before they are low-ered underground.

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 Cerenkov light when parti-cles pass through them faster than light can. The light produced provides an estimation of the en-ergy of particles traveling through the HFs.

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.

The green superstructure at-tached to the disk will house electronics for a part of the de-tector that registers muons (heavy relatives of the elec-tron). Moving the superstruc-ture is an exciting task: during the ten-hour journey under-ground the clearance between the disks and the shaft walls is just 20 centimeters!

The remaining endcap disks and 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, CERNPhoto: CERN

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essay: emily ewins

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Reality: Better than FictionLike many Americans, my taste for the sciences was soured at a young age. I recall lugging around heavy, impersonal textbooks full of con-fusing diagrams and bizarre word problems. I was frustrated by the rigidity of the left-brain dominant disciplines and emerged from high school with great animosity towards the subject as a whole. From the course material presented I learned that 17th century revolutionaries had reshaped primitive notions of an Earth-centric universe and cracked the governing codes of nature. Neither quantum mechanics nor general relativity had been introduced as anything other than far-fetched, ungraspable notions reserved for supercomputing brains like Albert Einstein’s.

My teachers taught classical physics as the ultimate doctrine, but I refused to accept it as the concluding step in scientific progress. Despite my opposition, my instructors dogmatically insisted that Newton’s laws and descriptions of the universe were as close to a complete understanding as I would get. I was able to ade-quately regurgitate that information on com-mand, but my rebellious nature would not allow me to personally accept such a definitive end of advancement in any subject matter. So, inspired by the adventurous tales of historical radicals, I rejected physical laws as universal and took it upon myself to develop a unique, alternative perception of my physical surroundings.

Up through the spring semester of 2006, I created intricate theories about the nature of reality; the more far-fetched, I thought, the better. I truly believed that our universe was freely inter-pretable and that empirical data was no more convincing than my own mental constructs. This notion came crashing down during the preview lecture for a course that would ultimately change my perspective on the universe.

“Cosmos” is an intense, upper-division general-education physics course. It allows non-science majors to appreciate the glory of cosmology and

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 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 processes, the multimethod technique used in this course brings an understanding of the cos-mos into the grasp of any interested person.

This newfound knowledge challenged me to reevaluate my spiritual constructs and provided the foundation for a richer appreciation of the complexity of our universe. I am now proud to call myself an utter and complete “Cosmos” nerd. Easily distracted by images of virtual particle eruptions, I am fascinated by the possibilities of intricate phase entanglements, and have night frights about matter-antimatter annihilation occurring in my room. I am a dork, and I love it! For the first time in my academic career I have become completely consumed by a subject…ironically, one that I had long rejected from years of negative exposure.

After fifteen weeks of rampant dendrite development, we wrapped up our semester by addressing the last of seven backbone conclu-sions: the the anthropic principle, to introduce the theory of evolutionary cosmology. After years of soul-searching for bizarre speculations about the nature of our universe, I finally discovered that empirical, scientific “truths” really are stranger than fiction. I would never have reached such an astounding conclusion on my own.

I have recently been inspired by a Serbian proverb that means infinitely more to me now than it ever could have prior to studying the cosmos. “Be humble, for you are made of earth. Be noble, for you are made of stars.” This guidance effec-tively summarizes the paradoxical duality I now face in feeling so small and insignificant in the universe, and simultaneously so priveleged to be part of an existence that developed with such finely-tuned precision.Emily Ewins

Emily Ewins is a student of International Studies and French language at Humboldt State University in Arcata, California. More information about the “Cosmos” course can be found at http://www.humboldt.edu/~cosmos/.

logbook: single top

In 1985, ten years before scientists at Fermilab discovered the top quark, Scott Willenbrock was a graduate 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

logbook: single top production

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SymmetryA joint Fermilab/SLAC publicationPO Box 500MS 206Batavia Illinois 60510USA

Office of ScienceU.S. Department of Energy

symmetry

explain it in 60 seconds

Simulations are used in physics to explore many “what if?” scenarios.

In particle physics, they are used from designing new types of accelerators and detectors to evaluating the final analy-sis 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 par-ticles 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 phys-ics. 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