To book a live or taped interview with Robert Kehoe in the SMU News Broadcast Studio call News and Communications at 214-768-7650 or email news@smu.edu.
The research of SMU physicist Robert Kehoe, a professor in the SMU Department of Physics, has been featured by Fermilab Today. The magazine is the official publication of the U.S. Department of Energy’s Fermi National Accelerator Laboratory near Chicago. Fermi is a high-energy particle physics laboratory credited in 1995 with discovery of the fundamental particle, the top quark.
Kehoe is part of the DZero collaboration of scientists who seek measurements of the top quark to determine the mass of the Higgs boson, another fundamental particle that has never been observed but which theoretical physicists have theorized generates mass for all particles that comprise matter. Others from SMU who were instrumental in the analysis include doctoral student Yuriy Ilchenko and post doctoral researcher Peter Renkel.
“The measurement precision is now down to 1.6% in these events, which is astounding given how rare dilepton events are,” Kehoe said. “Perhaps more importantly, we have pursued a new way of calibrating these events that dramatically lowered the systematic uncertainty, and will allow it to decrease with more data — we have half the data yet to analyze.”
Two major factors contribute to the ultimate precision of a measurement of the top quark mass: the amount of data used to make that measurement and the understanding of the uncertainty introduced by the detector. The amount of data used affects the size of the statistical uncertainty of the measurement, while accounting for the bias of the detector effects leads to the systematic uncertainty. Since the final precision of a measurement can’t be smaller than the larger of these two uncertainties, it is possible to have a measurement that is limited by the systematics. A systematically limited measurement won’t improve by simply taking more data. The most recent top quark mass measurement at DZero succeeded in turning a systematically limited analysis channel into a statistically limited one.
The top quark always decays into a W boson and a bottom quark. The W boson can decay into a neutrino and a charged lepton, such as an electron or muon, or into quarks. The major distinction between top quark pair analysis channels is the number of leptonic W boson decays allowed. In the dilepton channel, both W bosons decay leptonically and two neutrinos are produced. However, the incomplete reconstruction of neutrinos in the DZero detector leads to ambiguity when studying these top quark pair events. To account for this ambiguity, DZero physicists considered all possible values of the neutrino parameters to determine the value of the top quark mass that best fits the DZero data set.
SMU is a nationally ranked private university in Dallas founded 100 years ago. Today, SMU enrolls nearly 11,000 students who benefit from the academic opportunities and international reach of seven degree-granting schools. For more information see www.smu.edu.
SMU has an uplink facility located on campus for live TV, radio, or online interviews. To speak with an SMU expert or book an SMU guest in the studio, call SMU News & Communications at 214-768-7650.
Subatomic particle can explain why matter has mass
In a giant game of hide and seek, physicists say there are indications they finally may have found evidence of the long sought after fundamental particle called the Higgs boson.
Researchers at Switzerland-based CERN, the largest high-energy physics experiment in the world, have been seeking the Higgs boson since it was theorized in the 1960s.
The so-called “God” particle is believed to play a fundamental role in solving the important mystery of why matter has mass. (article continued below)
“It doesn’t matter how beautiful your theory is, it doesn’t matter how smart you are. If it doesn’t agree with experiment, it’s wrong.” — physicist Richard Feynman
By Fredrick Olness
Chairman and Professor
SMU Department of Physics
A 50 year search for the origin of particle mass nears an end. Maybe.
Mass is a seemingly simple property of everyday objects — atoms, humans, coffee cups. Yet, to understand the origin of mass on a fundamental level has been a challenging problem with a long history. The solution to this problem, suggested nearly 50 years ago, was the Higgs Boson (or just Higgs, for short). However, it has yet to be discovered.
On Tuesday, Dec. 13, 2011, an end to the Higgs search appeared much closer when the CERN Laboratory in Geneva, Switzerland presented the latest results from the Large Hadron Collider (LHC) in a colloquium broadcast around the globe on the World Wide Web.
The announcement was a joint presentation by researchers from ATLAS and CMS, the two largest independent experiments at the LHC, in which they presented evidence for the Higgs based on the results of their 2011 data set.
Both the ATLAS and CMS experiments observed evidence for the Higgs. While the evidence was significant, it was not yet sufficient to claim an unambiguous discovery; however, it is quite compelling that the Higgs mass range obtained by these two independent experiments is consistent.
These results represent a tremendous step forward in explaining why fundamental particles have mass, and whether the Higgs exists.
What is the Higgs boson?
The postulated Higgs boson is responsible for giving mass to the many fundamental particles that make up the universe. This includes the quarks that comprise protons and neutrons, which comprise atoms and molecules, which comprise humans and everything around them. In essence, the Higgs generates the mass of the fundamental particles that make up you and your coffee cup.
We know objects have mass — just lift a heavy suitcase or weigh yourself on a scale. But to explain this seemingly simple idea in the context of our current fundamental theories has been a struggle ever since the idea of the Higgs was introduced 50 year ago. The problem is that to give particles mass in a straightforward manner would spoil a particular symmetry of the theory known as the “gauge symmetry.” Who cares? you ask, and why should I be worried about symmetry?
Symmetries have been an important guiding aspect of physics dating back before Einstein, who used symmetry principles, in part, to conclude that “all reference frames are created equal,” which led to his Theory of Relativity — certainly one of the triumphs of the 20th Century.
And that is what is so special about the Higgs; it gives particles a mass without violating the rules of symmetry.
How does the Higgs solve the problem?
According to our current understanding, Higgs bosons permeate all of space. As fundamental particles move through space, Higgs bosons interact with the particles and effectively exert a drag on them; it is this drag effect which we interpret as the mass of the particle.
Consider the following experiment. First move your coffee cup through the air, and then repeat this motion underwater; the water provides more resistance on the cup and it “feels more massive” as you drag it through the water as compared to the air. It is the interaction between the water and the coffee cup that provides the resistance to motion of mass. In this analogy, the water is playing the role of the Higgs.
It is the same with a quark, one of the fundamental particles that matter is made from. As a quark moves through space it interacts with the Higgs, and this interaction exerts a drag on the quark so that it “feels heavy.” But this is an illusion; in the strict interpretation of the theory, the quark has “mass” only because of the interaction with the Higgs that simulates the effects of the weight.
DÉJÀ VU: Luminiferous aether
To recap, the current theoretical picture is that Higgs bosons are everywhere. They permeate all space, and they must exist so that fundamental particles (that make up you and your coffee cup) have mass.
Have we seen this situation before?
In the late 1800’s, physicists posited the existence of a “luminiferous aether” which permeated all space. Scientists knew that water waves traveled through water, sound waves through air, and so they believed that light waves also needed something to travel through; luminiferous aether was invented to serve this purpose and get the “right” answer. There were many experiments that gave indirect evidence for the aether; however, all attempts to directly measure it were unsuccessful. Eventually it was demonstrated that the luminiferous aether did not exist, and this paved the way for Einstein to show that it was unnecessary and to present an alternative, his theory of relativity.
Thus, the non-existence of luminiferous aether actually led to more fantastic discoveries than if it had been proven.
Direct vs. indirect evidence
So we come to the central question: does the Higgs exist?
There is ample indirect evidence that the Higgs exists. We know that fundamental particles have mass, and we believe this mass is due to particle interactions with Higgs bosons. Over the past 50 years physicists have performed a variety of sophisticated experiments, and they all point to the existence of the Higgs.
However, in many ways the Higgs is a contrived solution; inelegant, introduced into the theory because so far there has been no better way to get the right answer — that particles have mass.
Just because it is currently the only solution developed does not mean it is the one that nature chooses.
And that is why we need direct evidence of the Higgs; we need to produce an actual Higgs in the laboratory, study its properties, and verify our theoretical view of the world with cold, hard facts from experimental observation.
The 2011 LHC results
The LHC experiment is producing these facts and evidence.
If the Higgs is confirmed to exist, it would validate our theory of how particles acquire mass, and serve as the foundation for myriad experiments in the future. Many speculate this discovery would also warrant a Nobel Prize.
If the Higgs is confirmed to not exist, it would likely send many theorists back to the drawing board in hopes of finding that nature has an even more clever mechanism of how particles acquire mass than we have yet been capable of conceiving. And, just as the non-existence of the aether set the stage for relativity, the non-existence of the Higgs could set the stage for future surprises.
Either way it will be an exciting journey and the results from the LHC bring us one step closer to the answer.
Fredrick Olness is a theoretical physicist at SMU studying Quantum Chromodynamics (the fundamental force that binds nuclei) to help answer the questions: What are the fundamental building blocks of nature, and what holds them together?
Thousands of scientists from around the world seek evidence of the Higgs particle through experiments at CERN’s Large Hadron Collider. The researchers analyze a flood of electronic data streaming from the breakup of speeding protons colliding in the massive particle accelerator. Scientists on Tuesday announced in a seminar held at CERN that they’ve found hints of the Higgs.
“Now we have a strong indication, but not yet a confirmation, of a discovery,” said Southern Methodist University physicist Ryszard Stroynowski, the leader of SMU’s team of scientists working on the experiment.
Higgs: Attempting to discover Standard Model’s missing piece
Theorists have predicted that some subatomic particles gain mass by interacting with other particles called Higgs bosons. The Higgs boson is the only undiscovered part of the Standard Model of physics, which describes the basic building blocks of matter and their interactions.
Higgs bosons, if they exist, are short-lived and can decay in many different ways. Just as a vending machine might return the same amount of change using different combinations of coins, the Higgs can decay into different combinations of particles. Discovery relies on observing statistically significant excesses of the particles into which they decay rather than observing the Higgs itself.
“If indeed we are able to confirm sighting of the Higgs in the months ahead, this clearly focuses our future studies,” said Stroynowski, a professor in the SMU Department of Physics. “Now by the middle of next year we’ll know for sure if this particle exists and we can begin to study its properties. This is a very big step in the understanding of particle physics.”
SMU researchers contributed to the results announced Tuesday by CERN
Besides Stroynowski, the SMU team of researchers includes three other Physics Department faculty: Jingbo Ye, Robert Kehoe and Stephen Sekula, six postdoctoral fellows and five graduate students. Main contributions to the new analysis of the data were made by postdoctoral researcher Julia Hoffman and graduate student Ryan Rios.
Others in the department who have contributed include former postdoctoral fellow David Joffe, now an assistant professor at Kennesaw State University, graduate students Renat Ishmukhametov and Rozmin Daya and theoretical faculty Fredrick Olness and Pavel Nadolsky.
Stroynowski, Hoffman, and Rios are among the more than 70 scientists whose work directly contributed to the conference papers reporting the findings, said Olness, a professor and chairman of the SMU Department of Physics.
While thousands of scientists worldwide participated directly and indirectly in the experiments, SMU is one of only a few U.S. universities whose scientists are named among the 70 researchers directly cited on one of the three conference papers.
“Professor Stroynowski has demonstrated extraordinary scientific leadership in keeping our relatively small Department of Physics at SMU engaged in one of the most significant scientific experiments of our time,” said Jim Quick, SMU Associate Vice President for Research.
SMU’s role in the LHC experiments provides SMU students a chance to participate in pioneering discoveries, said Olness.
“SMU students helped build the ATLAS detector, they were in the control room when the experiment started up, and they contributed to the analysis,” he said. “The results presented today are historic, and they will help shape our view of the matter and forces that comprise our universe; SMU students have played a role in this achievement.”
Higgs discovery would confirm decades-old theory
Discovering the type of Higgs boson predicted in the Standard Model would confirm a theory first put forward in the 1960s.
“This year, the LHC has come roaring into the front of the hunt for the Higgs boson and may be poised to either identify it, or refute its existence, in the coming months,” said Robert Kehoe, associate professor in the SMU Department of Physics. “As I like to tell my students learning modern physics, ‘You still live in a world in which we do not know for sure the mechanism breaking the symmetry between electromagnetic and weak interactions. That world may be soon to change forever. We may soon see a truly new thing.’”
Even if the LHC experiments find a particle where they expect to find the Higgs, it will take more analysis and more data to prove it is a Standard Model Higgs, according to CERN researchers. If scientists found subtle departures from the Standard Model in the particle’s behavior, this would point to the presence of new physics, linked to theories that go beyond the Standard Model. Observing a non-Standard Model Higgs, currently beyond the reach of the LHC experiments with the data they’ve recorded so far, would immediately open the door to new physics, said an official statement from CERN.
Results constrain Higgs’ mass to a range more limited than before
In announcing the findings, CERN noted that two experiments at the LHC have nearly eliminated the space in which the Higgs boson could dwell. The ATLAS and CMS experiments see modest excesses in their data that could soon uncover the famous missing piece of the physics puzzle, the scientists said.
The experiments’ main conclusion is that the Standard Model Higgs boson, if it exists, is most likely to have a mass constrained to the range 116-130 giga-electron-volts (GeV) by the ATLAS experiment, and 115-127 GeV by CMS. Tantalizing hints have been seen by both experiments in this mass region, but these are not yet strong enough to claim a discovery.
Both ATLAS and CMS have analyzed several decay channels, and the experiments see small excesses in the low mass region that has not yet been excluded.
Taken individually, none of these excesses is any more statistically significant than rolling a die and coming up with two sixes in a row. What is interesting is that there are multiple independent measurements pointing to the region of 124 to 126 GeV. It’s far too early to say whether ATLAS and CMS have discovered the Higgs boson, but these updated results are generating a lot of interest in the particle physics community.
The experiments revealed the latest results as part of their regular report to the CERN Council, which provides oversight for the laboratory near Geneva, Switzerland.
Experiments in coming months will refine the analysis
More than 1,600 scientists, students, engineers and technicians from more than 90 U.S. universities and five U.S. national laboratories take part in the ATLAS and CMS experiments. The Department of Energy’s Office of Science and the National Science Foundation provide support for U.S. participation in these experiments.
Over the coming months, both the ATLAS and CMS experiments will focus on refining their analyses in time for the winter particle physics conferences in March. The experiments will resume taking data in spring 2012.
Another possibility, discovering the absence of a Standard Model Higgs, would point to new physics at the LHC’s full design energy, set to be achieved after 2014. Whether ATLAS and CMS show over the coming months that the Standard Model Higgs boson exists or not, the LHC program is closing in on new discoveries. — CERN, Southern Methodist University
SMU is a member of the ATLAS experiment at the LHC. It takes a large team of scientists to search for the Higgs and other new physics; the SMU delegation includes faculty members Ryszard Stroynowski, Jingbo Ye, Robert Kehoe, Stephen Sekula, and a number of research professors, postdoctoral fellows and graduate students.
In addition, recent SMU ATLAS contributors include postdoctoral fellows Julia Hoffman, David Joffe (now at Kennesaw State), Ana Firan, Haleh Hadavand, Sami Kama, Aidan Randle-Conde and Peter Renkel, and graduate students Ryan Rios, Rozmin Daya, Renat Ishmukhametov Tingting Cao and Kamile Dindar-Yagci. Theoretical support was provided by faculty member Pavel Nadolsky, electronics development by research professors Andy Liu and Annie Xiang, and computer support by Justin Ross.
New high-energy particle research by a team working with data from Fermi National Accelerator Laboratory further heightens the uncertainty about the exact nature of a key theoretical component of modern physics — the massive fundamental particle called the Higgs boson.
Analysis of data from particle collisions resulting in two leptons helps improve measurements of the mass of another heavy subatomic particle called the top quark, says physicist Robert Kehoe at SMU, who led the team that calculated the measurement.
Improving the measurement of the mass of the top quark bears on the nature of the Higgs, says Kehoe, an assistant professor in SMU’s Department of Physics.
The Higgs was postulated in the 1960s to help explain how basic elements of the universe fit together and interact. It is responsible for a phenomenon called the Higgs mechanism, which gives mass to the fundamental particles of nature.
Physicists have searched for more than four decades to observe the never-before-seen Higgs. Now they hope it will be observed in the next few years since data started flowing recently from the world’s newest and largest high-energy particle accelerator, the CERN laboratory’s Large Hadron Collider near Geneva, Switzerland.
Physicists theorize that the top quark — because of its sizable mass — is sensitive to the Higgs and therefore may point to it. They theorize that knowing the mass of the top quark narrows the range of where the Higgs will be detected in CERN’s LHC collisions. The top quark is one of 16 species of subatomic particles that physicists have observed. It was predicted in the 1970s and observed in 1995. Increasingly precise measurements of its mass have been achieved almost every year since, and physicists closely watch the incremental measurements of the top quark.
Fermilab’s DZero control room.
The two-lepton analysis by Kehoe and SMU post-doctoral researcher Peter Renkel looked at data taken over four years during high-energy collisions at Fermilab, a Department of Energy proton-antiproton collider in Batavia, Ill.
The two-lepton analysis is one of almost a dozen analyses of the mass of the top quark at a Fermilab experiment called “DZero.” The DZero experiment involves 500 physicists and is one of Fermilab’s two large experimental collaborations of scientists. The top quark mass was first observed simultaneously by these two experiments. Several measurements of the top quark’s mass from these two experiments are combined to a “world average” value.
The two-lepton analysis contributed to the latest world average measurement. The analysis looked at particles resulting from smashing protons that break apart and disintegrate. The events are very rare, and the detector can’t see two of the important “ghost” particles — neutrinos — produced by the collision. However, the two leptons are well-measured events and are not seen in other “background” collisions where top quarks are not produced. This allows a rapidly improving precision to be achieved.
The two-lepton research was published in November in the article “Measurement of the top quark mass in final states with two leptons” in “Physical Review D,” the American Physical Society’s journal of particles, fields, gravitation and cosmology. SMU physicists collaborated on the research with scientists at Boston University. The SMU portion of the work was funded by the Department of Energy.
The new world average is so precise that it constrains more tightly than ever the range of possible measurements for the mass of the Higgs, Kehoe says.
If the Higgs does prove different than currently expected, physicists may have to rework their long-standing theoretical framework, known as the Standard Model. Scientists worldwide are hoping to validate the Standard Model — which has worked well for more than 30 years to explain everything from radioactivity to computer chips — by actually observing the Higgs.
“The new results may be an indication that the Higgs boson has different properties than the Standard Model indicates,” Kehoe says. “It’s very difficult to devise a theory without some mechanism that mimics fairly well the Higgs mechanism. But if the underlying cause of this mechanism is significantly different, that will have a major impact on the fundamentals of the Standard Model. It could point to something deeper than the standard Higgs boson at work, and that is very interesting.”
The Standard Model of Fundamental Particles. Credit: Fermilab
The measured value of the top quark mass may even go beyond constraining the standard Higgs. It may suggest that our current understanding of the Higgs is not correct, he says.
If the Higgs does not show up where the constraints indicate, the top measurement may force consideration of new theoretical possibilities that lie outside the existing Standard Model, Kehoe says.
Previous measurements have put the top quark at almost the mass of a gold atom. The new world average measurement puts the top quark at about 186 times the mass of the proton. While the value has changed only a small amount from previous measurements, the percentage of error on the measurement is progressively smaller, in this case less than 1 percent.
“If we make a precise prediction of where the Higgs is and it’s not there, then something is wrong. We’ve just found a major flaw in the model,” says Kehoe, whose work has focused for 16 years on the top quark, including as a graduate student on DZero working directly on the discovery analysis. “It would tell us that the model is oversimplified and that reality is much more complicated.” — Margaret Allen
After a huge success in first testing, followed by a very public meltdown last September, the Large Hadron Collider may be ready for action again as early as June.
But before the science can proceed, the world’s scientists must come to terms with the complex organism they have created, says one project manager.
“We will have to understand the detector first,” says Ryszard Stroynowski, chair and professor of physics at SMU.
Stroynowski is U.S. Coordinator for the Liquid Argon Calorimeter, the literal and experimental heart of ATLAS, the largest particle detector in the LHC array.
Pictured right: Work progressing in the LHC tunnel.
Photo courtesy of CERN.
The first priority for operation of the ATLAS detector is “to get all those billions of elements to work together in synch again,” Stroynowski says. “We want to see during the summer whether the circulating beam will induce any noise in the system.”
Stroynowski leads an SMU delegation that includes Fredrick Olness, professor of physics, and Robert Kehoe and Jingbo Ye, assistant professors of physics, all in Dedman College. Kehoe is currently at CERN for his research.
The SMU team is focusing on three projects in parallel:
improvements of the graphic and software interfaces for control and monitoring of the detector and of the quality of its data
preparation of the software packages to analyze the data
design and prototyping of the modifications of the readout electronics that will be needed for future upgrades of the experiment to much higher-intensity beams — a six-year research and development project led by Jingbo Ye in SMU’s Physics Electronics Lab.
The LHC is considered the world’s largest physics experiment. The particle accelerator is a 27-kilometer circular tunnel that lies 100 meters underground near Geneva on the French-Swiss border. It uses a magnetic field to propel high-energy protons into each other.
A mechanical failure in September 2008 damaged 53 of the super-sized magnets that power and focus the accelerator’s beams. The final replacement magnet was lowered into place April 30. Repairs in the tunnel now focus on connecting the magnets together and installing new safety and monitoring systems to prevent similar incidents from happening again.
In addition, the 37 damaged magnets that were replaced by spares will be refurbished to serve as spares themselves. Sixteen magnets sustained only minimal damage and were repaired and reinstalled.
The earlier malfunction has resulted in a frustrating wait — one that has had a “rather demoralizing” effect on the students and postdoctoral fellows whose time at the LHC may come and go during downtime, Stroynowski says. Yet the importance of protecting the vast high-energy array from future trauma can’t be overstated, and “the goal is worth the wait, as the payoff may be enormous,” he says.
Scientists and technicians at the European Organization for Nuclear Research — called by its acronym, CERN — in Geneva have maintained an aggressive rehabilitation schedule. The ATLAS detector itself was closed on May 5, marking an end to checks and re-checks of the electronics, cables and other connections. Repairs to the accelerator’s underground ring are scheduled to be completed at the end of May.
Beams will start in June, initially at a relatively low 450 gigaelectron volts (GeV) per beam to ensure the integrity of the new parts and connections. Scientists will raise the energy over a couple of days to 2 teraelectron volts (TeV) per beam, and finally to the LHC’s target operational level of 5 TeV per beam.
The ATLAS team will start taking shifts in July and expects to have useful data starting in October 2009, Stroynowski says. The LHC will then run continuously for 11 months.
Stroynowski says he doesn’t expect any major discoveries by this time next year, but that he hopes “significant results” will come early in 2011.
The LHC’s proton collisions release even smaller pieces of matter, and the Atlas particle detector helps measure the tracks they leave. The huge, international project is directed at finding the “Higgs boson,” a subatomic “God particle” that physicists believe could help explain the origin of our Universe.
The theory behind the Higgs boson holds that all particles had no mass just after the “Big Bang.” As the Universe cooled and the temperature fell below a critical value, an invisible force field composed of subatomic particles called the “Higgs boson” developed throughout the cosmos. Particles that interact with the field gain mass and particles that never interact have no mass. But the theory remains unproven because no one has ever seen the Higgs boson at work. — Kathleen Tibbetts
SMU has an uplink facility on campus for live TV, radio or online interviews. To speak with Dr. Stroynowski or to book him in the SMU studio, call SMU News & Communications at 214-768-7650 or UT Dallas Office of Media Relations at 972-883-4321.
SMU is a private university in Dallas where nearly 11,000 students benefit from the national opportunities and international reach of SMU’s seven degree-granting schools. For more information see www.smu.edu.
At 10 p.m. on a Saturday night in April, a handful of SMU scientists continue working at the European Organization for Nuclear Research, called by its acronym CERN, in Geneva, Switzerland. A scattering of lights illuminates the windows in several buildings along the Rue Einstein, where researchers from dozens of countries and hundreds of institutions are combining their expertise on the Large Hadron Collider (LHC) — the biggest physics experiment in history.
Ryszard Stroynowski, chair and professor of physics at SMU, points out each building in succession to a group of visitors. “By October, every light in every one of these windows will be on all night,” he says.
By then, the LHC is expected to be fully tested and ready to work. When the largest particle accelerator ever constructed becomes fully operational, it will hurl protons at one another with precision to a fraction of a micron and with velocities approaching the speed of light. These conditions will allow physicists to recreate and record conditions at the origin of the universe — and possibly discover the mechanisms that cause particles in space to acquire their differences in mass.
For Stroynowski, who has worked for almost 20 years to help make the experiment a reality, words seem inadequate to capture the anticipation surrounding its imminent activation.
“It is somewhat like that of a 6-year-old kid on Christmas Eve, waiting for Santa Claus,” he says. “The time stretches almost unbearably long.”
The LHC will be the site of several experiments in high-energy physics with high-profile collaborators such as Harvard and Duke and national laboratories including Argonne, Brookhaven, Lawrence Berkeley and Fermilab. None of the experiments is more imposing than ATLAS, one of two general-purpose particle detectors in the LHC array. At about 42 meters long and weighing 7,000 tons, ATLAS fills a 12-story cavern beneath the CERN facilities in Meyrin, Switzerland, just outside Geneva. It is a tight fit: ATLAS overwhelms even the vast space it occupies. A catwalk, not quite wide enough for two people to stand side by side, encircles the device and allows an occasional dizzying view into its works.
Size Matters The detector’s scale will help to focus and release the maximum amount of energy from each subatomic collision. A series of bar codes on each of its parts ensure that the detector’s components, whether palm-sized or room-sized, are aligned and locked with the perfect precision required for operability. Scientists from 37 countries and regions and 167 institutions participated in its design and construction.
As U.S. coordinator for the literal and experimental heart of the ATLAS detector — its Liquid Argon Calorimeter — Stroynowski is helping to finalize the last details of the detector’s operation in anticipation of the extensive testing, scheduled to begin in August. He leads an SMU delegation that includes Fredrick Olness, professor, and Robert Kehoe and Jingbo Ye, assistant professors in the SMU Department of Physics in Dedman College.
SMU scientists are completing work on the computer software interfaces that will control the device, which measures energy deposited by the flying debris of smashed atoms. A cadre of University graduate students and postdoctoral fellows also is working on data processing for ATLAS’ 220,000 channels of electronic signals, an information stream larger than the Internet traffic of a small country.
An estimated 53,000 visitors crowded the CERN facilities on the organization’s “Day of Open Doors” April 6, eager for a glimpse of the work that CNN International has named one of the “Seven Wonders of the Modern World.”
At the beginning of May, the areas were sealed off in preparation for the first round of testing. Computers will remotely control the ATLAS experiment, which will not be touched by human hands because of the radiation released by the atomic collisions. Safety is the reason for the elaborate lockdown procedure involving more than 80 keys, each coded to a different individual’s biometric data. The system is designed to lock out any use of the device if even one key is unaccounted for.
“ATLAS has been built to run for at least 15 years with no direct human intervention,” Stroynowski says. “It will be as if we have shot it into space.”
Currently, the initial test run is scheduled to begin Sept. 1.
The Waiting Game Once data start streaming in, the game of expectations management begins. The ATLAS detector will produce a staggering amount of raw information from each collision, and the most useful bits will be few and far between. Out of 40 million events per second, the researchers hope to pinpoint 10 events a year. The challenge seems a little like looking for a needle in a haystack the size of Mars.
“We may get what we’re looking for on the first try, or it may take us three years to find anything we can use,” Stroynowski says. “A big part of our job is to make sure we’re ready when we do.”
Among those entrusted with that task are graduate students and postdoctoral fellows in SMU’s Physics Department, including Rozmin Daya, Kamile Dindar, Ana Firan, Daniel Goldin, Haleh Hadavand, Julia Hoffman, Yuriy Ilchenko, Renat Ishmukhametov, David Joffe, Azeddine Kasmi, Zhihua Liang, Peter Renkel, Ryan Rios and Pavel Zarzhitsky.
“I came to SMU for postdoctoral work specifically because of the department’s involvement in the ATLAS project,” says David Joffe, a native of Canada who received his Ph.D. in physics from Northwestern University. “For particle physicists, being part of this is really a once-in-a-lifetime opportunity.”
For Julia Hoffman, who received her doctorate from Soltans Institute for Nuclear Studies in her native Poland, that opportunity has meant expanding her own horizons.
“I learn new, and I mean really new, things every day,” she says. “Different programming languages, different views on physics analysis. I’m learning how it all works from the inside. I work with students and gain new responsibilities. This kind of experience means better chances to find a permanent position that will be as exciting as this one.”
The SMU group works with formulae based in Monte Carlo methods, the “probabilistic models that use repeated random sampling of vast quantities of numbers” to impose a semblance of order on the chaos created when atoms forcibly disintegrate. Results are highly detailed simulations of known physics that will help make visible the tiny deviations researchers hope to detect when ATLAS begins taking data.
These unprecedented computing challenges also have become an impetus for new SMU research initiatives. James Quick, SMU associate vice president for research and dean of graduate studies, hopes to contain ATLAS’ vast data-processing requirements with a large-capability computing center located on campus.
Quick visited CERN in April to discuss the details with Stroynowski and other key personnel. The proposed center would provide a first-priority data processing infrastructure for SMU physicists and a powerful new resource for researchers in other schools and departments. During the inevitable LHC downtime, as beams are calibrated and software is debugged, the SMU center’s computing power would be available for campus researchers in every field across engineering, the sciences and business.
“The ATLAS experiment presents an opportunity for the University to step up in a big way, and one that will benefit the entire campus,” Quick says.
He envisions a data processing farm of 1,000 central processing units, each connected to an Internet backbone to allow the fastest possible return on SMU’s ATLAS input. Speed and access are the keys, Stroynowski says, paraphrasing Winston Churchill: “The winner gets the oyster, and the runner-up gets the shell.”
Those who have made their careers in high-energy physics are well aware of the stakes involved in the LHC, he adds, and being the first to process certain data could separate a potential Nobel Prize winner from those who will make the same discovery a day late.
As a group, high-energy physicists are accustomed to taking the long view — and for SMU researchers, the long view has been especially helpful. The ghost of the Superconducting Super Collider, which would have made its home in North Texas, still shadows the recent triumphs at CERN.
The SSC brought Stroynowski to the University, and its 1993 demise through congressional defunding was the impetus for the LHC project. The questions haven’t gone away because the experiment has changed venues, Stroynowski says. Yet even now, as the first test nears, his anticipation is tempered by caution.
“I don’t think we’ll get a beam all the way around [the LHC tunnel] on the first try,” he says.
Indeed, the subject of whether scientists will achieve a beam collision during the first tests or after additional calibration has been the subject of a few lively wagers.
“I think we’ll have to wait at least a few more weeks for that milestone,” he adds. “But in this case, I’ll be more than happy to be wrong.” — Kathleen Tibbetts
SMU has an uplink facility on campus for live TV, radio or online interviews. To speak with Dr. Biehl or Dr. D’Mello or to book them in the SMU studio, call SMU News & Communications at 214-768-7650 or UT Dallas Office of Media Relations at 972-883-4321.
SMU is a private university in Dallas where nearly 11,000 students benefit from the national opportunities and international reach of SMU’s seven degree-granting schools. For more information see www.smu.edu.
Study: Nearly two-thirds of EU citizens are marginalized by English-language dominance
From ‘Green Card’ to ‘Thin Blue Line’: Lawtalk research looks at popular legal expressions
Public health insurance provides insured infants better, less costly care than private plans
Many top US scientists wish they had more children, with men especially dissatisfied
Anthropology study finds that immigrants from India and Vietnam become American over time
