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URA 2005 Annual Report
Fermi National Accelerator Laboratory
Overview
Fermi National Accelerator Laboratory, 30 miles west of Chicago, is a U.S. Department of Energy national laboratory with the primary mission to provide the facilities and resources necessary for advancing the understanding of the fundamental nature of matter and energy, and to provide leadership and resources for qualified experimenters to conduct basic research at the leading edge of high-energy physics and related disciplines.
Fermilab is the home of the Tevatron, the world's highest-energy particle accelerator. Particle beams circle through a ring of magnets four miles in circumference to generate collisions that produce experimental conditions equivalent to those that existed in the first quadrillionth of a second after the birth of the universe. Large detectors record and analyze these high-energy particle collisions to unveil the forces and particles that have governed the evolution of the universe since the Big Bang. Fermilab also has the world's most powerful proton beam for creating neutrinos, ghostlike particles that can cross the entire Earth without leaving a trace. The huge number of neutrinos produced at Fermilab allows scientists to conduct experiments that explore the role these particles have played in the formation of the universe. The detectors for both collider and neutrino experiments are built and operated by large teams of visiting scientists and Laboratory staff.
The Center for Particle Astrophysics at Fermilab includes groups investigating cosmic rays, supernovae, dark energy and other phenomena. Together with the collider and neutrino experiments, these research projects place Fermilab at the frontier of global particle physics and particle astrophysics research.
Fermilab currently provides research facilities for nearly 3,000 particle physicists and their students, from 259 institutions in 37 states (plus the Commonwealth of Puerto Rico) and 31 foreign countries. The U.S. scientists' research is usually supported by DOE and the National Science Foundation, and in some cases by university funds.
Evolution of the Laboratory
Today, the Fermilab accelerator complex consists of a chain of five machines that accelerate particles in sequence to increasing energy. Fermilab began operations in the early 1970s with a single beam of protons directed at fixed-target detectors. The Laboratory has upgraded its capabilities over the years to advance the exploration of the fundamental building blocks of matter. The first major upgrade was the development of the Tevatron, the world's first superconducting synchrotron, with beam energies of approximately one TeV or one trillion electron volts. It operated for the first time in 1983, and the leaders of its design and construction team received the National Medal of Technology in 1989.
Another vital upgrade enabled the Tevatron to become a collider, accelerating antiprotons as well as protons to TeV energies, in beams traveling in opposite directions, to produce collisions at selected interaction regions. The first proton-antiproton collisions were achieved in 1985, and now two 5,000-ton detectors, CDF and DZero, track and record the subatomic particles that emerge from proton-antiproton collisions. The collaborations that use these detectors announced in March 1995 the discovery of the top quark, a fundamental particle with an electric charge two-thirds that of the electron, and a mass nearly equal to that of one atom of gold. In late 1997, the Laboratory ended Tevatron Collider Run I in order to make major improvements to the Fermilab accelerator complex and the two big collider detectors for Run II. Meanwhile, the last run of the Tevatron fixed-target program was completed in early 2000, the same year one of the collaborations announced the discovery of the predicted, but hitherto unobserved, tau neutrino, thereby completing the discovery of the members of all the three families of elementary particles.
Major improvements in the accelerator complex since the end of Run I have led to an increase of the Tevatron collision energy to nearly 2 TeV and to a much higher collision rate. The two-mile Main Injector, completed in 1999, has increased the rate of antiproton production for Run II. The Recycler, a storage ring located in the Main Injector tunnel that began operation in 2005, has eliminated a bottleneck in the accelerator chain and allows for large bunches of antiprotons to be injected into the Tevatron collider. The Recycler's successful operation involves reducing the size of the antiproton beams. The smaller and denser the antiproton beams, the larger the collision rate with the proton beams. Increasing the density of the beam is achieved via cooling, and one way to cool the beam is to bathe it in “cold” electrons. This technique has been successfully used in relatively low-energy nuclear physics machines. In the Recycler, the technique is being applied for the first time to higher energy, 8 billion electron volt (8 GeV) beams, pushing electron cooling to new performance limits.
Fermilab's two collider detectors have reinvented themselves for the new, higher-event-rate environment of Collider Run II. The CDF and DZero collaborations began to overhaul their respective detectors after the end of Collider Run I, and then proceeded with a major rebuilding program. Foremost among the challenging schedule issues for both collaborations was delivery of specialized silicon sensors and readout chips for particle tracking. Collider Run II began in 2001, and scientists from U.S. universities and others around the world resumed using these more sophisticated, more technically agile and more powerful detectors to record data in the barrage of high-energy collisions created by the Tevatron. All of the accelerator improvements for Collider Run II combined could provide proton-antiproton collision data up to sixty times that of the entire Collider Run I. Work continues on improving the performance of all systems of the accelerator complex to achieve the Run II goals by 2009.
The Laboratory's current fixed-target program consists of two forefront neutrino experiments: MINOS, which receives 120 GeV protons from the Main Injector; and MiniBooNE, which receives 8 GeV protons from the Booster, the proton injector accelerator for the Main Injector. A proposed third neutrino experiment, called NOνA, has received approval from the Fermilab directorate. Experiment collaborations continue to analyze data and uncover new scientific results from current and preceding collider and fixed target runs.
Fermilab is moving ahead in its collaborations in non-accelerator projects at the forefront of research in astrophysics: the Cryogenic Dark Matter Search; the Pierre Auger (Cosmic Ray) Observatory Project; and the Sloan Digital Sky Survey. The Laboratory is also in collaborations for two proposed projects: the Super Nova Acceleration Probe (SNAP) and the Dark Energy Survey.
R&D continues on options for future accelerators, with the focus now on the proposed International Linear Collider (ILC) and an 8 GeV Proton Driver. Both machines would rely on superconducting acceleration structures. In an international collaboration, Fermilab is building the R&D facilities necessary to develop and test these components, and the Laboratory is preparing for a potential U.S. bid to host the ILC in Illinois.
In addition, the Laboratory is the center of U.S. activity in preparing for the scientific program at the Large Hadron Collider (LHC), now under construction at CERN, the European Laboratory for Particle Physics in Geneva, Switzerland. The LHC, which will collide particles at seven times the energy of the Tevatron, is currently scheduled to begin operations in 2007, and at that time, the high-energy frontier in particle physics will shift to Europe. The LHC Physics Center at Fermilab plans to provide U.S. physicists with a remote control room for the CMS experiment, as well as the computing resources for physics analysis.
The advances in scientists' understanding of the physical universe through progress in the interrelated fields of particle physics, astrophysics and cosmology over the past few decades are remarkable. Of the 18 fundamental subatomic particles that have been observed thus far, three have been discovered at Fermilab: the bottom quark in 1977, the top quark in 1995, and the tau neutrino in 2000. Yet these 18 particles make up less than five percent of the entire mass and energy of the universe. Experiments have shown that the total matter-energy content of the universe must include invisible dark matter that holds the universe together, and a mysterious dark energy that pushes the universe apart. The prospects for new fundamental discoveries in the next decade are as great as at any time in the history of these fields. New experiments and observations will be able to answer profound questions, some of which are related to discoveries within the last few years, and others which have been central to these fields for decades. In its report entitled “Quantum Universe, The Revolution in 21st Century Particle Physics,” a Department of Energy/National Science Foundation advisory committee formulated the following nine interrelated questions that define the research agenda ahead.
1. Are there undiscovered principles of nature: new symmetries, new physical laws?
The fundamental particles discovered so far reflect the underlying symmetries that make up the known physical laws of nature. Yet the quantum ideas that so successfully describe the familiar forms of matter in our environment fail when applied at the cosmic scale of the universe. Solving the problem requires the appearance of new forces and new particles signaling the discovery of new symmetries. The theory of “supersymmetry” predicts that for every known particle there also exits a “superpartner” particle. The experimental discovery of supersymmetry is an immediate challenge in particle physics.
2. How can we solve the mystery of dark energy?
Two independent discoveries imply the presence of a new form of energy that accounts for over two-thirds of the energy content of the universe. This dark energy that permeates empty space and accelerates the expansion of the universe must have a quantum explanation. Dark energy might be related to the so-called Higgs field, a force that fills space and gives particles their mass. The discovery of supersymmetry would provide crucial evidence for this possible connection.
3. Are there extra dimensions of space?
In trying to understand the quantum nature of gravity, physicists have developed “string theory,” which implies the existence of supersymmetry and predicts seven undiscovered dimensions of space that give rise to much of the apparent complexity of particle physics. The discovery of these extra dimensions would change our understanding of the birth and evolution of the universe and reshape our concept of gravity.
4. Do all of the forces in nature become one?
At the most fundamental level all forces and particles in the universe might be manifestations of a single grand unified force, as envisioned by Albert Einstein. We already know that remarkably similar mathematical laws and principles describe all the known forces except gravity. A grand unified force would relate all of the elementary particles and predict new ways that one kind of particle can transform into another.
5. Why are there so many kinds of elementary particles?
There are three families of particles with dramatically different masses. Patterns and variations in the families of these particles suggest undiscovered principles that tie together the “quarks” and “leptons” of the “Standard Model” of particle physics. Detailed studies of quarks and leptons at accelerator experiments will provide the clearest insight into these principles.
6. What is dark matter, and how can we make it in the laboratory?
Most of the matter in the universe is unknown dark matter, probably heavy particles produced at the very beginning of the universe, in the “Big Bang.” The leading candidates for dark matter are as yet unobserved particles whose existence is predicted by theories that go beyond the Standard Model. In particular, the theory of supersymmetry predicts new families of particles interacting very weakly with ordinary matter.
7. What are neutrinos telling us?
Among the particles that make up the Standard Model, neutrinos are the most mysterious. Neutrinos are both ubiquitous and elusive, interacting so weakly with other particles that they travel through the universe almost unimpeded by matter. Detailed studies of the neutrino's tiny mass relative to the other particles, and how they change from one type to another as they travel may lead to the discovery of new phenomena.
8. How did the universe come to be?
According to modern theories of cosmic evolution, the universe began with a singular explosion (the Big Bang), followed by an extremely rapid burst of expansion, termed “inflation.” To understand inflation requires breakthroughs in our understanding of physics, of quantum gravity, and of an ultimate unified theory. Following inflation, the universe passed through a series of transitions to allow the formation of stars, galaxies, and life on earth. Although the physical conditions during inflation are too high in energy to reproduce on earth, some of the conditions of the later cosmic transitions could be recreated for study in high-energy accelerator experiments.
9. What happened to the antimatter?
Experiments show that for every fundamental particle there exists an antiparticle, a particle that has identical mass and other properties, but has still other properties which are reversed, such as electrical charge. When a particle and an antiparticle interact, they annihilate each other, producing lighter particles and the release of energy in the form of massless photons. Current cosmological theories imply that the big bang and its immediate aftermath almost certainly produced particles and antiparticles in equal numbers. However, observations to date indicate that the universe is composed almost entirely of matter. A tiny imbalance between the particles and antiparticles must have developed early in the universe, or else most of them would have annihilated leaving only photons and neutrinos. Subtle asymmetries between matter and antimatter, some of which have been observed in the laboratory, must be responsible for this fortuitous imbalance.
The Fermilab program is addressing all nine of these important issues with new and proposed experiments. Over the next few years, the Tevatron collider remains at the center of the search for new physics at the highest energy available at any accelerator facility. For example, discovery of the predicted, but as yet unobserved, Higgs boson would lead to an understanding of what determines the masses of the elementary particles. Fermilab has also developed a world-leading neutrino program that will contribute essential information on the puzzling question of neutrino masses and oscillations. The Fermilab particle astrophysics program is exploring the questions of dark matter, dark energy, and mysterious high energy phenomena in the universe. Fermilab is actively engaged in planning and R&D for the future accelerators and experiments intended to address the above issues.
New Director
Pier Oddone became Fermilab's fifth Laboratory Director on July 1, 2005. Immediately after stepping down from his previous position as Deputy Director of Lawrence Berkeley National Laboratory, Dr. Oddone was appointed to a consulting position at Fermilab on April 1, and began an intensive three-month Director transition period at the Laboratory. The overlap period with the last three months of Micheal Witherell's tenure as Director afforded Dr. Oddone the opportunity to participate as a member of the Laboratory's management team in a number of important strategic planning activities and external reviews of Fermilab.
Publications
During 2005 the various collaborations of experimenters and theorists at Fermilab produced over 180 publications and made over 240 conference presentations. The results included the most precise measurement of the top quark mass, observation of quantum oscillations between particles containing bottom quarks and their antiparticles, and new limits on the size of extra dimensions and the mass of new particles proposed by theoretical models such as supersymmetry. In addition, during 2004 - 05 some 90 Ph.D. candidates completed theses on accelerator-based research they carried out at Fermilab, and another 55 completed theses based on the Laboratory's astrophysics activities. These students go on to exciting careers in particle physics, in related fields such as astronomy, computer sciences, and engineering, as well as careers in industry and commerce.
Safety
Fermilab has an ambitious and effective program to continuously improve safety in the workplace. The Laboratory's major benchmark accident rates have been reduced by a factor of about eight over the last eight years, and are currently among the lowest in the DOE laboratory system. In 2005, Fermilab received two National Safety Council awards: the Excellence Achievement Award recognizes Fermilab for outstanding safety performance in 2004, and a Certificate of Merit honors Fermilab for outstanding safety practices during installation activities of the NuMI neutrino project.
Collider Experiments
The CDF and DZero collaborations have an excellent opportunity for new discoveries, such as the Higgs boson, the lightest supersymmetric particles, and evidence for extra “dimensions” predicted by certain advanced theories. However, such discoveries require an aggressive program of further upgrades to the accelerator complex and the collider detectors over the next couple of years.
Since the March 2001 start-up of the collider complex for Run II, the Laboratory has been engaged in the technical challenge of steadily increasing collider luminosity, a measure of the proton-antiproton collision rate. The luminosity improvements over the past several years have been crucial for providing the 1,400 physicists who make up the CDF and DZero collaborations with the huge number of collisions they require for new discoveries. Since the beginning of 2005 the Laboratory has increased Tevatron peak luminosity by more than 50% and set a world record for the highest peak luminosity of any hadron collider. In addition the Laboratory exceeded the fiscal year design goal for integrated luminosity, a measure of the cumulative number of collisions delivered to CDF and DZero.
The upgraded CDF and DZero detectors are both taking data with high efficiency. The detector collaborations continue to report new measurements, both in support of leading theories and in the search for new phenomena beyond the current Standard Model. Some of these measurements provide the world's best limits on new phenomena. For example, in order to explain the relative weakness of gravity compared to the other three known forces, new theories have proposed that there are extra geometric dimensions beyond the normal three of everyday experience. The CDF collaboration has recently released a new result, based on data collected thus far, that places limits on the possible size of these extra dimensions. By mid-2005, the Collider collaborations had already submitted for publication some 60 papers on Run II research results. Fermilab's Tevatron collider program will represent the world's top research program at the energy frontier until the LHC detectors begin taking physics-quality data later this decade.
Neutrino Expirements
Scientists have discovered three different types, or “flavors,” of neutrinos: electron neutrinos, muon neutrinos, and tau neutrinos. The particles play an important role in stellar processes, such as the creation of energy in stars as well as supernova explosions. Experimental results obtained over the last five years have observed that the evasive neutrinos switch back and forth among their three different flavors while traveling through space and matter, suggesting that these particles have mass. Two current Fermilab experiments explore in detail the phenomenon of neutrino mass through neutrino oscillations. The results of these experiments concerning the properties of neutrinos, in conjunction with others around the world, could be profound because of the abundance of neutrinos in the universe. (Each cubic centimeter of the universe contains more than 100 neutrinos!)
The MiniBooNE experiment uses a proton beam from Fermilab's 8 GeV Booster to produce a neutrino beam. The MiniBooNE collaboration is searching for the change of muon neutrinos to electron neutrinos, and will provide a definitive answer to questions raised by evidence for such neutrino oscillations observed in an experiment at Los Alamos National Laboratory. The confirmation of the Los Alamos result would suggest the existence of a fourth type of neutrino and would revolutionize scientists understanding of the ghost-like particles.
Construction of the MiniBooNE experiment began in October 1999, and the MiniBooNE collaboration has been taking physics data since late 2002. All beam and detector systems are working well. During 2005, the total number of protons “on target” for the production of neutrinos exceeded the established milestone, an important measure for collecting the data sample that the experiment requires. The collaboration has made great progress in analyzing measurements and anticipates presenting results in 2006.
In the NuMI (Neutrinos at the Main Injector) project, with its associated experiment called Main Injector Neutrino Oscillation Search (MINOS), Fermilab uses the Main Injector to create a high intensity beam of muon neutrinos aimed first at the “near” MINOS detector, and continuing straight through the earth to the “far” MINOS detector, located deep underground at the Soudan Underground Laboratory, in a former iron mine in northern Minnesota. The MINOS experiment will directly confirm muon neutrinos changing to tau neutrinos during their 730-kilometer journey from Fermilab to Minnesota. Civil construction, which included challenging underground excavation activities, began in 1999, both on the Fermilab site and at Soudan. The first beam of 120 GeV protons was successfully transferred from the Main Injector to the NuMI beamline in late 2004. The first neutrino event was recorded in the near detector in January 2005. The official dedication of NuMI was held at Fermilab on March 4, 2005, with U.S. Speaker of the House Dennis Hastert pressing a computer key that sent the neutrino beam to the far detector at Soudan. Full MINOS data-taking commenced in May 2005. In December 2005 the MINOS experiment reached an important milestone of 1020 protons on target for the production of neutrinos, a new world record for long baseline experiments. The civil construction component of the NuMI project has received the Outstanding Civil Engineering Achievement Award from the Illinois Section of the American Society of Civil Engineers.
In 2005, Fermilab granted first stage approval for NOνA, a proposed large neutrino detector that would be located about 810 kilometers from the Laboratory in Minnesota, on the surface and off-axis to the NuMI beam. NOνA would provide the most sensitive search for muon neutrino to electron neutrino oscillations and a unique capability to resolve the mass hierarchy among the different types of neutrinos. The Laboratory also granted similar approval for MINERνA, a small experiment to be located on-site in the NuMI beamline upstream from the MINOS near detector. MINERνA would measure neutrino cross sections, an important interaction property. Fermilab's plans to increase proton intensity for the production of neutrinos would extend the physics benefits significantly for these experiments.
Large Hadron Collider Activities
As Collider Run II proceeds at Fermilab, the Laboratory also has a significant role in building the collider that will eventually overtake the Tevatron at the energy frontier. Through DOE and NSF, the United States is investing $531 million over eight years in the LHC accelerator at CERN and the two major LHC detectors. The U.S. is one of several non-CERN-member states, including Canada, Japan, India and Russia, contributing to the LHC.
When the LHC begins producing physics-quality data sometime in 2008, it will reach a beam energy seven times the energy of Fermilab's Tevatron. The LHC will provide a unique and affordable opportunity for U.S. scientists to continue to work at the energy frontier, and it will allow Fermilab to develop the technologies for building the accelerators that will someday surpass the LHC's capabilities.
Fermilab plays a major role in U.S. participation in the LHC. In the U.S. contribution to construction of the LHC accelerator, Fermilab leads a collaboration that includes Fermilab and the Brookhaven and Lawrence Berkeley National Laboratories. Most of the R&D for the advanced superconducting quadrupole magnets for the LHC's interaction regions has been done at Fermilab, and most of the fabrication of these quadrupoles is also taking place at Fermilab. The U.S. LHC accelerator project is nearly complete. To help commission the LHC and to carry out R&D to enhance LHC performance, Fermilab has been appointed the host laboratory for the U.S. LHC Accelerator Research Program (LARP), which was launched in February 2004.
DOE and NSF also asked Fermilab to oversee project management for the U.S. contribution to the international CMS detector, one of the LHC's two major detectors. Several years ago, the U.S. CMS collaboration asked Fermilab to serve both as one of its collaborating institutions and as its host laboratory, and Fermilab and URA agreed. In November 2005, the U.S. CMS collaboration celebrated the 97-percent completion milestone.
Fermilab has also been chosen to be the major U.S. regional computing center for CMS, one of the few such centers around the world. Planning is proceeding for Fermilab's role as host laboratory for the physics research phase of U.S. CMS once the LHC begins operations. Fermilab has established the LHC Physics Center (LPC) on the 11th floor of Wilson Hall to provide a research home for physicists from many institutions working on CMS physics analysis. Fermilab is studying the design of a remote LHC operations center, located at the Laboratory, to serve both LARP and LPC.