URA 2006-2007 Annual Report

Fermi National Accelerator Laboratory

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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’smost powerful proton beam for creating neutrinos, ghost-like particles that can cross through 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 matter, 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 some 2,500 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 ofmatter. 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 fixedtarget 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.

Fermilab’s Wilson Hall is a landmark for both the local neighborhood and the high-energy physics community

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.

TODAY’S RESEARCH PROGRAM

Fermilab’s two collider detectors were substantially overhauled for the new, higher-event-rate environment of Collider Run II, and there has been extraordinary improvement in the performance of the accelerator complex to achieve the Run II goals by 2009. 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, and thereby increase the potential for discoveries, from finding the Higgs particle to detecting extra dimensions of space.

The Laboratory’s current fixed-target program includes 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. Both experiments have published important new results about neutrino oscillations and the possible existence of a fourth type of neutrino. A third major neutrino experiment involving the Main Injector, called NOνA, has received initial approval for construction from DOE. Two smaller neutrino experiments, SciBooNE and MINERνA, are now in preparation.

Fermilab plays a key role in several 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.

With Collider Run II well underway, the CDF and DZero detectors are both taking data with high efficiency, R&D continues on future accelerator facilities, with the focus on the proposed International Linear Collider (ILC)

R&D continues on future accelerator facilities, with the focus on the proposed International Linear Collider (ILC), and on a phased approach to increasing proton beam intensity for extending the reach of the neutrino physics program. Both efforts would rely on superconducting acceleration structures. In an international collaboration, Fermilab is building the R&D facilities necessary to develop and test key ILC 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 nearing the end of 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 be commissioned in 2008, and at that time, the high-energy frontier in particle physics will shift to Europe. The LHC Physics Center at Fermilab provides U.S. physicists with a remote operations center for the LHC accelerator as well as the CMS experiment, computing resources for physics analysis, and access to experts in hadron collider physics.

The Frontiers of Particle Physics, Astrophysics and Cosmology

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 have been 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 amysterious 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 needed to provide answers to the above questions.

Programs and Activities, including Recent Highlights

SCIENTIFIC STRATEGY

With the formation of Fermi Research Alliance, LLC (FRA), an organization jointly owned by URA and the University of Chicago and dedicated to the management of Fermilab, Laboratory Director Pier Oddone and his senior management team strengthened Fermilab’s Scientific Strategy. The strategy focuses on the following primary scientific fronts.

Energy frontier: Run II of the Tevatron represents the leading edge in high-energy physics and will continue to be at the research frontier at least through 2009, overlapping with the startup of the LHC at CERN in 2008. Fermilab’s strong role in the CMS experiment at the LHC will ensure continuing access to the energy frontier during the next decade. In parallel, the Laboratory is making a significant investment in R&D towards the long-term goal of hosting the proposed ILC.

Neutrino physics: MINOS, MiniBooNE, SciBooNE and MINERνA are the current and near-term experiments in this field, to be followed by NOνA, which is soon to start construction. A campaign to increase the neutrino flux created by Fermilab accelerators by a factor of three is part of this program.

Particle astrophysics: This program includes current and future experiments to study dark energy (SDSS-II, DES and JDEM), current and future searches for dark matter (CDMS, CDMS-25, COUPP) and the observation of ultra-high-energy cosmic rays (Pierre Auger).

DEVELOPMENT OF A ROADMAP FOR THE FUTURE

In 2007, Fermilab Director Pier Oddone established a Steering Group to propose a roadmap for the future of the Fermilab accelerator-based particle physics program. The Steering Group, chaired by Deputy Director Young- Kee Kim has developed the roadmap based on the recommendations in the 2006 report of the National Academies’ Committee on Elementary Particle Physics in the 21st Century (EPP2010), and on the current recommendations of the Particle Physics Program Project Priorities (P5) subpanel of the DOE/NSF High Energy Physics Advisory Panel. The Steering Group has considered the Fermilab-based facilities in the context of the global particle physics program. Specifically, the group has developed a strategic roadmap that: supports the international R&D and engineering design for as early a start of the ILC as possible and supports the development of Fermilab as a potential host site for the ILC; develops options for an accelerator-based high energy physics program in the event the start of the ILC construction is slower than the technically-limited schedule; and includes the steps necessary to explore higher energy colliders that might follow the ILC or be needed should the results from LHC point toward a higher energy than that planned for the ILC. The roadmap will provide valuable input for the Laboratory’s recently initiated workforce planning effort.

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 nine years, and have been among the lowest in the DOE laboratory system. In 2006, Fermilab received the National Safety Council’s Occupational Excellence Achievement Award for the third consecutive year. To meet DOE’s increasingly stringent safety performance metrics, Dr. Oddone established in March 2006 a Director’s Panel on Injury Reduction. The Laboratory is in the process of implementing the Panel’s recommendations.

COLLIDER EXPERIMENTS

In 2006, the Tevatron Collider set new performance records, and provided world-class data to the CDF and DZero experiments. During the past year, the Collider collaborations made several key discoveries and important measurements. CDF and DZero have the potential to make major discoveries, such as the Higgs boson; the lightest supersymmetric particles; and extra dimensions of space predicted by string theories. Such discoveries have required an aggressive program of upgrades to the accelerator complex and the collider detectors over the past several years.

The luminosity improvements of the accelerator complex over the past several years—a measure of the proton-antiproton collision rate—have been the key to providing the 1,400 physicists who make up the CDF and DZero collaborations with an ever-increasing number of collisions—the foundation of discoveries. All CDF and DZero upgrades were completed in 2006, and both detectors have been taking data with high efficiency. The detector collaborations continue to report new measurements, refining our understanding of the Standard Model of particles and forces as well as setting constraints on new phenomena beyond the Standard Model. Some of these measurements provide the world’s best limits on new phenomena. Among the important results coming from the CDF and DZero experiments in the past year are: the discovery of rare matter-antimatter oscillations at ultrahigh frequency (3 trillion oscillations per second); discovery of two rare types of particles that are exotic relatives of the common proton and neutron; and the first evidence of single top quarks produced in a rare subatomic process involving the weak nuclear force.

In early 2007, the CDF collaboration announced the world’s most precise measurement of the W boson mass, the carrier of the weak nuclear force and a key parameter of the Standard Model. The new W mass value leads to an estimate for the yet-undiscovered Higgs boson that is lighter than previously predicted, in principle making observation of this elusive particle more likely by the experiments at the Tevatron Collider.

Fermilab has also developed a world-leading neutrino program that will contribute essential information on the puzzling question of neutrino masses and oscillations

Through 2006, the Collider collaborations submitted for publication some 80 papers and made 500 conference presentations on Run II research results. About 150 students have submitted Ph.D. theses from Run II thus far, and about 250 others are currently working towards their degrees. The 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. Each additional year of running time extends the Tevatron Collider’s discovery reach for the Higgs boson, and for physics beyond the standard model.

NEUTRINO EXPERIMENTS

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 decade have shown that the evasive neutrinos switch back and forth among their three different flavors (neutrino oscillations) while traveling through space and matter, suggesting that these particles have mass. Two current Fermilab experiments explore in detail the phenomenon of neutrinomass 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 has been searching for the change ofmuon neutrinos to electron neutrinos in order to provide a definitive answer to questions raised by evidence for such neutrino oscillations observed by the LSND experiment at Los Alamos National Laboratory. A confirmation of the LSND result would suggest the existence of a fourth type of neutrino and would throw serious doubt on the present structure of the Standard Model of particles and forces. In April 2007, the MiniBooNE collaboration reported its eagerly-awaited first results,which rule out the interpretation of the LSND signal as a simple two-neutrino oscillation effect (equal for neutrinos and antineutrinos). MiniBooNE has been running with antineutrinos for the past year, but the collaboration is also continuing its analysis of the earlier neutrino data at low energy that did not match expectations.

In the NuMI (Neutrinos at theMain Injector) project, with its associated experiment called Main Injector Neutrino Oscillation Search (MINOS), Fermilab uses a 120 GeV proton beam from the Main Injector to create a high intensity beam of muon neutrinos aimed first at the “near” MINOS detector located at the Laboratory, 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 northernMinnesota. Civil construction of NuMI, which included challenging underground excavation activities, began in 1999, both on the Fermilab site and at Soudan. The NuMI project received an Outstanding Civil Engineering Achievement Merit Award in 2006 from the American Society of Civil Engineers. By the end of 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 LHC will provide a unique and affordable opportunity for U.S. scientists to continue to work at the energy frontier

The MINOS experiment has confirmed neutrino oscillations as muon neutrinos travel the 730 kilometers from Fermilab to Minnesota. In 2006, the MINOS collaboration reported the “disappearance” of about half of the muon neutrinos sent to the far detector. MINOS confirmed that the number of “disappeared” muon neutrinos is consistent with the neutrino oscillation effect. The mass difference between the two oscillating neutrino states corresponds to an amount that is about one ten millionth of the mass of an electron. At present, MINOS provides the world’s best accelerator-based measurements for the neutrinomass difference and oscillation parameters.With Fermilab’s projected proton intensity improvements and planned running schedule, MINOS expects to reach its design goal of evenmore precise neutrinomeasurements. First results from a search for electron neutrino appearance are expected in the next year.

In 2007, Fermilab plans to start the NOνA project, a 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. NOνAwill provide the most sensitive search for muon neutrino to electron neutrino oscillations and a unique capability to resolve the mass hierarchy among the three different types of neutrinos known to exist.

The Laboratory installed the SciBooNE experiment in a newly constructed enclosure near the Booster neutrino beam target. SciBooNE will measure various cross sections for low-energy neutrinos that are important for the T2K experiment in Japan, as well as for MiniBooNE. The MINERνA collaboration is making good progress for a small experiment to be located on-site in the NuMI beamline upstream from the MINOS near detector. MINERνA will measure neutrino cross sections with unprecedented precision at higher energies. Fermilab’s plans to increase proton intensity for the production of neutrinos would extend the physics benefits significantly for each of these experiments.

LARGE HADRON COLLIDER ACTIVITIES

As Collider Run II continues at Fermilab, the Laboratory also has a significant role in the collider that will soon overtake the Tevatron at the energy frontier. Through DOE and NSF, the United States has invested $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 participate in the development of technologies for building the accelerators that will someday surpass the LHC’s capabilities.

In the U.S. contribution to construction of the LHC accelerator, Fermilab led a collaboration that included 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 took place at Fermilab. In March 2007, a support structure for one of these magnet assemblies failed a pressure test in the LHC tunnel at CERN, and the subsequent investigation revealed an engineering design flaw that required repairs on all nine such magnet assemblies delivered to CERN. Fermilab has collaborated closely with CERN to provide the technical solution to the problem, as well as to conduct a thorough analysis of the root causes of the design flaw. A redesigned support structurewas installed in one magnet assembly, and a subsequent pressure test was successful. The new support structure will be incorporated in each of the remaining magnet assemblies before their installation.

As the largest U.S. laboratory for particle physics, Fermilab would provide a strong base on which to build new facilities

With its construction responsibilities for the LHC accelerator now essentially completed, Fermilab is actively participating in the commissioning phase. 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. The main areas of LARP activities are accelerator physics (experiments and simulation), long-term magnet design and production for the LHC interaction region upgrade, and instrumentation and diagnostics.

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. Fermilab serves as one of the collaborating institutions in U.S. CMS and is its host laboratory. In July 2006 the U.S. CMS collaboration joined their CMS colleagues from around the world in announcing that the completed giant detector had been sealed and switched on for a series of tests using cosmic ray particles. During 2007 CMS is being installed, section by section, into its underground cavern at the LHC in preparation for commissioning activities.

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. Preparations are underway 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, and the LHC@FNAL remote operations center on the ground level of Wilson Hall to serve both LARP and LPC.

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