Fermilab A Plan for Discovery

Chapter 2
Fermilab's Future at the Three Frontiers

Fermilab's Future at the Three Frontiers

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Particle physics is entering a rich new age of discovery. Deep and long-standing questions about matter, energy, space and time are closer than ever to being answered, thanks to powerful new scientific tools. This search for answers is expected to reveal something profound, just as physicists in the early twentieth century penetrated within the atom and discovered the quantum theory, an epochal event that created new sciences and enabled technologies that shape the modern world.

Fermilab's scientific plan for the next twenty years sets the trajectory for the United States to lead the world in scientific research with intense beams of particles. Building on Fermilab's current world-class neutrino beam facilities and experiments, the plan will double neutrino beam intensity, create muon beams and launch a new set of neutrino and muon physics experiments in this decade. Two key facilities—the Long-Baseline Neutrino Experiment and the Project X accelerator complex—will follow in the 2020s and cement the laboratory's standing as the global leader at the Intensity Frontier of particle physics.

The Plan for Discovery also leverages Fermilab's considerable on-site expertise in accelerator and detector technologies and its high-caliber technical and computing infrastructure to enable Energy and Cosmic Frontier discoveries using accelerators, experiments and telescopes around the world.

The Intensity Frontier

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Leptons and rare processes

A Feynman diagram representing the quantum effect of new particles on the electromagnetic properties of charged leptons. Xcharged and Xneutral represent new heavy particles as predicted, for example, by supersymmetry. Depending on how these particles couple to charged leptons like the muon, this diagram could be a new physics effect on g-2, an EDM, or a process that allows muons to convert to electrons.

Experiments at the Intensity Frontier open new windows on physical phenomena that may not be accessible at particle colliders or through observations of the cosmos. At this frontier, particle physicists study extremely rare fundamental processes using intense beams of particles such as neutrinos, muons, kaons and nuclei. They seek to understand the mysterious properties of neutrinos and search for never-before-seen transitions among particles, hoping for a glimpse of new particles or forces.

Intensity Frontier experiments at Fermilab and other laboratories have recently discovered many surprising properties of neutrinos. Their ability to oscillate from one type to another as they travel over long distances may connect them to even more exotic particles that are otherwise invisible to experiment. A major goal of the worldwide neutrino physics community is to observe CP violation, which reflects the fundamental difference between matter and antimatter, in experiments with neutrinos. Fermilab is now upgrading its accelerator complex to provide higher-intensity and higher-energy beams of neutrinos starting in 2013. These beams will support the next phase of the MINOS experiment and the new NOνA experiment. A major goal of NOνA is to determine the ordering of neutrino masses, a key piece of information for understanding the role of neutrinos in a unified theory of matter. The Long-Baseline Neutrino Experiment, which could be operating in the 2020s, will represent the next giant step in the quest to understand neutrinos and the origins of a matter-dominated universe.

Muons may reveal new forces and new physics through measurements of their detailed properties. Starting in 2016, Fermilab's Muon g-2 experiment will study the magnetic moment of the muon, where possible evidence for new physics has already been detected. Muon g-2 will also search for an electric dipole moment for the muon, which if detected would imply a new source of CP violation. Searches for rare processes involving muons could also reveal a new stratum of physics: later this decade the Mu2e experiment at Fermilab will investigate whether muons can change identity like neutrinos.

The key to Fermilab's long-term leadership at the Intensity Frontier is Project X, a multi-megawatt proton accelerator. Fermilab is pursuing the design and construction of this unique facility in collaboration with national and international partner institutions. Project X's proton beam power and flexibility to support multiple experiments will be unmatched anywhere in the world. It will produce intense beams of neutrinos, muons and kaons and copious quantities of heavy nuclei. Starting in the 2020s, Project X experiments with kaons and muons will be the world's best, observing rare phenomena at up to a thousand times the sensitivity currently achieved and probing energies of hundreds of TeV. These experiments could discover new phenomena or provide the critical clues to explain new physics discovered elsewhere. Project X's powerful proton beams will support ultra-sensitive electric-dipole moment searches using heavy, short-lived nuclei. Project X will drive the Long-Baseline Neutrino Experiment to its next phase, and could eventually be coupled to a muon storage ring to create a Neutrino Factory that would be the ultimate tool for the exploration of neutrino physics.

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The charged leptons

Can one lepton change to another? Scientists have learned that neutrinos can change; experiments at Fermilab and around the world are searching for the answer for the charged leptons.

The puzzle of particle families

In the Standard Model, the quarks and leptons arise in families (vertical columns in the table). These families are interconnected by the forces in nature through the phenomenon of mixing. For example, the weak interactions, mediated by the W particle, mainly convert a u quark into a d quark, but can also convert a u quark into an s or b quark. The weak interactions also violate charge-parity symmetry, in other words, these interactions mysteriously sense the "arrow of time" in the universe. The origin of these family patterns, particle masses, and mixings through the weak forces remains a mystery. They are described by, but not predicted or explained by, the Standard Model. This situation is as puzzling as the Periodic Table of the Elements was in the 19th century. The development of the quantum theory in the early 1900s explained the pattern of the atomic elements and, in turn, gave a rational basis for understanding the atom, chemical bonding, the atomic nucleus and the properties of materials. This scientific revolution led to the economic growth of the 20th century. Today, experiments at all three frontiers are attempting to solve the particle puzzle. The Intensity Frontier enables detailed studies of the properties, mass relationships and mixings among the neutrinos and the charged leptons (e, μ and τ), as well as searches for possible departures from the family pattern that would signal new physics. Energy Frontier experiments search for new particles that may extend the pattern. The Cosmic Frontier addresses the mysterious role of gravity, which does not yet fit in an established way into the Standard Model. Physicists expect that profound discoveries could emerge from 21st century research at the frontiers of particle physics, just as the solution to the puzzle of the atom revolutionized science a century ago.

The Energy Frontier

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Physicist Enrico Fermi

Intensity and Energy Frontier physics have gone hand-in-hand since the early days of particle physics. Henri Becquerel, Marie Curie and Ernest Rutherford were Intensity Frontier pioneers, witnessing the weak interactions in rare decays of atomic nuclei decades before Enrico Fermi codified them into the first theoretical description of the weak force, and more than fifty years before the particles responsible for these forces were produced in a particle accelerator.

Energy Frontier accelerators enable the direct detection of new particles and forces. Fermilab's Tevatron Collider long led the world at the Energy Frontier, passing the baton to CERN's Large Hadron Collider at the start of its first physics run in 2010. Over the next few years, the Tevatron's CDF and DØ experiments will conclude the analyses of their full data sets. Over the next two decades, Fermilab and its user community will continue to use their scientific, technical and computing leadership to maximize the discovery potential of the LHC. Fermilab's accelerator and detector expertise will be used to its fullest extent as the laboratory contributes key components to the upgrades of the LHC detectors and the LHC accelerator. The laboratory's accelerator and detector R&D programs will continue to develop technologies for the next generation of particle physics instruments, while the physics community makes the discoveries that will point the way to the world's next new Energy Frontier accelerator.

The Cosmic Frontier

At the Cosmic Frontier, careful study of matter and radiation in the universe allows us to probe the inter-relationship of all matter with gravity and with any hidden ingredients that leave an imprint on matter and energy in the cosmos. Research at the Cosmic Frontier has already produced many signatures of new fundamental phenomena, the most prominent being the discoveries of dark matter and dark energy that challenge our basic understanding of physics. For decades Fermilab has been a world leader in studies of the cosmos as a laboratory for fundamental physics. Although these Cosmic Frontier experiments do not use accelerators, they do make use of Fermilab's cutting-edge technical capabilities and expertise in managing widely distributed international consortia of researchers.

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Dark matter

X ray and optical imaging of the sky combine to reveal clear evidence of dark matter (blue), separated from ordinary, luminous matter (red) by a merger of galaxy clusters.

Photo courtesy of Maruša Bradac.

Fermilab currently supports four kinds of experimental searches for the direct detection of dark-matter particles. Confirmed detection of dark-matter particles would link to the formation of structure in the cosmos, the possibility of producing dark matter in LHC collisions, and to potential signals of dark-matter annihilation in our galaxy. The effects of dark matter on the evolution of the expanding universe are entwined with the even more mysterious role of dark energy. Here again Fermilab is at the forefront as the leading laboratory for the Dark Energy Survey, which will be the deepest, most precise survey of cosmic structure on the largest scales.

Fermilab also brings its expertise to the Pierre Auger Observatory that studies the highest energy cosmic rays, and is developing a new adaptation of interferometer technology to study directly, in a laboratory experiment, the fine-grained quantum behavior of space and time and its relationship to matter and energy. The cosmos presents some of the most profound mysteries facing physics today, and some of the greatest opportunities for future discoveries.

A Laboratory at the Frontiers

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At the frontiers of technology

The Fermilab Test Beam Facility provides versatile beams for detector R&D to the international particle physics community. Every year more than 200 users test novel detector concepts and technologies at the facility.

Fermilab's Plan for Discovery lays out an ambitious blueprint for the evolution of the laboratory's Intensity Frontier accelerator complex, and for ongoing contributions to particle physics at all three frontiers. The scientific program described in this plan is broad by design, allowing Fermilab the best chance to take advantage of new physics discoveries. This breadth is critical for a successful future for the laboratory and for U.S. particle physics.

Successful execution of this plan requires all aspects of the laboratory to work in concert to build the infrastructure and drive the science that leads to new discoveries. Physicists and accelerator scientists work together with engineering and technical staV to design, build, operate and analyze data from particle detectors and accelerators. Fermilab's theoretical physics group connects the three frontiers as they define and sharpen the scientific cases for projects, provide strategies and tools for the analysis of experimental data, and meld experimental results into the big picture of nature.

Fermilab's computing efforts continue to expand possibilities for experimental and theoretical physicsists and spur innovation in particle physics and other fields of science. The laboratory's accelerator and detector R&D programs develop new tools and breakthrough technologies that have the potential to improve society as well as enable better accelerators and detectors. Every year, more than 200 users from the international particle physics community test new detector concepts and technologies using versatile beams from the Fermilab Test Beam Facility. Accelerator centers and test facilities now under development at Fermilab, including the Illinois Accelerator Research Center and the Advanced Superconducting Test Accelerator, seek to strengthen the connection between advanced accelerator R&D and industrial applications while building technologies for the future of the field of particle physics.