The International Linear Collider  A bold initiative to understand the nature of matter, energy, space and time.  The DOE Office of Science, the national labs, university researchers and international partners are promulgating an International Linear Collider to answer critical scientific questions.

What is the ILC? electron linacpositron linac 44 km e- damping ringe+ damping ring electron sources positron source collision point Powerful electric fields in superconducting cavities, in synchronization with the particle’s motion, provide the acceleration. Two 20 km long linear accelerators, bringing beams of electrons and positrons into collision in a spot only nanometers across at energies up to 1 Tera electron volts (trillion electron volts) – the Terascale. See companion paper for more on the ILC accelerator project.

The Terascale opportunity Experiments at accelerators and telescopes on the ground and in space have shown us that the Terascale is very fertile ground for discovery. We know that our current understanding is incomplete, and that surprises must lurk there. The Large Hadron Collider will enter the Terascale in 2007, and survey the terrain. New astrophysical experiments will tell us more about dark matter and dark energy. The ILC is the precision instrument capable of dissecting the new phenomena and telling us what they mean.

The ILC as telescope The unrivalled precision measurements from the ILC will allow a view of the universe at energies last seen back when it was only a picosecond old. At that time, all forces were on a common footing and long-lost particles shaped the future of the universe. The ILC recreates the conditions extant just after the big bang.

The ILC is conceived as an international project involving research centers in Europe, Asia and the Americas. Its cost and importance dictate that all regions will participate. The US should vigorously pursue building the ILC and hosting it here, once the technical blueprint is clearly established and the project is deemed to be cost effective. Substantial R&D is needed to validate the technical choices and determine the cost over the next few years. This is the primary near term challenge. The ILC and the U.S.

1.There are compelling scientific questions to be addressed 2.US leadership in science and technology requires world- class facilities at home 3.Economic value from high energy accelerator projects 4.Attracting the best minds to science and technology (and scientists and engineers to the US) 5.Symbiosis of the ILC and other scientific initiatives 6.Significant recent progress, nationally and internationally The Case for the ILC Six components:

1. Compelling scientific questions The “Quantum Universe” report prepared by DOE & NSF identifies key questions in three major sectors, these define the path to new understanding: Einstein’s dream Undiscovered principles, new symmetries? What is dark energy? Extra space dimensions? Do all forces become the same? The particle world New particles? What is dark matter? What do neutrinos tell us? Birth of universe How did the universe start? Where is the antimatter? Companion paper for more on the scientific questions motivating the ILC.

Why the Terascale?  The Higgs boson, responsible for giving mass to all particles and unifying Electromagnetic and Weak forces, should be found there.  The Standard Model becomes untenable above the teravolt scale. A range of possibilities to fix it (‘supersymmetry’, ‘technicolor’, ‘extra dimensions’) all have observable consequences at the terascale.  The Dark Matter particle seen in the cosmos should be there. Accelerator and cosmological experiments in the past two decades have assembled a ‘Standard Model’. It works well, but its shortcomings point to dramatic discoveries at the terascale. We have known for 20 years that experiments at the Terascale will reveal new secrets of matter; we now have a strategy for uncovering them.

2. Leadership in science and technology Scientific inquiry is a fundamental expression of our cultural values, and US leadership in science is a major national goal. The U.S. economy relies on a trained scientific manpower pool and technological expertise. Sen. John Pastore (hearing on funding the Fermilab Tevatron): “Dr. Wilson, can you explain the value of research in high energy physics for the defense of our country” Robert Wilson (first Fermilab director): “It has nothing to do directly with defending our country, except to make it worth defending.” Companion paper for societal benefits from fundamental research and the ILC.

3. Economic value Fundamental research drives the economy:  73% of papers cited in industrial patents were based on publicly financed research.  The World Wide Web, developed by particle physicists, exceeded $1T in revenue in 2001 and is growing exponentially.  The physical sciences bring advances in biomedical fields – MRI, PET scans, nuclear medical diagnostics, etc. The benefits from the ILC science discoveries are unpredictable, but history suggests they will be real; the knowledge generated from fundamental research in the past century has transformed society. The tools developed for that research often have had even more striking consequences. Harold Varmus, former NIH Director: “Medical advances may seem like wizardry. But pull back the curtain, and sitting at the lever is a high-energy physicist, a combinational chemist or an engineer. “

"Airplanes are interesting toys but of no military value" Marshal Ferdinand Foch, professor of strategy, Ecole Supérieure de Guerre "The wireless music box has no imaginable commercial value. Who would pay for a message sent to nobody in particular?" – David Sarnoff's associates, in response to his urgings for investment in the radio in the 1920s "I think there is a world market for maybe five computers." – Thomas Watson, chairman of IBM, 1943 Predicting economic value Gladstone, Chancellor of the Exchequer, asking about Faraday’s discoveries of electric induction (leading to the electric generator, and the basis for EM waves): “But after all, what use is it?” Faraday: “I do not know sir, but soon you will be able to tax it.” Our record of predicting economic impact of basic science is poor:

4. Attracting the best young minds Particle physics is one of the primary magnets for attracting the best minds to science and technology. The prospect for discovering supersymmetry or extra dimensions of space is a powerful motivator for young people to enter a career in science. Only about 1 in 6 PhDs in physics wind up in basic research positions; the others use their analytic problem solving skills in industry and government. The top quark discovery students at Fermilab

5. Relation to other scientific initiatives Particle accelerators are among the most significant exports from HEP to other areas of science and technology. The ILC superconducting rf technology will have strong impacts upon the future of :  Synchrotron light sources (materials science, structural biology, environmental science, plasma physics etc.)  Energy recovery linacs (spallation neutron sources for materials research and heavy ion colliders for nuclear research)  Radioactive isotope accelerators (nuclear science and astrophysics)

6. Significant international progress 2001: Panels in US, Europe and Asia recommend ILC as top priority for world’s next high energy facility. 2002: OECD Global Science Forum concurs that ILC is the next global facility, and should overlap with LHC running. 2003: International LC Steering Committee formed. 2003: Over 2700 physicists sign ILC ‘consensus document’ 2004: Choice of superconducting accelerator technology. 2005: International Global Design group (GDE) established. Companion paper for ILC organization, lessons from other projects

Learning from other large projects There are many lessons from other large projects:  ITER guidance for international scientific projects  We must learn from the failure of the SSC  Design and management techniques from NASA, very large telescope projects Initial GDE organization includes accelerator scientists, cost engineer, civil engineer and communications expert from each region (US, Europe, Asia). These people are developing common tools that can serve the global effort as well as adapt to regional needs.

The International Linear Collider  Exploring the deepest questions about the structure of matter, energy, space & time  An opportunity for promoting the scientific and technological leadership of the US  A vehicle for worldwide economic and scientific growth