REVEALING THE HIDDEN NATURE OF SPACE AND TIME

Charting the Course for Elementary Particle Physics

Committee on Elementary Particle Physics in the 21st Century

Board on Physics and Astronomy

Division on Engineering and Physical Sciences

NATIONAL RESEARCH COUNCIL OF THE NATIONAL ACADEMIES

THE NATIONAL ACADEMIES PRESS

Washington, D.C.
www.nap.edu



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Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics REVEALING THE HIDDEN NATURE OF SPACE AND TIME Charting the Course for Elementary Particle Physics Committee on Elementary Particle Physics in the 21st Century Board on Physics and Astronomy Division on Engineering and Physical Sciences NATIONAL RESEARCH COUNCIL OF THE NATIONAL ACADEMIES THE NATIONAL ACADEMIES PRESS Washington, D.C. www.nap.edu

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Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics THE NATIONAL ACADEMIES PRESS 500 Fifth Street, N.W. Washington, DC 20001 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This study was supported by Grant No. PHY-0432486 between the National Academy of Sciences and the National Science Foundation and Contract No. DE-FG02-04ER41327 between the National Academy of Sciences and the Department of Energy. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project. Library of Congress Cataloging-in-Publication Data National Research Council (U.S.). Committee on Elementary Particle Physics in the 21st Century. Revealing the hidden nature of space and time : charting the course for elementary particle physics / Committee on Elementary Particle Physics in the 21st Century, Board on Physics and Astronomy, Division on Engineering and Physical Sciences. p. cm. Includes bibliographical references. ISBN 0-309-10194-8 (pbk.) — ISBN 0-309-66039-4 (pdf) 1. Particles (Nuclear physics)— Research—United States. 2. Space and time—Research—United States. I. Title. QC793.4.N38 2006 539.7’2072073—dc22 2006027444 Additional copies of this report are available from the National Academies Press, 500 Fifth Street, N.W., Lockbox 285, Washington, DC 20055; (800) 624-6242 or (202) 334-3313 (in the Washington metropolitan area); Internet, http://www.nap.edu. Cover: Industrial designer Jan-Henrik Andersen, working with particle physicists Gordon Kane and David Gerdes, portrays the collision of a proton and an antiproton in the Fermilab Tevatron accelerator. By parameterizing the different properties of subatomic particles with different visual elements (color, number and direction of helical turns, visual weight of solid and void space, and so on), Andersen creates a visual interpretation of the particle physics at work. Courtesy of J.-H. Andersen. Copyright 2006 by the National Academy of Sciences. All rights reserved. Printed in the United States of America

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Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics THE NATIONAL ACADEMIES Advisers to the Nation on Science, Engineering, and Medicine The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Wm. A. Wulf is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Wm. A. Wulf are chair and vice chair, respectively, of the National Research Council. www.national-academies.org

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Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics COMMITTEE ON ELEMENTARY PARTICLE PHYSICS IN THE 21ST CENTURY HAROLD T. SHAPIRO, Princeton University, Chair SALLY DAWSON, Brookhaven National Laboratory, Vice Chair NORMAN R. AUGUSTINE, Lockheed Martin Corporation (retired) JONATHAN A. BAGGER, Johns Hopkins University PHILIP N. BURROWS, Oxford University SANDRA M. FABER, University of California Observatories STUART J. FREEDMAN, University of California at Berkeley JEROME I. FRIEDMAN, Massachusetts Institute of Technology DAVID J. GROSS, Kavli Institute for Theoretical Physics JOSEPH S. HEZIR, EOP Group, Inc. NORBERT HOLTKAMP, Oak Ridge National Laboratory TAKAAKI KAJITA, University of Tokyo NEAL F. LANE, Rice University NIGEL LOCKYER, University of Pennsylvania SIDNEY R. NAGEL, University of Chicago HOMER A. NEAL, University of Michigan J. RITCHIE PATTERSON, Cornell University HELEN QUINN, Stanford Linear Accelerator Center CHARLES V. SHANK, Lawrence Berkeley National Laboratory PAUL STEINHARDT, Princeton University HAROLD E. VARMUS, Memorial Sloan-Kettering Cancer Center EDWARD WITTEN, Institute for Advanced Study Staff DONALD C. SHAPERO, Director TIMOTHY I. MEYER, Senior Program Officer DAVID B. LANG, Research Associate VAN AN, Financial Associate STEVE OLSON, Consulting Editor

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Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics BOARD ON PHYSICS AND ASTRONOMY BURTON RICHTER, Stanford University, Chair ANNEILA L. SARGENT, California Institute of Technology, Vice Chair ELIHU ABRAHAMS, Rutgers University JONATHAN A. BAGGER, Johns Hopkins University RONALD C. DAVIDSON, Princeton University RAYMOND J. FONCK, University of Wisconsin at Madison ANDREA M. GHEZ, University of California at Los Angeles PETER F. GREEN, University of Michigan LAURA H. GREENE, University of Illinois at Urbana-Champaign WICK HAXTON, University of Washington FRANCES HELLMAN, University of California at Berkeley ERICH P. IPPEN, Massachusetts Institute of Technology MARC A. KASTNER, Massachusetts Institute of Technology CHRISTOPHER F. McKEE, University of California at Berkeley JULIA M. PHILLIPS, Sandia National Laboratories WILLIAM PHILLIPS, National Institute of Standards and Technology THOMAS M. THEIS, IBM T.J. Watson Research Center C. MEGAN URRY, Yale University Staff DONALD C. SHAPERO, Director TIMOTHY I. MEYER, Senior Program Officer MICHAEL H. MOLONEY, Senior Program Officer ROBERT L. RIEMER, Senior Program Officer NATALIA J. MELCER, Program Officer BRIAN D. DEWHURST, Senior Program Associate DAVID B. LANG, Research Associate PAMELA A. LEWIS, Program Associate PHILLIP D. LONG, Senior Program Assistant VAN AN, Financial Associate

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Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics Preface The principal charge to the Committee on Elementary Particle Physics in the 21st Century was to recommend priorities for the U.S. particle physics program for the next 15 years. Described in the Executive Summary and more fully presented in the Overview, the committee’s considered response is laid out in detail in the main text of this report, which begins by discussing the scientific challenges in particle physics and conveying the current status of the U.S. program and then presents the committee’s consensus on the best way to sustain a competitive and globally relevant U.S. particle physics program. Given the charge (see Appendix B), the composition of this committee was something of an experiment for the National Academies. The committee membership went well beyond particle physicists and accelerator scientists to include condensed matter physicists, astrophysicists, astronomers, biologists, industrialists, and a variety of experts in public policy, particularly science policy. As a result, a good deal of education was necessary during the course of the study, and we members who are not particle physicists would like to express our gratitude for the intellectual generosity and patience of the committee’s physicists as they provided us with the level of understanding necessary to proceed with the task. In the same vein, for their considerable assistance the committee owes a great deal to its colleagues at the major particle physics laboratories in the United States (Argonne National Laboratory, Brookhaven National Laboratory, Cornell Laboratory for Elementary Particle Physics, Fermi National Accelerator Laboratory, Lawrence

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Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics Berkeley National Laboratory, and Stanford Linear Accelerator Center) and to colleagues abroad at the Deutsches Elektronen-Synchroton (DESY) laboratory in Hamburg, the European Center for Nuclear Research (CERN) laboratory in Geneva, and the Japan Proton Accelerator Research Complex (J-PARC) and High Energy Accelerator Research Organization (KEK) laboratories in Japan. For the nonphysicists on the committee, the task was both intellectually exciting and sobering. Simply stated, we nonphysicists were not fully aware of the challenge faced by the U.S. particle physics program in sustaining its tradition of leadership. Given the globalization of particle physics (and with Europe investing twice as much as the United States and Japan investing nearly half as much as the United States in particle physics), identifying a compelling leadership role for the United States was not simple. Since the unfortunate demise of the Superconducting Super Collider in the early 1990s and the subsequent stagnation of support for U.S. efforts in particle physics, the U.S. program has lacked a long-term and distinguishing strategic focus that would give it a competitive and distinctive position within the worldwide effort in particle physics. The entire committee came to believe that it was essential to adopt a compelling set of national priorities within a well-defined, long-term strategic framework. Equally important, the committee accepted the need for the United States to shoulder some risk in order to maximize the opportunity to meet the leadership and scientific challenges in particle physics. With respect to the unusual composition of the committee (see Appendix D), others will judge whether this experiment should be repeated, but it is our judgment that all members of the committee contributed distinctive and important perspectives that helped the group as a whole to devise a more compelling set of recommendations. In particular, members from outside particle physics posed challenging questions to those inside the field and listened carefully to the arguments. The result was an overall sharpening of everyone’s thinking as well as stronger connections to a broader context. Finally, we both want to personally acknowledge and thank every committee member for the tremendous attention and effort each devoted to this activity. Some members traveled great distances to participate in the committee meetings, and everyone made difficult choices about other commitments to make this project a key priority. It is only through these generous and combined efforts that this report achieved clarity and closure. Harold T. Shapiro, Chair Sally Dawson, Vice Chair Committee on Elementary Particle Physics in the 21st Century

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Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics Acknowledgments This report is the product of large amounts of work by many people. The committee extends its thanks and appreciation to all who participated in this endeavor; it would be impossible to name them all individually. The committee thanks the speakers who made formal presentations at each of the meetings; their presentations and the ensuing discussions were extremely informative and had a significant impact on the committee’s deliberations. The committee is especially appreciative of efforts by members of the international community (Robert Aymar, Ian Halliday, Yoji Totsuka, and Albrecht Wagner) to participate in its May 2005 meeting in Illinois and its August 2005 meeting in New York. And in general, the committee acknowledges the extra work required to prepare remarks addressing the broad spectrum of expertise on the committee. The committee also expresses its deep gratitude to the hosts and facilitators for each of its meetings at the particle physics laboratories in the United States (Jonathan Dorfan at the Stanford Linear Accelerator Center (SLAC), Michael Witherell and Piermaria Oddone at Fermilab, and Maury Tigner at Cornell). Most especially, the committee is grateful for the hospitality and warmth of its hosts at site visits abroad (Robert Aymar at CERN, Brian Foster of the United Kingdom, Shoji Nagamiya at J-PARC, Roberto Petronzio of the Istituto Nazionale di Fisica Nucleare (INFN), Yoji Totsuka at KEK, and Albrecht Wagner at DESY). These visits overseas were tremendously valuable.

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Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics The committee also thanks those who sent in letters and e-mail messages in response to questions posed by the committee. In particular, the excellent efforts of the Lykken/Siegrist subpanel of the High Energy Physics Advisory Panel were very helpful. Finally, the committee thanks the staff of the Board on Physics and Astronomy (Donald Shapero, Timothy Meyer, and David Lang) for their guidance and assistance throughout this process.

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Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics Acknowledgment of Reviewers This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their review of this report: W.F. Brinkman, Princeton University Persis Drell, Stanford Linear Accelerator Center Ralph Eichler, Paul Scherrer Institute Paul H. Gilbert, Parsons Brinckerhoff, Inc. Ian Halliday, European Science Foundation and Scottish Universities Physics Alliance, University of Edinburgh Wick C. Haxton, University of Washington Bernadine P. Healy, U.S. News and World Report Rolf-Dieter Heuer, Deutsches Elektronen-Synchrotron, DESY John P. Huchra, Harvard-Smithsonian Center for Astrophysics Christopher Llewellyn-Smith, United Kingdom Atomic Energy Authority, Culham Division

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Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics Joseph Lykken, Fermi National Accelerator Laboratory Satoshi Ozaki, Brookhaven National Laboratory John Peoples, Fermi National Accelerator Laboratory Burton Richter, Stanford Linear Accelerator Center Yoji Totsuka, High Energy Accelerator Research Organization, KEK Charles M. Vest, Massachusetts Institute of Technology Bruce D. Winstein, University of Chicago Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations, nor did they see the final draft of the report before its release. The review of this report was overseen by Louis J. Lanzerotti of the New Jersey Institute of Technology and William Happer of Princeton University. Appointed by the National Research Council, they were responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the institution.

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Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics Contents     EXECUTIVE SUMMARY   1     OVERVIEW   5 1   THE SCIENTIFIC EXCITEMENT AND CHALLENGES   17      Challenges to the Standard Model,   20      Responding to the Challenges,   24      The Role of the United States in Particle Physics,   26 2   KEY QUESTIONS IN PARTICLE PHYSICS   33      Can All the Forces Between Particles Be Understood in a Unified Framework?,   34      What Do the Properties of Particles Reveal About the Nature and Origin of Matter and the Properties of Space and Time?,   39      What Are Dark Energy and Dark Matter and How Has Quantum Mechanics Influenced the Structure of the Universe?,   50      Roles of Accelerator- and Non-Accelerator-Based Experiments,   53 3   THE EXPERIMENTAL OPPORTUNITIES   56      High-Energy Beams: Direct Exploration of the Terascale,   57      Discoveries at the Terascale,   57      Tools for Exploring the Terascale,   57

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Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics                 Physics at the Terascale,   64      Toward the Terascale,   75      High-Intensity Beams,   77      Nature’s Particle Sources,   84      International Cooperation,   89      Global Activity in Particle Physics,   89      The International Linear Collider,   93      A Path Forward,   94      Opportunities Ahead,   97 4   THE STRATEGIC FRAMEWORK   101      The Scientific Challenge,   101      The Position of the U.S. Program,   102      The Strategic Principles,   104      The Budgetary Framework,   111      Recent Trends in Support for the U.S. Particle Physics Program,   111      Multiyear Plans and Budgets,   112      National Program Considerations,   113      Budget Considerations,   115 5   FINDINGS AND RECOMMENDED ACTIONS   118      The Scientific Agenda for Elementary Particle Physics,   118      Priorities,   119      Direct Exploration of the Terascale,   119      Explorations of Particle Astrophysics and Unification,   129      Implications of the Strategic Agenda Under Different Budget Scenarios,   133      Realizing the Strategic Vision for Elementary Particle Physics,   135     AFTERWORD   136     APPENDIXES          A  International Progress Toward the ILC   139      B  Charge to the Committee   143      C  Committee Meeting Agendas   144      D  Biographical Sketches of Committee Members and Staff   152