The Particle at the End of the Universe: How the Hunt for the Higgs Boson Leads Us to the Edge of a New World

THE PARTICLE AT THE END OF THE UNIVERSE

How the Hunt for the Higgs Boson Leads Us to the Edge of a New World

Sean Carroll

DUTTON

DUTTON

Published by Penguin Group (USA) Inc.

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Published by Dutton, a member of Penguin Group (USA) Inc.

First printing, November 2012

Copyright © 2012 by Sean Carroll

All rights reserved. No part of this book may be reproduced, scanned, or distributed in any printed or electronic form without permission. Please do not participate in or encourage piracy of copyrighted materials in violation of the author’s rights. Purchase only authorized editions.

REGISTERED TRADEMARK—MARCA REGISTRADA

Library of Congress Cataloging-in-Publication Data has been applied for.

ISBN 978-1-101-60970-5

While the author has made every effort to provide accurate telephone numbers, Internet addresses, and other contact information at the time of publication, neither the publisher nor the author assumes any responsibility for errors, or for changes that occur after publication. Further, the publisher does not have any control over and does not assume any responsibility for author or third-party websites or their content.

To Mom,

who took me to the library

People underestimate the impact of a new reality.

—JOE INCANDELA, SPOKESPERSON FOR THE CMS COLLABORATION AT THE LARGE HADRON COLLIDER

CONTENTS

PROLOGUE

ONE
THE POINT

TWO
NEXT TO GODLINESS

THREE
ATOMS AND PARTICLES

FOUR
THE ACCELERATOR STORY

FIVE
THE LARGEST MACHINE EVER BUILT

SIX
WISDOM THROUGH SMASHING

SEVEN
PARTICLES IN THE WAVES

EIGHT
THROUGH A BROKEN MIRROR

NINE
BRINGING DOWN THE HOUSE

TEN
SPREADING THE WORD

ELEVEN
NOBEL DREAMS

TWELVE
BEYOND THIS HORIZON

THIRTEEN
MAKING IT WORTH DEFENDING

APPENDIX ONE
MASS AND SPIN

APPENDIX TWO
STANDARD MODEL PARTICLES

APPENDIX THREE
PARTICLES AND THEIR INTERACTIONS

PHOTOGRAPHS

FURTHER READING

REFERENCES

ACKNOWLEDGMENTS

INDEX

PROLOGUE

J
oAnne Hewett is feeling giddy, smiling broadly as she speaks enthusiastically into a video camera. An excited buzz filters up from partygoers at the Swiss consulate in San Francisco. It’s a unique event, celebrating the first protons circulating in the underground tunnel of the Large Hadron Collider (LHC) outside Geneva—an enormous particle accelerator on the French-Swiss border that has begun its quest to unlock the secrets of the universe. The champagne flows freely, and no wonder. Hewett’s voice rises with emphasis: “I’ve been waiting for this day for Twenty. Five. Years.”

It’s a big moment. At this point in 2008, physicists have finally achieved what they have long insisted was necessary to make the next big step forward: a giant accelerator that would smash protons together at very high energies. For a while, they thought the United States was going to build such a machine, but things didn’t work out as anticipated. Hewett was just beginning graduate school in 1983, when the U.S. Congress first approved construction of the Superconducting Super Collider (SSC) in Texas. Slated to begin operation before the year 2000, it would have been the largest collider ever built. She, like so many of the brilliant and ambitious physicists of her generation, believed that discoveries there would form the foundation of their research careers.

But the SSC was canceled, pulling the rug out from under physicists who had counted on it to shape the course of their field for decades to come. Politics and bureaucracy and infighting got in the way. Now the LHC, similar in many ways to what the SSC would have been, is at long last about to fire up for the first time, and Hewett and her colleagues are more than ready for it. “What I’ve done over the past twenty-five years is take every new crazy theory that anybody’s ever come up with and calculated its signature [how we identify new particles] at the SSC or LHC,” she says.

There is another, more personal reason for Hewett’s giddiness. In the video, her red hair is very short, almost a crew cut. It’s not a fashion choice. Earlier in the year she was diagnosed with invasive breast cancer, with about a one-in-five chance that it would be terminal. She opted for an extremely aggressive treatment program, involving harsh chemotherapy and a seemingly endless series of surgeries. Her trademark red hair, usually reaching down to her waist, disappeared quickly. At times, she admits with a laugh, she kept her spirits up by thinking about what new particles would be found at the LHC.

JoAnne and I have known each other for years, as friends and colleagues. My own expertise is primarily in cosmology, the study of the universe as a whole, which has recently enjoyed a golden age of new data and surprising discoveries. Particle physics, which has become inseparable from cosmology as an intellectual discipline, has nevertheless been starved for new experimental results that will upend the theoretical applecart and lead us forward to new ideas. The pressure has been building for a long time. Another physicist at the party, Gordon Watts of the University of Washington, was asked whether the long anticipation for the LHC has been stressful. “Oh yeah, completely. I have this shock of gray hair here now. My wife claims it’s because of our kid, but it’s really because of the LHC.”

Particle physics stands on the brink of a new era, in which some theories are going to come crashing down, and perhaps others will turn out to be right on the money. Every physicist at the party has their favorite models—Higgs bosons, supersymmetry, technicolor, extra dimensions, dark matter—a tumble of exotic ideas and fantastic implications.

“My hope for what the LHC will find is ‘none of the above,’” Hewett enthuses. “I honestly think it’s going to be a surprise, because I think nature is smarter than we are, and she’s got some surprises in store for us, and we’re going to have a hell of a fun time trying to figure it all out. And it’s going to be great!”

That was 2008. In 2012, the San Francisco party to celebrate the inauguration of the LHC is over, and the era of discovery has been officially launched. Hewett’s hair has grown back. The treatments were agonizing, but they seem to have worked. And the experiment she’s been anticipating for her entire career is making history. After two and a half decades of theorizing, her ideas are finally being tested against real data—particles and interactions never seen before by human beings, surprises that nature has been keeping hidden from us. Until now.