Carroll - 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

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ISBN 978-1-101-60970-5

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To Mom,

who took me to the library

CONTENTS

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. Its a unique event, celebrating the first protons circulating in the underground tunnel of the Large Hadron Collider (LHC) outside Genevaan 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. Hewetts voice rises with emphasis: Ive been waiting for this day for Twenty. Five. Years.

Its 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 didnt 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 Ive done over the past twenty-five years is take every new crazy theory that anybodys 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 Hewetts giddiness. In the video, her red hair is very short, almost a crew cut. Its 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 its because of our kid, but its 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 modelsHiggs bosons, supersymmetry, technicolor, extra dimensions, dark mattera 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 its going to be a surprise, because I think nature is smarter than we are, and shes got some surprises in store for us, and were going to have a hell of a fun time trying to figure it all out. And its 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. Hewetts hair has grown back. The treatments were agonizing, but they seem to have worked. And the experiment shes 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 dataparticles and interactions never seen before by human beings, surprises that nature has been keeping hidden from us. Until now.

Jump to July 4, 2012, opening day of the International Conference on High Energy Physics. Its a biannual gathering, moving from city to city around the world, this year winding up in Melbourne, Australia. Hundreds of particle physicists, Hewett included, have filled the main auditorium to hear a special seminar. All the investment in the LHC, all the anticipation that has built up over the years, is about to pay off.

The presentation itself is beamed to Melbourne from CERN, the laboratory in Geneva that is home to the LHC. There are two talks, which would ordinarily have been presented in Melbourne as part of the conference program. At the last minute, however, the powers that be decided that a moment of this magnitude should be shared with the many people who had helped make the LHC such a success. The sentiment was appreciatedhundreds of physicists at CERN have lined up for hours before the talks were scheduled to begin at nine a.m., Geneva time, camping out overnight with sleeping bags in hopes of getting a good seat.