Fred Bortz - Understanding Higgs Bosons

To Rosie, whose field helps people gain a mass of knowledge

Published in 2016 by Cavendish Square Publishing, LLC
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Cataloging-in-Publication Data

Bortz, Fred.

Understanding Higgs bosons / by Fred Bortz.

p. cm. (Exploring the subatomic world)

Includes index.

ISBN 978-1-50260-550-4 (hardcover) ISBN 978-1-50260-551-1 (ebook)

1. Higgs bosons. 2. Particles (Nuclear physics) Juvenile literature.

I. Bortz, Fred, 1944-. II. Title.

QC793.5.B62 B67 2016

539.721d23

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Editor: Andrew Coddington

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Contents

Inside the Atom

Discovering the Particle Zoo

Quarks, Leptons, and Bosons

The Higgs Boson and Beyond

W hat is matter? That is one of humanitys most ancient questions about nature. Yet it continues to be at the heart of some of the most exciting modern research. To study the tiniest particles of matter, scientists have designed and built some of the largest, most powerful, and most complex machines in the world. Their discoveries have changed our fundamental understanding of matter, and each discovery has led to even more questions. That is certainly true of the story of a long-sought subatomic particle called the Higgs boson.

When physicistsscientists who study the physical world of matter and energyofficially announced the Higgs boson discovery by the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) in Switzerland on July 4, 2012, it made headlines around the world. Yet some still questioned whether the discovery met all the criteria for the elusive particle.

Further research persuaded most doubters that the particle was indeed the Higgs. In 2013, the Nobel Prize committee honored Peter Higgs (1929) and Franois Englert (1932) with that years award in physics for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERNs Large Hadron Collider.

Men of the Hour. Peter Higgs (right) and Franois Englert respond to a cheering audience at CERN on July 4, 2012, where two teams of scientists announced the discovery of the Higgs boson after a nearly fifty-year quest.

What are CERN, ATLAS, and CMS?

The announcement of the 2013 Nobel Prize in Physics included three acronyms: CERN, ATLAS, and CMS. CERN stands for the original French name of the institution where researchers discovered the Higgs boson, Conseil Europen pour la Recherche Nuclaire (European Council for Nuclear Research). That acronym is still used even though Conseil in the name has been replaced by Organisation.

ATLAS and CMS are two of the detectors that scientists use at the LHC. ATLAS stands for A Toroidal LHC Apparatus, referring to its doughnut (torus) shape and reflecting the fact that physicists love to invent acronyms. CMS stands for Compact Muon Solenoid. A solenoid is a coil of wire that acts as an electromagnet. A muon, as you will read later, is a type of subatomic particle that may reveal where a Higgs boson was produced.

Rarely is a Nobel Prize awarded so soon after a discovery, but this one was fifty years in the making. Higgs and two groups of physicists, including Englert and four others, had proposed their theories in 1964. Many scientists were wondering whether they would live long enough to see their ideas validated or ruled out by experimental evidence. Indeed, Englerts collaborator Robert Brout (born 1928) died in 2011 while the LHC was still gathering the key data that led to the award. Many physicists think he would have shared the Nobel Prize, which is only given to living scientists and never divided more than three ways. Others, including Higgs, argue that Tom Kibble (1932), lead author of a paper on the subject with Gerald Guralnik (19362014) and Carl Richard Hagen (1937), deserved a share of the prize.

The discovery of the Higgs boson was historic because it completed the set of particles that physicists expected in what they call the Standard Model of particle physics. But that discovery is not the end of the story of the quest to understand the subatomic world. As is often the case in science, many unanswered questions remain. They are like dangling threads of a carefully woven fabric, and no one can be sure what might unravel when other scientists give those loose ends a tug. Just as science is built around questions such as this, so is this book. Read on to learn about the Higgs boson, why it is important, and what remains to be discovered.