Hermes Experiment, The: A Personal Story

by Richard Milner, Erhard Steffens

Overview

This book describes the story of how a collaboration of several hundred physicists from Europe and North America formed in 1988 to design, construct, install, commission and operate, for the years 1995-2007 the technically innovative HERMES experiment at the DESY laboratory in Hamburg, Germany to study the spin structure of the fundamental structure of matter. The authors begin by introducing the fascinating world of subatomic physics and relate their personal story of how the HERMES experiment came about. Guided by the exciting idea to use a new type of target internal to an electron storage ring, the HERMES collaboration was born to realize this innovative experimental approach at the new HERA accelerator at DESY. The book describes the technical design of HERMES; the successful effort to secure the necessary funds to construct the experiment in different countries; the fabrication of the different components by the different HERMES institutes; and the story of the installation and commissioning of HERMES in the East Hall of HERA in the hot summer of 1995. Until 2007, when the operation of HERA ceased, the collider ran typically about 9 months per year continuously, during which HERMES data taking shifts were manned to ensure that data of the highest quality were acquired. The book describes the HERMES scientific results, their considerable impact, how HERMES shaped an entire generation of young people into scientific leaders, and ends with a description of the twenty-first century picture of the proton that has subsequently been developed.The authors played a leading role within the HERMES collaboration. They describe, using non-technical language, the various phases of the thirteen years of running, the social life in such an international collaboration, and their personal reminiscences over several decades.

Product Details

ISBN-13:	9789811215339
Publisher:	World Scientific Publishing Company, Incorporated
Publication date:	04/08/2021
Pages:	244
Product dimensions:	6.00(w) x 9.00(h) x 0.63(d)

Table of Contents

Preface vii

Acknowledgments ix

1 Quest to Understand the Fundamental Structure of Matter 1

1.1 Structure of Matter 1

1.1.1 Atoms: The building blocks of matter 2

1.1.2 Mysterious quantum world 3

1.1.3 Standard Model of physics 5

1.2 Spin: Provider of Order and Structure to the Universe 9

1.3 Modern View of the Proton 12

1.4 Experimental Methods to Study the Fundamental Structure of Matter 14

1.5 Experimental Study of the Quark and Gluon Structure of Matter 16

2 The Proton's Spin 23

2.1 Introduction 23

2.2 The Origins of Spin 23

2.3 Quarks Arrive 28

2.4 Challenges to Experimental Study of Spin 31

2.4.1 Polarized electron sources 32

2.4.2 Polarized proton targets 33

2.5 First Experiments to Study the Proton's Spin Structure 34

2.6 The Proton Spin Crisis 34

2.7 Where Do the Proton and Neutron Really Get Their Spin? 36

3 HERMES: A New Way to Study the Origin of Proton and Neutron Spin 39

3.1 Overview 39

3.2 North American Origin of HERMES 42

3.2.1 Context 42

3.2.2 1987: SLAC internal target workshop and first contacts with DESY 47

3.3 European Origin of HERMES 51

3.3.1 Surprising results from EMC 51

3.3.2 Early years in Hamburg 53

3.3.3 Particle physics in Europe in the 1980s 58

3.4 1988: HERMES is Born 61

3.5 Conceptual Description of the HERMES Experiment 66

3.6 Development of Polarized Internal Gas Targets 68

3.6.1 Polarized neutron (3He) target 69

3.6.2 Polarized hydrogen/deuterium target 73

3.7 Polarized Electrons in the HERA Electron Ring 77

4 Realizing the HERMES Experiment 81

4.1 1989-1992: HERMES is Realized 81

4.2 Funding the HERMES Experiment 85

4.3 Groups at DESY Relevant for HERMES 90

4.3.1 MEA group 90

4.3.2 Machine department with HERA operations crew 90

4.4 Wagner Meetings 91

4.5 Design and Construction of the HERMES Experiment in the HERA East Hall 92

4.5.1 Infrastructure at the HERA east hall 93

4.5.2 Preparation and installation of the detector components 97

4.6 HERMES Running I: 1995-2000 with Longitudinal Target Spin 104

4.6.1 Installation and commissioning of the HERMES experiment with the polarized ³He target 104

4.6.2 Installation and running of the hydrogen and deuterium (H/D) target 112

4.6.3 Evolution of the HERMES spectrometer 1996-2000 and running 121

4.7 HERMES Run II, 2001-2007 125

4.7.1 HERA machine upgrade and impact on HERMES 125

4.7.2 Implementation and running with transverse hydrogen spin 126

5 HERMES Scientific Output 129

5.1 Overview 129

5.2 Target Spin Along Beam Direction 130

5.2.1 Detecting only scattered electron 130

5.2.2 Detecting the struck quart 134

5.3 Detecting Photons 138

5.4 Target Spin Transverse to Beam Direction 139

5.5 What about Nuclei? 142

5.6 Role of Theory 144

5.7 Scientific Impact of the HERMES Experiment 146

6 Building on the Legacy of HERMES 149

6.1 Introduction 149

6.2 SLAC End Station A Experiments 149

6.3 HERA Collider Experiments H1 and ZEUS 150

6.4 Jefferson Laboratory 150

6.5 MIT-Bates Linear Accelerator Center 152

6.6 RHIC: Hot, Dense Matter and the World's First Polarized Proton Collider 154

6.7 CERN Muon Beam Experiments 156

6.8 Fermilab: Annihilating Quarks and Antiquarks 158

6.9 LHCspin: A Storage Cell in the 7-TeV Beam 158

6.10 Towards the Electron-Ion Collider 160

7 HERMES Collaboration 167

7.1 Introduction 167

7.2 Contributions of the Different Institutes 167

7.3 Leading Contributors to HERMES 170

7.4 HERMES Spanned the Pre-email Era, through the Fax Machine to the Modern Digital Age 182

7.4.1 HERMES collaboration meetings 185

7.4.2 HERMES offsite meetings 188

7.4.3 HERMES editorial board 188

7.5 A New Generation of Physicists 189

7.6 Epilogue 191

Appendix A Primer oil Units, Scientific Notation, and Technical Terms 193

A.1 International System of Units 193

A.2 Scientific Notation 195

A.3 Structure in the Universe 196

A.4 Explanation of Commonly-Used Technical Terms 197

Appendix B List of Acronyms 201

Appendix C A Short History of Spin 205

C.1 Introduction 205

C.2 Explaining the Fundamental Structure of Matter: 1925-1950 206

C.3 Developing Spin as an Experimental Tool: 1950-1975 208

C.3.1 Polarized ion sources 209

C.3.2 Polarized electron sources 210

C.3.3 Polarized proton targets 211

C.3.4 Polarized ³He beams and targets 212

C.4 Using the Tool: 1975-1995 212

C.4.1 High energy lepton scattering 213

C.4.2 High energy proton scattering 214

C.4.3 Spin in storage rings 215

C.4.4 Spin at medium energy accelerators 215

C.4.5 Hadronic parity violation 216

C.5 Spin in Use Worldwide: 1995-present 217

C.6 International Spin Physics Meetings 220

Bibliography 223