U.S. ATOMIC ENERGY COMMISSION Division of Technical Information MiCROSTRUCTURE OF MATTER by Clifford E. Swartz CONTENTS iNTRODUCTION 1 NATURE OF THE PARTICLES 4 Their Reality 4 Wave-Particle Duality 5 Relativistic Effects ." 10 Nuclear energy is playing a vital role in Identification Properties 12 the life of every man, vi^oman, and chjld in the INTERACTIONS, OR FORCES 22 United States today. In the years ahead it will Gravity 22 affect increasingly all the peoples of the earth. Electromagnetism 24 It is essential that all Americans gain an Strong Nuclear Force 26 Weak Interaction 27 understanding of this vital force if they are to Comparison of the Interactions 28 discharge thoughtfully their responsibilities as Model of the Way Particles Interact 29 citizens and if they are to realize fully the CONSERVATION LAWS 32 myriad benefits that nuclear energy offers Mass-Energy 32 them. Momentum 34 The United States Atomic Energy Com­ Angular (Rotational) Momentum 34 Electric Charge 35 mission provides this booklet to help you Leptons and Baryons 35 achieve such understanding. Strangeness and Isotopic Spin 35 Parity 36 THE PARTICLES 37 Particles Stable Against Decay Through the Strong Nuclear Interaction 37 Particles That Decay Through the Strong Nuclear Interaction 42 APPENDIX I THETOOLS OF EXPLORATION 46 APPENDIX II THELANGUAGEOFTHE MICROWORLD 53 APPENDIX III TRACKING THE PARTICLES 54 SUGGESTED REFERENCES 58 United States Atomic Energy Commission Division of Technical Information Library of Congress Catalog Card Number 65-61766 1965, 1967(rev.) MICROSTRUCTURE OF MATTER by Clifford E. Swartz CONTENTS INTRODUCTION 1 NATURE OF THE PARTICLES 4 Their Reality 4 Wave-Particle Duality 5 Relativistic Effects ." 10 Nuclear energy is playing a vital role in Identification Properties 12 the life of every man, woman, and child in the INTERACTIONS, OR FORCES 22 United States today. In the years ahead it will Gravity 22 affect increasingly all the peoples of the earth. Electromagnetism 24 Strong Nuclear Force 26 It is essential that all Americans gain an Weak Interaction 27 understanding of this vital force if they are to Comparison of the Interactions 28 discharge thoughtfully their responsibilities as Model of the Way Particles Interact 29 citizens and if they are to realize fully the CONSERVATION LAWS 32 myriad benefits that nuclear energy offers Mass-Energy 32 them. Momentum 34 The United States Atomic Energy Com­ Angular (Rotational) Momentum 34 Electric Charge 35 mission provides this booklet to help you Leptons and Baryons 35 achieve such understanding. Strangeness and Isotopic Spin 35 Parity 36 THE PARTICLES 37 Particles Stable Against Decay Through the Strong Nuclear Interaction 37 Particles That Decay Through the Strong Nuclear Interaction 42 APPENDIX I THETOOLS OF EXPLORATION 46 APPENDIX II THELANGUAGEOFTHE MICROWORLD 53 APPENDIX III TRACKING THE PARTICLES 54 SUGGESTED REFERENCES 58 United States Atomic Energy Commission Division of Technical Information Library of Congress Catalog Card Number- 65-61766 1965, 1967(rev.) MicnoaxRucTUnE OF MATTEP* MICROSTRUCTURE OF MATTER By CLIFFORD E, SWARTZ THE COVER In this artist's conception, a cube, symbolic of the "building blocks" described in this booklet, carries on its surfaces photographs of bubble- chamber tracks made by some of the fundamental particles making up the Microstructure of Matter. INTRODUCTION Beyond our solar system and local galaxy of stars, ten billion other galactic systems swarm to the edges of the universe. Within each of our fingertips, each atom, a mil­ lion times smaller than the width of ahuman hair, is, itself, ten thousand times as large as its central nucleus. This enormous range of sizes seems to defy unifying explanations (Figure 1). SIZE OF OBJECTS IN UNIVERSE -2 = 0 01 Centimeter DISTANCE 0=1 Centimeter TO GALAXY I 2 = 1 Meter NEAREST SIZE OF » 6 = 1,000,000 Centimeters STAR etc EARTH'S THE AUTHOR ORBIT EARTH 'I'V*- CLIFFORD E. SWARTZ is professor of MAN physics at the State Lniversity of New York and was for many years a consul­ WAVELENGTH OF tant to the Brookhaven National Labora­ VISIBLE LIGHT tory. He received his A.B., M.S., and 1cm DINOSAUR WAVELENGTH OF i Ph. D. degrees from the University of Rochester. For the past 12 years, Dr. 1 MEV X RAY Swartz has given about 30 talks a year ' BACTERIA on high-energy research, machines, and particles to Brookhaven ^y\j>^ ATOM visitors, many of whom were high school students and teachers. !8» These talks led to his giving numerous lectures to high school NUCLEONS classes and to his planning and judging of annual science fairs. He IS a member of the Committee for the Revision of the New York State High School Physics Syllabus, and he has taught an in-service T" -13-12 -10 -8 -6 -4 8 10 12 16 18 n—m r 28 institute to high school physics teachers as well as one year of 14 20 22 24 26 physics to a high school class. MICpOBTnUCTUPE OF MATTER MICROSTRUCTURE OF MATTER By CLIFFORD E. SWARTZ THE COVER In this artist's conception, a cube, symbolic of the "building blocks" described in this booklet, carries on its surfaces photographs of bubble- chamber tracks made by some of the fundamental particles making up the Microstructure of Matter. INTRODUCTION Beyond our solar system and local galaxy of stars, ten billion other galactic systems swarm to the edges of the universe. Within each of our fingertips, each atom, a mil­ lion times smaller than the width of ahuman hair, is, itself, ten thousand times as large as its central nucleus. This enormous range of sizes seems to defy unifying explanations (Figure 1). SIZE OF OBJECTS IN UNIVERSE -2 = 0.01 Centimeter DISTANCE 0 = 1 Centimeter TO GALAXY 2 = 1 Meter NEAREST SIZE OF 6 = 1,000.000 Centimeters STAR etc. EARTH'S THE AUTHOR ORBIT EARTH CLIFFORD E. SWARTZ is professor of MAR physics at the State University of New WAVELENGTH OF York and was for many years a consul­ VISIBLE LIGHT tant to the Brookhaven National Labora­ tory. He received his A.B., M.S., and Icm DINOSAUR WAVELENGTH OF I Ph.D. degrees from the University of Rochester. For the past 12 years, Dr. IMEV XRAY Swartz has given about 30 talks a year ' BACTERIA on high-energy research, machines, and particles to Brookhaven ~W/^ ATOM visitors, many of whom were high school students and teachers. These talks led to his giving numerous lectures to high school NUCLEONS classes and to his planning and judging of annual science fairs. He is a member of the Committee for the Revision of the New York State High School Physics Syllabus, and he has taught an in-service T institute to high school physics teachers as well as one year of -13-12 -10 -8 8 10 12 14 16 18 20 22 24 26 28 physics to a high school class. 1 T PRELIMINARY CHART OF SOME OF THE PARTICLES Size is not the only obstacle to understanding the nature Electric of matter. The material of the universe assumes a million Family Name Symbol Mass charge Function and behavior different forms—gas, liquid, solid, animate, inanimate — Proton-like Omega a 1.78 times proton + 01 - Decays to lambda and K-meson. thwarting any general classification. particles Xi 3; 1.40 times proton +, -, 0 Decays to lambda and pi-meson. Sigma 2 1.27 times proton +, -, 0 Decays to proton and pi-meson. Still, there has always been the feeling—or, at least, a Lambda A 1.19 times proton Zero Decays to proton and pi-meson. wistful hope—that nature could be explained in terms of •proton P 1839 times electron + or - Main constituents of atomic nuclei; Neutron n \ (1.7 X 10"'* gram) Zero m our world, protons are usually simple building blocks, which join together or break apart positive. in simple ways. The Greeks thought that there might be Huclear- Eta-meson T; 1070 times electron Zero One of nuclear force agents when basic atoms, out of which everything else could be formed. force protons and neutrons are very Empedocles, in 400 B.C., taught that everything was made ' agents close together. K-meson K 970 times electron +,-, 0 One of nuclear force agents when from four elements and four essences. His geometric ar­ protons and neutrons are very rangement of these is shown in Figure 2. Ordinary sub­ close together. Pi-meson TT 270 times electron +,-, 0 One of nuclear force agents. Exchange stances were supposed to be composed of combinations of of mesons between protons and the pure elements linked by neutrons provides "nuclear glue". differing essences. Wood Hectron- Muon M 207 times electron + or- Descendant of meson decays. Forms like half of "cosmic rays" at sea level. might appear to be made particles Electron e Vi839 mass of + or — Negative electrons m atom balance of earth, but if you added proton positive charge of nucleus. Neutrino V Zero Zero Emitted m radioactive beta decay heat you could see that it along with electron. also contained fire and air. Massless Photon y Zero Zero Agent of electromagnetic force (light, The system was profound water bosons X rays, etc). but useless; it was a mys­ Graviton - Zero Zero Agent of gravitational force; not yet detected. tic's scheme, leading only to alchemy and its vain ef­ Only the proton, electron, neutrino, photon, and graviton are stable against radioactive decay A symbol with a superscript indicates a particle with forts to turn lead into gold. t particular charge For example, ir (pi lero) is the zero-charge pi- Figure 3 Yet today we have ar- Earth rived at a scheme of Figure 2 The elements and es- lists of particles and their properties are presented in building blocks that su- sences of the Greek universe.