Suppersymmetry unveiling the ultimate law of nature

Free ebooks ==> www.Ebook777.com - www.Ebook777.com Free ebooks ==> www.Ebook777.com www.Ebook777.com Supers~mmetry Other books by Gordon Kane For general readership: The Particle Garden More technical books: Modem Elementary Particle Physics Perspectives on Supersymmetry (editor) Perspectives on Higgs Physics (editor) The Higgs Hunters Guide (with J Gunion, H Haber, and S Dawson) Free ebooks ==> www.Ebook777.com Supersymmetry Squarks, Photinos, and the Unveiling of the Ultimate Laws of Nature •ooao2t8GlllG>CDeeeeoci•o•oo•e o GORDON KANE HELIX BOOKS PERSEUS PUBLISHING Cambridge, Massachusetts www.Ebook777.com Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks Where those designations appear in this book and Perseus Publishing was aware of a trademark claim, the designations have been printed in initial capital letters A CIP record for this book is available from the Library of Congress ISBN: 0-7382 0489-7 Copyright © 2000 by Gordon Kane All rights reserved No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher Printed in the United States of America Perseus Publishing is a member of the Perseus Books Group Find us on the World Wide Web at http://www.perseuspublishing.com Text design by Jeff Williams Set in 11-point Minion by Perseus Publishing Services 10-03 02 First paperback printing, June 2001 Perseus Publishing books are available at special discounts for bulk purchases in the U.S by corporations, institutions, and other organizations For more information, please contact the Special Markets Department at the Perseus Books Group, 11 Cambridge Center, Cambridge, MA 02142, or call (617) 252-5298 To Hal, Mollie, David, and Noah ··························· Contents Foreword by Edward Witten Preface XI xv WHERE DO WE COME FROM? WHAT ARE WE? WHERE ARE WE GOING? To understand nature we need to know about particles, forces, and rules • Research in progress (RIP) • Equations? • Prediction, postdiction, and testing • Where are the superpartners? • The boundaries of science have moved THE STANDARD MODEL OF PARTICLE PHYSICS 16 The forces • Mass, decays, and quanta • The particles: Do we really know the fundamental constituents of matter? • Particles and fields • There are more particles • New ideas and remarkable predictions of the Standard Model • Experimental foundations of the Standard Model • Picturing Standard Model processes: Feynman diagrams • Spin, fermions, and bosons • Beyond the Standard Model WHY PHYSICS IS THE EASIEST SCIENCEEFFECTIVE THEORIES 40 Organizing effective theories by distance scales • Supersymmetry is an effective theory too • vii viii Free ebooks ==> www.Ebook777.com Contents The physics of the Planck scale • Effective theories replace renormalization • The human scales SUPERSYMMETRY AND SPARTICLES 53 What is supersymmetry? • Some mysteries supersymmetry would solve • The superpartners • Supersymmetry as a spacetime symmetry: superspace • Hidden or "broken" supersymmetry TESTING SUPERSYMMETRY EXPERIMENTALLY 72 Detectors and colliders • Recognizing superpartners • Sparticles: their personalities, backgrounds, and signatures at LEP and Fermilab • Visit Fermilab • Future colliders • Can we the experiments we need to do? WHAT IS THE UNIVERSE MADE OF? 98 What particles are there in the universe? • Is the lightest superpartner the cold dark matter of the universe? HIGGS PHYSICS 108 Finding Higgs bosons • Current evidence • LEP, Fermilab, and LHC • Studying Higgs bosons at Fermilab SOME ADDITIONAL HELP FROM SUPERSYMMETRY, AND SOME CHALLENGES Matter and antimatter asymmetry • Proton decay? • Rare decays • CP violation • Inflation • Perspectives and concerns www.Ebook777.com 117 186 ° " SUPERS YMME TRY Quark A fundamental particle Quarks are very much like electrons, but they also carry strong charge and thus have another interaction, one that can bind them into protons and neutrons There are six quarks, called up (u), down (d), charmed (c), strange (s), top (t), and bottom (b) Quark Jet Because quarks must end up in hadrons, quarks that are produced in collisions actually appear in detectors as a narrow jet of hadrons, mostly pions See also Gluon Jet Radioactive Decay Some nuclei are unstable but live long enough to exist as matter until they decay When they decay, they can emit several particles: photons, electrons, positrons, neutrinos, neutrons, and even helium nuclei For historical reasons, such decays are called radioactive decays Sometimes scientists use the emitted particles as tools to experiments Reductionist One way to study the natural universe is to study very detailed aspects of nature, to take things apart and see what they are made of, and to focus on small steps This approach is called reductionist It has been a powerful success, enabling us to build up the remarkably complete description of nature we now have Whenever possible, scientists have tried to unify subfields as they became understood Recently in particle physics, the trend toward unification has been increasingly successful For physicists, reductionism includes the associated unification See also Unification Relativistic, Relativistic Invariance Whenever particles can move at speeds near the speed of light, and whenever fields are involved, the description of nature must satisfy the requirements of Einstein's "special relativity" theory RIP An acronym I use to emphasize that some of the subjects we cover are "Research in Progress;' whereas others are well-established areas that may be extended but will not be significantly modified (such as the Standard Model) Glossary o c "' l 87 Rules In order to have a complete understanding of nature, it is necessary to know the particles, the forces that determine the interactions of the particles, and the rules for calculating how the particles behave For the motion of objects normally on earth or in the sky, the rule to use to calculate the behavior of particles is Newton's second law, F = ma When atomic or smaller distances are involved, the Schrodinger equation of quantum theory replaces Newton's second law In particle physics, additional relativistic requirements are added to make the complete set of rules: quantum theory and Einstein's special relativity See Chapter Schrodinger Equation The equation from quantum theory that tells how to calculate the effects of the forces on the particles It is the quantum theory equivalent of Newton's second law Science Science can be defined as a self-correcting way to get knowledge about the natural universe, plus the body of knowledge obtained that way It is both a method and the resulting understanding and knowledge The method requires making models to explain phenomena, testing them experimentally, and revising them until they work The goal of science is understanding Once part of the natural world is understood, it may be possible to develop applications of the new knowledge The process of developing such applications is properly called technology, not science Although scientific knowledge may, and usually does, lead to technology, science is not necessary for technology, and technological developments have led to new science as much as the opposite Before the time of Galileo, many technological developments occurred that had no scientific connection Since the time of Maxwell and his formulation of the electromagnetic theory, nearly all technological developments have depended on earlier science In recent years the words science and technology have been frequently misused, as though they were interchangeable Because science and technology are really different, it is better to distinguish carefully between them Selectron The supersymmetric partner of the electron 188 FreeSUPERSYMMETRY ebooks ==> www.Ebook777.com c c " Signature A new particle will have some characteristic behavior in a detector that allows it to be recognized Particles that decay into others so in a unique way that is different for every kind of particle Knowing the properties of the particle allows us to calculate how it will decay The features that allow a new particle to be identified in a detector are called its signature Slepton The supersymmetric partner of any of the leptons Smatter The superpartners of the Standard Model particles This book argues that the experimental discovery of smatter will provide us with information that will be essential for gaining insights into the ultimate laws of nature, the primary theory Solar Neutrinos The reactions that fuel the sun lead to the emission of photons, which reach the earth as sunlight, and of neutrinos, which we not see with our eyes but which can be detected in special neutrino detectors At present there is great interest in these neutrinos, because the number being detected is fewer than expected, and this may be a signal that neutrinos have mass, in which case we could account for the lesser number detected If they have mass, the experiments to detect them will allow the value of their mass to be measured Special Relativity The constraints of special relativity are two conditions that Einstein pointed out should be satisfied by any acceptable physical theory Somewhat oversimplified, these conditions are, first, that light moves at the same speed in vacuum regardless of how it is emitted and, second, that scientists working in different labs moving with different relative speeds should formulate the same natural laws The constraints imposed by these conditions have surprising implications for the structure of acceptable theories For example, the Schrodinger equation of quantum theory does not satisfy these conditions But when it was generalized by Dirac to so, the resulting equation led to the prediction of antiparticles, which need not have existed from the point of view of quantum theory alone www.Ebook777.com Glossary ' ,, 89 Spectra Atoms can exist in a number of discreet energy levels They emit or absorb photons when they make transitions from one level to another The energies of the photons emitted or absorbed by one atom are different from those of all other atoms The photon energies are directly related to their frequencies, which set their colors in the spectrum, so by observing the colors of the photons, it is possible to determine which atoms are being observed This can be done in a laboratory, and it can also be done with the light reaching us from stars, near or distant, which enables us to identify the atoms that stars are made of Only the same ninety-two elements we find on earth are seen throughout the universe Speed of light Light and all other massless particles travel in vacuum with a speed, usually labeled c, whose value is about three hundred million meters a second Special relativity implies that no particle or signal can move faster than the speed of light and that photons always have this speed, regardless of the speed of their source Spin Spin is a property that all particles have It is as though particles were always spinning at a fixed rate (which could be zero), which can be different according to the type of particle It is not quite right to think of them actually spinning, because the particles not have to have spatial extension to have spin; calling this property spin is an analogy The amount of spin is required by the quantum theory to come in definite amounts; if the unit is chosen to be Planck's constant, h, divided by 2, then particles can have zero spin, half a unit of spin, one unit of spin, etc Spontaneous Symmetry Breaking Often the equations of a theory may have certain symmetries, though their solutions may not; the symmetries are hidden, or broken For example, the equations may describe several particles in identical ways, so the equations are unchanged if the particles are interchanged, but the solutions may give the particles different properties (A simple example is given in Chapter 1.) This phenomenon is called spontaneous symmetry breaking Squark The supersymmetric partner of any of the quarks 190 "e" SUPERSYMMETRY Stable Particle Particles that not decay into others See also Decay Standard Model The very successful theory of quarks and leptons and their interactions that is described in this book is called the Standard Model by particle physicists The name arose historically as the theory developed and then was difficult to change because it is widely used The Standard Model is the most complete mathematical theory of the natural world ever developed and is well tested experimentally String Theory String theory is a theory that aims to unify all of the forces and particles of nature and explain why they are as they are In string theory, there is only one force (gravity), in ten space-time dimensions, but when looked at from our four-dimensional world, the extra dimensions imply the other forces we observe Particles are strings that vibrate in different ways to account for their various properties String theories appear to allow the construction of a quantum theory of gravity String theory is RIP Strong Force See Force Structure Objects have structure if they have parts-that is, if they are made of other things Whether objects have structure can be learned from experiments that probe them with projectiles Over the past century, each stage of matter that was found as it became possible to search for ever-smaller things turned out to have structure Quarks and leptons appear not to have structure, so perhaps the search for the basic constituents has finally ended There are also theoretical arguments that quarks and leptons are the basic constituents Subatomic Particle Any particle that is contained in an atom, or any particle that can be created in collisions of such particles, is loosely called subatomic, whether it is composite like a proton or elementary like a quark or electron Glossary " " 191 Superportner If the theory that describes nature has a symmetry called supersymmetry, then every normal particle (the ones we know) has associated with it a partner that differs only in its spin and its mass Superspoce Supersymmetry can be formulated in several ways One is to imagine associating another coordinate that has special properties with each of our normal spacetime coordinates, giving a kind of space called superspace Writing theories in superspace makes them supersymmetric This way of constructing supersymmetric theories is harder to picture than associating superpartners with each Standard Model particle, but it leads to the same results and sometimes facilitates deriving mathematical properties of the theories Superstring String theories are expected to be supersymmetric and are often called superstring theories Supersymmetry A hypothetical symmetry that describes nature and says that even though fermions and bosons seem to us to be very different in their properties and their roles, in the theory itself they appear in a symmetric way If supersymmetry is indeed realized in nature, then every particle has a superpartner SUSY A common abbreviation for supersymmetry Technology See Science Theory The word theory is usually used precisely in physics Theories are not conjectures but sets of equations whose solutions describe physical systems and their behavior Theory of Everything A "theory of everything" would not only describe how things work but also explain why things are the way they are The name is unfortunate in 192 c c c S U P ERSY M M ET RY one way, because it does not tell how to deduce the behavior of complex systems from a knowledge of their components In this book I have used the name primary theory instead Transmit See Mediate Uncertainty Principle The uncertainty principle is a consequence of quantum theory It implies that a pair of observables cannot both be measured simultaneously to arbitrary accuracy It can often be used to understand quantum theory results in a simple way Unification Scientists have sought for centuries to unify the descriptions of apparently different phenomena by showing that they were due to the same underlying natural laws and that complex levels of matter were made of simpler levels This unification process is a subject of very active research about the forces of nature today The possible unification of the strong, electromagnetic, and weak forces is called a grand unification There is a continuing effort to unify these forces with gravity String theories seem to that successfully Unstable Particle See Decay Vacuum Any physical system will settle into the lowest-energy state it can, which in particle physics we call its vacuum state For most systems, this is the state where the fields making up the system are zero, but theorists hypothesize that for systems containing Higgs fields, the lowest energy occurs when the Higgs field takes on a constant value different from zero The value of the Higgs field in that system is called its vacuum expectation value Vacuum Expectation Value See Vacuum Weak Charge See Charge Glossary Weak Force See Force The weak force is described in Chapter Wino The supersymmetric partner of the W boson Zino The supersymmetric partner of the Z boson c c 193 ·································· Index accelerators, 30, 73, 142, 166 anthropic questions, 143, 159 antiparticles, 24, 166 antiprotons, 25, 77 atoms, 40, 139 universal size, 48 backgrounds, 78, 80 b-factories, 125 Big Bang, 14, 19, 98, 125, 139, 140, 146, 155 big questions, 15 biology, 14, 130 black hole, 50 bosons,35,53,57,66,67 broken supersymmetry, 68 See also supersymmetry, hidden CDF detector, 125, 166 CERN, 75, 166 charge, 28 charge conjugation invariance, 69 charge conservation, 19 charginos, 86, 157 charm quark, 28, 39 chemical elements, 21 cold dark matter, IO colliders, 14, 47, 90, IOS collider scale, 46 compactification, 134 constituents, cosmic rays, 14, 74, 121 cosmological constant, 17, 127, 147 cosmology, 41, 160 CP violation, 96, 124, 139 originating from supersymmetry, 125 Curie, Marie, 76 dark matter, 36, 42, 58, 96, IO Darwin, Charles, 14, 138 data, 30 role of, 12, 133, 140, 161 decay, 18 DELPHI detector, 112 detectors, 14, 30, 73, 78, 125 dimensions, 159 compact, 161 extra, 160 fermionic, 67 large extra, 161 of space, 52 superspace, 67 ten space-time, 131 dinosaurs, 139, 144 Dirac, Paul, 24, 44 direct detection, I03 distance scale, 49 DO, 166 doubling of particles, 62 down quarks, 28, 38, 146 Duff, Michael, 55 effective theories, 41, 126, 134, 153 Ehrenfest, Paul, 159 Einstein's constant, 165 195 196 Index electrical force, 17 electric charge, 19, 160 electromagnetic force, 17, 21, 41, 145, 160 electromagnetic waves, 61, 140 electrons, 17, 21, 28, 31, 33, 38 indistinguishable, 35 mass,43 emergent properties, 44 energy conservation, 19, 66 equations, 4, 6, 10 solutions, 2, 8, 11, 24, 61 unchanged when particles interchanged, 28 evolution, 145 experimental foundations, 30 experimental input in primary theory formulation, 60 experiments, 40 near Planck scale, 46 vs theory, historically, 39 explicit detection, 103 families, 26, 38, 132, 139, 161 family problem, 26 Faraday, Michael, 23 Fermilab, 28, 76, 84, 88, 106, 166 fermions, 35, 53, 57, 66, 67 Feynman diagrams, 30 Feynman,Richard,30 fields, 22, 149 final theory, 46 FMC,91, 166 forces, 4, 6, 17, 33 unification, 17, 21, 36, 38, 57, 145 unified, 145 fundamental particles, 24 funding, 94, 140 galaxies, 41 general relativity, 67 gluinos, 84, 165 gluons, 18, 20, 35, 39, 45 must exist if particles have strong charge,30 Godel's incompleteness theorem, 137 Goldhaber, Maurice, 121 gravitational field, 23 gravitational force, 17 gravitino, 63 gravitons, 18 gravity, only force, 159 half-life, 121 Havel, Vaclav, 142 Hawking, Stephen, 55 helium, 98 hidden symmetry, 12 Higgs bosons, 27, 29, 70, 108, 120 atheists, 129 current evidence, 111 detection, 110 direct evidence, 27 Fermilab, 113, 114 fundamentalists, 129 indirect evidence, 27 interactions, 110 LEP, 111 LHC, 113 masses, 110 production, 111 recognizing, 113 studying, 114 Higgs field, 17, 70, 150 higgsinos, 63, 83, 157 Higgs mechanism, 70, 87, 149 Higgs, Peter, 108 Higgs physics, 36, 56, 69, 108 higher energies, 96 hot dark matter, 101 how understanding, 44, 131 hydrogen atom, radius, 48 indistinguishable particles, 35 inelastic scattering of electrons and neutrinos, 30 inflation, 125 inputs to an effective theory, 43 intensity, 75, 77, 96 interactions Index new,64 not allowed by the Standard Model, 31 Kaluza, Theodor, 159 Klein, Oskar, 159 Lagrangian, 24 LEP, 27, 59, 76, 84, 166 leptons, 26, 35, 38, 45, 121 masses, 29, 155 masses by Higgs mechanism, 109, 152 LHC, 76, 90, 106, 166 life, 44, 48, 145, 146 lightest superpartner, 14, 37, 102, 105, 158 dark matter, 58, 98 missing energy, 79 LSP, 166 Lucretius, 22 magnetic field, 23 magnetic force, 17 mass, 18 matter asymmetry, 37, 118 matter particles, 20 mediating the forces, 18 missing energy, 79, 82, 85 models, molecules, 44 M-theory, 132, 134 muons, 26, 27, 38 national laboratories, 141 neutral currents, 30 neutralinos, 86, 157 neutrinos, 25, 28, 31, 38, 139 masses, 37, 96, 100 neutrons, 145 made of quarks, 20 Newton's constant, 49, 165 Newton's laws, 4, 5, 8, 23, 41 NLC, 91, 106, 166 nuclear force, 17, 20 197 nuclei, 20 parity violation, 30 Particle Garden, The, 39 particle physics, goals, 53, 130 particles,4, 17, 19, 160 form our world, 20 fundamental, 22 interact, 30 point-like, 21 periodic table of the elements, 42 philosophy, 7, 10, 14, 23, 36, 41 photino, 63, 157, 165 photons, 18, 19,31,35,42,45,72,100, 119 must exist if electrons do, 30 Plancklength,45,49 Planck mass, 47, 49 Planck, Max, 49 Planck scale, 46, 51, 56, 153, 154 supersymmetry provides a window, 59, 134 Planck scale physics, testing, 47 Planck's constant, 43, 47, 48, 147, 165 Planck time, 49 planets, 159 polarized beams, 90 positrons, 25 postdictions, 13 predictions, 13 primary theory, 44, 46, 48, 51, 53, 88, 96,107,130,135,140 testing, 60, 136, 138, 141 unique, 145 proton decay, 60, 97, 121, 139 protons, 145 made of quarks, 20 quanta, 19, 23 quantum theory, 4, 6, 21, 23, 24, 35, 56, 67, 121 quarks,20,27,35,39,41,45,77,122 bottom,27 charm,27 mass, 29, 152 198 Free ebooks ==> www.Ebook777.com °" o Index masses, 155 masses by Higgs mechanism, 109 strange, 27 top, 27 radioactive decays, 17 rare decays, 60, 123 reductionist, 41 relativistic invariance, relativistic quantum theory, relics, 98, 139 renormalization, 51 research in progress, research universities, 141 Richter, Burton, 141 RIP, 9, 166 rules, 4, 52, 130 Sakharov, Andrei, 37, 119 science, l, 6, 7, 8, 13, 14, 35, 136, 138, 141 end of?, 147 open ended except for particle physics and cosmology, 45 selectrons, 63, 83, 165 sfermion, 63 signatures, 78 SLAC, 166 SLC, 59, 166 smuons, 82, 165 sneutrino, 63, 165 solutions, 11 which solutions describe nature, 12 space, 104 space station, 105 sparticles, 63, 68 special relativity, 4, 24, 61 speed oflight, 5, 23, 48, 139, 147 spin, 34, 54 spinoffs, 94, 141 squarks, 63, 165 SSC, 110 Standard Model, 6, 9, 16, 149 invariance under particle interchange,28,38,62 stars, 41 stau, 104, 165 stop, 69, 120 strings, 22 string theory, 59, 130, 131, 139, 146, 160 strong charge, 20 strong force, 18, 145 structure, 20 superpartners, 13, 64, 78, 88, 96, 98, 133 masses, 71, 78, 155 superspace, 66 supersymmetric Standard Model, supersymmetry doubling number of particles, 25, 62,69 as effective theory, 46 hidden,29,52,69,128,133 idea,53,64 importance of, 2, 88 last space time symmetry, 67 not introduced to solve problems, 55 relate fermions and bosons, 35 when,2 supersymmetry theorists, 133 symmetry, 11, 66, 68 hidden, 29, 52 oflaws, 12 not exhibited by solutions, 12 under particle interchange, 29 Tade, Greg, 105 tau, 26, 27 terminology, 39 tests, 13 theory,6 Theory of Everything, 46 Ting, Samuel C.C., 105 topology of space, 134 top quark, 28, 34, 39, 155 heavy, 56, 70 triggering, 80 trilepton events, 87 www.Ebook777.com Index unifying interactions and particles, 41 universal constants, 48 universe, 41, 60, 102, ll8, 130, 134, 142, 146,149,155 up quarks, 28, 39, 146 up squark, 69 vacuum state, 151 Wand Z bosons, 18, 35, 45 masses, 29, 152, 155 masses by Higgs mechanism, 109 """ must exist if particles have weak charge, 30 predicted to exist and found, 30 weak charge, 20 weak force, 17 why questions, 14 why understanding, 44, 131 Wilson, Robert, 89 Winos,63,86,157,165 Witten, Edward, xiii, xvi World Wide Web, 94, 141 Zinos,86,157,165 199 Free ebooks ==> www.Ebook777.com www.Ebook777.com ... stated as follows: (1) The laws of nature are the same regardless of where they are formulated and tested (2) The speed of light in vacuum (denoted by c) is the same regardless of the conditions under... testing of the Standard Model of particle physics The Standard Model (summarized in Chapter 2) gives a comprehensive description of the basic particles and forces of nature and of how all of the. .. image of the mechanisms of the subatomic universe -the stuff that makes the world run That image is formulated in what we call the Standard Model of particle physics It is a description of the underlying