內容簡介
The last few decades have seen major advances in the physics of elementary particles. New generations of particle accelerators and detectors have come into operation, and have successfully contributed to improving the quantity and quality of data on diverse interaction processes and to the discoveries of whole new families of particles. At the same time, important new ideas have emerged in quantum field theory, culminating in the developments of theories for the weak and strong interactions to complement quantum electrodynam-ics, the theory of the electromagnetic force. The simplest of the new theories that are at the same time mathematically consistent and physically successful constitute what is known as the standard model of the fundamental interac-tions. This book is an attempt to present these remarkable advances at an elementary level, making them accessible to students familiar with quantum mechanics, special relativity, and classical electrodynamics.
內頁插圖
目錄
1 Particles and Interactions:An Overview
1.1 A Preview
1.2 Particles
1.2.1 Leptons
1.2.2 Quarks
1.2.3 Hadrons
1.3 Interactions
1.4 Symmetries
1.5 Physical Units
Problems
Suggestions for Further Reading
2 B080n Fields
2.1 Lorentz Symmetry
2.1.1 Lorentz TraIlsformations
2.1.2 Tensor Algebra
2.1.3 llensor Fields
2.2 Scalar Fields
2.2.1 Space-Time Translation of a Scalar Field
2.2.2 Lorentz Transformation of a Scalar Field
2.3 Vector Fields
2.4 The Klein-Gordon Equation
2.4.1 Free-Patticle Solutions
2.4.2 Particle Probability
2.4.3 Second Quantization
2.4.4 Operator Algebra
2.4.5 Physical Significance of the Fock Operators
2.5 Quantized Vector Fields
2.5.1 Maesive Vector Fields
2.5.2 The Maxwell Equations
2.5.3 Quantization of the Electromagnetic Field
2.5.4 Field Energy and Momentum
2.6 The Action
2.6.1 The Euler-Lagrange Equation
2.6.2 Conserved Current
Problems
Suggestions for Further Reading
3 Fermion Fields
3.1 The Dirac Equation
3.2 Lorentz Symmetry
3.2.1 Covariance of the Dirac Equation
3.2.2 Spin of the Dirac Field
3.2.3 Bilinear Covariants
3.3 Free.Particle Solutions
3.3.1 Normalized Spinors
3.3.2 Completeness Relations
3.3.3 Helicities
3.4 The Lagrangian for a Free Dirac Particle
3.5 Quantization of the Dirac Field
3.5.1 Spins and Statistics
3.5.2 Dirac Field Observables
3.5.3 F0ck Space
3.6 Zero-Mass Fermions
Problems
Suggestions for Further Reading
4 Collisions and Decays
4.1 Interaction Representation
4.1.1 The Three Pictures
4.1.2 Time E:volution in the Interaction Picture
4.1.3 The S.matrix
4.2 Cross.Sections and Decay Rares
4.2.1 General Formulas
4.2.2 Two-Body Reaction to Two-Body Final States
4.2.3 Decay Rates
4.3 Interaction Models
4.4 Decay Modes of Scalar Particles
4.4.1 Neutral Decay Mode
4.4.2 Charged Decay Mode
4.5 Pion Scattering
4.5.1 The Scalar Boson Propagator
4.5.2 Scattering Processes
4.5.3 Summary and Generalization
4.6 Electron-Proton Scattering
4.6.1 The Electromagnetic Interaction
4.6.2 Electron-Proton Scattering Cross-Section
4.7 Electron-Positron Annihilation
4.8 Compton Scattering
Problems
Suggestions for Further Reading
5 Discrete Symmetries
5.1 Parity
5.1.1 Parity in Quantum Mechanics
5.1.2 Parity in Field Theories
5.1.3 Parity and Interactions
5.2 Time Inversion
5.2.1 Time Inversion in Quantum Mechanics
5.2.2 Time Inversion in Field Theories
5.2.3丁and Interactions
5.3 Charge Conjugation
5.3.1 Additive Quantum Numbers
5.3.2 Charge Conjugation in Field Theories
5.3.3 Interactions
5.4 The CPT Theorem
5.4.1 Implications of CPT Invariance
5.4.2 C.P,T.and CPT
Problems
Suggestions for Further Reading
6 Hadtons and Isospln
6.1 Charge Symmetry and Charge Independence
6.2 Nucleon Field in Isospin Space
6.3 Pion Field in Isospin Space
6.4 G.Parity
6.4.1 Nucleon and Pion Fields
6.4.2 Other Unflavored Hadrons
6.5 Isospin of Strange Particles
6.6 Isospin Violations
6.6.1 Electromagnetic Interactions
6.6.2 Wlealc Interactions
Problems
Suggestions for Further Reading
7 Quarks and SU(3)Symmetry
7.1 Isospin:SU(2) Symmetry
7.2 Hypercharge:SU(31 Symmetry
7.2.1 The Fundamental Representation
7.2.2 Higher.Dimensional Representations
7.2.3 Physical Significance of F3 and F3
7.2.4 3×3*Equal Mesons
7.2.5 3×3×3 Equal Baryons
7.3 Mass Splitting of the Hadron Multiplets
7.3.1 Baryons
7.3.2 Mesons
7.4 Including Spin:SU(6)
7.4.1 Mesons
7.4.2 Baryons
7.4.3 Application:Magnetic Moments of Hadrons
7.5 The Color of Quarks
7.6 The New Particles
7.6.1 J/tf,and Charm
7.6.2 The TaU Lepton
7.6.3 From Bottom to ToP
Problems
Suggestions for Further Reading
8 Gauge Field Theories
8.1 Symmetries and Interactions
8.2 Abelian Gauge Invariance
8.3 Non.Abelian Gauge Invariance
8.4 Quantum Chromodynamics
8.5 Spontaneous Breaking of Global Symmetries
8.5.1 The Basic Idea
8.5.2 Breakdown ofDiscrete Symmetry
8.5.3 Breakdown of Abelian Symmetry
8.5.4 Breakdown of Non-Abelian Symmetry
8.6 Spontaneous Breaking ofLocal Symmetries
8.6.1 Abelian Symmetry
8.6.2 Non.Abelian Symmetry
Problems
Suggestions for Further Reading
9 The Standard Model of the Electroweak Interaction
9.1 The Wleak Interaction Before the Gauge Theories
9.2 Gauge.Invariant Model of One.Lepton Family
9.2.1 Global Symmetry
9.2.2 Gauge Invariance
……
精彩書摘
1.4 SymmetriesThe recent history of physics gives us several examples that illustrate theimportance of the symmetry considerations in explaining empirical observa.tions or in developing new ideas .Thus,the intriguing regularities found in the atomic periodic table can be naturally explained as resulting from the rotational symmetry that characterizes atoms in their ground states;similarly,the relativity theory owes the clarity and the elegance of its fornmlation toits guiding principle,Lorentz in variance .However,more than any other field,particle physics,perhaps because of the very nature of the subject or becauseof the absence of relevant macroscopic analogies or useful classical correspon.dences,has by necessity conferred upon the symmetry concept a key role that has become essential in fornmlating new theories.The existence of the Q-particle and the reality of quarks are two outstanding demonstrations of thepower of this line of reasoning.but no less impressive is the prediction of theexistence of the electronic neutrino by Wolfgang Pauli back in 1 930 solely onthe basis of the conservation of energy, momentum,and angular nlomentum,the validity of which was still in doubt at the time.Pauli took a road less traveled by and opened up a whole new world. The prominent place taken by the symmetry considerations throughout this book only reflects their importance in particle physics.In this section .we will sketch a general picture of the idea. and briefly define various symmetry operations. As we have seen above .every particle js identified by a set of quantumnumbers.These numbers summarize the intrinsic properties of the particleand,for this reason,are called the internal quantum numbers,meaning thatthey have nothing to do with the kinetic state of the particle.which is de.scribed by other conserved quantities that depend on the state the particleis in,such as the energy,momentum,or angular momentum. The existence of a quantum number in a system always arises from theinvariance of the system under a qlobal geometrical transformation.that is。one that does not depend on the coordinates of the space.time point whereit is applied.A simple example suffices to illustrate the general situation.Consider two particles in a refefence frame iu which their interaction energydepends only on the relative distance of the particles.It follows then,first,that a displacement of the origin of the coordinates by an arbitrary distanceproduces no measurable physical effects on the system,and second,that thetotal momentum of the system remains constant in time because its rate ofchange,given by the total gradient of the interaction energy,is strictly zero.So,generally.if we have a physicaI system in which the absolute positions arenot observable fits energy depending off the relative distance rather than in.dividual particle positionsl and if we apply on it a geometrical transformation(spatial translation),then we obtain as direct consequences the invariance ofthe systern to the applied transformation(translational invariance)and theexistence of a conservation rule fmomentum conservation).These are,inshort,the interdepelldent aspects found in every symmetry principle.
前言/序言
The last few decades have seen major advances in the physics of elementary particles. New generations of particle accelerators and detectors have come into operation, and have successfully contributed to improving the quantity and quality of data on diverse interaction processes and to the discoveries of whole new families of particles. At the same time, important new ideas have emerged in quantum field theory, culminating in the developments of theories for the weak and strong interactions to complement quantum electrodynam-ics, the theory of the electromagnetic force. The simplest of the new theories that are at the same time mathematically consistent and physically successful constitute what is known as the standard model of the fundamental interac-tions. This book is an attempt to present these remarkable advances at an elementary level, making them accessible to students familiar with quantum mechanics, special relativity, and classical electrodynamics.
The main content of the book is roughly divided into two parts; one on theories to lay the foundation and the other on further developments of concepts and descriptions of phenomena to prepare the student for more advanced work. After a brief overview of the subject and a presentation of some basic ideas, two chapters which deal mostly with relativistic one-body wave equations, quantization of fields, and Lorentz invariance follow. In the spirit of the practical approach taken in this book, a heuristic derivation of the Feynman rules is given in the fourth chapter, where the student is shown how to calculate cross-sections and decay rates at the lowest order.The following chapter contains a discussion on discrete symmetries and the concept of symmetry breaking. Isospin is introduced next as the simplest example of internal symmetries in order to ease the reader into the notion of unitary groups in general and of SU(3) in particular, which is discussed next together with the recent discoveries of new particles. The next two chapters present the standard model of the fundamental interactions. We make contact with experiments in subsequent chapters with detailed studies of some fundamental electroweak processes, such as the deep inelastic lepton-nucleon scattering, the CP violation in the neutral K mesons, the neutrino oscillations and the related problem of the solar neutrino deficit, and finally,the r lepton decay, which touch upon many aspects of weak interactions. The very high precision of the data that is now attained in some of these processes requires a careful examination of higher-order effects. This leads to a detailed study of one-loop QCD corrections to weak interactions. The next chapter demonstrates the remarkable property of asymptotic freedom of quantum chromodynamics and introduces the powerful concept of the renormalization group which plays a central role in many phenomena. The heavy flavors of quarks, which pose new questions on several aspects of interactions and could open windows on the new physics, form the subject of a separate chapter.We close with a review of the present status of the standard model and,briefly, of its extensions. Selected solutions to problems are given. Finally,important formulas are collected in an Appendix for convenient reference.
物理學的邊界:探索宇宙的深層結構 本書將引導讀者進入一個微觀世界的奇妙領域,一個由看不見的、基本構成單元和它們之間復雜交織的作用力所主宰的領域。這不是對任何特定教材的重復,而是對粒子物理學這一迷人學科核心概念、實驗發現和理論框架的深度剖析,重點在於構建對現代物理學圖景的整體理解,而非對某一特定教科書內容的復述。 我們將從對“基本”的哲學和實驗定義開始。什麼是基本粒子?它們是構成物質的最小單元嗎?我們如何通過實驗手段,在宏觀世界中探測到這些微小到令人難以想象的實體?本書不會拘泥於列舉標準模型的粒子列錶,而是深入探討發現這些粒子的曆史背景、實驗技術的演進,以及每一次重大發現(如電子、質子、中子、中微子以及後來的誇剋和希格斯玻色子)如何重塑瞭我們對物質本質的認知。 第一部分:物質的基石——粒子分類與對稱性原理 本書首先構建一個理解粒子世界的框架,即粒子分類的係統性。我們不會僅僅停留在費米子和玻色子(物質粒子與媒介粒子)的簡單二分法上。更關鍵的是,我們將探討朗道-楊-米爾斯(Landau-Yang-Mills)理論背景下的內在對稱性原理如何在粒子物理學中扮演核心角色。 對稱性在物理學中的地位: 強大的自然定律往往根植於某種對稱性。本書將詳細討論內稟對稱性,特彆是那些與規範場論緊密相關的對稱群。我們將解釋為什麼 $SU(3) imes SU(2) imes U(1)$ 這樣的數學結構,能夠精確地描述我們觀察到的所有基本相互作用(電磁力、弱核力和強核力)。讀者將理解,這些對稱性不僅僅是理論傢的數學工具,它們是實驗觀測的必然結果,並且指導瞭對新粒子的預測。 量子場論的語言: 我們將介紹量子場論(QFT)作為描述粒子和相互作用的唯一有效語言。這並非是深入到復雜的正則化和重整化細節,而是側重於理解QFT的基本哲學:粒子是場的激發態。我們會探討如何用這種語言來描述粒子如何産生、湮滅以及相互轉化,這些過程是所有高能物理實驗的核心現象。 第二部分:力的本質——從宏觀到微觀的統一嘗試 本書的第二部分聚焦於自然界的四種基本力,但視角將著重於它們在微觀尺度上的唯象描述和統一前景。 電磁相互作用的量子描述: 量子電動力學(QED)是第一個成功的量子場論。我們將分析QED的核心概念,例如光子作為媒介粒子,以及拉格朗日量如何編碼瞭電子和光子的相互作用。關鍵在於理解費曼圖作為計算工具的意義,它們如何直觀地錶示瞭微觀過程的概率振幅。 強相互作用的復雜性: 強力的描述是粒子物理學中最具挑戰性的部分。本書將深入探討量子色動力學(QCD)的特點,特彆是漸近自由和誇剋禁閉這兩個看似矛盾的特性是如何並存於理論之中的。我們將討論疇壁、真空結構等概念,它們是理解強子(如質子和中子)內部動態結構的關鍵。這種討論將超越簡單的誇剋模型,觸及到手徵對稱性的自發破缺等深層物理。 弱相互作用與規範理論的統一: 弱相互作用的描述,尤其是它能夠改變粒子味(例如中微子的振蕩),是電弱統一理論成功的基石。我們將詳細討論希格斯機製,它不僅僅是賦予粒子質量的“粘性”概念,更是規範對稱性自發破缺的必然産物。讀者將理解,電弱統一如何通過引入規範玻色子 $W^pm$ 和 $Z^0$ 來實現,以及這些玻色子質量的起源。 第三部分:超越標準模型——未解之謎與前沿探索 標準模型在描述已知的基本粒子和三種相互作用方麵取得瞭空前的成功,但它並非終極理論。本書的最後部分將轉嚮當前物理學傢麵臨的重大挑戰和潛在的新物理學領域。 引力問題的懸而未決: 最大的難題在於如何將引力(由廣義相對論描述)納入量子場論的框架。我們將探討量子引力研究的睏難所在,以及諸如弦理論或圈量子引力等嘗試如何試圖調和這兩大支柱理論。本書將側重於概念上的區彆,例如時空在量子尺度上的離散化或漲落的可能性。 暗物質與暗能量的謎團: 觀測證據明確指嚮宇宙中存在大量不與已知粒子相互作用的物質(暗物質)和驅動宇宙加速膨脹的能量(暗能量)。本書將詳細分析目前主流的暗物質候選者(如WIMPs、軸子)的實驗搜索策略,以及它們如何與粒子物理學標準模型相銜接或相悖。對於暗能量,我們將探討其與真空能的聯係,以及宇宙學常數問題所揭示的理論缺陷。 中微子物理學的革命: 中微子質量的發現(通過中微子振蕩)已經確鑿地證明標準模型是不完備的。我們將探討這些發現對粒子物理學意味著什麼——例如,它們可能暗示瞭西斯(See-Saw)機製或更高能級的新物理。 CP破壞與物質-反物質不對稱性: 宇宙中物質遠多於反物質,這要求CP對稱性在早期宇宙中被破壞。本書將分析標準模型內CP破壞的來源(主要來自誇剋扇區的卡比博-小林-高大(CKM)矩陣)及其不足,並探討超越標準模型的新CP破壞機製,如在輕子扇區或希格斯扇區的可能性。 本書旨在培養讀者一種結構化的、批判性的思維方式,使他們能夠理解現代物理學是如何從數學對稱性推導齣物質的性質,並認識到目前理論框架的邊界所在。重點在於構建對相互作用如何通過規範場傳遞的深刻理解,以及對實驗觀測如何驅動理論創新的深刻認識。