Elements of High Energy Physics Julián Félix Elements of High Energy Physics e-libro.net © 2004, por Julián Félix Valdez © Primera edición virtual y en papel, e-libro.net, Buenos Aires, julio de 2004 ISBN 1-4135-3536-4, de la edición virtual ISBN 1-4135-3537-2, de la edición impresa Education is the most precious gem that someone can give to someone else. Material possessions are ephemeral; education skills, perennial. Human beings perceive and interpret the external world through their glass window education. Give them a sane education, and the world will look level-headed. Give good education and noble motives to people and you will make the world moves rightly. To those that have been original enough to think by themselves, to trace, and to open new roads to educate people. And to those that have been courageous enough to try them. Juli´an F´elix Instituto de F´ısica, Universidad de Guanajuato Le´on Guanajuato, M´exico. With the help of la Fundacio´n DELTA, A.C. and of the grant CoNaCyt-2002-C01-39941/A-1. v Preface There are many wrong practices, procedures, and policies in the south countries: Theworseisinpeopleeducation. Sometimes,thishasnodefined purposes and orientations. The idea of the state is to provide education to people,evenifthateducationhasnothingtodowiththeState;evenifthat education is not integrated in one project of State -or nation-, that hits its economy, security, integrity, etc. The policies to introduce, to teach, and to learn, science in that south countriesareevenworse: Scienceistaughtlikeifitwereareligion,without relationwithengineeringandtheexternalworld;onlyatthetextbooklevel andusingrepetitiveandmemoriterprocedures. Completelyseparatedfrom the physical and economical country reality. Physics is not excluded from that situation. It is taught completely separated from the physical reality of the external world and from the economical reality of the state. The Mexican schools of sciences -physics- reach the 5% of efficiency. And teach physics with a parody of physics laboratories-whentherehavebeensomeeffortstoconstructthem,because in some universities students never enter a physics laboratory- and using textbookstranslatedintoSpanish,generallyfromEnglish. Itisworthlessto saythatphysicsstudentsneveraccomplishaseriousexperimentinphysics; andthattheygraduatefromphysicsimplicitlybelievingthatphysicsisnot from this world. Because that situation, students -also teachers and professors- are in- volved in a paradoxical situation and perverse circle: They learn wrongly physics because their mentors learnt badly physics; teachers teach in a wrongwayfortheyweretoughalsoinawrongmanner. Andthecountryis ElementsofHighEnergyPhysics technological underdeveloped because the poor way physics is tough, and because the poor way science is tough the country is technological under- developed. This book Elements of High Energy Physics is an intent to change that paradoxicalsituationsinteachingandlearningphysics;tobreakdownthat vicious circle of bad teaching physics and technological underdevelopment, that engulfs the majority of the countries in these times. The worse those country people teach and learn physics, the more un- derdeveloped nations they form. Country technological development and country good education are very close related. The more skillful those na- tion people are, the richest they are. Mexico country exemplifies very well this situation. This book will have a Spanish version, for use in Mexico and other Spanish speaker countries. To alleviate the situation, the vicious circle, in learning and teaching physics and technological underdevelopment. Contents Preface vi 1. Introduction 1 2. Physics 5 2.1 Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1.1 Physics and the External World . . . . . . . . . . . . 9 2.1.2 Precepts of Physics . . . . . . . . . . . . . . . . . . . 12 2.1.2.1 Classical Precepts . . . . . . . . . . . . . . . 12 2.1.2.2 Quantum Precepts . . . . . . . . . . . . . . 15 2.1.3 Theorization and Experimentation . . . . . . . . . . 20 2.1.3.1 Theorization . . . . . . . . . . . . . . . . . . 20 2.1.3.2 Experimentation . . . . . . . . . . . . . . . 26 2.2 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 3. Experimental High Energy Physics 43 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3.2 Atom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3.3 Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.4 Families of Particles . . . . . . . . . . . . . . . . . . . . . . 53 3.5 Classification of Particles . . . . . . . . . . . . . . . . . . . 56 3.6 Quark Model . . . . . . . . . . . . . . . . . . . . . . . . . . 59 3.7 A High Energy Physics Experiment. . . . . . . . . . . . . . 62 3.7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 63 3.7.2 Scintillator Detectors . . . . . . . . . . . . . . . . . . 65 3.7.3 Multiwire Proportional Chambers . . . . . . . . . . . 66 ElementsofHighEnergyPhysics 3.7.4 Cerenkov Counters . . . . . . . . . . . . . . . . . . . 67 3.7.5 Monte Carlo Method . . . . . . . . . . . . . . . . . . 68 3.7.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . 69 4. High Energy Physics Practical Utility 85 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 4.2 To know the Nature of Nature . . . . . . . . . . . . . . . . 86 4.3 Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 4.4 New Materials . . . . . . . . . . . . . . . . . . . . . . . . . 99 4.5 Computation . . . . . . . . . . . . . . . . . . . . . . . . . . 100 4.6 New Technologies . . . . . . . . . . . . . . . . . . . . . . . . 102 4.7 Medicine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 4.7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 105 4.7.2 X Rays . . . . . . . . . . . . . . . . . . . . . . . . . . 106 4.7.3 Other Techniques . . . . . . . . . . . . . . . . . . . . 109 4.7.4 Study of the Brain . . . . . . . . . . . . . . . . . . . 111 4.7.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . 112 4.8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Bibliography 117 Index 119 Chapter 1 Introduction Teachershavenotpronouncedthelastwordonteaching;norphysicsteach- ers have pronounced the last word on teaching physics. And researchers have not pronounced the last word on research and physics researchers nor on physics research. In formal courses of physics, teachers or instructors do not leave explic- itly what physics is and what is its utility, nor what is its relation with external world, or technology, or daily life objects and machines. Or how physics leads to a deep understanding of the external world behavior. At least in Latin America, the main problem is from the teacher -in all levels of instruction- who presents and conduces the course. The problem is akin in the rest of the world, especially in the underdeveloped countries. The teacheristheultimateresponsiblepersononthewayheconducesthecourse and on the way students are taught and of what and how students learn. Most of the time, teachers deliver to students as a science -physics- a col- lection of dead facts, data, and technical terms, in a way that is more akin to religion than to science; in both contents and way of learning. Without immediateconnectionwithexternalworld. Studentslearnphysicsbelieving facts. Scienceisnotthat. Physicsisnotthat. Scienceisalivehumanactivity. Physics is alive science, growing and changing continuously, and everyday. Very close to the way human beings perceive the external world. Physics is alive, always growing, science, not a static religion. Physics isthedescriptionandinterpretationoftheexternalworld. Thedescription and the interpretation of external world let physicist understand the way