Weak Interactions
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Quantum Field Theory*
Quantum Field Theory y Frank Wilczek Institute for Advanced Study, School of Natural Science, Olden Lane, Princeton, NJ 08540 I discuss the general principles underlying quantum eld theory, and attempt to identify its most profound consequences. The deep est of these consequences result from the in nite number of degrees of freedom invoked to implement lo cality.Imention a few of its most striking successes, b oth achieved and prosp ective. Possible limitation s of quantum eld theory are viewed in the light of its history. I. SURVEY Quantum eld theory is the framework in which the regnant theories of the electroweak and strong interactions, which together form the Standard Mo del, are formulated. Quantum electro dynamics (QED), b esides providing a com- plete foundation for atomic physics and chemistry, has supp orted calculations of physical quantities with unparalleled precision. The exp erimentally measured value of the magnetic dip ole moment of the muon, 11 (g 2) = 233 184 600 (1680) 10 ; (1) exp: for example, should b e compared with the theoretical prediction 11 (g 2) = 233 183 478 (308) 10 : (2) theor: In quantum chromo dynamics (QCD) we cannot, for the forseeable future, aspire to to comparable accuracy.Yet QCD provides di erent, and at least equally impressive, evidence for the validity of the basic principles of quantum eld theory. Indeed, b ecause in QCD the interactions are stronger, QCD manifests a wider variety of phenomena characteristic of quantum eld theory. These include esp ecially running of the e ective coupling with distance or energy scale and the phenomenon of con nement. -
Frstfo O Ztif
FRStfo o ztif * CONNISSARIAT A L'ENERGIE ATOMIQUE CENTRE D'ETUDES NUCLEAIRES DE SACLAY CEA-CONF -- 8070 Service de Documentation F9119! GIF SUR YVETTE CEDEX L2 \ PARTICLE PHYSICS AND GAUGE THEORIES MOREL, A. CEA CEN Socloy, IRF, SPh-T Communication présentée à : Court* on poxticlo phytic* Cargos* (Franc*) 15-28 Jul 1985 PARTICLE PHYSICS AND GAUGE THEORIES A. MOREL Service de Physique Théorique CEN SACLA Y 91191 Gif-sur-Yvette Cedex, France These notes are intended to help readers not familiar with parti cle physics in entering the domain of gauge field theory applied to the so-called standard model of strong and electroweak interactions. They are mainly based on previous notes written in common with A. Billoire. With re3pect to the latter ones, the introduction is considerably enlar ged in order to give non specialists a general overview of present days "elementary" particle physics. The Glashow-Salam-Weinberg model is then treated,with the details which its unquestioned successes deserve, most probably for a long time. Finally SU(5) is presented as a prototype of these developments of particle physics which aim at a unification of all forces. Although its intrinsic theoretical difficulties and the. non- observation of a sizable proton decay rate do not qualify this model as a realistic one, it has many of the properties expected from a "good" unified theory. In particular, it allows one to study interesting con nections between particle physics and cosmology. It is a pleasure to thank the organizing committee of the Cargèse school "Particules et Cosmologie", and especially J. Audouze, for the invitation to lecture on these subjects, and M.F. -
Weak Interaction Processes: Which Quantum Information Is Revealed?
Weak Interaction Processes: Which Quantum Information is revealed? B. C. Hiesmayr1 1University of Vienna, Faculty of Physics, Boltzmanngasse 5, 1090 Vienna, Austria We analyze the achievable limits of the quantum information processing of the weak interaction revealed by hyperons with spin. We find that the weak decay process corresponds to an interferometric device with a fixed visibility and fixed phase difference for each hyperon. Nature chooses rather low visibilities expressing a preference to parity conserving or violating processes (except for the decay Σ+ pπ0). The decay process can be considered as an open quantum channel that carries the information of the−→ hyperon spin to the angular distribution of the momentum of the daughter particles. We find a simple geometrical information theoretic 1 α interpretation of this process: two quantization axes are chosen spontaneously with probabilities ±2 where α is proportional to the visibility times the real part of the phase shift. Differently stated the weak interaction process corresponds to spin measurements with an imperfect Stern-Gerlach apparatus. Equipped with this information theoretic insight we show how entanglement can be measured in these systems and why Bell’s nonlocality (in contradiction to common misconception in literature) cannot be revealed in hyperon decays. We study also under which circumstances contextuality can be revealed. PACS numbers: 03.67.-a, 14.20.Jn, 03.65.Ud Weak interactions are one out of the four fundamental in- systems. teractions that we think that rules our universe. The weak in- Information theoretic content of an interfering and de- teraction is the only interaction that breaks the parity symme- caying system: Let us start by assuming that the initial state try and the combined charge-conjugation–parity( P) symme- of a decaying hyperon is in a separable state between momen- C try. -
Investigations of Nuclear Decay Half-Lives Relevant to Nuclear Astrophysics
DE TTK 1949 Investigations of nuclear decay half-lives relevant to nuclear astrophysics PhD Thesis Egyetemi doktori (PhD) ´ertekez´es J´anos Farkas Supervisor / T´emavezet˝o Dr. Zsolt F¨ul¨op University of Debrecen PhD School in Physics Debreceni Egyetem Term´eszettudom´anyi Doktori Tan´acs Fizikai Tudom´anyok Doktori Iskol´aja Debrecen 2011 Prepared at the University of Debrecen PhD School in Physics and the Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI) K´esz¨ult a Debreceni Egyetem Fizikai Tudom´anyok Doktori Iskol´aj´anak magfizikai programja keret´eben a Magyar Tudom´anyos Akad´emia Atommagkutat´o Int´ezet´eben (ATOMKI) Ezen ´ertekez´est a Debreceni Egyetem Term´eszettudom´anyi Doktori Tan´acs Fizikai Tudom´anyok Doktori Iskol´aja magfizika programja keret´eben k´esz´ıtettem a Debreceni Egyetem term´eszettudom´anyi doktori (PhD) fokozat´anak elnyer´ese c´elj´ab´ol. Debrecen, 2011. Farkas J´anos Tan´us´ıtom, hogy Farkas J´anos doktorjel¨olt a 2010/11-es tan´evben a fent megnevezett doktori iskola magfizika programj´anak keret´eben ir´any´ıt´asommal v´egezte munk´aj´at. Az ´ertekez´esben foglalt eredm´e- nyekhez a jel¨olt ¨on´all´oalkot´otev´ekenys´eg´evel meghat´aroz´oan hozz´a- j´arult. Az ´ertekez´es elfogad´as´at javaslom. Debrecen, 2011. Dr. F¨ul¨op Zsolt t´emavezet˝o Investigations of nuclear decay half-lives relevant to nuclear astrophysics Ertekez´es´ a doktori (PhD) fokozat megszerz´ese ´erdek´eben a fizika tudom´any´agban ´Irta: Farkas J´anos, okleveles fizikus ´es programtervez˝omatematikus K´esz¨ult a Debreceni Egyetem Fizikai Tudom´anyok Doktori Iskol´aja magfizika programja keret´eben T´emavezet˝o: Dr. -
1 Drawing Feynman Diagrams
1 Drawing Feynman Diagrams 1. A fermion (quark, lepton, neutrino) is drawn by a straight line with an arrow pointing to the left: f f 2. An antifermion is drawn by a straight line with an arrow pointing to the right: f f 3. A photon or W ±, Z0 boson is drawn by a wavy line: γ W ±;Z0 4. A gluon is drawn by a curled line: g 5. The emission of a photon from a lepton or a quark doesn’t change the fermion: γ l; q l; q But a photon cannot be emitted from a neutrino: γ ν ν 6. The emission of a W ± from a fermion changes the flavour of the fermion in the following way: − − − 2 Q = −1 e µ τ u c t Q = + 3 1 Q = 0 νe νµ ντ d s b Q = − 3 But for quarks, we have an additional mixing between families: u c t d s b This means that when emitting a W ±, an u quark for example will mostly change into a d quark, but it has a small chance to change into a s quark instead, and an even smaller chance to change into a b quark. Similarly, a c will mostly change into a s quark, but has small chances of changing into an u or b. Note that there is no horizontal mixing, i.e. an u never changes into a c quark! In practice, we will limit ourselves to the light quarks (u; d; s): 1 DRAWING FEYNMAN DIAGRAMS 2 u d s Some examples for diagrams emitting a W ±: W − W + e− νe u d And using quark mixing: W + u s To know the sign of the W -boson, we use charge conservation: the sum of the charges at the left hand side must equal the sum of the charges at the right hand side. -
Introduction to Supersymmetry
Introduction to Supersymmetry Pre-SUSY Summer School Corpus Christi, Texas May 15-18, 2019 Stephen P. Martin Northern Illinois University [email protected] 1 Topics: Why: Motivation for supersymmetry (SUSY) • What: SUSY Lagrangians, SUSY breaking and the Minimal • Supersymmetric Standard Model, superpartner decays Who: Sorry, not covered. • For some more details and a slightly better attempt at proper referencing: A supersymmetry primer, hep-ph/9709356, version 7, January 2016 • TASI 2011 lectures notes: two-component fermion notation and • supersymmetry, arXiv:1205.4076. If you find corrections, please do let me know! 2 Lecture 1: Motivation and Introduction to Supersymmetry Motivation: The Hierarchy Problem • Supermultiplets • Particle content of the Minimal Supersymmetric Standard Model • (MSSM) Need for “soft” breaking of supersymmetry • The Wess-Zumino Model • 3 People have cited many reasons why extensions of the Standard Model might involve supersymmetry (SUSY). Some of them are: A possible cold dark matter particle • A light Higgs boson, M = 125 GeV • h Unification of gauge couplings • Mathematical elegance, beauty • ⋆ “What does that even mean? No such thing!” – Some modern pundits ⋆ “We beg to differ.” – Einstein, Dirac, . However, for me, the single compelling reason is: The Hierarchy Problem • 4 An analogy: Coulomb self-energy correction to the electron’s mass A point-like electron would have an infinite classical electrostatic energy. Instead, suppose the electron is a solid sphere of uniform charge density and radius R. An undergraduate problem gives: 3e2 ∆ECoulomb = 20πǫ0R 2 Interpreting this as a correction ∆me = ∆ECoulomb/c to the electron mass: 15 0.86 10− meters m = m + (1 MeV/c2) × . -
Fundamental Physical Constants: Looking from Different Angles
1 Fundamental Physical Constants: Looking from Different Angles Savely G. Karshenboim Abstract: We consider fundamental physical constants which are among a few of the most important pieces of information we have learned about Nature after its intensive centuries- long studies. We discuss their multifunctional role in modern physics including problems related to the art of measurement, natural and practical units, origin of the constants, their possible calculability and variability etc. PACS Nos.: 06.02.Jr, 06.02.Fn Resum´ e´ : Nous ... French version of abstract (supplied by CJP) arXiv:physics/0506173v2 [physics.atom-ph] 28 Jul 2005 [Traduit par la r´edaction] Received 2004. Accepted 2005. Savely G. Karshenboim. D. I. Mendeleev Institute for Metrology, St. Petersburg, 189620, Russia and Max- Planck-Institut f¨ur Quantenoptik, Garching, 85748, Germany; e-mail: [email protected] unknown 99: 1–46 (2005) 2005 NRC Canada 2 unknown Vol. 99, 2005 Contents 1 Introduction 3 2 Physical Constants, Units and Art of Measurement 4 3 Physical Constants and Precision Measurements 7 4 The International System of Units SI: Vacuum constant ǫ0, candela, kelvin, mole and other questions 10 4.1 ‘Unnecessary’units. .... .... ... .... .... .... ... ... ...... 10 4.2 ‘Human-related’units. ....... 11 4.3 Vacuum constant ǫ0 andGaussianunits ......................... 13 4.4 ‘Unnecessary’units,II . ....... 14 5 Physical Phenomena Governed by Fundamental Constants 15 5.1 Freeparticles ................................... .... 16 5.2 Simpleatomsandmolecules . ..... -