particle physics: status and perspectives part 1: particles manfred jeitler

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  • Particle Physics: Status and Perspectives Part 1: ParticlesManfred Jeitler

  • *Overview (1)what are elementary particles?the first particles to be discoveredhistorical overviewa few formulasrelativistic kinematicsquantum mechanics and the Dirac equationcommon units in elementary particle physicsthe Standard Modeldetectorsaccelerators

  • *Overview (2)completing the Standard Modelthe second generation (charm and J/)the third generation (beauty (bottom) and (upsilon), top)gauge bosons of electroweak interactions: the W and Z bosonstesting at the Precision Frontier: the magnetic moment of the leptonsthe Higgs bosonfundamental symmetries and their violationparity violationCP-violationT-violation

  • *Overview (3)neutrinos and neutrino oscillationsparticle physics and cosmology, open questionsthe Energy Frontier and the Precision FrontierSupersymmetrydark mattergravitational waves

    slides and formulas athttp://wwwhephy.oeaw.ac.at/u3w/j/jeitler/www/LECTURES/ParticlePhysics/

  • *LiteratureA few useful books are:

    Donald Perkins, Introduction to High Energy PhysicsOtto Nachtmann, Elementary Particle Physics

    You will find many other good books in your library

    On recent experiments, much useful information can be found on the internet (Wikipedia, home pages of the various experiments etc.)

  • *

  • What are (elementary) particles?*

  • *1897the electronThomson

  • *J.J. Thomsons plum-pudding model of the atom... the atoms of the elements consist of a number of negatively electrified corpuscles enclosed in a sphere of uniform positive electrification, ...

  • *1897the proton1900-19241914Rutherfordp

  • *

  • *

  • *1897the photon1900-1924PlanckEinsteinCompton

  • *1897the neutron1900-19241914n1932Chadwick

  • *1897the positron (anti-matter)1900-19241914e+193219371947 Anderson Dirac

  • *

  • *

  • *1897the muon1900-1924191419321937 Hess Anderson, Neddermeyer

  • muon lifetimemuon lifetime ~ 2.2 s

    speed of muons: almost speed of light

    speed of light = ?

    path travelled by muons = ?

    *

  • *

  • *relativistic kinematicselementary particles travel mostly at speeds close to speed of lightbecause their masses are small compared to typical energies (almost) always use relativistic kinematicsin particle physics, special relativity is sufficient most of the timeremember a few basic formulae !

  • a bit of mathsSpecial RelativityQuantum MechanicsDirac Equation*

  • *relativistic kinematics1v1/

    v

    1/ =

    0.5

    0.87

    0.7

    0.71

    0.9

    0.44

    0.99

    0.14

    0.999

    0.04

    _1160376736.unknown

  • *10-4 eV: 3 K cosmic background radiation (~0.25 meV)10-2 eV: room temperature (~30 meV) eV: ionisation energy for light atoms (13.6eV in hydrogen)103 eV (keV): X-rays in heavy atoms106 eV (MeV): mass of electron me=511 keV/c2109 eV (GeV): mass of proton (~1GeV/c2)~100 GeV/c2: mass of W, Z~ 200 GeV/c2: mass of top 1012 eV (TeV): range of present-day man-made accelerators1020 eV: highest energies seen for cosmic particles1028 eV (1019 GeV/c2): ~ Planck massunits: energy and mass

  • *units: speed and distancevelocity: speed of light ~ 3 * 108 m/s~ 30 cm/nsapproximately, all speeds are equal to the speed of light in high-energy particle physics !all particles are relativistic

    distance: fm (femtometer)1 fm = 10-15 msometimes also called Fermi

  • *

  • *relations and constants

  • *natural units

  • *gravitation is weak!

  • *1897the pion1900-19241914p193219371947

    EXPI, Aug. 2012

    *Force carriersInteraction between particles due to exchange of other (virtual) particlesgauge bosons

  • *1897the neutrino1900-19241914n193219371947 Pauli Reines

  • *

  • *1897strange particles1900-19241914193219371947Rochester,Butler,...1947-...

  • Too many particles!

  • *life time (s)nmpcKLDKcKSp0htBfJ/y1s2s3s4swrD*ScS0W-mass (GeV/c2)the particle zoo1s1 ms1 s10-15s10-20s10-25s100000E=1eV e- W, Zo p1 ns

  • *1897I have heard it said that the finderof a new elementary particle usedto be rewarded by a Nobel Prize,but that now such a discovery ought to be punished by a $10,000 fine.1900-192419141932193719471947-...In his Nobel prize speech in 1955, Willis Lamb expressed nicely the general attitude at the time: Lamb

  • The particle zoo of the subatomic worldIs there something analogous to the Periodic Table of the elements?

  • ???????

    Is there something missing?

  • The periodic table today

  • *TeilchenWechselwirkungenstarkschwachLadung0-1+2/3-1/3+1/3+1 0 ProtonNeutronLeptonenQuarks

  • *Anti-TeilchenWechselwirkungenstarkschwachLadung0+1-2/3+1/3+1 Pion (p)

  • *

  • *fermions (spin )charge0-1+2/3-1/3leptonsquarksthe Standard Model +1 0 protonneutronbaryons

  • *anti-particlesinteractionsstrongweakecharge0+1-2/3+1/3electromagneticgnemtnmntleptonsquarksforce carriers = bosons (spin 1)

  • *anti-particlesinteractionsstrongweakecharge0+1-2/3+1/3electromagneticgnemtnmntleptonsquarksforce carriers = bosons (spin 1)

  • *the 4 fundamental interactionsGravitationStrong InteractionElectromagnetismWeak Interaction

  • *

  • *lifetime and width

  • *cross sectiondefined via scattering probability W = n . n ... number of scatterers in beam ... cross section of individual scatterernaive picture: each scatterer has a certain area and is completely opaqueabsorption cross sectioncan also be used for elastic scattering ...into certain solid angle d: d/d... or particle transformationdifferential cross section for a certain reactionunit: barn: (10 fm)2 = 100 fm2 = 10-28 m2 = 10-24 cm2

  • *fundamental interactions

    interactionStrongelectro-magneticWeakgravitygauge bosongluonphotonW, Zgravitonmass00~ 100 GeV0range 1 fm10-3 fmsourcecolor chargeelectric chargeweak chargemasscoupling~ 1 ~ 1/13710-510-38typical fm210-3 fm210-14 fm2-typical lifetime (s)10-2310-2010-8-

  • *Feynman diagrams

  • *electron scattering(Bhabha scattering)

  • *Feynman diagrams for electromagnetic interactions

  • *Feynman diagramsfor Weak interactions

  • *

  • *

  • *experimental setup for measuring deep-inelastic electron-proton scattering (from Robert Hofstadters Nobel prize lecture, 1961)

  • *

  • *

  • *color chargeApart from their electric charge, quarks also have color charge. The particles which convey this interaction and keep the quarks together are called gluons.

    coloranticolorREDCYANBLUEYELLOWGREENMAGENTA

  • *Free quarks have never been observed, they always appear in bound states (quark confinement). 2 types of bound states are observed: 3 quarks of three different colors: baryons 2 quarks of a color and its anticolor: mesons

  • *Feynman diagramsfor Strong interactions

  • *3-jet event(Aleph experiment, LEP Collider, CERN, Geneva, Switzerland)

  • *D++uuup+ddusL0dD+suK-bbprotonneutronmesonsbaryons......nucleusHe nucleus(a-particle)atommatter

  • *Robert Hofstadter (Nobel prize lecture, 1961)

  • *decayne 26 ns 2200 nsscatteringKWhat do we observe?decays & scatteringKp

  • *fermions (spin )charge0-1+2/3-1/3leptonsquarksthe Standard Model

    **Often, elementary particle physics is also called High Energy Physics because most particles become visible only at high energies, or can only be produced via high energies.

    A specialized course on the frontier (perspectives) of High Energy Physics is held by Claudia Wulz (Perspektiven der experimentellen Hochenergie-physik; 1 hour, held in blocks, winter semester) However, Medium Energy Physics also has to do with elementary particles.

    The ancient Greek philosophized already about elementary particles ( that which cannot be separated into parts, from to cut; even today, this idea is valid in a certain sense: atoms cannot be split up by chemical means). There reasoning was not based on experiment but only on philosophical speculation (Can one always continue dividing things into smaller parts? Or do we arrive at something that cannot be divided any more? Both concepts seem problematic!)But what is really elementary? Which particles do YOU consider elementary?

    Apart from the physics, I will also present the basics of the techniques of Elementary Particles. For more in-depth information, there are specialized courses: detectorsManfred Krammer (summer semester)acceleratorsMichael Benedikt (held in blocks, winter semester)*

    *

    *The ancient Greek philosophized already about elementary particles ( that which cannot be separated into parts, from to cut; even today, this idea is valid in a certain sense: atoms cannot be split up by chemical means). Their reasoning was not based on experiment but only on philosophical speculation. (Can one always continue dividing things into smaller parts? Or do we arrive at something that cannot be divided any more? Both concepts seem problematic!)But what is really elementary? Which particles do YOU consider elementary?

    ** the modern, scientific investigation into elementary particles starts with the discovery of the electron as a particle by Thomson to date, the electron appears as an elementary particle; its size is too small to be measured (with present-day instruments) and is below one millionth of the size of an atom Tho