1 / 54

Some High Energy Physics

Some High Energy Physics. Course Summary. Historical/Philosophical introduction Antiparticles Detectors & accelerators Standard Model of Particles (SM) Connection with Cosmology Why do we think that the SM is not the final word ?. What it is made of ? How does it work?.

jmitchell
Download Presentation

Some High Energy Physics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Some High Energy Physics A. Bay Beijing October 2005

  2. Course Summary Historical/Philosophical introduction Antiparticles Detectors & accelerators Standard Model of Particles (SM) Connection with Cosmology Why do we think that the SM is not the final word ? A. Bay Beijing October 2005

  3. What it is made of ? How does it work? A. Bay Beijing October 2005

  4. Historical/Philosophical introduction • Physical (fundamental) questions: • what is matter made of • what is water ? • what animates the matter constitutive of an animal, a tree ? • what is the origin of interactions ? • elementary: gravitation • complex: hate & love • Cosmological question: when and how the Cosmos was built. There will be an end ? • Theological question: why the Universe? What are the reasons for life (and death)? • Many, many attempt in the old time to try to answer this questions. • If we leave aside the (too difficult) Theological question, trying to answer to • the other questions constitute the "quest" for a (scientific) system of Nature. • I will give you a short list of milestones of this quest. • (This is the "European' point of vie, sorry !) A. Bay Beijing October 2005

  5. Some history Anaxagoras (500-428 BC) the Sun is a big ball of fire and the Moon is reflecting its light theory of minute constituents of things emphasis on mechanical processes in the formation of order many consider him the father of the Atomic model Empedocles (484-424 BC) four elements (earth, fire, water, air) light: particles emitted by a source, they travel to the eye and then they return to the source ! Democritus (460-370 BC) Universe is an empty space ("void") filled with atoms in fixed number milky way are distant stars 0ther worlds should exist with life A. Bay Beijing October 2005

  6. Some history .2 Aristotle (384-322 BC) Earth is spherical at the middle of the Universe (cannot "fall"). Aristarcs (310-230 BC) Sun, stars are fixed. Earth turns around the Sun. He searches a way to measure the distance of stars. Archimedes (287-212 BC) computes the volume of the Aristarc's Universe: 1063 grains of sands . . . Galileo Galilei (1564-1642) mathematical attack of the physical problem experimental foundation of science inertia, relativity of motion he adopts Copernicus model of solar system (almost gets to jail !) A. Bay Beijing October 2005

  7. Some history .3 Christian Huygens (1650) wave model of light Isaac Newton mechanics, gravitation, particle model of light Thomas Young (1773-1829) , Augustin Fresnel (1788-1827) wave model of light, interference, polarization En 1847 Annalen der Physik refuses to publish a Helmoltz paper based on the impossibility of perpetual motion to demonstrate the conservation of Energy ! James Clerk Maxwell (1831-1879) electromagnetism A. Bay Beijing October 2005

  8. Some history : 4 At this point (~ 1880) a physicist affirmed something like that: " 1800 physics has almost accomplished the full comprehension of Nature. A couple of small problems need still some explanation: the black body radiation and the Michelson and Morley experiment " The most famous experiment with "negative outcome" of history of science A. Bay Beijing October 2005

  9. Some history .5 • W. Konrad Roentgen: in 1895 discovers X rays • J. J. Thomson: in 1897 measures the electron e/m ratio • 1900 : beginning of Quantum Theory • M. Plank: describes the black body emission A. Einstein: in 1905 explain the photoelectric effect. Theory of relativity. 1912 observation of cosmic rays 1913 atomic model of Bohr. Beta decay observed 1921 spin of particles 1924 wave model of de Broglie 1925 uncertainty principle of Heisenberg 1926 Shroedinger equation 1928 Dirac equation A. Bay Beijing October 2005

  10. Some history: a few considerations 1) We need to be patient (no "Mac Donald physics"): it took a lot of time to our ancestors to mature the ideas and concepts we use today. Fundamental concepts like "symmetry", "energy", "atom", ripened for centuries. 2) Some physicists (around 1900) believed that Relativity and QM were not important for everyday life ("too fast", "too small"). Wrong: the decades around 1900 were enough to make a revolution which has brought us transistors and lasers (90% of the GNP of an industrial nation). 3) Some (solid state,...) physicist (today) believes that particle physics is not important for everyday life (too fast, too small)... Stay tuned ! A. Bay Beijing October 2005

  11. Antiparticles Antimatter Matter A. Bay Beijing October 2005

  12. Genesis of the concept of antiparticles Albert Einstein Max Planck Paul A. M. Dirac In 1927 P.A.M. Dirac attempts to marry Quantum theory and Relativity A. Bay Beijing October 2005

  13. Genesis of the concept of antiparticles Previous attempt Klein-Gordon equation had some problems with probabilistic interpretation Schroedinger equation, non relativistic A. Bay Beijing October 2005

  14. The Schroedinger equation a potential p2/2m energy operator TOTAL ENERGY this equation was very successful for the description of atoms (but needs some corrections...) A. Bay Beijing October 2005

  15. The Schroedinger equation .2 ATTENTION: unless otherwise specified we will use the particle physicists "natural units" h = c = 1 For V= 0 the Schroedinger equation becomes this equation is a "non-relativistic" approximation ! first order time derivative second order space derivative A. Bay Beijing October 2005

  16. The Schroedinger equation .3 The Schroedinger equation is the non-relativistic approximation of a more general "relativistic theory": * It does not contain the rest energy E=mc2 * It was known that "relativistic corrections" are needed for the atomic model of Bohr/Sommerfeld to much experimental results. The electron velocity in the Bohr atom is ~0.01c, hence from Th. of relativity it was found that its total energy on a orbit is modified by a factor where is the "fine structure constant" • in principle O(10-4)error if one uses the Schroedinger eq. to get the energy of the electron A. Bay Beijing October 2005

  17. The Dirac equation The quest for a quantum relativistic theory brought Dirac to this very very simple formula but with many many consequences for our life: this is mc2 this is a 4-dimensional derivative: space and time get same treatment This equation is very successful in the description of many things. It has 2 fundamental consequences: incoroprates the existence of a spin of particles like the electron predicts the existence of an antiparticle sector A. Bay Beijing October 2005

  18. The Dirac equation .2 Here Y is a "double spinor" (i.e. a 2x2 components vector) which can encode the information of the particle spin. But why there are two spinors ? Dirac was puzzled by the presence of this second degree of freedom. What is its origin ? classical energy : E = mv2/2 = p2/2m relativistic: E2 = m2c4 + p2c2 2 solutions: A. Bay Beijing October 2005

  19. The Dirac equation .3 electron proton ? How to deal with a negative energy ??? Dirac introduces the (unlikely) hypothesis of a sea of electrons with E<0. A photon rises one of these particles to a E>0 level, leaving a hole which behaves also like an E>0 particle, with positive charge. He makes the hypothesis that this is the proton. E>0 E<0 A. Bay Beijing October 2005

  20. Antiparticles .1 The electron - proton hypothesis does not work: the 2 particles must have identical mass Solution to this problem came from Oppenheimer, Stückelberg, Feynman: they replace the E<0 particles with other (anti)particles of opposite charge. Nice theory! Now we have just an experimental problem: we are in 1930; where to search for the anti-electron ? A. Bay Beijing October 2005

  21. Dirac equation (technical) gamma matrices contain Pauli matrices double-spinor How to get a current from 2 spinors: y Satisfies gm y A. Bay Beijing October 2005

  22. Non relativistic limit of the the Dirac eq. In the non-relativistic limit, the Dirac eq. gives the Pauli eq.  is now a spinor for the particle Interaction of the charged spin 1/2 particle with B = rot A is "Dirac" particles have g = 2 => experiments g-2 A. Bay Beijing October 2005

  23. Solutions of Dirac Equation of the form Oppenheimer, Stückelberg, Feynman A. Bay Beijing October 2005

  24. Antiparticles .2 Observation of "positrons" at CAL-Tech par C. D. Anderson en 1932. positron electron A. Bay Beijing October 2005

  25. BEBC au Cern BEBC detector at CERN A. Bay Beijing October 2005

  26. Antiparticles .4 Several isotopes are b+ emitters (Positron Emission Tomography uses O15, le F18…) positron discovered in cosmics (Anderson et al.) 1947-1956 Kaon / antiKaon 1955 antiproton (Bevatron of Berkeley, Chamberlain et al.) 1956 antineutron (idem) 1950-1960 neutrino/antineutrino … A. Bay Beijing October 2005

  27. Pair creation Particle and its antiparticle have the same mass. To create a couple e+ e- (or other kind of particle-antiparticle) the minimum of energy needed is Etotal m(e+) + m(e-) = 2 (511 keV) ~ 1.2 MeV Energy-momentum conservation does not allow A pair creation can only happen in the presence of another particle, an atomic nucleus, for instance: a real gamma virtual gamma representing the e.m. field of the nucleus A. Bay Beijing October 2005

  28. Pair annihilation, the positronium Slow (~eV) positrons interacts with ordinary electrons and can form a pseudo-atom state called "positronium" Ps, similar to a Hydrogen atom (E levels ~1/2 of H). In 75% of the cases the 2 spins are parallel: ortho-Ps (3S1) In 25% of the cases they are anti-parallel: para-Ps (1S0) hyperfine splitting : DE = 8.4x10-4 eV This pseudo-atom has a lifetime of: (singlet)~10-8 s (triplet)~10-10 s (3S1) (1S0) Etotal m(e+) + m(e-) => for the 2g decay Eg = 511 keV A. Bay Beijing October 2005

  29. Positronium a ~1/137 A. Bay Beijing October 2005

  30. Is it possible to assemble positrons and antiprotonsto make anti-Hydrogen atoms ? If yes, next questions will be : - Is the antiH stable ? - May we find antistars in the Universe ? A. Bay Beijing October 2005

  31. To build an antiH atom we need … a positron ...an antiproton - - …. and an assembly line eV (atomic) binding energies involved. Particles must be slow A. Bay Beijing October 2005

  32. anti-p decelerator lot of particles after the chock accelerator fast p anti-p selector target experiments beam of p The production of slow antiprotons p = protons (ionized H) A. Bay Beijing October 2005

  33. Production of slow anti-p at CERN protons accelerator production and selection of antiprotons experiments AD: antiprotons decelerator A. Bay Beijing October 2005

  34. production 2 A. Bay Beijing October 2005

  35. production of anti-proton at CERN A. Bay Beijing October 2005

  36. AD magnets A. Bay Beijing October 2005

  37. Assembly linewith Penning traps input of positrons - input of antiprotons positrons trap assembly region anti-p trap A. Bay Beijing October 2005

  38. antiH A. Bay Beijing October 2005

  39. We have crated antiH Scientific studies : • Are the masses of H and antiH identical? • Are the energy levels identical ? • Production and studies of antiH2 • Production and studies of antiD ... A. Bay Beijing October 2005

  40. Which kind of applications for antiparticles ? A little technological interlude... 1) Today: medical applications 2) Ongoing studies for very high density energy storage, fuel for space travel, … A. Bay Beijing October 2005

  41. Positron emission tomography A. Bay Beijing October 2005

  42. PET .2 Injection of a positron emitter with specific metabolic activity particle detectors The drug gets concentrate in target regions of the body (cancers, brain regions in activity,...) gamma gamma Positon+electron annihilation gives 2 photons travelling back to back A. Bay Beijing October 2005

  43. Isotopes in use for PET A. Bay Beijing October 2005

  44. PET allows to study brain activity brain listening brain reading a text on a screen A. Bay Beijing October 2005

  45. PET in diagnostics A. Bay Beijing October 2005

  46. PET allows to... create 3D images and to follow the metabolism of a substance A. Bay Beijing October 2005

  47. Space travel with a SATURNE V: Total weight2950 t First stage Weight of propellent 2150 t Thrust3300 t 3300 > 2950 OK: the motor can lift the spacecraft dM/dt (Burning speed) (duration 160 s) 13 t/sec Ejection velocity 2.8 cm/s Le yield of the engine is given by Specific Impulse = Thrust / Burning speed = 253 sec and (Thrust/total wght) = 3300/2950 ~1 A. Bay Beijing October 2005

  48. Propulsion type spec. impulse Thrust/wght chimique 200-400 s 0.1 - 10 fission nucléaire 500-3000 s 0.1 - 10 fusion nucléaire 10 4 - 10 5 s 10 -5 - 10 -2 annihilation 10 3 -10 6 s 10 -3 - 1 Only antimatter annihilation offers the qualities required for a travel to Pluto or a pre-interstellar journey …well, how to build an anti-matter motor? A. Bay Beijing October 2005

  49. An antimatter thruster plasma is expulsed at very high velocity 1) produce (on Earth) the necessary amount of antiprotons. 2) store in a reservoir prototype: HIPAT High Performance Antimatter Trap 3) anti-p are put in contact with HLi pellets. The microexplosions produce hot plasma. A. Bay Beijing October 2005

  50. prototype HIPAT Pennsylvania State University storage of 109 antiprotons A. Bay Beijing October 2005

More Related