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Astroparticle Physics

Astroparticle Physics. Claudia-Elisabeth Wulz Institute of High Energy Physics, Vienna TU Vienna c/o CERN, Geneva. Part 1 Winter semester 2013/2014. Bibliography. D. Perkins: Particle Astrophysics (Second edition, 2011) C. Grupen : Astroparticle physics (2010).

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Astroparticle Physics

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  1. Astroparticle Physics Claudia-Elisabeth Wulz Institute of High Energy Physics, Vienna TU Vienna c/o CERN, Geneva Part 1 Winter semester 2013/2014

  2. Bibliography D. Perkins: Particle Astrophysics (Second edition, 2011) C. Grupen: Astroparticlephysics (2010)

  3. Subjects of these lectures • Standard Model of particle physics • Particles and radiation in the cosmos • Expansion of the Universe • Baryogenesis and nucleosynthesis • Dark matter • Dark energy 2

  4. What is Astroparticle Physics? • New field at the intersection of particle physics, astronomy and cosmology • What is the Universe made of? • How did it emerge and what is its future? • Connection between the smallest and largest scales

  5. What is Astroparticle Physics? Astroparticle physics is the science of studying the Universe through particles that arrive on earth First indications of particles from the cosmos: Studies by Victor Hess (1912-1913) Birth of neutrino astroparticle physics: Neutrinos from sun studied in Homestake mine (1967) 4

  6. Victor Hess 1883 - 1964 1936 with C. Anderson 5

  7. Homestake and the solar neutrino deficit Beginning in the 1960s Ray Davis built an experiment to detect solar neutrinos deep in the Homestake Mine in South Dakota, but he found only about a third the number of neutrinos predicted by theorist John Bahcall. Homestake- Experiment 610t C2Cl4 Result: Measured flux: 2.56 SNU Expected: 8.5 SNU ne + 37Cl  37Ar + e-

  8. neproduction processes p + p2H + e+ + e(pp)0 - 0.4 MeV p + e-+ p2H + e(pep)1.4 MeV 2H + p3He +  3He + 3He 4He + 2p 3He + 4He7Be +  3He + p4He +e+ + e(hep) 1.5 - 17 MeV 7Be +e- 7Li + e (Be) 0.38, 0.86MeV 7Li + p4He + 4He 7Be + p8B +  8B 8Be + e+ + e (B) 0 - 15 MeV 8Be*4He + 4He Solar Neutrinos Energies Energy spectrum of solar neutrinos

  9. Special relativityandbasic units

  10. relativistic kinematics • elementary particles travel mostly at speeds close to speed of light • because their masses are small compared to typical energies •  (almost) always use relativistic kinematics • in particle physics, “special relativity” is sufficient most of the time • for massive astronomical bodies general relativity becomes important • remember a few basic formulae !

  11. relativistic kinematics v 1/γ 1

  12. the electron-volt (eV) + e- 1V - units: energy and mass • 10-4 eV: 3 K cosmic background radiation (~ 0.25 meV) • 10-2 eV: room temperature (~ 30 meV) • eV: ionisation energy for light atoms (13.6 eV in hydrogen) • 103 eV (keV): X-rays in heavy atoms • 106 eV (MeV): mass of electron me = 511 keV/c2 • 109 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 accelerators • 1020 eV: highest energies seen for cosmic particles • 1028 eV (1019 GeV/c2): ~ Planck mass

  13. units: mass and energy • proton mass in kg: 1 / (6 × 1026 ) = 1.7 × 10-27 kg • ~ 1 GeV/c2  = 109 eV/c2 • highest energy of cosmic particles: 1020 eV ~ 16 J • ~ 1.7 × 10-16 kg • Planck mass: 1028 eV ~ 1.7 × 10-8 kg • Earth’s mass: : 6 × 1024 kg • solar mass: 2 × 1030 kg • our galaxy (Milky Way): 1042 kg • including dark matter • observable universe: ~1052 kg

  14. units: speed and distance • velocity: speed of light • ~ 3 * 108 m/s • ~ 30 cm/ns • all speeds are approximately equal to the speed of light in astro-particle physics ! • all particles are “relativistic” • distance (short): fm (femtometer) • 1 fm = 10-15 m • sometimes also called “Fermi” • distance (long): • lightyear (~ 1016 m) • parsec (“pc”, ~ 3 lightyears) • diameter of our galaxy: 30 kpc (1021 m) • distance to Andromeda galaxy: ~ 0.8 Mpc (3 * 1022 m) • distance to Virgo cluster: ~ 18 Mpc (7 * 1023 m) • observable universe: ~ 30 Gpc (1027 m) • related: redshift z = (λ – λ0) / λ0

  15. parsec: Living on Earth may be expensive, but it includes an annual free trip around the sun. Ashleigh Brilliant 1 pc = 3.08567758 × 1016 m 1 AU (astronomical unit) = 149 597 871 km

  16. relations and constants • waves • λ * ν = c • ω = 2π ν • quantum mechanics • h Planck constant (“Planck’schesWirkungsquantum”) • h = h / 2π • hν =hω = E • numerical survival kit • c = h = 1 • as long as you need no “usual” units; and then, use: • c ~ 3 * 108 m/s speed of light • hc ~ 200 MeV * fm • ~ 6 * 1026 protons / kg (~ GeV / kg) Avogadro’s number • e ~ 1.6 × 10−19  As (Coulomb) • 1 eV ~ 104  K Boltzmann’s constant • 1 Tesla = 10000 Gauss

  17. “natural” units • c = h = 1 • c ~ length/time speed of light • hc ~ energy*length •  length ~ time ~ 1/energy • 1 GeV−1 ~ 10−16 m (=0.1 fm) ~ 10−24 s • V = -G m1m2 / r gravitational attraction •  G ~ m-2 • G = MPlanck-2particles with this mass would at ~proton-size distance have gravitational energy of ~proton mass • MPlanck~ 1019 GeV • LPlanck= 1/MPlanck ~ 10-31 m • tPlanck= 1/MPlanck ~ 10-43 s

  18. gravitation is weak! • Vgrav = - G m1m2 / r gravitational potential = - MPlanck-2 m1m2 / r ~ - 10-38m1m2 / r • Velec = (1 / (4πε0) ) q1e q2e / r electrostatic potential = (e2 / (4πε0hc) )q1q2 / r = α q1q2 / r α = fine structure constant ~ (1/137) q1q2 / r ~ 10-2 q1q2 / r •  Vgrav/ Velec ~ 10-38/ 10-2 = 10-36

  19. Standard Model of particle physics • Particles and radiation in the cosmos • Expansion of the Universe • Baryogenesis and nucleosynthesis • Dark matter • Dark energy • Development of structure • Particle physics in stars and galaxies Subjects of these lectures 20

  20. Standard Model of Particle Physics 21

  21. e- the electron Thomson 1897

  22. e- p the proton Rutherford 1914 1897 1900-1924

  23. e- g p the photon Einstein Planck Compton 1900-1924 1897

  24. The Standard Model of Particle Physics The Standard Model is a theory of the strong, weak and electromagnetic forces, formulated in the language of quantum gauge field theories, and of the elementary particles that take part in these interactions. It does, however, not include gravity. Interactions are mediated by the exchange of virtual particles. Fundamental forces

  25. Particle Content of the Standard Model Matter particles: Fermions (half-integer spin, s = ½ħ) and their antiparticles. There are 3 families (generations) of fermion fields, which are identical except for their masses. Fermions come as leptons and quarks. Mediator particles: Gauge bosons (integer spin, s = 1ħ). There are 3 types of gauge bosons, corresponding to the 3 interactions described by the Standard Model. Higgs particle: Needed to explain that the symmetries of the electroweak theory are broken to the residual gauge symmetry of QED. Particles that interact with the Higgs field cannot propagate at the speed of light and acquire masses through coupling to the Higgs boson (s = 0ħ).

  26. Gravitational interaction Long-range force Only attractive Gravity is currently described by General Relativity Different assumptions about the Universe at the macroscopic scale than those made by quantum mechanics at the microscopic scale Quantum gravity: theories that attempt to unify gravity with the other forces (e.g. string theory, loop quantum gravity) Examples of systems Black holes Universe

  27. Electromagnetic interaction Long-range force Much stronger than gravity but effectively shielded over long distances Repulsive or attractive Unified description of electricity and magnetism. Examples of systems: Atoms (electrons and nuclei) Electromagnetic waves (light, radio waves)

  28. Weak interaction Short-range force Very weak Only force that can change the flavor of quarks (e.g. d -> u) Unified with electromagnetic force CP violation (charge conjugation, parity not conserved) Examples of systems Neutrino interactions Beta decays Nuclear fusion

  29. e- g p n e+ the positron (anti-matter) Anderson Dirac 1932 1947 1914 1897 1937 1900-1924

  30. Weak interaction Occurs for example in radioactive b-decay (e.g. 3H 3He) : 2 1 Particles without the strong interaction are called LEPTONS (e.g. electron, muon, neutrino). The weak interaction is mediated by the INTERMEDIATE VECTOR BOSONs(W±, Z). These are almost 100x as heavy as the proton and were detected in 1983 at the experiments UA1 and UA2 at the CERN SppS collider.

  31. Nobel Prize 1984 C. Rubbia S. van der Meer “…for their decisive contributions to the large project which led to the discovery of the field particles W and Z, communicators of weak interaction”

  32. W -> en at the UA1 experiment 34

  33. Z -> e+e- at the UA1 experiment ino 35

  34. Strong interaction Short-range force Very strong Holds quarks (and nuclei) together Mediated by gluons Neither gluons nor quarks are free particles (“Confinement”) Particles that experience the strong force are called hadrons Examples of systems Proton and other atomic nuclei

  35. »» Ü u Þ u d Strong interaction Gluons and quarks carry a charge (“COLOR”)QUANTUM CHROMODYNAMICS Existing particles are colorless, however. Ü Þ u u d Proton »» d d u d d u d + Neutron p

  36. Yukawa Theory Protons and neutrons in nuclei are attracted by a field. The field quantum should have properties conform with the strong interaction, it must therefore be relatively heavy due to the short range of the strong force. Yukawa predicted that its mass should be around 300 me. It was called meson (mass between meand mp). Particles with compatible properties were indeed found in cosmic rays. However, there were discrepancies in the measurements of masses and lifetimes. In addition, only a weak interaction with atomic nuclei was found. What was found were muons.

  37. e- g p n e+ Who ordered this ? • Hess • Anderson, • Neddermeyer µ the muon 1937 1914 1897 1900-1924 1932

  38. Marietta Blau 1894 - 1970 Developed a photographic method based in nuclear emulsions to study cosmic rays, which led to the discovery of new particles. With her method the pion was discovered in 1947 by Cecil Powell et al., and much later, in 2000, the tau neutrino. Powell received the Nobel prize in 1950. Blau should probably have shared it with with due to her decisive contributions. She was nominated for the prize twice by Erwin Schrödinger. Marietta Blau at the “InstitutfürRadiumforschung” in Viennaabout 1925 40

  39. Marshak, Bethe: Muons could be decay products of heavier particles, which in turn could be Yukawa’s mesons. Indeed pmesons (pions) were identified with Yukawa’s field quanta. Their decay products, the muons, do not have strong interactions. They generally decay before reaching the surface of the earth into electrons and two neutrinos (as the energy of the eis not constant - 3-body decay): +e++e+m -e-+e+m e 600 mm m - - ++ +  p Lattes, Powell, Occhialini, Muirhead (1947) Pic du Midi Observatory

  40. K+ } 3 cm lead m+ 1947 it appeared as if the biggest problems in elementary particle physics were more or less understood, apart from the role of the muon (I. Rabi: “Who ordered that?”). The discovery of “Strange Particles” changed the picture … Rochester, Butler: K0 K+ K+ etc. Anderson et al.: L Charged V event: K+m + + nm

  41. “Strange Particles” were indeed strange as they were produced copiously (typical time scale 10-23 s), but decayed relatively slowly (time scale 10-10s). This means that production and decay mechanisms are different. Strange particles are produced by the strong interaction, but they decay through the weak interaction. Gell-Mann and Nijishimaattributed a property called “Strangeness”to each particle, which is conserved in the strong interaction, but which is not conserved in the weak interaction. Therefore strange particles are only produced in pairs, such as p- + p+ K0 + LStrangeness is not conserved in their decay, e.g.  p + p- .

  42. Willis Lamb in his Nobel speech 1955: When the Nobel Prizes were first awarded in 1901, physicists knew something of just two objects which are now called « elementary particles»: the electron and the proton. A deluge of other « elementary » particles appeared after 1930; neutron, neutrino, μ meson, π meson, heavier mesons, and various hyperons. I have heard it said that « the finder of a new elementary particle used to be rewarded by a Nobel Prize, but such a discovery now ought to be punished by a $10,000 fine ». Something similar was said by Enrico Fermi (to Leon Lederman) in connection with hadron spectroscopy: Young man, if I could remember all the names of these particles, I would have become a botanist.

  43. The Quark Model 1964: Gell-Mann, Zweig Elementary building blocks of matter:

  44. Quark Model S: Strangeness (S = - 1 for s quark) Mesons are made of quark-antiquark pairs, baryons consist of 3 quarks.

  45. K0 (ds) K+ (us) p0, h - - - - - p - (du) (uu,dd,ss) - - - K- (su) The eightfold way - - Gell-Mann, Ne’eman (1961) p + (ud) K0 (sd) Meson octet

  46. The eightfold way n (udd) p (uud) S0 (uds) S- (dds) S+ (uus) L (uds) X- (dss) X0 (uss) Baryon octet

  47. The eightfold way L- (ddd) L0 (udd) L+ (uud) L++ (uuu) S*0 (uds) S*- (dds) S* (uus) X*- (dss) X*0 (uss) L+has the same quark content as the proton, but different energy level, in analogy to the hydrogen atom in different levels of excitation. Quarks: spin 1/2! Pauli principle -> COLOR (O.W. Greenberg) W- (sss) Baryon decuplet

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