things big small n.
Skip this Video
Loading SlideShow in 5 Seconds..
THINGS BIG & SMALL PowerPoint Presentation
Download Presentation


177 Vues Download Presentation
Télécharger la présentation


- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. THINGS BIG & SMALL Dhiman Chakraborty ( Northern Illinois University, Northern Illinois Center for Accelerator and Detector Development THINGS BIG AND SMALL

  2. Know thyself … • Where did we come from? • Where are we going? • What/who else is out there? These are the most human of questions. For most part of its history, mankind has turned to myth and religion for answers (eventually being told to shut up & listen). Of late, science is yielding verifiable, factual explanations that are proving to be far wilder and more fascinating than the most fanciful of fictions. THINGS BIG AND SMALL

  3. Did you know? • We are all STARFOLKS: more than 95% of our body weights are accounted for by atoms baked inside a star (or stars)? • We would not exist if some of the constants of nature were ~1% different from what they are? Are these special values a mere coincidence? Do they change over time? • Of all the sources of gravity that holds the universe together, only 4% can be seen (even with the most powerful and sensitive telescopes)? Most (73%) is not even matter! THINGS BIG AND SMALL

  4. Composition of the Universe . THINGS BIG AND SMALL

  5. The extremes are connected… • To understand the structure and phenomena at the largest scales (cosmology), we must first know those at the smallest (particle physics). • The particle physicists, in turn, get their cues from cosmological observations. • The two are inextricably coupled. • Particle astrophysics is a rapidly growing field. • 96% of what constitutes the Universe is yet unknown/unobserved. • A revolution of unparalleled proportions is around the corner – DRIVERS WANTED! THINGS BIG AND SMALL

  6. Down to the tiniest… What are the “fundamental” building blocks of nature? Can we ever reach a point where we are confident that there is no further substructure? The question only makes sense in the context of the tiniest distances, or, equivalently, the highest energies that we are able to probe (E=hn). THINGS BIG AND SMALL

  7. Matter and interactions “Matter”: made of Fermions. Spin-(2n+1)/2 particles that do not share a quantum state. Consequently, their production and decay must be associated with an “antifermion”. “Interactions” (not just among Fermions): mediated by Bosons. Integer-spin particles that gladly share a quantum state, and can be radiated or absorbed singly. THINGS BIG AND SMALL

  8. The Four forces: • Gravity • Mediated by “graviton”s (s=2, m=0, qe=0, Y=0, qc=0). • Couples to energy (no known “neutralization” of charge) • Weakest of all: insignificant at single-particle level, but • Infinite range and absence of neutralization combine to make it the dominant force at large scales. Holds celestial bodies together. Keeps us on the planet, a planet on orbit around a star, a star in a galaxy, a galaxy in a cluster, a cluster in a supercluster, … • Also responsible for stellar structure and collapse (supernova) leading formation of neutron stars, black holes. • Only a geometrical description: curvature of space described by (Einstein’s) principles of general relativity. • No fully-developed quantum description yet (weakness at small distances make experimental measurements very difficult, but sub-mm measurements are being made). • Important probe to extra spatial dimensions, if they exist. THINGS BIG AND SMALL

  9. The Four forces: 2. Electromagnetism • Mediated by “photon”s (s=1, m=0, qe=0, Y=0, qc=0). • Couples to electric (and magnetic) charge (qe). • No self-coupling. • Infinite range, but formation of neutral bound states of +ve & -ve charges (e.g. atoms and molecules) makes it the primary force mainly in the intermediate scales (but also prevents/ counters gravitational collapse of multiparticle systems) • Keeps electrons in orbit around atomic neuclei. • Coupling strength ideal for perturbative calculations. • Extremely precise and well-tested quantum-mechanical description: Quantum Electrodynamics (Dirac, Feynman). • Until recently, our only means for astronomical observations. • The only force we can control. THINGS BIG AND SMALL

  10. The Four forces: 3. Weak • Mediated by W’s & Z’s (s=1, m=80 GeV (W) / 91 GeV (Z), qe=1 (W) / 0 (Z), Y0, qc=0). • Couples to weak hypercharge (Y). • Has self-coupling, although not of much significance. • Much weaker than EM & strong forces down to nuclear scales. • Because of large mass of mediators, shortest in range of all forces (lifetime of W, Z ~10-25 s), but • Unique in two respects: • The only force, other than gravity, that couples to neutrinos. • The only way for matter to mutate. No other mediator has qe  0. • Not a “binding force”, but causes some types of radioactivity. • The main mechanishm behind solar energy (4H  He + 2ne). • Unifies with EM at energies >100 GeV: “electroweak” interactions (Lee, Yang, Glashow, Salam, Weinberg, t’Hooft, …) THINGS BIG AND SMALL

  11. The Four forces: 4. Strong • Mediated by “gluon”s (s=1, m=0, qe=0, Y=0, qc 0 (8 types)). • Couples to “color” charge (qc). • Strongest of all known forces. • Strong self-coupling of gluons limits range to nuclear scales. • Screening  fall-off at shorter distances (“asymptotic freedom”) • Strong neutralization forbids isolation of q/g (“confinement”) • Binds quarks in protons and neutrons, p’s & n’s in neuclei. • Described by Quantum Chromodynamcis (Gell-Mann et al.) but • Strength makes perturbative calculations very challenging. • Dominant force at hadron colliders. • (Grand) Unification with Electroweak theory believed possible, but requisite energies are beyond terrestrial reach. THINGS BIG AND SMALL

  12. The Standard Model A description of PARTICLES that make up matter and the FORCES of interaction between them. Three generations each of quarks & leptons. Subjects of forces: • strong: quarks only • EM: q’s & charged l’s. • weak: all fermions THINGS BIG AND SMALL

  13. Unification theories . THINGS BIG AND SMALL

  14. Particle acceleration & collisions • To probe small distances, we need high energies: E  l-1. • Only EM fields useful for acceleration, and only charged particles that are not too short-lived can be accelerated. • This limits us to electrons, protons & ions • Photons piggyback on charged particles • Protons and ions are not point-like, but heavy • e’s are light  E loss due to synchrotron radiation • High-energy muons have been used in fixed-target mode, collider mode in development. • Two options: • Look to the heavens (high-E Cosmic rays) • Build your own (earthbound machines) THINGS BIG AND SMALL

  15. Particle acceleration & collisions: Energy vs. Luminosity • High energies are necessary, but not sufficient. Unfortunately, the size of our detectors (microscopes) is limited, and God will not focus his beams to them. • Cosmic rays have little use except for n’s & g’s created at very high energies. • We build our own accelerators to get high luminosities, although Emax is limited. • Fixed target: higher luminosity, lower E • Collider (beam-beam): higher E, lower L. THINGS BIG AND SMALL

  16. Particle Colliders . THINGS BIG AND SMALL

  17. Particle Colliders . THINGS BIG AND SMALL

  18. Particle Colliders Hadron colliders: Higher energies, but energy of collision of point-like constitutents have large variance. Lepton (ep) colliders: Lower energies, but well-known, controllable ECM of collisions, much cleaner final states. THINGS BIG AND SMALL

  19. The Tevatron pp collider at Fermilab . THINGS BIG AND SMALL

  20. Fermilab . THINGS BIG AND SMALL

  21. Fermilab . THINGS BIG AND SMALL

  22. Fermilab . THINGS BIG AND SMALL

  23. Indentifying particles . THINGS BIG AND SMALL

  24. Indentifying particles . THINGS BIG AND SMALL

  25. Calorimetry . THINGS BIG AND SMALL

  26. Collider Detectors . THINGS BIG AND SMALL

  27. Collider Detectors DØ CDF . THINGS BIG AND SMALL

  28. The most common events at hadron colliders Production of two jets (narrow showers of high-energy particles) to be read by the detector and reconstructed with sophisticated algorithms THINGS BIG AND SMALL

  29. Finding needles in haystacks Bump-hunting THINGS BIG AND SMALL

  30. Data acquisition At the Tevatron detectors, events pour out through ~1 million electronic channels at rates of ~1 MHz. Only a small fraction of these is interesting, and must be sifted in real time through multilevel trigger systems to record as many of the interesting ones while minimizing the volume of uninetersting events. THINGS BIG AND SMALL

  31. The top : a quark apart . THINGS BIG AND SMALL

  32. A top-antitop event . THINGS BIG AND SMALL

  33. A top-antitop event . THINGS BIG AND SMALL

  34. A top-antitop event . THINGS BIG AND SMALL

  35. The Higgs . THINGS BIG AND SMALL

  36. Extra Dimnesions? . THINGS BIG AND SMALL

  37. A high-energy diphoton event at DØ We do expect a few events like this from known Standard Model processes. No siginificant excess observed so far. Much effort goes into estimating signal efficiency and background contamination. State-of-the art pattern-recognition algorithms and statistical analysis methods employed. THINGS BIG AND SMALL

  38. Magnetic monopoles? If they exist, they could explain the quantization of electric charge. The quantum will be O(104) stronger than that of qe. Thus, magnetic monopoles should cause very strong scattering of light, resulting in diphoton final states at colliders. THINGS BIG AND SMALL

  39. Up to the grandest… . THINGS BIG AND SMALL

  40. Evolution of the Universe . THINGS BIG AND SMALL

  41. Detecting the elusive neutrinos LSND Neutrinos ghost-like particles are stable, and more abundant than all other fermions combined, but very hard to detect due to their lack of interactions. Fascinating, nonetheless THINGS BIG AND SMALL

  42. Sloan Digital Sky Survey (SDSS) . THINGS BIG AND SMALL


  44. The M78 nebula – a nursery of stars SDSS It is extremely important to know how the mass and energy, most of it dark, is distributed throughout the universe. A particle theory that contradicts cosmological observations will not be viable. THINGS BIG AND SMALL

  45. Geometry of the Universe . THINGS BIG AND SMALL

  46. Peeking into the Universe’s infancy: the Wilkinson Microwave Anisotropy Probe . THINGS BIG AND SMALL

  47. WMAP talk about thermal resolution! . THINGS BIG AND SMALL

  48. WMAP talk about spatial resolution! . THINGS BIG AND SMALL

  49. Evolution of the Universe THINGS BIG AND SMALL

  50. NICADD The Photoinjector at Farmilab THINGS BIG AND SMALL