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THINGS BIG & SMALL Dhiman Chakraborty ([email protected]) Northern Illinois University, Northern Illinois Center for Accelerator and Detector Development Dhiman Chakraborty THINGS BIG AND SMALL 1 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. Dhiman Chakraborty THINGS BIG AND SMALL 2 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! Dhiman Chakraborty THINGS BIG AND SMALL 3 Composition of the Universe . Dhiman Chakraborty THINGS BIG AND SMALL 4 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! Dhiman Chakraborty THINGS BIG AND SMALL 5 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). Dhiman Chakraborty THINGS BIG AND SMALL 6 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. Dhiman Chakraborty THINGS BIG AND SMALL 7 The Four forces: 1. 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. Dhiman Chakraborty THINGS BIG AND SMALL 8 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. Dhiman Chakraborty THINGS BIG AND SMALL 9 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), Y0, 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, …) Dhiman Chakraborty THINGS BIG AND SMALL 10 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. Dhiman Chakraborty THINGS BIG AND SMALL 11 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 Dhiman Chakraborty THINGS BIG AND SMALL 12 Unification theories . Dhiman Chakraborty THINGS BIG AND SMALL 13 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 fixedtarget mode, collider mode in development. • Two options: – Look to the heavens (high-E Cosmic rays) – Build your own (earthbound machines) Dhiman Chakraborty THINGS BIG AND SMALL 14 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. Dhiman Chakraborty THINGS BIG AND SMALL 15 Particle Colliders . Dhiman Chakraborty THINGS BIG AND SMALL 16 Particle Colliders . Dhiman Chakraborty THINGS BIG AND SMALL 17 Particle Colliders Hadron colliders: Higher energies, but energy of collision of point-like constitutents have large variance. Lepton (ep) colliders: Lower energies, but wellknown, controllable ECM of collisions, much cleaner final states. Dhiman Chakraborty THINGS BIG AND SMALL 18 The Tevatron pp collider at Fermilab . Dhiman Chakraborty THINGS BIG AND SMALL 19 Fermilab . Dhiman Chakraborty THINGS BIG AND SMALL 20 Fermilab . Dhiman Chakraborty THINGS BIG AND SMALL 21 Fermilab . Dhiman Chakraborty THINGS BIG AND SMALL 22 Indentifying particles . Dhiman Chakraborty THINGS BIG AND SMALL 23 Indentifying particles . Dhiman Chakraborty THINGS BIG AND SMALL 24 Calorimetry . Dhiman Chakraborty THINGS BIG AND SMALL 25 Collider Detectors . Dhiman Chakraborty THINGS BIG AND SMALL 26 Collider Detectors DØ CDF . Dhiman Chakraborty THINGS BIG AND SMALL 27 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 Dhiman Chakraborty THINGS BIG AND SMALL 28 Finding needles in haystacks Bump-hunting Dhiman Chakraborty THINGS BIG AND SMALL 29 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. Dhiman Chakraborty THINGS BIG AND SMALL 30 The top : a quark apart . Dhiman Chakraborty THINGS BIG AND SMALL 31 A top-antitop event . Dhiman Chakraborty THINGS BIG AND SMALL 32 A top-antitop event . Dhiman Chakraborty THINGS BIG AND SMALL 33 A top-antitop event . Dhiman Chakraborty THINGS BIG AND SMALL 34 The Higgs . Dhiman Chakraborty THINGS BIG AND SMALL 35 Extra Dimnesions? . Dhiman Chakraborty THINGS BIG AND SMALL 36 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 patternrecognition algorithms and statistical analysis methods employed. Dhiman Chakraborty THINGS BIG AND SMALL 37 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. Dhiman Chakraborty THINGS BIG AND SMALL 38 Up to the grandest… . Dhiman Chakraborty THINGS BIG AND SMALL 39 Evolution of the Universe . Dhiman Chakraborty THINGS BIG AND SMALL 40 Detecting the elusive neutrinos LSND Neutrinos ghostlike particles are stable, and more abundant than all other fermions combined, but very hard to detect due to their lack of interactions. Fascinating, nonetheless Dhiman Chakraborty THINGS BIG AND SMALL 41 Sloan Digital Sky Survey (SDSS) . Dhiman Chakraborty THINGS BIG AND SMALL 42 SDSS . Dhiman Chakraborty THINGS BIG AND SMALL 43 SDSS The M78 nebula – a nursery of stars 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. Dhiman Chakraborty THINGS BIG AND SMALL 44 Geometry of the Universe . Dhiman Chakraborty THINGS BIG AND SMALL 45 Peeking into the Universe’s infancy: the Wilkinson Microwave Anisotropy Probe . Dhiman Chakraborty THINGS BIG AND SMALL 46 WMAP talk about thermal resolution! . Dhiman Chakraborty THINGS BIG AND SMALL 47 WMAP talk about spatial resolution! . Dhiman Chakraborty THINGS BIG AND SMALL 48 Evolution of the Universe Time Since the Big Bang The state of the Universe Human Equivalent 379,000 years This is a time when the pattern of the Cosmic Microwave Background light was set. The Universe was just cool enough for atoms to form for the first time. At this stage, the Universe is the equivalent of a baby just 19 hours old. 200 million years The matter in the Universe condensed by gravity until the first stars ignited. WMAP has detected this event at about 200 million years after the Big Bang. (WMAP does not see the light of the first stars directly, but has detected a polarized signal that is the tell-tale signature of the energy released by the first stars.) The Universe is the equivalent of a baby of 13 months, just old enough to begin taking its first steps. 1 billion years The first galaxies began to form at about this time. Unlike a human child, the Universe has reached the end of its formative years at this young age. There are no further notable cosmic events past this stage. At this age, the Universe is equivalent to a child just under six years old. 13.7 billion years The present day Universe with its billions upon billions of stars and galaxies is found to be 13.7 billion years old, an age with a margin of error of close to 1 percent. An adult person at 80. Dhiman Chakraborty THINGS BIG AND SMALL 49 NICADD The Photoinjector at Farmilab Dhiman Chakraborty THINGS BIG AND SMALL 50 The next Linear Collider A prototype 9-cell superconducting RF cavity capable of gradiantes >50 MeV/m One of two contenders, the winner will be picked in 2004. Dhiman Chakraborty THINGS BIG AND SMALL 51 NICADD: simulations GEANT4 simulation of a calorimeter module for beam tests. Dhiman Chakraborty THINGS BIG AND SMALL 52 NICADD: scintillator DHCal 10 cm2, 5 mm thick scintillating plastic cells produced in house. ~1 million of these could be used in digital mode at the linear collider detector. Novel algorithms for unprecedented energy resolution. Dhiman Chakraborty THINGS BIG AND SMALL 53 NICADD Designing a thin, yet strong, end-plate for a cylinder to hold liquid hydrogen to focus muon beams in energymomentum space. Dhiman Chakraborty THINGS BIG AND SMALL 54 Spin-offs from HEP WWW Dhiman Chakraborty THINGS BIG AND SMALL 55 Spin-offs from HEP Dhiman Chakraborty THINGS BIG AND SMALL 56 THANK YOU! Feel free to contact the speaker for more information [email protected] Dhiman Chakraborty THINGS BIG AND SMALL 57