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Particle Physics - High Energy Physics High energy particles have extremely small wavelengths and can probe subatomic distances: high energy particle accelerators serve as super-microscopes. The higher the energy the closer particles can come to each other, revealing the smaller details of their structure. The energy of the collisions produces new particles : E=mc 2 The higher the energy the heavier the new particles that can be created. 1 like smashing two cars together and getting a bulldozer out 2 3 21st century particle physics (e.g.) Fermilab’s Tevatron is the highest energy accelerator in the world today. Beams of protons collide with beams of antiprotons 4 antimatter particle accelerators create antimatter by smashing high energy particles onto metals the total amount of antimatter produced in particle accelerators per year ~ 1 microgram even one microgram of antimatter would provide enough energy to drive your car for a month (E=mc2) 5 The SNO detector is more than a mile underground no mass? Yes, photons are massless We thought neutrinos were massless too In 1998 underground experiments discovered that neutrinos have tiny masses 6 32? 7? 6? extra dimensions? Experiments can actually discover them! String theory demands extra dimensions. 7 detection of high energy particles positron in cloud chamber 8 e m p Pion picture in a streamer chamber; gas glows brightly along the tracks of the particles. 9 Jack Steinberger “ I remember in 1949, on a bulletin board at the Princeton Institute for Advanced Study, a photomicrograph of a nuclear emulsion event, showing what is now known a a K-meson decaying into three pions. We all saw it. No doubt that something interesting was going on, very different from what was then known, but it was hardly discussed because no one knew what to do with it” 10 11 1st circular accelerator (11 inches!) uses both electric and magnetic fields. particles orbit in circles Lawrence and Livingston built the first cyclotron in 1932. It was about 30 cm across, in a magnetic field of about 5000 Gauss and accelerated protons to roughly 1.2 MeV 12 professor’s view 13 mechanical engineer’s view 14 computer scientist’s view 15 theoretical physicist’s view 16 visitor’s view 17 Synchro-cyclotron, Betatron, synchrotron Lawrence McMillan 18 LBL Cosmotron 3 GeV protons Brookhaven National Laboratory(1952) 19 major invasions in accelerator technology Strong Focusing (1952) Colliding Beams (60s) Superconducting magnets (80s) Stochastic Cooling (80s) 20 21 P2K/NASATV movie excerpt After the pion a plethora of new particles called 22 hadrons were discovered in accelerators the Big picture The universe is made out of matter particles and held together by force particles fermions quarks leptons bosons gauge bosons graviton 23 Feynman Graph The electron and quark interact electromagnetically by the exchange of a photon. The lines, wiggles and vertices represent a mathematical term in the 24 calculation of the interaction. Quantum Weirdness The interactions of particles obey the rules of quantum mechanic and of special relativity And particles aren’t really particles, they are quantum fields The fermions (quarks and leptons) are especially weird… 25 Guess 26 the Model What is a model? After 50 years of effort, we have a quantum theory which explains precisely how all of the matter particles interact via all of the forces — except gravity. For gravity, we still use Einstein’s General Relativity, a classical theory that has worked pretty well because gravity effects are so weak. 27 the Standard Model a list of particles with their “quantum numbers”, about 20 numbers that specify the strength of the various particle interactions, a mathematical formula that you could write on a napkin. 28 e e e e u u u d d d u u u m m L d d d Z 0 W W m m L c c c s s s c c c t t t b b b t t t s s s t t t g 29 e e e e u u u d d d u u u m m L d d d Z 0 W W m m L c c c s s s c c c t t t b b b t t t s s s t t t g 30 e e e e u u u d d d u u u m m L d d d Z 0 W W m m L c c c s s s c c c t t t b b b t t t s s s t t t g 31 e e e e u u u d d d u u u m m L d d d Z 0 W W m m L c c c s s s c c c t t t b b b t t t s s s t t t g 32 33 hierarchy of scales 10-17 cm 10-33 cm Planck scale GN ~lPl2 =1/(MPl)2 Electroweak scale range of weak force mass is generated (W,Z) strong, weak, electromagnetic forces have comparable strengths 1028 cm Hubble scale size of universe lu 16 orders of magnitude puzzle What kind of physics generates and stabilizes the 16 orders of magnitude difference between these two scales 1027 eV 1011 eV 10-33 eV 34 unification of couplings The gauge couplings of the Standard Model converge to an almost common value at very high energy. what’s up with that? 35 what does the Standard Model explain ? your body atoms electrons protons, neutrons quarks 36 what does the Standard Model explain ? 37 neutrino () sky 38 what does the Standard Model explain ? 39 what does the Standard Model not explain ? quantum gravity HST image of an 800 light-year wide spiral shaped disk of dust fueling a 1.2x10^9 solar mass black hole in the center of NGC 4261 40 what does the Standard Model not explain ? quantum gravity dark matter and dark energy 41 what does the Standard Model not explain ? quantum gravity dark matter and dark energy Higgs 42 Arrange it so delicately that it will fall down in 19 minutes. the Bigger Big picture The Standard Model describes everything that we have seen to extreme accuracy. 43 the Bigger Big picture Now we want to extend the model to higher energies and get the whole picture For this we need new experiments and ideas 44 Dirac (1928) matter antimatter special relativity & quantum mechanics 45 supersymmetry (SUSY) fermions bosons every particle has a superpartner particle 46 supersymmetry fermions bosons every particle has a superpartner particle 47 supersymmetry fermions bosons electron quark photino gravitino selectron squark photon graviton none of the sparticles have been discovered yet most of the dark matter in the universe maybe the lightest sparticle 48 unification of couplings SUSY changes the slopes of the coupling constants For MSUSY=1 TeV, unification appears at 3x1016 GeV 49 50 what do explain ? quantum gravity HST image of an 800 light-year wide spiral shaped disk of dust fueling a 1.2x10^9 solar mass black hole in the center of NGC 4261 51 require 7 extra space dimensions and give us ways to hide them 52 compactification 53 brane-worlds There could be other branes which would look like dark matter to us Standard Model particles are trapped on a brane and can’t move in the extra dimensions how do we see a hidden dimension? ? what particles can move in that dimension ? how big is that dimension ? what is its shape some dimensions are easier to detect than others slice of a 6 dimensional Calabi-Yau space 55 gravitons are the most robust probe of extra dimensions gravity is so weak that we have never even seen a graviton. melectronmelectron F=GN r2 melectron r melectron The gravitational attraction between two electrons is about 1042 times smaller than the electromagnetic repulsion. 56 think about this: gravity gets stronger at extremely high energies (or short distances). it gets stronger at lower energies if there are extra dimensions…. 57 …in which case high energy gravitons may be produced in collider experiments: quark gluon (becomes “jet” of hadrons) antiquark graviton these gravitons probably “escape” into the extra dimension(s) 58 graviton emission simulation: we don’t see the graviton we see a jet from the gluon 59 Collider Detector at Fermilab 60 61 concentric cylindrical layers energy deposited from the particle debris of the collision in the middle 62 “lego” event display 63 Two events are graviton simulation and one is real CDF data: Can you pick the gravitons? 64 two events are real CDF data and one is graviton simulation; Can you pick the graviton? 65 Higgs simulation 66 new accelerators for new physics Linear Collider (?,~2012) Large Hadron Collider (CERN, 2006) 67 underground and in the sky SuperNova Acceleration Probe (SNAP) 68 underground and in the sky KamLAND neutrino detector 69 The coming experiments in particle physics, cosmology and astrophysics will answer (among many other questions) what is the physics that connects the gravitational scale and the scale of the typical mass of the elementary particles what is dark energy and what is dark matter do protons decay what is string theory what are the dimensions and dynamics behind spacetime 70 Space and time may be doomed. E. Witten I am almost certain that space and time are illusions. N. Seiberg The notion of space-time is clearly something we’re going to have to give up. A. Strominger If you ask questions about what happened at very early times, and you compute the answer, the answer is: Time doesn’t mean anything. S. Coleman 71 SCIENCE: The Glorious Entertainment …for any important assertion evidence must be produced; …prophecies and bugaboos must be subjected to scrutiny; … guesswork must be replaced by exact count; ….accuracy is a virtue and inquiry is a moral imperative. To the hegemony of science we owe a feeling for which there is no name, but which is akin to the faith of the innocent that the truth will out and vindication will follow. In its purest form science is justice as well as reason. Jacques Barzun 72 73 “let there be light” is what we say when the experiment starts taking data ; usually in particle physics and astronomy/cosmology wednesday lunch oct 9 2002 maria spiropulu 74