Arizona at the Large Hadron Collider: the ATLAS Detector, the Particle Zoo, the Higgs Boson, and the Search for New Phenomena. OLLI Presentation. October 24, 2014. Michael Shupe, Professor Department of Physics The University of Arizona At least 156 billion light years Physics Lets Us Touch The Universe At All Scales zoom 10,000,000,000 Astrophysics Biophysics zoom 100,000 more Condensed Matter Physics Atomic, Molecular, and Optical (AMO) At least 1000 Nuclear Physics more High Energy Physics “Inner space” is as “empty” as outer space. But the vacuum is filled with dancing quanta! High Energy Physics Research focused on the fundamental building blocks in nature, and the interactions among them. Electromagnetic Force Strong (Nuclear) Force Weak Force (Changes particle types) Gravity (Gravitons?) The Higgs Boson How do we “see” new phenomena at this level? By studying the debris from head-on collisions between particles. Shown below are proton-antiproton collisions leading to the production of top (t) quark pairs. This was used at Fermilab, west of Chicago, to discover the top quark in 1995. Arizona was there! - Arizona’s Impact on the Design and Construction of the ATLAS Detector at the Large Hadron Collider Arizona HEP Faculty Members - John Rutherfoord Michael Shupe Ken Johns Elliott Cheu Erich Varnes The University of Arizona Team Faculty Research Associates & Staff Graduate Students 7 This is the Full Experimental High Energy Physics Group at The University of Arizona Faculty Graduate Students John Rutherfoord ATLAS Jeff Temple D0 Michael Shupe ATLAS Bryan Gmyrek D0 Kenneth Johns D0/ATLAS Susan Burke D0 Elliott Cheu D0/ATLAS Xiaowen Lei ATLAS Erich Varnes D0/ATLAS Caleb Parnel-Lampen ATLAS Research Scientists Walter Freeman ATLAS Peter Loch ATLAS Technical Sasha Savine ATLAS Charlie Armijo D0 Postdoctoral Gabe Facini ATLAS Stefan Anderson D0 Anna Malin D0 Peter Tamburello D0 Robert Walker ATLAS Jessica Leveque D0 Secretary Walter Lampl ATLAS Claudia Miller Engineers Leif Shaver Mech. Joel Steinberg Elect. Dan Tompkins Elect. The size and breadth of this group has enabled us to make a substantial impact on D0 at the Fermilab Tevatron, and on ATLAS at the Large Hadron Collider. Now for what we did. A quick virtual tour of CERN and Arizona Large Hadron Collider, CERN, Geneva, CH pp collision @ 7 TeV 14 TeV - The ATLAS Detector at the LHC (Proton-Proton Collisions at 14 TeV) The high energy group at The University of Arizona joined the ATLAS experiment in 1994, and had major impact—from the start—on the design of the experiment! Collisions began in 2009. First big data set in 2010. Magnets in the LHC Tunnel 27 kilometer tunnel. More than 1600 magnets. ATLAS, In Its Underground Cavern The ATLAS Detector: ~$1.5B – “World’s Largest Experiment” Tracking Calorimeters Muon: Air Core Toroids Integrated Forward Calorimeters ($16M) Massive Forward Radiation Shield (~700 Metric Tonnes) Arizona was the only U.S. group to make a major change in the ATLAS design! We conceived the integrated FCal and shield design, adopted by ATLAS in June,1994. Our research group, constructing the ATLAS Integrated Forward Calorimeter in a clean room in the basement of the Physics building. Arizona conceived, engineered and supervised this $16M project for ATLAS. Some of our research group, at CERN, during the installation of the ATLAS Integrated Forward Calorimeter ATLAS - 2005 ATLAS - 2007 ATLAS - 2007 CSC Chambers 19 - The structure of matter, and the “Zoo” of Particles That We Know About Today The underlying patterns of matter In Chemistry, all the types of molecules we see are made from just 92 naturally occurring elements (the Periodic Table). The atoms in this table, are made of protons, neutrons, electrons + photons, for the electric force + “nuclear glue”. 21 ATOMS NUCLEI NUCLEONS QUARKS Helium The only quarks needed to build up protons and neutrons are u and d. u has charge 2e/3, and d has charge minus e/3. What quarks do neutrons contain? Who ordered this one? The only particles needed to What else can we build the periodic table of the make from the six elements are protons, quarks? Thousands of neutrons, and electrons! not-so-stable particles! (Plus photons and gluons!) 22 Distance Scales: From Atoms, to Nucleons, to Quarks 23 By the late 1970’s, hundreds of new particles had been detected, and more quarks had been Spin1/2 found: u,d,s,c,b. Neutron Proton Spin 3/2 24 The Fundamental Particles We Know at Present Six quarks (and antiquarks), six leptons (and antileptons), four force-carrying particles. Electromagnetic Force Strong (Nuclear) Force Weak Force (Changes particle types) Gravity (Gravitons?) The Higgs Boson Particle Mass Ratios, With “Zoo” Comparisons 26 10/22/2014 26 - The Beginnings of Quantum Mechanics (particles waves), and Why We Talk About “Particles” and “Fields” The Beginnings of Quantum Mechanics 1900: Max Planck discovers that electromagnetic waves deliver their energy in “bundles”, E = hf Planck’s constant: h 6.6260693(11) 1034 J s 1905: Albert Einstein claims that these waves are composed of particles, “photons” (), each of energy E = hf, explaining the photoelectric effect. 1924: Louis de Broglie suggests 1927: that particles, such as the Davisson- electron, are also waves of Germer wavelength = h/p p = h/ experiment says yes! Waves are particles, and particles are waves. They are really all “quanta”, with energy E = hf and momentum p = h/ A given type of particle has “additional” properties: spin, mass, electric charge, weak charge, strong charge, parity, etc. (Photons are mass-less particles with spin 1.) “Nature forces us to the conclusion that quanta are real, but offers no additional ‘guidance’ to help us create a mental picture of how quanta act as both waves and particles. The best we can do currently is to label this two-sided behavior as ‘wave particle duality’. Quantum mechanics still fascinates and mystifies the people who work most closely with it.” (Richard Feynman) What is a “Field”? * Each force has a “carrier” particle,- and these carriers can be emitted or absorbed by particles with the right type of charge. * We have seen these “charges” in previous slides. Photons carry the electromagnetic force, and interact with particles that have electric charge (+ or -). Gluons carry the strong force and interact with particles with strong charge (R,G,B,or the “anticolors”). The heavy bosons W+, W-, and Z0, carry the weak force and interact with particles that have weak charge. * Photons are neutral, and cannot interact with other photons, but gluons can interact with other gluons, and the W’s and Z can interact among themselves. * Electromagnetic force fields can extend to infinity, strong force fields are self containing with the size scale of a proton, and weak interactions are very short ranged. Sketch of an electric field caused by three electric charges. The lines show the directions- of the field, and the field is strongest where the lines are densely packed together. Feynman Diagrams: the Horizontal Lines are Field Carriers A “simple” strong interaction between a neutron and proton: A u-quark is exchanged, and a d-quark pair pops out of the vacuum. Later, a d-quark pair annihilates. At every step, gluons are holding the proton and neutron together. In the end, the n and p have swapped identities! Just another day at the office… Superficially, strong interaction fields carried by gluons (below), look a bit like electric fields carried by photons (right), especially at short range. But since gluons interact with each other, as quarks are driven apart, the gluon field pulls together into a “string” (aka “flux tube”). When the energy in the string get high enough, it breaks, and new quarks are created! Particles interact through the exchange of “field quanta” such as photons (if they have electric charge). The interactions can be represented by Feynman diagrams, which are then translated into mathematical expressions (“Lagrangians”) next slide The Standard Model Lagrangian: Quantum Field Theory quarks, leptons and their strong, quarks & leptons have mass electromagnetic and weak interactions gauge sector flavour sector EWSB sector mass sector neutrinos have Higgs bosons … and mass too! beyond? 36 A Summary of the Interactions Among Particles/Fields - How Do We Study Quarks and Leptons, and Search for New Particles, at the LHC? By Sifting Through the Debris of Proton-Proton Collisions. The higher the proton beam energies, the shorter the distance scale we can explore. The de Broglie equation: h/p The bigger the momentum of colliding particles, the shorter their wavelengths. Shorter quantum wavelengths improve the resolution! 39 Fantasy Machine: A Quark Collider Quark Detector q1 q Quark Beam 1 1 Quark Beam 2 3.5 TeV gBRbar 3.5 TeV q2 The momentum of the “force q2 carrying” particle (here a gluon) determines its wavelength, and the distance scale that can be probed. Quark Detector 40 Reality: the LHC 7 TeV Proton-Proton Collider •Each proton is a chaotic mix of 3 “valence quarks” + other quarks + gluons. •The two that collide typically carry a small fraction of the proton momentum: parton distribution functions (PDF’s). •Outgoing quarks, or gluons, barely escape the protons before they cascade in to more quarks and gluons (a parton shower). And this is just the start! 41 Factorization makes this calculable. P 0 1 q(x1) Dq (z) xP11Hard Scattering Process sˆ Parton Jets xP22 P 2 qgqg X g(x2) ˆ 42 The momentum distributions of quarks and gluons: For two-jet (dijet) events, the jets do not emerge from the collision back-to- back in the longitudinal direction! To access the information about the original collision, we rely on kinematics to “undo” the effects of the Lorentz boost, and study the collision in the 2- parton rest frame.