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Discover the innermost aspects of nature through the study of high energy particle physics. Explore the nature of the universe after the Big Bang and physics at temperatures not seen in the past 15 billion years. Unravel the mysteries of the Quantum Universe and search for new forces and symmetries. Join us on this exciting journey at Fermilab.
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Innermost Space High Energy Particle Physics is a study of the smallest pieces of matter. It investigates the deepest and most fundamental aspects of nature. It investigates (among other things) the nature of the universe immediately after the Big Bang. It also explores physics at temperatures not common for the past 15 billion years (or so).
Helium Neon Periodic Table u u u d d d Neutron Electron Proton Gluons hold quarks together Photons hold atoms together All atoms are made of protons, neutrons and electrons
t u d b While quarks have similar electric charge, they have vastly different masses (but zero size!) c s
Why three dimensions? What gives particles their mass? Mysteries of the Quantum Universe Are there new forces and symmetries that we don’t yet know? Are the forces and particles of which we do know just different faces of a deeper, unifying principle?
Fermi National Accelerator Laboratory(a.k.a. Fermilab) • Begun in 1968 • First beam 1972 (200, then 400 GeV) • Upgrade 1983 (900 GeV) • Upgrade 2001 (980 GeV) Jargon alert:1 Giga Electron Volt (GeV) is 100,000 times more energy than the particle beam in your TV. If you made a beam the hard way, it would take 1,000,000,000 batteries
The Main Injector upgrade was completed in 1999. • The new accelerator increases the number of • possible collisions per second by 10-20. • DØ and CDF have undertaken massive • upgrades to utilize the increased • collision rate. • Run II began March 2001 Expected Number of Events Huge statistics for precision physics at low mass scales 1000 Formerly rare processes become high statistics processes 100 Increased reach for discovery physics at highest masses 10 Run II 1 Run I Increasing ‘Violence’ of Collision
How Do You Detect Collisions? • Use one of two large multi-purpose particle detectors at Fermilab (DØ and CDF). • They’re designed to record collisions of protons colliding with antiprotons at nearly the speed of light. • They’re basically cameras. • They let us look back in time.
Typical Detector (Now) • Weighs 5,000 tons • Can inspect 10,000,000 collisions/second • Will record 50 collisions/second • Records approximately 10,000,000 bytes/second • Will record 1015(1,000,000,000,000,000) bytes in the next run (1 PetaByte). 30’ 30’ 50’
Remarkable Photos In this collision, a top and anti-top quark were created, helping establish their existence This collision is the most violent ever recorded (and fully understood). It required that particles hit within 10-19 m or 1/10,000 the size of a proton
Modern Cosmology • Approximately 15 billion years ago, all of the matter in the universe was concentrated at a single point • A cataclysmic explosion (of biblical proportions perhaps?) called theBig Bangcaused the matter to fly apart. • In the intervening years, the universe has been expanding, cooling as it goes.
Fermilab 4x10-12 seconds Now (13.7 billion years) Stars form (1 billion years) Atoms form (380,000 years) Nuclei form (180 seconds) Nucleons form (10-10 seconds) Quarks differentiate (10-34 seconds?) ??? (Before that)
Why three dimensions? What gives particles their mass? Mysteries of the Quantum Universe Are there new forces and symmetries that we don’t yet know? Back to the Mysteries Are the forces and particles of which we do know just different faces of a deeper, unifying principle?
In 1964, Peter Higgs postulated a physics mechanism which gives all particles their mass. This mechanism is a field which permeates the universe. If this postulate is correct, then one of the signatures is a particle (called the Higgs Particle). Fermilab’s Leon Lederman co-authored a book on the subject called The God Particle. bottom top Undiscovered!
Hunting for Higgs For technical reasons, we look for Higgs bosons in association with a W or Z boson. In the region where the Higgs boson is expected, we expect it to decay nearly-exclusively into b-quarks b jet electron neutrino (MET)
Symmetries Translational Rotational
More Complex Symmetries In a uniform gravitational field, a ball’s motion is independent of vertical translation. The origin from where potential energy is chosen is irrelevant. The equations of motion are “symmetric under vertical or horizontal translations.”
Complex Familiar Symmetries x y r r2 r1
Complex Familiar Symmetries y r2 r1 r2 r1 x r Translations: x x + Dx y y + Dy
Complex Familiar Symmetries x x y r Reflections: x -x y -y r2 r1 y
Complex Familiar Symmetries y x r Rotations: f-f r2 r1
Complex Familiar Symmetries y x r Charge Flip: q - q r2 r1
Complex Familiar Symmetries y x r Bottom Line: Electromagnetic force exhibits a symmetry under: Translation Rotation Reflection Charge Congugation (and many others) r2 r1
Fermions and Bosons Fermions: matter particles ½integer spin Bosons: force particles integer spin
Unfamiliar Symmetries One possible symmetry that is not yet observed is the interchange of fermions (spin ½ particles) and bosons (integral spin particles) Known equation Equation = Fermions + Bosons Interchanged equation (pink green) Equation = Fermions + Bosons
Unfamiliar Symmetries Interchanged equation (pink green) Equation = Fermions + Bosons One possible symmetry that is not yet observed is the interchange of fermions (spin ½ particles) and bosons (integral spin particles) + Fermions + Bosons Known equation Equation = Fermions + Bosons + Fermions + Bosons This New Symmetry is called SuperSymmetry (SUSY)
SUSY Consequence • SUSY quark “squark” • SUSY lepton “slepton” • SUSY boson “bosino”
The Golden Tri-lepton SuperSymmetry Signature muons electron neutrino This is the easiest to observe signature for SUSY. No excess yet observed.
The Conundrum of Gravity • Why is gravity so much weaker (~10-35×) the other forces? • Completely unknown • One possibility is that gravity can access more dimensions than the other forces
The Dimensionality of Space Affects a Force’s Strength • Gauss Law 2D 3D
Are More Dimensions Tenable? • Newton’s Law of Gravity • Clearly indicates a 3D space structure. Or does it?
Nature of Higher Dimensions • What if the additional dimensions had a different shape? • What if the additional dimensions were small?
Access to Additional Dimensions • What if gravity alone had access to the additional dimensions?
Access to Additional Dimensions • What if gravity alone had access to the additional dimensions?
A Model with “n” Dimensions. p e q q’ G p e • Gravity communicating with these extra dimensions could produce an unexpectedly large number of electron or photon pairs. • Thus, analysis of the production rate of electrons and photon provides sensitivity to these extra dimensions. • Large energies are required to produce such pairs.
Once again there are interesting events! (way out on the mass tail.) electrons photons ee pair gg pair
Summary • Particle physics allows us to study some of the deepest mysteries of reality. • We know a whole bunch of stuff. • The things we don’t know, we’re studying like mad. • The mysteries mentioned here are unsolved. We need help. Send students.
