Jefferson Lab Presentation to Teacher Education Program November 8, 2006 Subatomic Particles: What do we study at Jefferson Lab? Dr. Allison Lung 12 GeV Upgrade Project Director & Senior Staff Physicist

Nuclear Physics: All About Atoms nucleons education.jlab.org/atomtour

Building atoms……

The tiniest particles……or are they?

Just how big are they? What about all that empty space?

Even tinier particles!

Fundamental Particles Quarksu up c charm t top Quarksd down s strange b bottom Leptons e e-neutrino  mu-neutrino  tau-neutrino Leptonse electron  muon  tau Generation IIIIII All visible matter in universe is made of Generation I particles. electric charge 2/3 -1/3 0 increasing mass

Held together by a powerful force: STRONG FORCE

Four Fundamental Forces fundamental particles interact by responding to a force from another particle FORCECARRIERPARTICLE gravitygravitonleptons weakW +, W -, Z 0 electro- magnetic photonquarks stronggluon

And still more empty space…. filled with force fields Atoms are % empty space !!

World of Atoms – a little background education Atom: nucleus of neutrons & protons with orbiting electrons go down one layer Electron: very light particle with negative charge Proton: weight equals ~2000 electrons, positive charge Neutron: weight almost equal to proton, no net charge go down one layer Quarks: fundamental particles, 6 types, up/down/strange are the lightest and most common Forces: strong, electromagnetic, weak, gravity; strong force holds quarks together go down one layer ??? is there another layer ???

Structure of Matter

World of Atoms – a little background education we are more “empty space” than matter, “empty space” is filled with carefully balanced forces, get students to expand on the solar system model of atoms great Web pages for students: great Web pages for teachers:

What really cool, tiny stuff do we study? What forces hold the neutrons and protons together in an atom? What forces hold the quarks inside a proton together? How is electric charge distributed within a neutron or proton? How is magnetic field distributed within a neutron or proton? Does a “free” quark behave the same as a quark bound inside a proton? Does a “free” quark behave the same as a quark bound inside a heavy atom?

Jefferson Lab’s Scientific Purpose Study how quarks and gluons combine to form protons and neutrons Study how protons, neutrons, and electrons combine to form atoms

Jefferson Lab Lay-out accelerator schematic aerial photo 7/8 mile racetrack superconducting 3 experimental Halls 6 billion electron volts Dept. of Energy Laboratory ~700 employees >2000 scientists from 18 countries

South Linac Cryomodules

Recirculation Arc Configuration Arc 10

Hall C

Detector Systems study strange quarks in proton (G-zero) hydrogen target proton detectors electron beam ~ $10 Million cost ~ 5 year construction ~ 5 year measurements ~ 50 ton weight ~ 20 feet height superconducting magnet

What are we studying right now ? How do strange quarks contribute to the properties of the proton? Do they contribute to the spin? Are the strange quark’s electric interactions different from their magnetic interactions?

quark’s spin doesn’t match neutron’s spin What have we learned lately ? proton can take many shapes…… Pentaquark – 5 quark combinations may exist?

6 GeV CEBAF 11CHL-2 12 Upgrade magnets and power supplies Two 0.6 GV linacs 1.1 New cryomodules get new rf zones FUTURE JEFFERSON LAB

Tagging spectrometer and photon beamline review Jan 23-24, 2006 GlueX / Hall D Detector Electron Beam from CEBAF Lead Glass Detector Solenoid Coherent Bremsstrahlung Photon Beam Tracking Target Cerenkov Counter Time of Flight Barrel Calorimeter Note that tagger is 80 m upstream of detector

Tagging spectrometer and photon beamline review Jan 23-24, 2006 Architect’s rendering of Hall D complex Service Buildings Hall D Cryo Plant Counting House

Tagging spectrometer and photon beamline review Jan 23-24, 2006 Site Preparation, Roads, & Parking Concrete Retaining Walls Hall D & Counting House N Earth Berm over Beam Line

SUMMARY Jefferson Lab: studies how protons and neutrons make up the nucleus of atoms studies how quarks and gluons make up neutrons and protons collides electrons with atomic targets and measures the energy, speed, and trajectory of scattered particles for your students introduce the solar system model of the atom go further...introduce forces (gravity, weak, electromagnetic, strong) gee whiz factor! –we are more “empty space” than matter –there are incredible forces acting in that “empty space” physics is a great career !

Nuclear Physics as a Career college degree(s) required in physics, math, or computer science possible career paths: –government laboratory scientist –university professor & researcher –computer firms –modeling economic trends on Wall Street –start-up technology companies (medical imaging, cryogenic helium…..) salary range at Jefferson Lab (comparable to university professors): –Staff Scientist I (approx. $48,000 to $75,000) –Staff Scientist II (approx. $60,000 to $95,000) –Staff Scientist III (approx $75,000 to $120,000)