Jefferson LabPresentation to Teacher Education Program

November 8, 2006

Subatomic Particles:

What do we study at Jefferson Lab?

Dr. Allison Lung12 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

Quarks uup

ccharm

ttop

Quarks ddown

sstrange

bbottom

Leptons e

e-neutrino

mu-neutrino

tau-neutrino

Leptons eelectron

muon

tau

Generation I II IIIAll visible matter in universe is made of Generation I particles.

electric charge

2/3

-1/3

0

-1

increasing mass

Held together by a powerful force:STRONG FORCE

Four Fundamental Forces

fundamental particles interact by responding to a force from another particle

FORCE CARRIER PARTICLE

gravity graviton leptons

weak W+, W-, Z0

electro-

magnetic

photon quarks

strong gluon

And still more empty space…. filled with force fields

Atoms are 99.999999999999% 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 chargeProton: 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 ???

Structureof

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:

http://www.particleadventure.org

http://education.jlab.org

http://www2.slac.stanford.edu/vvc

great Web pages for teachers:

http://www.colorado.edu/physics/2000

http://www.fnal.gov/pub/education/k-12_programs.html

http://csee.lbl.gov

http://www.nsta.org

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 Systemsstudy 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 heightsuperconducting 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 CEBAF11

CHL-2CHL-2

12Upgrade magnets Upgrade magnets

and power and power suppliessupplies

Two 0.6 GV linacs1.1

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 GlassDetector

Solenoid

Coherent BremsstrahlungPhoton Beam

Tracking

TargetCerenkovCounter

Time ofFlight

BarrelCalorimeter

Note that tagger is80 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

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)