SLAC
<p class="default">Nov 9, 2009 7:49 PM  NOTE:  <b>SLAC Monday AFTERNOON Lectures are always at 4:15PM</b> and not 4 PM
4PM is when they put out the goodies.  (fruit, cookies, cheese)
 
04:19 PM, June 24, 2007
 
Exclt lecture by Sara Demers: see SLAC LHC on June 19, 2007
 
She was undergrad at Hvd; PhD Rochester;
 
STADIUM = 1 km in diameter; raisin is 1cm; so takes 10,000 raisin diameters = 1 stadium.
 
<b>If atom is a football stadium; proton is the size of a raisin.</b>
 
Apple is 10 cm: an atom is one angstrom, which is one hundred millionth the size of the apple.
 
Say sun is 100 million miles (call it 100 million km) and an apple is one ten thousandth of a km.
 
Then an apple is 10 12 times as small as that distance ... that does not work.
 
<b>Radius</b> of LHC = 2.8 miles; circum is 27 KM. biggest machine on earth.
 
Speed of protons = .99 (6 sig figs) of speed of light.
 
LHC magnets operate at 1.8 Kelvin (-273 + 1.8)
 
........................
 
What will it find:
 
There is no magical action at a distance: all interations work by exchange of particles (a belief)
 
Goal: categorize particles and their interactions
 
4 FORCES: gravity, strong, weak, and EM.
 
STANDARD MODEL has
6 quarks: up, down; charm, strange; top and bottom; 6 leptons; and some force carriers (photons, gravitons, etc)
 
 
Proton is 2 up and 1 down; neutron is 1 up and 2 down Q's.
 
Protons and neutrons are hadrons.
 
We emit about 340M neutrinones every day cuz of out radioactive K40 (potas) in our bodies.
 
About 400B neutrinos from sun go thru your body every day.
 
Poem by Joh Updike on Neutrinos.
 
NOTE: all those protons crammed into the nucleus ... what is enabling them to stay that close together:
Answer: the STRONG FORCE ... it overcomes the EM force that repels them.
The Up quarks exchange gluons to glue them to one another.
 
a muon decays to an electron and a neutrino.
 
W and Z particles are the exchange particles for the weak force.
Sarah actually detecged Z bosons in one of her experiments.
 
There are GAPS in the Standard model. and we have no model of gravity.
Gravity is really weak; entire earth cannot overcome a magnet.
 
<u>And look at entire universe ... it is like a glacier</u> :
<b>Only 5% of the universe is visible matter!!</b>
<u>25% is dark matter and 70% is dark energy</u> !
 
Universe is like blowing up a balloon: everything is moving apart.
Everything is accelerating apart .. why, cuz of dark energy.
 
Also, why do particles have mass.
 
Standard model is a 4 by 4 matrix of particles and forces.
 
Now back to the LHC;
 
Most of LHC is in France: right on France swiss border;
 
LHC is the biggest refridgerator in the world.
 
They will do proton proton collisions wwith hydrogen nucleai.
 
Start with hydrogen and get rid of electrons then inject them into the ring and accelerate using electric fields.
 
The size of the ring is limited by the strength of the magnets. To make it smaller, you'd need more powerful magnets ... they don't exist.
 
9,000 magnets in LHC; super conductors operate at 1 degr Kelvin.
 
Each collision takes 25 nanosecs. and they occur 40M times per sec.
 
The data from the collisions occupies at stack of CD's 20 km tall per year.
 
ATLAS detector: weight is the same as the Eiffel Tower;
 
will employ 2000 people from 31 countries.
 
the detector is s coke can with concentric shells of instruments to detect photons, electrons/postr, muons, etc.
they all must balance.
 
EM calorimeter, Hadron calorimeter, Muon chamber.
 
LHC is 200X more energy then Fermilab Tevatron.
 
1995 Top Q discovered. LHC will make lots of top Q's.
 
HIGGS BOSON; like people in a cocktail party: a rumor starts and people clump together.
 
(another metaphor: bebe vs a tennis ball moving thru mollases) very viscous medium.
 
will all test SUSY: Super Symmetry:
 
SUSY is required by String theory and helps with quatum gravity.
 
The lightest SUSY will be produced.
Also mini black holes.
 
Extram dimensions: are gravitons escaping into extra dimensions.
 
There appears to be non-conservation of energy (with dark energy).
 
NEIL CALDER is communic director at SLAC: he answered my questions.
 
He also mentioned LCLS: Linac Coherent Light Source ... next major project at SLAC.
 
Giant microscope to detect ... fast events at molec level, eg. biological macromolecule interactions.
 
How will LHC test string theory?
 
1) extra dimensions and supersymmetry.
 
Neil thinks String theory is very much NOT a majority view; is only worked on by a minority of theoret physicists and there is a lot of skepticism.</p>