standard model
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Standard Model
Physicists have developed a theory called “The Standard Model” that
explains what the world is and what holds it together.
Standard Model
• It was once thought that the fundamental particles were electrons, protons, neutrons.
• Now we find smaller subatomic particles – quarks & leptons that comprise matter.
• Forces are carried by particles too!
All matter either Hadrons or Leptons.
p+ & no
Quarks can’t exist alone.
Protons, Neutrons: baryons made of only up & down quarks.
• How many up & down quarks in a p+?
• Charge = +1 • Baryons have 3 quarks only.• 2 up & 1 down.• u + u + d• +2/3 +2/3 – 1/3 = +1
• How many up & down quarks in a no?
• Charge = 0• 1 up & 2 down.• u d d• +2/3 -1/3 -1/3 = 0
The Atom
Leptons
• The most familiar member of this group is the electron e, but there are also heavier particles called the muon and the tau .
• For each of those, there is a smaller “partner” called a neutrino .
• The leptons are all capable of independent existence.
All particles have anti-particles same mass.
Antiparticles behave just like their corresponding matter particles, except they have opposite charges. A proton is electrically positive - an antiproton is negative. Gravity affects matter and antimatter the same way. When a matter & corresponding antimatter meet, they annihilate into pure energy!
Notation add bar: Mesons quark & antiquark.
A particle is composed of 2 charm, & 1 bottom quark.
• Is it a meson, lepton or baryon? • Baryon.
What is it’s charge? • +1.
• Write the symbols & charges for all the particles.• c c b• +2/3 +2/3 -1/3
A particle is composed of 1 anti-strange, & 1 down quark.
• Is it a meson, lepton or baryon? • Meson.
What is it’s charge? • 0.
• Write the symbols & charges for all the particles.• s d• +1/3 -1/3
Forces & Force Exchange Particles4 Fundamental Forces
• Strong Nuclear (Nuclear)• Electromagnetic• Weak (Nuclear)• Gravity
The universe exists because the fundamental particles interact. These interactions include 4 attractive & repulsive forces, decay, & annihilation.
Strong Force
• Short Range, Attractive only – holds nuclear particles together.
• Particle = gluons.
Electromagnetic Force
• Long range. Attracts & repels charged particles (Coulomb’s Law).
• Carrier particle = photon.
Weak Force
• In the nucleus. Involved with decay of particles. Short range.
The carrier particles of the weak interactions are the W+, W-, and the Z bosons.
Gravity
• Long range weakest force. Attractive only.
• The gravity force carrier particle has not been found. It, however, is predicted to exist and may someday be found: the graviton.
Quarks & Leptons 5:40 min.http://www.youtube.com/watch?
v=aTFCKbZw8QY
Hwk: Read Text 25-4 pg 917-923Do pg 923 #1,2 Pg 928 #30 - 37
List 2 pieces of evidence that light is a wave.
• Diffraction• Interference.
List 1 piece of evidence that light is a stream of particles. • Photoelectric effect
List 1 piece of evidence for the Bohr model of the atom.
• Emission or Absorption spectra
The charge on an anti-up quark would be:
• +1• -1• +2/3• -2/3
Note: Antiparticles have a bar over the symbol.
This particle is a:
a. Lepton
b. Proton
c. Meson
a. neutron
Cern Standard Modelhttp://www.youtube.com/watch?
v=V0KjXsGRvoA&feature=related5 minutes
Comprehensive Standard Model Summery(15 minutes)Cassiopeia
http://www.youtube.com/watch?v=K6i-qE8AigE
Quantum Song
• http://www.youtube.com/watch?feature=player_detailpage&v=DZGINaRUEkU
• What is Higgs Boson 3:30• http://www.youtube.com/watch?
v=RIg1Vh7uPyw
• What now for the Higgs 8:00 min w/ad.• http://www.youtube.com/watch?
v=649iUqrOKuE
Regents Problems Wksht.
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