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.