Post on 23-Feb-2016
description
Hands-on Particle Astrophysics
Introduction to Particle PhysicsPart II
Make up hadrons baryons: mesons:
Fermions (spin ½) Bosons (spin 1)
electromagnetic
strong
weak
Smallest Building Blocks (Fermion Interactions)
• Quarks:
• Neutrinos (neutral leptons):
• Charged leptons:
Smallest Building Blocks (Fermion Interactions)
• Quarks:
• Neutrinos (neutral leptons):
• Charged leptons:
Symmetries andconservation laws determine what is allowed
Smallest Building Blocks (Force Carrier Interactions)
g
g g gg
gg
Gluon self-interactions
W
W
WW
W
WW W
W W
Electroweak interactions
ZZ
Z
ZW
W W
W
Smallest Building Blocks (Force Carrier Interactions)
g
g g gg
gg
Gluon self-interactions
W
W
WW
W
WW W
W W
Electroweak interactions
ZZ
Z
ZW
W W
W
Symmetries andconservation laws determine what is allowed
Symmetries of Standard Model
• Excellent description of all interactions• Masses are not allowed!• Works well for photons/gluons• BUT W, Z massive• Fermions have mass!
• Way out?
Symmetries of Standard Model
• Excellent description of all interactions• Masses are not allowed!• Works well for photons/gluons• BUT W, Z massive• Fermions have mass!
• Way out? “Hide” the symmetry• Interactions with new particle obey symmetries• the “ground state” is not symmetric• Familiar example:
gravitational interactions: spherical symmetry(force: inverse square law)
and yet solar system not spherically symmetric
Simplest model – the standard model Higgs mechanism
• specific allowed interactions• allows massive W’s, Z’s• allows fermion masses
• specific relations among - masses of W’s, Z - interaction rates of various processes
+ verified by data over last 40 years!
• one spin 0 Higgs boson• specific
- production modes/rates - decay modes/rates
• unknown mass• discovered this year!• m = 125 GeV
Higgs self-interactions
H
H
H
H H H
H
HHH
H
H H H
W
f
ZW W WZ Z Z
f
Smallest Building Blocks (Higgs Interactions)
H
Higgs – fermion interactions
Higgs- force carrier interactions
ATLAS
CMS
LHC detectors