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ASTROPARTICLE PHYSICS
1. Organisation of the course2. Introduction3. What have we learnt from particle and astrophysics4. Cross sections
Course organisation
Each Session:1 hr. Lecture15 min Break1 hr. Exercises 15 min. Break1 hr. Lecture
Lecture Notes will be handed out.
Course organisation
week date subject
6 07‐Febintroduction‐particle vs astroparticle physics pk N328
6 10‐FebCosmic Rays pk N328
7 14‐FebCosmic Rays pk N328
7 17‐FebNucleosynthesis pk N328
8 21‐FebSolar Neutrinos pk H331
8 24‐FebNeutrino Oscillations (+matter enhanced) pk N328
9 28‐FebNeutrino velocity pk H331
9 02‐Mar Dark Matter gb N328
10 06‐Mar gb H331
10 09‐Mar gb N328
11 13‐Mar gb N328
11 16‐Mar gb N328
12 20‐Mar gb H331
12 23‐Mar gb N328
13 30‐MarExam Gb/pk
Course organisation
•Exam 3 hours questions similar to the exercises•After 2 weeks there will be a series of publications on subjects related to the lectures handed out. Students provide a 3‐4 page summary/critique to be handed in at exam. Counts for 1/3 of the exam.
Introduction
What is astroparticle physics?
The science of studying the universe by investigating particles that arrive on earth
Which particles?Must be stable:
protons, neutrinos, photons, nuclei, electronsand their antiparticlesGravitational waves (stretching it a bit)Dark matter particles, monopoles, nuclearites, strange quark condensates
Introduction
First indications of particles from CosmosIsolated electroscopes dischargedEffect increased with heightMain experiments done by Victor Hess in 1912‐1913
What was not known then was that the measured cosmic rays were SECONDARY and the products of interactions of the real PRIMARY cosmic rays in the atmosphere
These cosmic rays were producers of many new –unknown – particles.Cosmic rays gave rise to particle physics – later done with accelerators to fix the energy and the intensity and the interaction position and the particle type.
Introduction
lead
Magnetic field perpendicular to the sheet
Momentum larger here
Than here
POSITRON
Introduction
Particles with equal momentum but different ionisation in cloud chamber
Search for Yukawa particle
Introduction
MUON
Introduction
Stopping muons
All sam
e length –same en
ergy
Different length different energy
CHARGED PION From these pictures conclude muon decay is 3‐body
Introduction
The initial particle physics was done with cosmic rays
Lots of information towards the Standard ModelMore accurate with accelerators
I3
S
0
K0K
0KK
pn
‐ 0 +
‐ 0
‐ 0 +
‐ 0
S=0
S=‐1
S=‐2
Introduction
This led to the very successful quark model and indirectly to the Standard
Model
Fam 1 Fam 2 Fam 3
e
e uuu ccc ttt
ddd sss bbb
Introduction
Interactions are mediated by Bosons
weak electromagnetic strong
W+ g (x8)
Z0
W‐
You have learned or will learn lots about the SMHowever
For astroparticle physics we don’t need much of it
Introduction
In astroparticle physics we tend to be able to see only the major interactions
The SM is a perturbative theory and allows one to calculate maybe 0.0001 fraction of the total pp cross
section. The quark model can give us general rules about the interactions, but the magnitude of cross sections are
experimental quantities.
We are interested in total cross sections rather than small calculable cross sections
Introduction
Why?
For instance:•A particle interacting in the atmosphere will produce several thousand pions several hundred kaons a few charm particles.•If an interaction happens in a stellar object, we will see the stable particles that have been copiously produced, like photons and neutrinos and protons.•Other particles are hard to find – charm, top, W’s only modify spectra of muons or neutrinos slightly•We don’t use the details of the interaction but the general features to conclude what sort of particles are actually interacting
Introduction
We need the particle physics part of astroparticle physics to
1. Give plausible interpretation of astrophysical phenomena2. Calculate how spectra are affected by the material the
encounter on the way to the earth 3. Give us ways of detecting them when they get here 4. Allow for us to interpret the interactions with our detectors or
earth5. Identify the particles6. Measure their energy
Introduction
What is the total pp cross section:
Answer: 30 – 100 mbarn (1 barn = 10‐24 cm2 = 10‐28 m2 )
fm8m108m103)2(
15
2272
RR
So not that far off being a black disc
From that one can conclude that the total cross section for a proton on a nucleus grows as A2/3
Introduction
dlAlA
NdN A )()(
Number of interactions in an infinitesimal length dl is given by:
Used for interaction of particles with the atmosphere, neutrinos with the earth, particles
with restgas in the galaxy, or universe.
Introduction
Orders of magnitude:
Cross section pp 30‐100 mbarnp 100‐200 barnp E*10‐14 mbarn
pp and p grow as approximately s1.08
p grows less steeply after s=10000 GeV2
Introduction
This is why we are interested in astroparticles
They have higher energies than we can make on earth by 7‐8
orders of magnitude
LHC making this energy would have a diameter of 4.0 108 km
Diameter of earths orbit around sun is 2.8 108 km