Transcript Teilchenastrophysik in der Schule oder Lichtblitze in der

Cosmic rays in a thermos flask
1.European Physics Education Conference
Bad Honnef
Thomas Trefzger
Universität Mainz
Motivation
 Mystic experiments in school
 Introduction to special relativity
 Introduction to (astro-)particle physics
 Minor complexity
Cosmic radiation
 Interaction of high
energetic primary
particles (85%
protons, 14% alpha
particles) with
nuclei of the
atmosphere
 Surface of the
earth: a few
hundred charged
particles per qm per
second
 Mostly muons
The muon




Group of leptons
mass (muon) ~200 x mass of the electron
Mean lifetime 2.2 microseconds
Decay of the muon:
  e  e  


  e  e  


Decay of the muon
Radioactive decay law
N t   N0 exp( t   ) mit    2.2s
Muons should not reach the surface of the earth
6
s  v  t  0.9999 c  2.2 10 s  660m
1 muon
per second
Special Relativity
 time dilation (observer at earth)
v=0.9999c: muon lives longer:
 
1
v2
1 2
c
 71

     1.6 10  4 sec
 Length contraction, 20km
(observer moves along with the muon)
s 
1

 s  282 m
Experiment set-up
Praxis der
Naturwissenschaften 4/51
Cherenkov radiation
First Experiment
Measurement without water
-> no signal
Measurement with water
-> signals
Existence of something which gives a
reaction in the thermos flask
Applied Statistics
 Rate of muons (15 min),
10 second intervals
0
10
20
Events/10 s
Applied Statistics
 Rate of muons (40 hours),
10 second intervals
0
10
20
Events/10s
Second experiment
 Koincidence with two thermos flasks
Third experiment
 Measurement at different places
Life after death
 Fourth experiment: Lifetime
   e  e  
   e  e  
Lifetime– it is relative !
logarithmic
linear
Number of events vs. microseconds
0
Microseconds
5
0
Microseconds
5
What can we learn ?
 Cosmic radiation is omnipresent and
can be detected
 Frequency of occurence, penetration
rate, angular rate dependence
 Statistical aspects, randomness of
events
Didactic Potential
Exotic particles in school
Statistical aspects
Aspects of special relativity
Ongoing research
Elementary particles as part of our
world
 Computer in measurement control
and analysis



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
Jugend forscht 2004 – state winner