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

Muons should not reach the surface of the earth

1 muon per second

smittNtN 2.2)exp(0

msctvs 660102.29999.0 6

Special Relativity time dilation (observer at earth)v=0.9999c: muon lives longer:

Length contraction, 20km (observer moves along with the muon)

sec106.171

1

1 4

2

2

cv

mss 2821

Experiment set-up

Praxis der Naturwissen-schaften 4/51

Cherenkov radiation

First Experiment

Measurement without water -> no signalMeasurement 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

ee ee

Lifetime– it is relative !

Number of events vs. microseconds

0 5 0 5 Microseconds Microseconds

linea

r

loga

rithm

ic

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

Jugend forscht 2004 – state winner