Speaker
Claus Grupen
(Siegen University)
Description
Cosmic rays after Hess is the birthplace of elementary particle physics.
The 1936 Nobel prize was shared between Victor Hess and Carl Anderson.
Anderson discovered the positron in a cloud chamber. The positron was
predicted by Dirac several years earlier, but Anderson was not aware of it.
In his subsequent cloud chamber investigations Anderson found - together
with Neddermeyer - the muon, which for some time was considered to
be a candidate for the Yukawa particle responsible for nuclear binding.
Only emulsion measurements by Perkins, Powell, Occhialini and Muirhead
clarified the situation by the discovery of the charged pions in cosmic rays.
The cloud chamber continued to be a powerful instrument in cosmic ray
studies. Rochester and Butler using the cloud chamber of the Blackett
group in Manchester found Vs, which turned out to be shortlived neutral
kaons decaying into a pair of charged pions. Also s were found in cosmic
rays. But after that the period of accelerators and storage rings took
over. The unexpected renaissance of cosmic rays started with the search
for solar neutrinos and the observation of the supernova 1987A. With
the observation of neutrino oscillations one began to look beyond the
standard model of elementary particles. Interesting results from X-ray and
gamma-ray astronomy and the detailed observations of the cosmological
background radiation disclosed that we are living in a universe dominated
by dark matter and dark energy. After 100 years of cosmic ray research
we are at the beginning of a new era, and we still aim “To understand
what holds the core of the world together”.
Primary author
Claus Grupen
(Siegen University)
