Cosmic Air Shower Experiments

1
Cosmic Air Shower Experiments
2

• Cosmic Rays in a Nutshell
• High energy particles traveling throughout
• our galaxy at close to the speed of light.
• Consist of elementary particles such as
• electrons (and positrons) and
• nuclei of atoms, mostly single
• protons (a few are much heavier).

Cosmic Rays continually bombard the Earth. In
fact, about 100,000 cosmic rays will pass
through a person every hour!
3
How do they reach the earth surface ?

• - Primary Cosmic Rays of high energy penetrate
  the atmosphere.
• Lower energy particles get deflected in the
  magnetic field of the
• earth or they get absorbed in the atmosphere.
• - Secondary particles get produced due to
  collisions and interactions
• of the primaries with air molecules.

4
Questions that have been answered - What are
these particles made of ? - What different kinds
are there ?
But not Where are they coming from ?
How are they made ?
5
Possible Sources within our Galaxy
Rate

• Supernovae
• - Ejects particles
• Capable of accelerating
• particles up to 1015eV.

Stellar Winds, Flares, Coronal Mass Ejections
The Sun Solar Wind Low Energy mostly do not make it to the earth surface.
Partcle showers do not reach ground
Note Energy of visible light particle (photon)
1 eV
6
Detectors (Air Shower Experiments)
Kascade in Germany Forschungszentrum Karlsruhe
Auger Observatory, Argentina
Flys Eye, Utah
7
Discoveries

• Energy 1020 eV ?
• Confirmation of very high energy cosmic rays !
  (?)
• D. J. Bird et al Astrophys J.
  424(1994)491
• Hayashida et al PRL73(1994)3491
• Swiss group reports correlations in arrival
  times of cosmic
• ray showers at four locations in Switzerland
  separated by
• more than 50 km1).
• O. Carrel and M. Martin, Phys. Lett. B325
  (1994) 526
• High schools form an ideal location for a
  sparse detector array.
• Renewed interest in cosmic rays as a result of
  new detection
• capabilities giant arrays planned (e.g. Auger
  Observatory).

Particles with energies greater 1020 eV Cannot
travel far in our galaxy!
Energy in eV
Higher energetic particles detected. Such
powerful sources and accelerators Must lie
outside our Milky Way Galaxy!
8
Puzzle

• Astrophysical Sources ?
• Active Galactic Nuclei ?
• Gamma Ray Bursters ?
• ????
• Decay of Exotic Particles ?
• Superheavy relics from early Universe
• Topological Defects from phase transitions
  during expansion/inflation period of
  early universe
• Yet unknown Particles and Interactions among
  them ???????

9
Why measure Time Correlations ?

• count Ultra High Energy events by looking for
• correlated events in nearby schools
• (pointing to origin helps)
• Might get lucky and see an even larger shower
  than has
• been recorded so far !
• search for
• Horizontal showers
• Widely separated correlated showers ??
• Secondarys from primary collisions far from
  earth
• Correlated primarys (supernova?)

contribute to todays fore front research !