Groping%20for%20the%20(Cosmic%20Ray)%20Knee

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Groping for the (Cosmic Ray) Knee
Frank Jones, Robert Streitmatter and Demos Kazanas
Physics at the End of the Galactic Cosmic Ray
Spectrum Aspen, April 25 May 1, 2005
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If Simon Swordy didnt exist we would have to
invent him.
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Two Component CR Spectrum
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0
Flux X E2.7
-1
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Log E (eV)
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One Knee Scenario There is another proton
component that would explain the drop in ltlnAgt
just below the knee.
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Why was the knee discovered? New Physics?

• Vernov, Zatsepin, Khristiansen, and Chudakov,
  Report to the All Union Conference on Cosmic
  Rays, Tbilisi, 1956

• Kulikov and Khristiansen, JETP 35, 635, 1958

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• The Idea!
• A new production channel opens up in the particle
  collision cross section.
• Some products are invisible resulting in lost
  energy.
• Produces apparent steepening of the cosmic-ray
  spectrum.
• We follow the approach of Kazanas and Nicolaidas

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Toy Model
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Toy Model Spectrum at Knee
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(Arbitrary Units)
Differential Flux X E2.8
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Energy (GeV)
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What could make the mass look heavier?
Typically, the mass of a primary particle is
determined by the depth in the atmosphere of the
shower maximum.
To make the mass appear to become heavier we need
to make the hadronic cross sections increase at
the same energy that the new channel opens up.
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Toy Model Shower Maximum

• In an air shower that involves the new process
  there are two effects that can raise the position
  of the shower maximum.
• If the cross section increases for energies gt Ec
  then each leg of the cascade in this energy
  region will be shorter.
• If the multiplicity increases there is an
  additional raising of the maximum because the
  energy is diluted quicker.

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