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The Heavy Composition of UHECR p (A,Z) Based on work with: Dan - - PowerPoint PPT Presentation
The Heavy Composition of UHECR p (A,Z) Based on work with: Dan - - PowerPoint PPT Presentation
The Heavy Composition of UHECR p (A,Z) Based on work with: Dan Hooper Subir Sarkar + astro-ph/0910.1842 astro-ph/1007.1306 e UHECR Air Showers UHECR Air Showers Recent Measurements of Moments by Auger Interpretation
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UHECR Air Showers
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Recent Measurements
- f Moments by Auger
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Interpretation- What Does this Mean for Source Composition?
Assume Source Energy Distribution: Spectral index and max energy are considered in the range: + Assume Sources have a uniform Spatial Dist.
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Iron Only Composition?
hard to fit both of these simultaneously for Iron
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Iron Only Composition?
Cause of difficulty in fitting both and simultaneously for Iron
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Silicon Only Composition?
reasonable fits obtained, though hard spectral index required is worrying
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Nitrogen Only Composition?
poor spectral fit is a problem for Nitrogen only composition
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Nitrogen Only Composition?
poor spectral fit is a problem for Nitrogen only composition reason
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(Silicon) Magnetic Field- B=0 G
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(Silicon) Magnetic Field- B=0.1 nG
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(Silicon) Magnetic Field- B=0.3 nG
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Other Handles on the UHECR Composition
Nitrogen (Z=7) Silicon (Z=14) Iron (Z=26)
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Other Handles on the UHECR Composition
Nitrogen (Z=7) Silicon (Z=14) Iron (Z=26) Basically proportional to Z/A for a Emax>>EGZK
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Other Handles on the UHECR Composition
Nitrogen (Z=7) Silicon (Z=14) Iron (Z=26)
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Other Handles on the UHECR Composition
Nitrogen (Z=7) Silicon (Z=14) Iron (Z=26)
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Summary
If pure composition at source is assumed: Heavy(ish) composition required; Difficult to get good agreement with Iron
- nly composition to both
and data; The presence of a ~0.1 nG extragalactic magnetic fields can help improve fits; The UHECR photon fraction has some potential to differentiate the composition.
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Extra Slides
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Mixed Composition Scenario?
50 % protons + 50% Silicon
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Proton Only Scenario Still Possible?
Change Interaction Properties:
1) cross-section 2) multiplicity 3) elasticity
Modify these properties with logarithmic scaling from values at 1018 eV
work by Ulrich et al. (Karlsruhe) astro-ph/0906.0418
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Change Interaction Properties: 1) cross-section
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