Status of Top-Down Models for the Origin of Ultra-High Energy Cosmic Rays

I. Observation of ultra-high energy cosmic rays before the Pierre Auger Observatory

II. The puzzle: ● The universe is opaque to UHECRs (Greisen 1966; Zatsepin & Kuzmin 1966) ● Strong magnetic fields are needed (Hillas 1984) ● Not known how to defeat radiation losses during acceleration phase ● No correlation with astronomical objects within 100 Mpc

III. The preliminary results for the UHECR spectrum from the Pierre Auger Observatory

IV. A window to new particle physics and inflation? Top-down scenarios ● “Wimpzillium decay” (Hill 1983; Dubrovich, Fargion & Khlopov 2003) ● “Wimpzilla decay” (Berezinsky, Kachelriess & Vilenkin 1997; Kuzmin & Rubakov 1997) ● “Wimpzilla annihilation” (Blasi, Dick & Kolb 2001; Dick, Hopp & Wunderle 2005)

V. Superheavy dark matter from inflation

VI. The power of anisotropy!

Rainer Dick, Physics & Engineering Physics

The cosmic ray spectrum

compiled by Simon Swordy

Ultrahigh energy cosmic ray spectrafrom AGASA and HiRes

Image courtesyof AGASA

Image courtesy of HiRes

Arrival directions of ultrahigh energy cosmic raysobserved by AGASA

Image courtesy of AGASA

Top-down models:

● Direct conversion of rest mass energy into cosmic rays through decay or annihilation of superheavy dark matter no need for extremely powerful and efficient acceleration mechanism no correlation with local supernovae or AGNs

● No GZK cutoff length visible in the spectrum due to UHECR generation in our galactic halo

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● Very different anisotropy signatures for Wimpzillium or Wimpzilla decay vs. Wimpzilla annihilation

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The Pierre Auger observatory will tell the good from the bad:

● Correlation with local AGNs: Standard (or non-standard?) bottom-up acceleration.

● No correlation in event distribution with AGNs but with local superstructures: Local gamma ray bursts or bottom-up with strong intergalactic magnetic fields.

● Isotropic distribution without visible correlation with local structure: Z-bursts. ● Uniform increase in event distribution towards galactic center: Wimpzilla or Wimpzillium decay.

● About 1000 pointlike sources with increasing density towards galactic center: Wimpzilla annihilation.

Conclusions

● If there is no GZK cutoff in the spectrum, the anisotropy pattern observed by the Pierre Auger observatory will decide between local gamma ray bursts, Z-bursts, Wimpzilla (or Wimpzillium) decay, and Wimpzilla annihilation.

● Wimpzilla annihilation would appear in dense core regions of dark matter substructure (“Wimpzilla stars”).

● Wimpzilla annihilation still predicts a cutoff between 1012 GeV and 1013 GeV because the unitarity bound indicates that the flux from annihilation of more massive superheavy dark matter particles is negligible.