UHE CR
and
The GZK
Suppression
Ultra High Energy
Cosmic Rays (E > 1019 eV)
Energy Loss Mechanisms for of High Energy Particles
Interactions on the photons of the Microwave Cosmic Background (2.7 oK background)
Energy Loss Mechanisms
Redshift
PhotoProduction Pair Production
Photo Disintegration
Cosmic (2.7 K) Background Radiation
Stellar Light Stellar Light
reprocessed by dust
Average Photon Density in the Universe
Threshold for photoproduction:
Is determined by the threshold for pion production
The Greisen ZatsepinKuzmin “cutoff”
Photoproduction Threshold
cos e = -1
)
)
Energy Loss in one interaction
At threshold:
The pion and the proton are produced at rest in the center of mass frame,
therefore they have the same velocity (and the same Lorentz Factor)
Laboratory (Proton Rest) Frame
General Frame
Ep
2Epmp>= (mp+m)2
Computation of the Absorption Length of a proton in the intergalactic photon Field.
Peak ++ at ~300 MeV
Qualitative analyisis
Log 10[E (eV)]
Size of the visible Universe
GZK on CMB
GZK on all
Effect of Pair Production interactions The threshold is lower
The cross section is higher
The energy loss per interaction is smaller Photoproduction of pions
Pair production
Absorption of High Energy Photons Center of mass cross section
Inverse of absorption length for pair creation
Absorption for extragalactoc sources in Cherenkov Telescopes (TeV) is important
Due to starlight where there is high uncertainties
Propagation of Nuclei
Discrepancy
between the two largest experiments
AGASA
HIRES
Structure in the Spectrum
Density of Cosmic Rays at the Present Epoch
Homogeneous Universe
Injection Rate
at the epoch t
Energy Loss
S0 (E0) * f (t) S0 (E0) * f (z)
Magnetic Deviation
d
Models for the UHECR
BOTTOMUP (Acceleration of particles) Active Galactic Nuclei
Gamma Ray Bursts ...
TOPDOWN
(Decay of Massive Objects) Topological Defects
SuperMassive Particles Wimpzillas
Absence of Cutoff :
Neutrinos
with anomalous large cross sectionNew Particles
Zburst Model
(“Neutrino Carrier”)VIOLATIONS of LORENTZ INVARIANCE
Excess of Nearby Sources
WIMPZILLA's
M = 109 1019 GeVTOP - DOWN Models
High Energy Cosmic Rays as DECAY products of
Massive "Exotic" Objects (Relics of the Early Universe) Topological Defects. SuperMassive Particles
Phenomenology of QUANTUM GRAVITY ?!
Effective speed of photons in quantum space foam
