Diapositive 1

1
Are Ultra-High Energy Cosmic Rays made of nuclei
?
E. Khan
S. Goriely
2
Ultra High energy Cosmic Rays
E1018-21 eV
GZK
Ankle
E-3
Redressed spectrum (x E3)
3
Composition, acceleration propagation

• Open question !
• Extra-galactic particles protons
• nuclei (56Fe, ) ?

COMPOSITION

• Open question !
• Gamma Ray Bursts, Active Galaxy Nucleus ?
• N(E)E-b

ACCELERATION

• Quantitative answers
• Interaction with the 2.7 K Cosmic microwave
  background
• Extra-galactic Magnetic fields

PROPAGATION
Comparison with the measured spectrum on Earth
(AUGER, )
4
Accelerators of the Universe
5
Propagation of UHECR
2.7 K Cosmic Microwave Background
Photodisintegration cross section
g2.1010
GDR
56Fe 1021 eV

Photons density
Lorentz boosted
10
100
0.1
1
10
100
1000

E (MeV)
E (MeV)
Photodisintegration rate (1h-1)
6
Photodisintegration (I)

• Pheno. and microscopic models to predict the GDR
  strength
• Photodisintegration calculated within
  Hauser-Feshbach formalism

55Mn (g,1nx)
51V (g,1nx)
Full network with beta decay rate ( r-process)
7
Photodisintegration (II)
8
Impact on astroparticle propagation
Source 56Fe
E. Khan et al., Astroparticle Phys. 23 (2005) 191
9
Comparison with the data

• Monte-Carlo using a extragalactic source with
  energy distribution E-b
• CMB Protons p photoproduction and e-e-
  pairs production
• Nuclei photodisintegration and
  e-e- production
• Infra Red background

Non-negligible effect with the forthcoming AUGER
data
10
Interpretation of the ankle
Protons only b2.6
Protons Nuclei b2.3
Needs for a galactic CR Ankle is the
galactic/extra-galactic transition
D. Allard et al., in preparation
11
Outlook

• Magnetic field effect on the propagation of UHECR
• Nuclei in the acceleration process
• Comparison with the AUGER data