UHECR photons

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UHECR photons

• Dmitry Semikoz
• APC (Paris)

G.Gelmini (UCLA), O.Kalashev (INR, Moscow)
and I.Tkachev (CERN), 2005
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INTRODUCTION
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AUGER experiment combining ground array with
fluorescence such will resolve most of this
issues in 1-2 years from now.
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Statistics is not a problem anymore! Expect
445000 events/year 1017 - 1018 eV
125000 events/year 1018 - 1919 eV

5000
events/year gt 1019 eV
350 events/year gt 4 x 1019 eV
10 of these are hybrid
(scaling from present yields)
compare to AGASA 72 events with
E gt 4 x 1019 eV in 10 years

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Propagation of protons and photons
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The Greisen-Zatsepin-Kuzmin (GZK) effect
Nucleons can produce pions on the cosmic
microwave background
?
nucleon

• sources must be in cosmological backyard
• within 50-100 Mpc from Earth
• (compare to the Universe size 5000 Mpc)

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Proton deflections in extragalactic magnetic
field within 105 Mpc from our Galaxy
Extragalactic magnetic field in R50 Mpc large
scale structure box
Dolag et al, 2003
Sigl et al, 2002-2003
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Galactic Magnetic field

• In average cosmic ray with energy 41019 eV will
  be deflected on 5 degrees and deflection
  decreases as 1/E at higher energies.
• Models are not very good to follow individual CR
  at 1019 eV but at higher energies E gt 1020 eV
  deflection is only 1-2 degrees.

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• From G. Medina Tanco et al, astro-ph/9707041
• Protons with energy 41019 eV deflection in
  galactic magnetic field.

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• From G. Medina Tanco et al, astro-ph/9707041
• Iron with energy 2.51020 eV deflection in
  galactic magnetic field.

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HiRes stereo data Egt 1019 eV
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AGASA data Egt 1019 eV
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Pion production
n
p
Conclusion proton, photon and neutrino fluxes
are connected in well-defined way. If we know one
of them we can predict other ones
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Radio backgrounds
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Photon energy losses
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Dependence on parameters
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Minimal distance to sources.
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Maximal proton energy.
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Average extragalactic magnetic field.
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Radio background.
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Fit to AGASA and HiRes data
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Fit to AGASA data.
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Fit to HiRes data
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Exotic models?
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Z-burst mechanism

• Resonance energy E 4 1021 (1
  eV/mn) eV
• Works only if
• mn lt 1 eV
• Mean free path of neutrino is
  L 150 000 Mpc gtgt Luniv

T.Weiler, 1982 Fargion, Weiler, 1997
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Cross sections for neutrino interactions
withrelict background n and g
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EGRET diffuse gamma-ray flux
The high energy gamma ray detector on the Compton
Gamma Ray Observatory (20 MeV - 20 GeV)
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Secondary gamma-rays obey EGRET limit
O.Kalashev, V.Kuzmin, D.S. and G.Sigl,
hep-ph/0112351
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Sources of both g and n
O.Kalashev, V.Kuzmin, D.S. and G.Sigl,
hep-ph/0112351
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FORTE and WMAP practically exclude Z-burst model
D.S. and G.Sigl, hep-ph/0309328
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But only to explain AGASA
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Top-down models

• Topological defects were produced in early
  Universe.
• Today they decay through GUT-scale particles with
  masses 1013-15 GeV
• UHECR are protons and photons from their decay.

V.Berezinsky and collaborators 1980-90th, See
review by G.Sigl
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Top-down models disfavored by EGRET data
D.S. and G.Sigl, hep-ph/0309328
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Top-down models still alive with lower flux
normalization
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Super-heavy dark matter model

• Particles with mass 1012-14 GeV created in
  early Universe. Today they decay and produce
  UHECR.
• Main signature UHECR are photons. Arrival
  directions follow DM profile.

V.Berezinsky, M.Kachelriess and
A.Vilenkin V.Kuzmin and V.Rubakov , 1997
Annihilations Disfavored by SUGAR data. Decay
OK. M.Kachelriess and D.S., 2003 Kim and
P.Tinyakov, 2003
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SHDM photons protons
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Sensitivity to fraction of photons AGASA case
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Sensitivity to fraction of photons HiRes case
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Conclusion UHECR photons

• UHECR with energies below GZK cutoff Elt1020eV
  most probably are protons from astrophysical
  sources. Those protons would produce GZK
  neutrinos GZK photons.
• GZK photons are 0.01 50 fraction of UHECR
  depending from energy, proton spectrum,
  distribution of sources, extra-galactic magnetic
  fields, radio backgrounds.
• They can be used to identify UHECR sources.
• UHECR with energies Egt1020eV require new physics
  or very extreme astrophysics. Absence of near
  sources in direction of highest energy cosmic
  rays makes possibility to have new physics
  practically unavoidable.
• Top-down models are difavorate by existing data.
  Z-burst model is excluded by neutrino and CMB
  experiments. Measurement of photon flux or limit
  will critically test all those models in near
  future!

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