Constraints on Non-Acceleration Models

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Constraints on Non-Acceleration Models

• A comment on extragalactic magnetic fields
• Top-down models
• Avoiding the GZK cut-off The Z-burst and new
  physics
• Summary

Günter Sigl GReCO, Institut dAstrophysique de
Paris, CNRS et Fédération de Recherche
Astroparticule et Cosmologie, Université Paris
7 http//www2.iap.fr/users/sigl/homepage.html
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Some results on propagation in structured extragal
actic magnetic fields
Scenarios of extragalactic magnetic fields using
large scale structure simulations with magnetic
fields followed passively and normalized to a few
micro Gauss in galaxy clusters.
Filling factors of magnetic fields from the large
scale structure simulation.
Observer immersed in fields of 10-11
Gauss. Sources of density 10-5 Mpc-3 assumed
to follow baryon density.
Sigl, Miniati, Ensslin, Phys.Rev.D 68 (2003)
043002 astro-ph/0309695 astro-ph/0401084.
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The spectrum in the magnetized source scenario
shows a pronounced GZK cut-off (spectrum shown is
for AGASA acceptance).

• Deflection in magnetized structures
• surrounding the sources lead to
• off-sets of arrival direction from
• source direction up to gt10 degrees
• up to 1020 eV in our simulations.
• This is contrast to Dolag et al.,
• JETP Lett. 79 (2004) 719.
• Particle astronomy not
• necessarily possible, especially
• for nuclei !

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Generalization to Heavy Nuclei Structured Fields
and Individual Sources
Spectra and Composition of Fluxes from Single
Discrete Sources considerably depend on Source
Magnetization, especially for Sources within a
few Mpc
Sigl, astro-ph/0405549
Source in the center weakly magnetized observer
modelled as a sphere shown in white at 3.3 Mpc
distance.
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With field blue Without field red Injection
spectrum horizontal line
Iron primaries
Composition for iron primaries
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Ultra-High Energy Cosmic Rays and the Connection
to ?-ray and Neutrino Astrophysics
accelerated protons interact
gt energy fluences in ?-rays and neutrinos
are comparable due to isospin symmetry.
The neutrino spectrum is unmodified, whereas
?-rays pile up below the pair production
threshold on the CMB at a few 1014 eV.
The Universe acts as a calorimeter for the total
injected electromagnetic energy above the pair
threshold. This constrains the neutrino fluxes.
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A possible acceleration site associated with
shocks in hot spots of active galaxies
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The total injected electromagnetic energy is
constrained by the diffuse ?-ray flux measured by
EGRET in the MeV 100 GeV regime
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Top-Down Scenarios
Decay of early Universe relics of masses 1012
GeV
Benchmark estimate of required decay rate
This is not a big number!
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Two types of Top-Down scenarios
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Topological defects are unavoidable products of
phase transitions associated with symmetry change
Examples
1.) Iron
Bloch wall
2.) breaking of gauge symmetries in the early
Universe 1 defect per causal horizon
(Higgs-Kibble mechanism) in Grand Unified
Theories (GUTs) this implies magnetic monopole
production which would overclose the
Universe. This was one of the motivations
that INFLATION was invented. gt particle
and/or defect creation must occur during
reheating after inflation. Microwave
background anisotropies implies scale
Hinflation1013 GeV. gt natural scale for
relics to explain ultra-high energy cosmic rays!
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Flux calculations in Top-Down scenarios
c) fold in injection history and solve the
transport equations for propagation
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The X-particle decay cascade
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At the highest energies fluxes in increasing
order are nucleons, ?-rays, neutrinos,
neutralinos.
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A typical example
Semikoz, Sigl, JCAP 0404 (2004) 003
Reduced estimate of extragalactic
?-ray background limits extragalactic
top-down contribution to highest energy cosmic
rays.
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Future neutrino flux sensitivities and top-down
models
Semikoz, Sigl, JCAP 0404 (2004) 003
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Correlations with extragalactic Sources
Farrar, Biermann radio-loud quasars 1
Virmani et al. radio-loud quasars 0.1
Tinyakov, Tkachev BL-Lac objects 10-4
G.S. et al. radio-loud quasars 10
Surprise Deflection seems dominated by our
Galaxy. Sources in direction of voids?
BL-Lac distances poorly known Are they
consistent with UHECR energies ?
Tinyakov, Tkachev, Astropart.Phys. 18 (2002) 165
Tinyakov, Tkachev, hep-ph/0212223
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Avoiding the GZK Cutoff
If correlated sources turn out to be farther away
than allowed by pion production, one can only
think of 4 possibilities
1.) Neutrino primaries but Standard Model
interaction probability in atmosphere is 10-5.

• resonant (Z0) secondary production on massive
  relic neutrinos
• needs extreme parameters and huge neutrino
  fluxes.

• strong interactions above 1TeV only moderate
  neutrino fluxes required.

2.) New heavy neutral (SUSY) hadron X0 m(X0) gt
mN increases GZK threshold. but basically
ruled out by constraints from accelerator
experiments.
3.) New weakly interacting light (keV-MeV)
neutral particle electromagnetic coupling
small enough to avoid GZK effect hadronic
coupling large enough to allow normal air
showers very tough to do.
In all cases more potential sources, BUT charged
primary to be accelerated to even higher energies.
4.) Lorentz symmetry violations.
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The Z-burst mechanism Relevant neutrino
interactions
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The Z-burst mechanism Sources emitting neutrinos
and ?-rays
Kalashev, Kuzmin, Semikoz, Sigl, PRD 65 (2002)
103003
Sources with constant comoving luminosity density
up to z3, with E-2 ?-ray injection up to 100 TeV
of energy fluence equal to neutrinos, m?0.5eV,
B10-9 G.
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The Z-burst mechanism Exclusive neutrino emitters
Semikoz, Sigl, JCAP 0404 (2004) 003
Sources with comoving luminosity proportional to
(1z)0 up to z3, m?0.33eV, B10-9 G.
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Even for pure neutrino emitters it is now
excluded that the Z-burst contributes
significantly to UHECRs
For homogeneous relic neutrinos GLUEFORTE2003
upper limits on neutrino flux above 1020 eV imply
(see figure).
Cosmological data including WMAP imply
Solar and atmospheric neutrino oscillations
indicate near degeneracy at this scale
For such masses local relic neutrino
overdensities are lt 10 on Mpc scales. This is
considerably smaller than UHECR loss lengths gt
required UHE Neutrino flux not significantly
reduced by clustering.
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Probes of Neutrino Interactions beyond the
Standard Model
Note For primary energies around 1020 eV

• Center of mass energies for collisions with relic
  backgrounds
• 100 MeV 100 GeV ?gt physics well understood

• Center of mass energies for collisions with
  nucleons in the atmosphere
• 100 TeV 1 PeV ?gt probes physics beyond
  reach of accelerators

This increase is not sufficient to explain the
highest energy cosmic rays, but can be
probed with deeply penetrating showers.
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However, the neutrino flux from pion-production
of extra-galactic trans-GZK cosmic rays allows
to put limits on the neutrino-nucleon cross
section
Future experiments will either close the window
down to the Standard Model cross section,
discover higher cross sections, or find sources
beyond the cosmogenic flux. How to disentangle
new sources and new cross sections?
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Solution Compare rates of different types of
neutrino-induced showers
Deeply penetrating (horizontal)
Earth-skimming
upgoing
Figure from Cusumano
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Earth-skimming t-neutrinos
Air-shower probability per t-neutrino at 1020 eV
for 1018 eV (1) and 1019 eV (2) threshold energy
for space-based detection.
Comparison of earth-skimming and horizontal
shower rates allows to measure the
neutrino-nucleon cross section in the 100 TeV
range.
Kusenko, Weiler, PRL 88 (2002) 121104
Telescope Array
HiRes (mono)
Effective aperture for t-leptons. Tau-flux
8.5x10-4 x t-neutrino flux independent of s?N
for ground-based detectors.
Flys Eye
Feng et al., PRL 88 (2002) 161102
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Sensitivities of LHC and the Pierre Auger project
to microscopic black hole production in
neutrino-nucleon scattering
MD fundamental gravity scale Mbhmin minimal
black hole mass
LHC much more sensitive than Auger, but Auger
could scoop LHC
Ringwald, Tu, PLB 525 (2002) 135
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Sensitivities of future neutrino telescopes
to microscopic black hole production in
neutrino-nucleon scattering
Through-going events Rate Area
Contained events Rate Volume
Ringwald, Kowalski, Tu, PLB 529 (2002) 1
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Conclusions1
1.) Deflection in extragalactic magnetic fields
is currently hard to quantify. Sources are
likely immersed in magnetic fields of fractions
of a microGauss. Such fields can strongly
modify spectra and composition even if
cosmic rays arrive within a few degrees from the
source direction. Extragalactic magnetic
fields will therefore play a prominent role
in interpretation of future data.
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Conclusions2
5.) Pion-production establishes a very important
link between the physics of high energy
cosmic rays on the one hand, and ?-ray and
neutrino astrophysics on the other hand. All
three of these fields should be considered
together.
6.) There are many potential high energy neutrino
sources including speculative ones. But the
only guaranteed ones are due to pion
production of primary cosmic rays known to exist
Galactic neutrinos from hadronic
interactions up to 1016 eV and cosmogenic
neutrinos around 1019 eV from photopion
production. Flux uncertainties stem from
uncertainties in cosmic ray source distribution
and evolution.
7.) The highest neutrino fluxes above 1019 eV are
predicted by top-down models, the Z-burst,
and cosmic ray sources with power increasing
with redshift. However, extragalactic
top-down models and the Z-burst are unlikely
to considerably contribute to ultra-high energy
cosmic rays.
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Conclusions3
8.) At energies above 1018 eV, the center-of
mass energies are above a TeV and thus
beyond the reach of accelerator experiments.
Especially in the neutrino sector, where
Standard Model cross sections are small,
this probes potentially new physics beyond the
electroweak scale.
9.) The coming 3-5 years promise an about
100-fold increase of ultra-high energy
cosmic ray data due to experiments that are
either under construction or in the proposal
stage. This will constrain primary cosmic
ray flux models.