Transcript Diapositive 1

Ultra-High Energy Neutrino
Fluxes




Neutrinos: A general connection to cosmic rays
Neutrino fluxes in top-down models
The Z-burst
Summary
Günter Sigl
GReCO, Institut d’Astrophysique de Paris, CNRS
http://www.iap.fr/users/sigl/homepage.html
Ultra-High Energy Cosmic Rays and the Connection to
-ray and Neutrino Astrophysics
accelerated protons interact:
   neutrinos 
p  X  o


    rays 
N
=> 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.
A possible acceleration site associated with shocks in hot spots of active galaxies
The total injected electromagnetic energy is constrained by the diffuse -ray
flux measured by EGRET in the MeV – 100 GeV regime
Neutrino flux upper limit
for opaque sources
determined by EGRET
bound
Neutrino flux upper limit
for transparent sources
more strongly constrained
by primary cosmic ray
flux at 1018 – 1019 eV
(Waxman-Bahcall;
Mannheim-ProtheroeRachen)
The cosmogenic neutrino flux produced by pion production by cosmic rays
during propagation can violate the Waxman-Bahcall bound for injection
spectra harder than ~E-1.5 and source luminosities increasing with redshift
WB bound
WB bound
-ray and cosmic ray fluxes must be
consistent with observations.
Example: dependence on injection
spectral index
Kalashev, Kuzmin, Semikoz, Sigl, PRD 66 (2002) 063004
Example: diffuse sources injecting E-1 proton spectrum extending up to
2x1022 eV with (1+z)3 up to redshift z=2. Shown are primary proton flux
together with secondary -ray and neutrino fluxes.

ni
RICE AGASA
2002
GLUE
Amanda, Baikal
2004
AABN
AUGER nt
Anita
2007
2012
km3
Auger
Salsa
EUSO,
OWL
Future neutrino flux sensitivities
Semikoz, Sigl, hep-ph/0309328
Alternative: Top-Down Scenario
Decay of early Universe relics of masses ≥1012 GeV
Benchmark estimate of required decay rate:
1
dN
dN
1  E

X
j(E) 
l
( E ) n
; now assume


4 mean free decay 
dE
dE mX  mX
measured flux
path
rate
decay
spectrum
 1.5
E 2 j ( E )  10Mpc
E

-3
-1 

 n X  13AU yr 
 16


- 2 -1 -1  
 eVcm s sr   l ( E )  10 GeV 
with mX the X - particlemass.
This is not a big number!




1
 mX 
 16

 10 GeV 
Two types of Top-Down scenarios
1.) long-lived massive free particles (“WIMPZILLA” dark matter)


 X  1012 t X 1010 yr
 Fine tuning problem of normalizing ΩX/tX to observed flux.
 predicted -ray domination probably inconsistent with data.
2.) particles released from topological defects
scaling defect  critical  t 2
 Fine tuning problem of normalizing  X  f defect  t 3 to observed flux.
But for cosmic strings (or necklaces) the Higgs-Kibble mechanism yields
string  v 2t 2 , with v  symmetrybreakingscale
normalization 
f v  1013  1014 GeV
 Fine tuning problem only by few orders of magnitude if f  O(1)
 Absorption in radio background can lead to nucleon domination.
Topological defects are unavoidable products of phase transitions
associated with symmetry change
Examples:
1.) Iron:
Bloch wall
T  TCurie : G  SO(3)
T  TCurie : H  SO(2)
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.
=> particle and/or defect creation must occur during reheating after inflation.
Microwave background anisotropies implies scale Hinflation~1013 GeV.
=> natural scale for relics to explain ultra-high energy cosmic rays!
Flux calculations in Top-Down scenarios
a) Assume mode of X-particle decay in GUTs
Example : X  l  q
q
hadronic jets
b) Determine hadronic quark fragmentation
spectrum extrapolated from accelerator
data within QCD:
SUSY-QCD
modified leading log approximation (Dokshitzer et al.)
with and without supersymmetry versus older
approximations (Hill). More detailed calculations by
Kachelriess, Berezinsky, Toldra, Sarkar, Barbot, Drees:
results not drastically different.
Fold in meson decay spectra into
neutrinos and -rays to obtain injection
spectra for nucleons, neutrinos, and
c) fold in injection history and solve the
transport equations for propagation
QCD
The X-particle decay cascade
At the highest energies fluxes in increasing order are: nucleons, -rays,
neutrinos, neutralinos.
A typical
example:
X  q  q , mX  2 1013 GeV , B  10-12 G ,
homogeneous sources with  X  t 3
Semikoz, Sigl, hep-ph/0309328
Future neutrino flux sensitivities and top-down models
Semikoz, Sigl, hep-ph/0309328
New Particles and New Interactions
The Z-burst effect
Motivated by possible correlations with high redshift objects:
Farrar, Biermann
radio-loud quasars
Virmani et al.
radio-loud quasars
Tinyakov, Tkachev
BL-Lac objects
G.S. et al.
radio-loud quasars
~1%
A Z-boson is produced at the
~0.1%
neutrino
resonance energy
~10-5
 eV 
En  4 10 eV 
If this is confirmed, one can only think of 3 possibilities:
 mn 
~10%
res
21
1.) Neutrino primaries
“Visible” decay products
have
-5.
but Standard Model interaction probability inenergies
atmosphere
is
~10
10-40 times smaller.
 resonant (Z0) secondary production on massive relic neutrinos:
needs extreme parameters and huge neutrino
fluxes.
Main
problems of this scenario:
 strong interactions above ~1TeV: only moderate
neutrino
fluxes
required. up
* sources
have
to accelerate
to ~1023eV.
0
2.) New heavy neutral (SUSY) hadron X0: m(X ) > mN increases GZK threshold.
* -rays emitted from the
but basically ruled out by constraints from accelerator experiments.
sources and produced by
3.) New weakly interacting light (keV-MeV) neutral particle
neutrinos during propagation
electromagnetic coupling small enough to avoid GZK
effect;
hadronic coupling
tend
to over-produce
diffuse
large enough to allow normal air showers: very tough
to do. in GeV regime.
background
In all cases: more potential sources, BUT charged primary to be accelerated to
Fargion, Weiler, Yoshida
even higher energies.
The Z-burst mechanism: Relevant neutrino interactions
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 z=3, with E-2 -ray
injection up to 100 TeV of energy fluence equal to neutrinos, mν=0.5eV, B=10-9 G.
The Z-burst mechanism: Exclusive neutrino emitters
Semikoz, Sigl, hep-ph/0309328
Sources with comoving luminosity proportional to (1+z)0 up to z=3, mν=0.33eV,
B=10-9 G.
A compilation of neutrino flux predictions
EGRET bound
MPR bound
WB bound
Cline, Stecker, astro-ph/0003459
Conclusions
1.) 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.
2.) 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.
3.) The highest fluxes above 1019 eV are predicted by top-down models,
the Z-burst, and cosmic ray sources with power increasing with redshift.
4.) 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.
5.) Many new interesting ideas on a modest cost scale for ultra-high energy
neutrino detection are currently under discussion, see experimental
talks.