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Transcript Physik am Samstag - Istituto Nazionale di Fisica Nucleare
Neutrino flavor ratios from cosmic
accelerators on the Hillas plot
NOW 2010
September 4-11, 2010
Conca Specchiulla (Otranto, Lecce,
Italy)
Walter Winter
Universität Würzburg
Contents
Introduction
Meson photoproduction
Our model
Flavor composition at source
Hillas plot and parameter space scan
Flavor ratios/flavor composition at detector
Summary
2
From Fermi shock acceleration to
n production
Example: Active galaxy
(Halzen, Venice 2009)
3
Meson photoproduction
Often used: D(1232)resonance approximation
Limitations:
No p- production; cannot predict p+/ p- ratio
High energy processes affect spectral shape
Low energy processes (t-channel) enhance charged pion production
Charged pion production underestimated compared to p0 production by
factor of > 2.4 (independent of input spectra!)
Solutions:
SOPHIA: most accurate description of physics
Mücke, Rachen, Engel, Protheroe, Stanev, 2000
Limitations: Often slow, difficult to handle; helicity dep. muon decays!
from:
Parameterizations based on SOPHIA
Hümmer, Rüger,
Kelner, Aharonian, 2008
Spanier, Winter,
Fast, but no intermediate muons, pions (cooling cannot be included)
ApJ 721 (2010) 630
Hümmer, Rüger, Spanier, Winter, 2010
Fast (~3000 x SOPHIA), including secondaries and accurate p+/ p- ratios;
T=10
eV
also individual contributions of different
processes
(allows for comparison
with D-resonance!)
Engine of the NeuCosmA („Neutrinos from Cosmic Accelerators“) software
4
NeuCosmA key ingredients
What it can do so far:
Photohadronics based on SOPHIA
(Hümmer, Rüger, Spanier, Winter, 2010)
Weak decays incl. helicity
dependence of muons
(Lipari, Lusignoli, Meloni, 2007)
Cooling and escape
Kinematics of
weak decays:
muon helicity!
Potential applications:
Parameter space studies
Flavor ratio predictions
Time-dependent AGN simulations
etc. (photohadronics)
Monte Carlo sampling of diffuse
fluxes
Stacking analysis with measured
target photon fields
Fits (need accurate description!)
…
from: Hümmer, Rüger, Spanier,
Winter, ApJ 721 (2010) 630
5
A self-consistent approach
Target photon field typically:
Put in by hand (e.g. GRB stacking analysis)
?
Thermal target photon field
From synchrotron radiation of co-accelerated
electrons/positrons
Requires few model parameters
(synchtrotron cooling dominated only overall normalization factor)
Purpose: describe wide parameter ranges with a
simple model; no empirical relationships needed!
6
Model summary
Dashed arrows: include cooling and escape
Dashed arrow: Steady state
Balances injection with energy losses and escape
Optically
thin
Injection
to neutrons
Energy losses
Escape
Q(E) [GeV-1 cm-3 s-1] per time frame
N(E) [GeV-1 cm-3] steady spectrum
Hümmer, Maltoni,
Winter, Yaguna,
Astropart. Phys.
(to appear), 2010
7
A typical example
a=2, B=103 G, R=109.6 km
Maximum energy: e, p
Cooling: charged m, p, K
Hümmer, Maltoni, Winter, Yaguna, Astropart. Phys. (to appear), 2010
8
A typical example (2)
a=2, B=103 G, R=109.6 km
m cooling
break
Pile-up
effect
Synchrotron
cooling
p cooling
break
Pile-up effect
Flavor ratio!
Spectral
split
Slope:
a/2
Hümmer, Maltoni, Winter, Yaguna, Astropart. Phys. (to appear), 2010
9
The Hillas plot
Hillas (necessary)
condition for highest
energetic cosmic rays
(h: acc. eff.)
Protons, 1020 eV, h=1:
We interpret R and B as
parameters in source
frame
High source Lorentz factors G
relax this condition!
Hillas 1984; version adopted from M. Boratav
10
Flavor composition at the source
(Idealized – energy independent)
Astrophysical neutrino sources produce
certain flavor ratios of neutrinos (ne:nm:nt):
Pion beam source (1:2:0)
Standard in generic models
Muon damped source (0:1:0)
at high E: Muons loose energy
before they decay
Muon beam source (1:1:0)
Heavy flavor decays or muons pile
up at lower energies
Neutron beam source (1:0:0)
Neutrino production by
photo-dissociation
of heavy nuclei or neutron decays
At the source: Use ratio ne/nm (nus+antinus added)
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However: flavor composition is energy
dependent!
Muon beam
muon damped
Pion beam
Energy
window
with large
flux for
classification
Typically
n beam
for low E
(from pg)
Undefined
(mixed source)
Pion beam
muon damped
Behavior
for small
fluxes
undefined
(from Hümmer, Maltoni, Winter, Yaguna, 2010;
see also: Kashti, Waxman, 2005; Kachelriess, Tomas, 2006, 2007; Lipari et al, 2007)
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Parameter space scan
All relevant regions
recovered
GRBs: in our model
a=4 to reproduce
pion spectra; pion
beam muon
damped
a=2
(confirms Kashti, Waxman,
2005)
Some dependence
on injection index
Hümmer, Maltoni, Winter, Yaguna, Astropart. Phys. (to appear), 2010
13
Flavor ratios at detector
Neutrino propagation in SM:
At the detector: define observables which
take into account the unknown flux normalization
take into account the detector properties
Example: Muon tracks to showers
Do not need to differentiate between
electromagnetic and hadronic showers!
Flavor ratios have recently been discussed for many
particle physics applications
(for flavor mixing and decay: Beacom et al 2002+2003; Farzan and Smirnov, 2002; Kachelriess,
Serpico, 2005; Bhattacharjee, Gupta, 2005; Serpico, 2006; Winter, 2006; Majumar and Ghosal,
2006; Rodejohann, 2006; Xing, 2006; Meloni, Ohlsson, 2006; Blum, Nir, Waxman, 2007; Majumar,
2007; Awasthi, Choubey, 2007; Hwang, Siyeon,2007; Lipari, Lusignoli, Meloni, 2007; Pakvasa,
Rodejohann, Weiler, 2007; Quigg, 2008; Maltoni, Winter, 2008; Donini, Yasuda, 2008; Choubey,
Niro, Rodejohann, 2008; Xing, Zhou, 2008; Choubey, Rodejohann, 2009; Bustamante, Gago,
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Pena-Garay, 2010, …)
Effect of flavor mixing
Basic dependence
recovered after
flavor mixing
However: mixing
parameter
knowledge ~ 2015
required
Hümmer, Maltoni, Winter, Yaguna,
Astropart. Phys. (to appear), 2010
15
In short: Glashow resonance
Glashow resonance at 6.3 PeV can identify
Can be used to identify pg neutrino production
in optically thin (n) sources
Depends on a number of conditions, such as G
Hümmer, Maltoni,
Winter, Yaguna,
Astropart. Phys. (to
appear), 2010
16
Summary
Flavor ratios should be interpreted as energy-dependent
quantities
Flavor ratios may be interesting for astrophysics: e.g.
information on magnetic field strength
The flavor composition of a point source can be predicted
in our model if the astrophysical parameters are known
Our model is based on the simplest set of self-consistent
assumptions without any empirical relationships
Parameter space scans, such as this one, are only
possible with an efficient code for photohadronic
interactions, weak decays, etc.: NeuCosmA
For fits, stacking, etc. one describes real data, and therefore one
needs accurate neutrino flux predictions!
References:
Hümmer, Rüger, Spanier, Winter, arXiv:1002.1310 (astro-ph.HE), ApJ 721 (2010) 630
Hümmer, Maltoni, Winter, Yaguna, arXiv:1007.0006 (astro-ph.HE),
Astropart. Phys. (to appear)
17
Outlook: Magnetic field and flavor
effects in GRB fluxes
Recipe:
1. Reproduce WB flux
with D-resonance
including magnetic
field effects explicitely
2. Switch on additional n
production modes,
magnetic field effects,
flavor effects (m,
flavor mixing)
Normalization
increased by order of
magnitude, shape
totally different!
Implications???
Baerwald, Hümmer, Winter, to
appear; see also: Murase, Nagataki,
2005; Kashti, Waxman, 2005; Lipari,
Lusignoli, Meloni, 2007
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BACKUP
Neutrino fluxes – flavor ratios
Hümmer, Maltoni, Winter, Yaguna, 2010
20
Dependence on a
Hümmer, Maltoni, Winter, Yaguna, 2010
21
Neutrino propagation
Key assumption: Incoherent propagation of
neutrinos
(see Pakvasa review,
arXiv:0803.1701,
and references therein)
Flavor mixing:
Example: For q13 =0, q12=p/6, q23=p/4:
NB: No CPV in flavor mixing only!
But: In principle, sensitive to Re exp(-i d) ~ cosd
Take into account Earth attenuation!
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Different event types
Muon tracks from nm
Effective area dominated!
(interactions do not have do be
within detector)
Relatively low threshold
Electromagnetic showers
(cascades) from ne
Effective volume dominated!
nt: Effective volume dominated
Low energies (< few PeV) typically
hadronic shower (nt track not
separable)
Higher Energies:
nt track separable
Double-bang events
Lollipop events
Glashow resonace for electron
antineutrinos at 6.3 PeV
t
nt
nt
e
ne
m
nm
(Learned, Pakvasa, 1995; Beacom et
al, hep-ph/0307025; many others)
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Flavor ratios (particle physics)
The idea: define observables which
take into account the unknown flux normalization
take into account the detector properties
Three observables with different technical issues:
Muon tracks to showers
(neutrinos and antineutrinos added)
Do not need to differentiate between
electromagnetic and hadronic showers!
Electromagnetic to hadronic showers
(neutrinos and antineutrinos added)
Need to distinguish types of showers by muon
content or identify double bang/lollipop events!
Glashow resonance to muon tracks
(neutrinos and antineutrinos added in denominator
only). Only at particular energy!
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