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
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Introduction
Meson photoproduction
Our model
Flavor composition at source
Hillas plot and parameter space scan
Flavor ratios/flavor composition at detector
Summary
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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
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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
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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!
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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
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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
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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
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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
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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
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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
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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)
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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
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Dependence on a
Hümmer, Maltoni, Winter, Yaguna, 2010
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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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