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Neutrino physics Lecture 3: Neutrino astrophysics. Herbstschule für Hochenergiephysik Maria Laach 04-14.09.2012 Walter Winter Universität Würzburg. TexPoint fonts used in EMF: A A A A A A A A. Contents. Introduction: Neutrinos and the sources of the UHECR Simulation of sources - PowerPoint PPT Presentation
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Neutrino physicsLecture 3: Neutrino astrophysics
Herbstschule für Hochenergiephysik
Maria Laach04-14.09.2012
Walter Winter
Universität Würzburg
2
Contents
Introduction:Neutrinos and the sources of the UHECR
Simulation of sources Example:
Neutrinos from Gamma-Ray Bursts (GRBs) Neutrino oscillations in the Sun (if time) Summary and conclusions
3
Nobel prize 2002
"for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos“
Raymond Davis Jr detected over 30 years 2.000 neutrinos from the Sun Evidence for nuclear fusion in the Sun‘s interior!
Masatoshi Koshiba detectedon 23.02.1987 twelve of the 10.000.000.000.000.000 (1016) neutrinos, which passed his detector, from an extragalactic supernovaexplosion. Birth of neutrino astronomy
5
Neutrinos as cosmic messengers
Physics of astrophysical neutrino sources = physics of
cosmic ray sources
6
galactic extragalactic
Evidence for proton acceleration,
hints for neutrino production Observation of
cosmic rays: need to accelerate protons/hadrons somewhere
The same sources should produce neutrinos: in the source (pp,
p interactions) Proton (E > 6 1010
GeV) on CMB GZK cutoff + cosmogenic neutrino flux
In the source:
Ep,max up to 1012 GeV?
GZKcutoff?
UHECR(heavy?)
7
Delta resonance approximation:
+/0 determines ratio between neutrinos and high-E gamma-rays
High energetic gamma-rays;typically cascade down to lower E
If neutrons can escape:Source of cosmic rays
Neutrinos produced inratio (e::)=(1:2:0)
Cosmic messengers
Cosmogenic neutrinos
Cosmic ray source(illustrative proton-only scenario, p interactions)
8
The two paradigms for extragalactic sources:
AGNs and GRBs Active Galactic Nuclei (AGN blazars)
Relativistic jets ejected from central engine (black hole?) Continuous emission, with time-variability
Gamma-Ray Bursts (GRBs): transients Relativistically expanding fireball/jet Neutrino production e. g. in prompt phase
(Waxman, Bahcall, 1997)
Nature 484 (2012) 351
10
Example: IceCube at South PoleDetector material: ~ 1 km3 antarctic ice
Completed 2010/11 (86 strings) Recent data releases, based on
parts of the detector: Point sources IC-40 [IC-22]
arXiv:1012.2137, arXiv:1104.0075 GRB stacking analysis IC-40+IC-59
Nature 484 (2012) 351 Cascade detection IC-22
arXiv:1101.1692 Have not seen anything (yet)
What does that mean? Are the models too simple? Which parts of the parameter space
does IceCube actually test? Particle physics reason?
Neutrino detection:Neutrino telescopes
http://icecube.wisc.edu/
http://antares.in2p3.fr/
12
Different interaction processes
(Photon energy in nucleon rest frame)
(Mücke, Rachen, Engel, Protheroe, Stanev, 2008; SOPHIA;
Ph.D. thesis Rachen)
Multi-pionproduction
Differentcharacteristics(energy lossof protons;
energy dep.cross sec.)
res.
r
Direct(t-channel)production
Resonances
13
(1232)-resonance approximation:
Limitations:- No - production; cannot predict / - ratio (Glashow resonance!)- High energy processes affect spectral shape (X-sec. dependence!)- Low energy processes (t-channel) enhance charged pion production
Solutions: SOPHIA: most accurate description of physics
Mücke, Rachen, Engel, Protheroe, Stanev, 2000Limitations: Monte Carlo, slow; helicity dep. muon decays!
Parameterizations based on SOPHIA Kelner, Aharonian, 2008
Fast, but no intermediate muons, pions (cooling cannot be included) Hümmer, Rüger, Spanier, Winter, ApJ 721 (2010) 630
Fast (~1000 x SOPHIA), including secondaries and accurate / - ratios
Engine of the NeuCosmA („Neutrinos from Cosmic Accelerators“) software+ time-dependent codes
Source simulation: p(particle physics)
from:Hümmer, Rüger, Spanier, Winter,
ApJ 721 (2010) 630
14
Opticallythin
to neutrons
“Minimal“ (top down) model
from:
Baerwald, Hümmer, Winter, Astropart. Phys. 35 (2012) 508
Dashed arrows: include cooling and escape Q(E) [GeV-1 cm-3 s-1] per time frame
N(E) [GeV-1 cm-3] steady spectrum
Input: B‘
15
Kinetic equations Energy losses in continuous limit:
b(E)=-E t-1loss
Q(E,t) [GeV-1 cm-3 s-1] injection per time frameN(E,t) [GeV-1 cm-3] particle spectrum including spectral effects
For neutrinos: dN/dt = 0 (steady state)
Simple case: No energy losses b=0
Injection EscapeEnergy losses
often: tesc ~ R
16
Typical source models
Protons typically injected with power law (Fermi shock acceleration!)
Target photon field typically: Put in by hand (e.g. obs. spectrum: GRBs) Thermal target photon field From synchrotron radiation of co-accelerated
electrons/positrons (AGN-like) From a more complicated combination of
radiation processes
?
17
Peculiarity for neutrinos:
Secondary cooling
Baerwald, Hümmer, Winter, Astropart. Phys. 35 (2012) 508; also: Kashti, Waxman, 2005; Lipari et al, 2007
Decay/cooling: charged , , K Secondary spectra (, , K) loss-
steepend above critical energy
E‘c depends on particle physics only (m, 0), and B‘
Leads to characteristic flavor composition and shape
Very robust prediction for sources? [e.g. any additional radiation processes mainly affecting the primaries will not affect the flavor composition]
The only way to directly measure B‘?
E‘cE‘c E‘c
Pile-up effect Flavor ratio!
Spectralsplit
Example: GRB
Adiabatic
19
The “magic“ triangle
CR
Satellite experiments(burst-by-burst)
?(energy budget, CR “leakage“, quasi-diffuse extrapolation, …)
Model-dependent prediction
GRB stacking
(next slides)
CR experiments (diffuse)Neutrino telescopes
(burst-by-burst or diffuse)
Robust connectionif CRs only escape as neutrons produced in
p interactions
Partly common fudgefactors: how many GRBsare actually observable?
Baryonic loading? …
20
Idea: Use multi-messenger approach
Predict neutrino flux fromobserved photon fluxesevent by event
GRB stacking
(Source: NASA)
GRB gamma-ray observations(e.g. Fermi GBM, Swift, etc)
(Source: IceCube)
Neutrino observations
(e.g. IceCube, …)Coincidence!
(Example: IceCube, arXiv:1101.1448)
Observed:broken power law(Band function)
E-2 injection
21
Gamma-ray burst fireball model:IC-40 data meet generic bounds
Nature 484 (2012) 351Generic flux based on the assumption that GRBs are the sources of (highest
energetic) cosmic rays (Waxman, Bahcall, 1999; Waxman, 2003; spec. bursts:Guetta et al, 2003)
IC-40+59 stacking limit
Does IceCube really rule out the paradigm that GRBs are the sources of the ultra-high energy cosmic rays?
22
IceCube method …normalization
Connection -rays – neutrinos
Optical thickness to p interactions:
[in principle, p ~ 1/(n ); need estimates for n, which contains the size of the acceleration region]
(Description in arXiv:0907.2227; see also Guetta et al, astro-ph/0302524; Waxman, Bahcall, astro-ph/9701231)
Energy in electrons/photons
Fraction of p energyconverted into pions f
Energy in neutrinos
Energy in protons½ (charged pions) x
¼ (energy per lepton)
23
IceCube method … spectral shape
Example:
First break frombreak in photon spectrum
(here: E-1 E-2 in photons)
Second break frompion cooling (simplified)
3-
3-
3-+2
24
Revision of neutrino flux predictions
Analytical recomputationof IceCube method (CFB):
cf: corrections to pion production efficiency
cS: secondary cooling and energy-dependenceof proton mean free path(see also Li, 2012, PRD)
Comparison with numerics:
WB -approx: simplified p
Full p: all interactions, K, …[adiabatic cooling included]
(Baerwald, Hümmer, Winter, Phys. Rev. D83 (2011) 067303;Astropart. Phys. 35 (2012) 508; PRL, arXiv:1112.1076)
~ 1000 ~ 200
25
Consequences for IC-40 analysis
Differential limit illustrates interplay with detector response
Shape of prediction used to compute sensitivity limit
Peaks at higher energies
(Hümmer, Baerwald, Winter, Phys. Rev. Lett. 108 (2012) 231101)
IceCube @ 2012:observed two events
~ PeV energies from GRBs?
26
Systematics in aggregated fluxes
z ~ 1 “typical“ redshift of a GRBNeutrino flux
overestimated if z ~ 2 assumed(dep. on method)
Peak contribution in a region of low statisticsSystematical error on
quasi-diffuse flux (90% CL) ~ 50% for 117 bursts, [as used in IC-40 analysis]
Distribution of GRBsfollowing star form. rate
Weight function:contr. to total flux
10000 bursts
(Baerwald, Hümmer, Winter, Astropart. Phys. 35 (2012) 508)
(strongevolution
case)
27
Quasi-diffuse prediction Numerical fireball
model cannot be ruled out with IC40+59 for same parameters, bursts, assumptions
Peak at higher energy![optimization of future exps?]
“Astrophysical uncertainties“:tv: 0.001s … 0.1s: 200 …500: 1.8 … 2.2e/B: 0.1 … 10
(Hümmer, Baerwald, Winter, Phys. Rev. Lett. 108 (2012) 231101)
28
Comparison of methods/models
from Fig. 3 of Nature 484 (2012) 351; uncertainties from Guetta, Spada, Waxman, Astrophys. J. 559 (2001) 2001:target photons from synchrotron emission/inverse Compton
from Fig. 3 of Hümmer et al, arXiv:1112.1076, PRL;origin of target photons not specified
completely model-independent (large collision radii allowed): He et al, Astrophys. J. 752 (2012) 29
(P. Baerwald)
29
Particle physics depletion/reason:
Neutrino decay?
Reliable conclusions from astrophysical neutrino flux bounds require cascade (e) measurements!
(from: Baerwald, Bustamante, Winter, 2012)
Decay hypothesis: 2 and 3 decay with lifetimes compatible with SN 1987A bound
30
Neutrinos-cosmic rays If charged and n produced together:
GRB not exclusive sources of UHECR? CR leakage?
CR
(Ahlers, Gonzalez-Garcia, Halzen, Astropart. Phys. 35 (2011) 87)
Fit to UHECR spectrum
Consequences for (diffuse) neutrino fluxes
32
Constant vs. varying matter density
For constant matter density:
H is the Hamiltonian in constant density
For varying matter density: time-dep. Schrödinger equation (H explicitely time-dependent!)
Transition amplitudes; x: mixture and
33
Adiabatic limit
Use transformation:
… and insert into time-dep. SE […]
Adiabatic limit:
Matter density varies slowly enough such that differential equation system decouples!
Amplitudes of mass eigenstates in matter
34
Propagation in the Sun Neutrino production as e (fusion) at high ne
Neutrino propagates as mass eigenstate in matter (DE decoupled); : phase factor from propagation
In the Sun: ne(r) ~ ne(0) exp(-r/r0) (r0 ~ Rsun/10); therefore density drops to zero!
Detection as electron flavor:Disappearance
of solarneutrinos!
35
Solar oscillations In practice: A >> 1 only for E >> 1 MeV For E << 1 MeV: vacuum oscillations
Borexino, PRL 108 (2012) 051302
Averaged vacuumoscillations:
Pee=1-0.5 sin22Adiabatic
MSW limit:Pee=sin2~ 0.3
36
Some additional comments… on stellar environments
How do we know that the solarneutrino flux is correct?SNO neutral current measurement
Why are supernova neutrinos so different?Neutrino densities so high that neutrino-self
interactionsLeads to funny „collective“ effects, as gyroscope
B. Dasgupta
37
Summary
Are GRBs the sources of the UHECR? Gamma-rays versus neutrinos
Revised model calculations release pressure on fireball model calculations
Baryonic loading will be finally constrained (at least in “conventional“ internal shock models)
Neutrinos versus cosmic rays Cosmic ray escape as neutrons under tension
Cosmic ray leakage? Not the only sources of the UHECR?
Solar neutrinos: MSW effect credible thanks to Borexino
CR