Neutrino physicsLecture 3: Neutrino astrophysics

Herbstschule für Hochenergiephysik

Maria Laach04-14.09.2012

Walter Winter

Universität Würzburg

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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

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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

Neutrinos and the sources of the UHECR

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Neutrinos as cosmic messengers

Physics of astrophysical neutrino sources = physics of

cosmic ray sources

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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?)

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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)

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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

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Neutrino emission in GRBs

(Source: SWIFT)

Prompt phasecollision of

shocks: dominant s?

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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/

Simulation of sources

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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

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(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

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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‘

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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

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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

?

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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

Example:

Neutrinos from GRBs

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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? …

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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

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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?

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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)

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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

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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

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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?

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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)

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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)

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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)

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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

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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

Neutrino oscillations in the Sun

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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

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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

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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!

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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

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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

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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