Neutrino phenomenologyLecture 3: Aspects of neutrino astrophysics

Winter school Schladming 2010“Masses and constants”02.03.2010

Walter WinterUniversität Würzburg

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Contents (overall)

Lecture 1:Testing neutrino mass and flavor mixing

Lecture 2:Precision physics with neutrinos

Lecture 3:Aspects of neutrino astrophysics

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Contents (lecture 3)

Introduction/repetition Solar oscillations (varying matter density) Neutrinos from cosmic accelerators … and the

determination of „other“ neutrino properties: The sources The fluxes Flavor composition and propagation Detection Flavor ratios Compementarity to Long baseline searches? Test of „other“ new physics properties

Example: Neutrino lifetime Summary

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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

Repetition

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Standard Solar Model

Neutrinos are produced as electron neutrinos at the source, in the deep interior of the Sun

Neutrinos propagate to the surface of the Sun and leave it

The neutrinos loose coherence on the way to the Earth, i.e., propagate as mass eigenstates

pp-fusion chain Neutrino spectra

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Matter effects (MSW) Ordinary matter:

electrons, but no , Coherent forward

scattering in matter: Net effect on electron flavor

Matter effects proportional to electron density ne and baseline

Hamiltonian in matter (matrix form, two flavors):

Y: electron fraction ~ 0.5

(electrons per nucleon)

(Wolfenstein, 1978; Mikheyev, Smirnov, 1985)

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Parameter mapping In vacuum:

In matter:

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

Galbiati, Neutrino 2008

Averaged vacuumoscillations:

Pee=1-0.5 sin22

AdiabaticMSW limit:

Pee=sin2~ 0.3Standardprediction

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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

Neutrinos from cosmic accelerators

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galactic extragalactic

Neutrino fluxes

Cosmic rays of high energies:Extragalactic origin!?

If protons accelerated, the same sources should produce neutrinos

(Source: F. Halzen, Venice 2009)

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Different messengers

Shock accelerated protons lead to p, , fluxes p: Cosmic rays:

affected by magnetic fields

(Te

resa

Mo

nta

ruli, N

OW

2008)

: Photons: easily absorbed/scattered : Neutrinos: direct path

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Different source types

Model-independent constraint:Emax < Z e B R(Lamor-Radius < size of source)Particles confined to

within accelerator!

Interesting source candiates: GRBs AGNs …

(Hillas, 1984; version from M. Boratav)

(?)

The sources

Generic cosmic accelerator

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From Fermi shock acceleration to production

Example: Active galaxy(Halzen, Venice 2009)

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Synchroton radiation

Where do the photons come from?Typically two possibilities: Thermal photon field (temperature!) Synchroton radiation from

electrons/positrons (also accelerated)

?

(example from Reynoso, Romero, arXiv:0811.1383)

B

~ (1-s)/2+1determined by spectral index s of injection

Determined by particle‘s

minimum energy Emin=m c2

(~ (Emin)2 B )

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Pion photoproduction

(Photon energy in nucleon rest frame)

(Mücke, Rachen, Engel, Protheroe, Stanev, 2008; SOPHIA)

Resonant production,

direct production

Multi-pionproduction

Differentcharacteristics(energy lossof protons)

Powerlaw injection

spectrumfrom Fermishock acc.

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Pion photoproduction (2) Often used: (1232)-resonance approximation In practice: this

resonance hardly ever dominates for charged pions. Example: GRB

The neutrino fluxes from the -approximation are underestimated by a factor > 2.4 (if norm. to photons from 0)

(Hümmer, Rüger, Spanier, Winter,

2010)

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Neutrino production

Described by kinematics of weak decays(see e.g. Lipari, Lusignoli, Meloni, 2007)

Complication:Pions and muons loose energy through synchroton radiation for higher E before they decay – aka „muon damping“

(example from Reynoso, Romero,

arXiv:0811.1383)

Dashed:no lossesSolid:with losses

The fluxes

Single source versus diffuse flux versusstacking

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Neutrinos from a point source

Example: GRBs observed by BATSE

Applies to other sources in atmosphericBG-free regime as well …

Conclusion: Most likely (?) no significant statistics with only one source!

(Guetta et al, astro-ph/0302524)

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Diffuse flux (e.g. AGNs)

Advantage: optimal statistics (signal)

Disadvantage: Backgrounds(e.g. atmospheric,cosmogenic)

(Becker, arXiv:0710.1557)

Single sourcespectrum

Sourcedistributionin redshift,luminosity

Comovingvolume

Decreasewith

luminositydistance

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Stacking analysis Idea: Use multi-messenger approach

Good signal over background ratio, moderate statistics

Limitations: Redshift only measured for

a small sample (BATSE) Use empirical relationships

A few bursts dominate the rates Selection effects?

(Source: NASA)

GRB gamma ray observations(e.g. BATSE, Fermi-GLAST, …)

(Source: IceCube)

Neutrino observations

(e.g. AMANDA,IceCube, …)

Coincidence!

(Becker et al, astro-ph/0511785;from BATSE satellite data)

Extrapolateneutrino spectrum

event by event

Flavor composition and propagation

Neutrino flavor mixing

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Astrophysical neutrino sources producecertain flavor ratios of neutrinos (e::):

Pion beam source (1:2:0)Standard in generic models

Muon damped source (0:1:0)Muons loose energy before they decay

Neutron beam source (1:0:0)Neutrino production by photo-dissociationof heavy nulcei

NB: Do not distinguish between neutrinos and antineutrinos

Flavor composition at the source(Idealized)

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Pion beam source (more realistic)

(Hümmer, Rüger, Spanier, Winter, 2010;

see also Lipari, Lusignoli, Meloni, 2007)

Nominal line 1:2

Neutrondecays

Kinematics ofweak decays: muon helicity!

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Flavor composition at the source(More realistic)

Flavor composition changes as a function of energy

Pion beam and muon damped sources are the same sources in different energy ranges!

Use energy cuts?

(from Kashti, Waxman, astro-ph/0507599;see also: Kachelriess, Tomas, 2006, 2007;

Lipari et al, 2007 for more refined calcs)

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Neutrino propagation

Key assumption: Incoherent propagation of neutrinos

Flavor mixing: Example: For 13 =0, 12=/6, 23=/4:

NB: No CPV in flavor mixing only!But: In principle, sensitive to Re exp(-i ) ~ cos

Take into account Earth attenuation!

(see Pakvasa review, arXiv:0803.1701,

and references therein)

The detection

Neutrino telescopes

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High-E cosmic neutrinos detected with neutrino telescopes

Example: IceCube at south poleDetector material: ~ 1 km3 antarctic ice (1 million m3)

Short before completion

IceCube

http://icecube.wisc.edu/

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Neutrino astronomy in the Mediterranean: Example ANTARES

http://antares.in2p3.fr/

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Different event types

Muon tracks from Effective area dominated!(interactions do not have do be within detector)Relatively low threshold

Electromagnetic showers(cascades) from eEffective volume dominated!

Effective volume dominated Low energies (< few PeV) typically

hadronic shower ( track not separable) Higher Energies:

track separable Double-bang events Lollipop events

Glashow resonace for electron antineutrinos at 6.3 PeV (Learned, Pakvasa, 1995; Beacom et

al, hep-ph/0307025; many others)

e

e

Flavor ratios

… and their limitations

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Definition

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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Applications of flavor ratios

Can be sensitiveto flavor mixing,neutrino properies

Example: Neutron beam

Many recent works inliterature

(e.g. for neutrino 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, Pena-Garay, 2010, …)

(Kachelriess, Serpico, 2005)

Complementarity to long-baseline experiments

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Oscillation probability of interest to measure 13, CP, mass hierachy (in A)

Appearance channels

(Cervera et al. 2000; Akhmedov et al., 2004)

Almost zerofor narrow band superbeams

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Flavor ratios: Approximations

Astro sources for current best-fit values:

Superbeams:

(Source: hep-ph/0604191)

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SB-Reactor-Astrophysical

Complementary information for specific best-fit point:

Curves intersect in only one point!

(Winter, 2006)

Particle properties

… from flavor ratios (examples)

see Pakvasa, arXiv:0803.1701 for a review of other examples: mass varying neutrinos, quantum decoherence, Lorentz/CPT violation, …

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Constraining CP

No CP in Reactor exps Astro sources

(alone)

Combination:May tell something on CP

Problem: Pion beam has little CP sensitivity!

(Winter, 2006)

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Neutrino lifetime Neutrino flux (oscillations averaged):

i(E)=0 E/m: lab frame lifetime of mass eigenstate i

Strongest bound from SN1987A: /m > 105 s/eV on e

Lifetime refers to mass eigenstates, but flavor eigenstates are observed Unclear if bound on 1 or 2

Astrophysical neutrinos probably best direct test of neutrino lifetime

Distinguish: Complete decays: L >> i(E) Incomplete decays: L <~ i(E)

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R

Complete decays

Using the observables R and S, some complete decay scenarios can be excluded!

99% CLallowed regions

(present data)

(Maltoni, Winter, 2008)

1

1

Unstable

Stable

R

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Incomplete decays

Decay into 1 with /m ~ 0.1:

Bhattacharya, Choubey, Gandhi, Watanabe, 2009

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Summary and conclusions

Matter effects in the Sun tests Neutrino oscillations in vacuum MSW effect Standard solar model

The observation of astrophysical neutrinos is important for Identification of cosmic ray accelerators Test of source properties Test of neutrino properties

Literature: e.g. Giunti, Kim: Fundamentals of neutrino physics and astrophysics, Oxford, 2007

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Limitations of flavor ratios

Flavor ratios dependon energy if energylosses of muonsimportant

Distributionsof sources oruncertainties withinone source

Unbalanced statistics:More useful muontracks than showers

(Lipari, Lusignoli, Meloni, 2007; see also:

Kachelriess, Tomas, 2006, 2007)

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Complementarity LBL-Astro

Superbeams have signal ~ sin CP

(CP-odd) Astro-FLR have

signal ~ cos CP (CP-even)

Complementarity for NBB

However: WBB, neutrino factory have cos-term!

(Winter, 2006)

Smallestsensitivity

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Neutrino decays on cosmological distances?

23 possibilities for complete decays

Intermediate states integrated out

LMH: Lightest, Middle, Heaviest

I: Invisible state(sterile, unparticle, …)

123: Mass eigenstate number(LMH depends on hierarchy)

(Maltoni, Winter, 2008; see also Beacom et al 2002+2003; Lipari et al 2007; …)

H ?LM

#7a 1-a

1-b

b