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Flavor ratios in neutrino telescopes for decay and oscillation measurements. NuPAC meeting Chennai (Mahabalipuram), India April 6, 2009 Walter Winter Universität Würzburg. TexPoint fonts used in EMF: A A A A A A A A. Contents. Motivation The sources The fluxes

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Flavor ratios in neutrino telescopes for decay and oscillation measurements

Flavor ratios in neutrino telescopes for decay and oscillation measurements

NuPAC meeting

Chennai (Mahabalipuram), India

April 6, 2009Walter Winter

Universität Würzburg

TexPoint fonts used in EMF: AAAAAAAA

Contents oscillation measurements

  • Motivation

  • The sources

  • The fluxes

  • Flavor composition and propagation

  • The detectors

  • Flavor ratios, and their limitations

  • The LBL complementarity

  • Particle physics applications

  • Summary and conclusions

Neutrino fluxes

galactic extragalactic oscillation measurements

Neutrino fluxes

  • Cosmic rays of high energies:Extragalactic origin!?

  • If protons accelerated, the same sources should produce neutrinos

(Source: F. Halzen, Venice 2009)

Different messengers
Different messengers oscillation measurements

  • Shock accelerated protons lead to p, g, n fluxes

    • p: Cosmic rays:affected by magnetic fields

  • g: Photons: easily absorbed/scattered

  • n: Neutrinos: direct path

(Teresa Montaruli, NOW 2008)

Different source types
Different source types oscillation measurements

  • 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; Boratav et al. 2000)

Motivation this talk

Motivation (this talk) oscillation measurements

What can we learn from neutrinos coming from astrophysical sources about neutrino properties?Especially: Neutrino flavor mixing and decays

The sources

The sources oscillation measurements

Generic cosmic accelerator

From fermi shock acceleration to n production
From Fermi shock acceleration to oscillation measurements n production

Example: Active galaxy(Halzen, Venice 2009)

Synchroton radiation
Synchroton radiation oscillation measurements

  • Where do the photons come from?Typically two possibilities:

    • Thermal photon field (temperature!)

    • Synchroton radiation from electrons/positrons (also accelerated)



Determined by particle‘s minimum energy Emin=m c2(~ (Emin)2 B )

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

(example from Reynoso, Romero, arXiv:0811.1383)

Pion photoproduction
Pion photoproduction oscillation measurements

Powerlaw injection spectrumfrom Fermishock acc.


Differentcharacteristics(energy lossof protons)

(Photon energy in nucleon rest frame)

Resonant production

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

Neutrino production
Neutrino production oscillation measurements

  • 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“

Dashed:no lossesSolid:with losses

(example from Reynoso, Romero, arXiv:0811.1383)

The fluxes

The fluxes oscillation measurements

Single source versus diffuse flux versusstacking

Neutrinos from a single source
Neutrinos from a single source oscillation measurements

  • 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)

Diffuse flux e g agns
Diffuse flux oscillation measurements (e.g. AGNs)

(Becker, arXiv:0710.1557)

  • Advantage: optimal statistics (signal)

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


Single sourcespectrum

Sourcedistributionin redshift,luminosity

Decreasewith luminositydistance

Stacking analysis
Stacking analysis oscillation measurements

(Source: IceCube)

  • 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)


Neutrino observations(e.g. AMANDA,IceCube, …)

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

Extrapolateneutrino spectrumevent by event

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

Flavor composition and propagation

Flavor composition and propagation oscillation measurements

Neutrino flavor mixing

Flavor composition at the source oscillation measurements (Idealized)

  • Astrophysical neutrino sources producecertain flavor ratios of neutrinos (ne:nm:nt):

  • 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 more realistic
Flavor composition at the source oscillation measurements (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)

Neutrino propagation
Neutrino propagation oscillation measurements

  • Key assumption: Incoherent propagation of neutrinos

  • 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!

(see Pakvasa review, arXiv:0803.1701, and references therein)

The detection

The detection oscillation measurements

Neutrino telescopes

IceCube oscillation measurements

  • High-E cosmic neutrinos detected with neutrino telescopes

  • Example: IceCube at south poleDetector material: ~ 1 km3antarctic ice (1 million m3)

  • Status 2008: 40 of 80 Strings


Neutrino astronomy in the mediterranean example antares
Neutrino astronomy in the Mediterranean: oscillation measurements Example ANTARES


Different event types
Different event types oscillation measurements

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

  • Electromagnetic showers(cascades) from neEffective 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








(Learned, Pakvasa, 1995; Beacom et al, hep-ph/0307025; many others)

Flavor ratios

Flavor ratios oscillation measurements

… and their limitations

Definition oscillation measurements

  • 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!

Applications of flavor ratios
Applications of flavor ratios oscillation measurements

  • 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)

(Kachelriess, Serpico, 2005)

The limitations
The limitations oscillation measurements

  • 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)

Terrestrial neutrino sources
Terrestrial neutrino sources oscillation measurements

There are three possible ways to create neutrinos artificially:

  • Beta decays:

    • Example: Nuclear fission reactors

  • Pion decays:

    • From accelerators:

  • Muon decays:

    • Muons created through pion decays!












Reactor experiment double chooz
Reactor experiment: Double Chooz oscillation measurements

~ Identical Detectors, L ~ 1.1 km

Start: 2009?

(Source: S. Peeters, NOW 2008)

Beam experiment minos
Beam experiment: MINOS oscillation measurements

  • Running experiment in the USfor the determination of the atmospheric osc. parameters

  • Uses pion decays

Beam line (Protons)

Near detector: 980 t

Ferndetektor: 5400 t

735 km

Source: MINOS

Narrow band superbeams
Narrow band superbeams oscillation measurements

  • Off-axis technology to suppress backgrounds

  • Beam spectrum more narrow

  • Examples:T2KNOnA

T2K beamOA 1 degreeOA 2 degreesOA 3 degrees


Appearance channels
Appearance channels oscillation measurements

  • Oscillation probability of interest to measure q13, dCP, mass hierachy (in A)

Almost zerofor narrow band superbeams

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

Flavor ratios approximations
Flavor ratios: Approximations oscillation measurements

  • Astro sources for current best-fit values:

  • Superbeams:

(Source: hep-ph/0604191)

Complementarity lbl astro
Complementarity LBL-Astro oscillation measurements

  • Superbeams have signal ~ sin dCP(CP-odd)

  • Astro-FLR have signal ~ cos dCP(CP-even)

  • Complementarity for NBB

  • However: WBB, neutrino factory have cosd-term!

(Winter, 2006)


Sb reactor astrophysical
SB-Reactor-Astrophysical oscillation measurements

  • Complementary information for specific best-fit point:Curves intersect in only one point!

(Winter, 2006)

Octant complementarity
Octant complementarity oscillation measurements

  • In principle, one can resolve the q23 octant with astrophysical sources

(Winter, 2006)

Particle physics applications

Particle physics applications oscillation measurements

… of flavor ratios

Constraining d cp
Constraining oscillation measurements dCP

  • No dCP in

    • Reactor exps

    • Astro sources(alone)

  • Combination:May tell something on dCP

  • Problem: Pion beam has little dCP sensitivity!

(Winter, 2006)

Earlier mh measurement
Earlier MH measurement? oscillation measurements



(Winter, 2006)

R: 10%


Decay scenarios
Decay scenarios oscillation measurements

  • 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; …)

Scenario identification
Scenario identification oscillation measurements

(Maltoni, Winter, 2008)

99% CLallowed regions(present data)


Some informationeven if only ~ 10 useful events!(Pion beam source;L: no of eventsobserved in #1)

Generalized source
Generalized source oscillation measurements

  • Define (fe:fm:ft)=(X:1-X:0) at source (no nt in flux)

X=0: Muon damped source

X=1/3: Pion beam sourceX=1: Neutron beam source

(Maltoni, Winter, 2008)http://theorie.physik.uni-wuerzburg.de/~winter/Resources/AstroMovies.html

Unknown source diff flux
Unknown source/diff. flux oscillation measurements

  • Cumulative flux (X marginalized X<=Xmax)

X<=1/3: Cosmic accelerator with arbitrary pion/muon coolingX<=1: Any source without nt production

(Maltoni, Winter, 2008)http://theorie.physik.uni-wuerzburg.de/~winter/Resources/AstroMovies.html

Synergies with terrestrial exps
Synergies with terrestrial exps oscillation measurements

  • Pion beam, 100 muon tracks, only m1 stableDouble Chooz + Astrophysical, only R measured!

  • Independent of flavor composition at source!

(Maltoni, Winter, 2008)

Summary and conclusions
Summary and conclusions oscillation measurements

  • In this talk: argumentation from sources via propagation to detection with the purpose of physics applications

  • Flavor ratio measurements might be complementary to LBL physics if

    • Neutrinos decay (or have other exotic properties) or

    • Discovery of High-E neutrino flux within 5-10 years (T2K/NOvA-timescales) and

    • At least some statistics (esp. in showers)

Discussion oscillation measurements

  • Individual sources: In which cases can we predict the flavor ratio at the source?

  • Fluxes: If we accumulate statistics, which additional uncertainties enter?

  • Detector:

    • Ability to detect showers?

    • What about double bang and lollipop events?

  • Timescales: Can we expect some information at the timescale of the upcoming terrestrial experiments?



(Huber, Lindner, Schwetz, Winter, in prep.)