Flavor ratios in neutrino telescopes for decay and oscillation measurements

NuPAC meetingChennai (Mahabalipuram), India

April 6, 2009

Walter WinterUniversität Würzburg

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Contents

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

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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; Boratav et al. 2000)

Motivation (this talk)

What can we learn from neutrinos coming from astrophysical sources about neutrino properties?

Especially: Neutrino flavor mixing and decays

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

Multi-pionproduction

Differentcharacteristics(energy lossof protons)

Powerlaw injection

spectrumfrom Fermishock acc.

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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 single 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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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)

Status 2008: 40 of 80 Strings

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)

(Kachelriess, Serpico, 2005)

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The limitations

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)

Complementarity to long-baseline experiments

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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!

Muons,Neutrinos

Terrestrial neutrino sources

Protons

Target Selection,Focusing

Pions

Decaytunnel

Absorber

Neutrinos

Reactorexperiments

Beams,Superbeams

Neutrinofactory

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Reactor experiment: Double Chooz

~ Identical Detectors, L ~ 1.1 km

(Source: S. Peeters, NOW 2008)

Start: 2009?

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

Uses pion decays

Beam experiment: MINOS

Ferndetektor: 5400 tNear detector: 980 t

735 km

Beam line (Protons)

Source: MINOS

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Narrow band superbeams

Off-axis technology to suppress backgrounds

Beam spectrum more narrow

Examples:T2KNOA

T2K beamOA 1 degreeOA 2 degreesOA 3 degrees

(hep-ex/0106019)

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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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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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SB-Reactor-Astrophysical

Complementary information for specific best-fit point:

Curves intersect in only one point!

(Winter, 2006)

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Octant complementarity

In principle, one can resolve the 23 octant with astrophysical sources

(Winter, 2006)

Particle physics applications

… of flavor ratios

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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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Earlier MH measurement?(W

inter, 2006)

R: 10%

Mattereffects

8

8

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Decay scenarios 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

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R

Scenario identification

Some informationeven if only ~ 10

useful events!(Pion beam source;

L: no of eventsobserved in #1)

99% CLallowed regions

(present data)

(Maltoni, Winter, 2008)

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Generalized source

Define (fe:f:f)=(X:1-X:0) at source (no in flux)

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

X=0: Muon damped source

X=1/3: Pion beam source

X=1: Neutron beam source

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Unknown source/diff. flux

Cumulative flux (X marginalized X<=Xmax)

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

X<=1/3: Cosmic accelerator with arbitrary pion/muon cooling

X<=1: Any source without production

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Synergies with terrestrial exps

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

Independent of flavor composition at source!

(Maltoni, Winter, 2008)

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Summary and conclusions

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)

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Discussion

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.)

?