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
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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.)
?