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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 NuPAC meeting Chennai (Mahabalipuram), India April 6, 2009Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAAAAA
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
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)
Different messengers • 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 • 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
From Fermi shock acceleration to n production Example: Active galaxy(Halzen, Venice 2009)
Synchroton radiation • Where do the photons come from?Typically two possibilities: • Thermal photon field (temperature!) • Synchroton radiation from electrons/positrons (also accelerated) ? B 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 Powerlaw injection spectrumfrom Fermishock acc. Multi-pionproduction Differentcharacteristics(energy lossof protons) (Photon energy in nucleon rest frame) Resonant production (Mücke, Rachen, Engel, Protheroe, Stanev, 2008; SOPHIA)
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“ Dashed:no lossesSolid:with losses (example from Reynoso, Romero, arXiv:0811.1383)
The fluxes Single source versus diffuse flux versusstacking
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)
Diffuse flux (e.g. AGNs) (Becker, arXiv:0710.1557) • Advantage: optimal statistics (signal) • Disadvantage: Backgrounds(e.g. atmospheric,cosmogenic) Comovingvolume Single sourcespectrum Sourcedistributionin redshift,luminosity Decreasewith luminositydistance
Stacking analysis (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) Coincidence! 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 Neutrino flavor mixing
Flavor composition at the source(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 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 • 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 Neutrino telescopes
IceCube • 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 http://icecube.wisc.edu/
Neutrino astronomy in the Mediterranean: Example ANTARES http://antares.in2p3.fr/
Different event types • 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 t nt nt e ne m nm (Learned, Pakvasa, 1995; Beacom et al, hep-ph/0307025; many others)
Flavor ratios … and their limitations
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!
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)
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)
Terrestrial neutrino sources 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! Reactorexperiments Beams,Superbeams Muons,Neutrinos Pions Neutrinos Protons Target Selection,Focusing Decaytunnel Absorber Neutrinofactory
Reactor experiment: Double Chooz ~ Identical Detectors, L ~ 1.1 km Start: 2009? (Source: S. Peeters, NOW 2008)
Beam experiment: MINOS • 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 • Off-axis technology to suppress backgrounds • Beam spectrum more narrow • Examples:T2KNOnA T2K beamOA 1 degreeOA 2 degreesOA 3 degrees (hep-ex/0106019)
Appearance channels • 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 • Astro sources for current best-fit values: • Superbeams: (Source: hep-ph/0604191)
Complementarity LBL-Astro • 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) Smallestsensitivity
SB-Reactor-Astrophysical • Complementary information for specific best-fit point:Curves intersect in only one point! (Winter, 2006)
Octant complementarity • In principle, one can resolve the q23 octant with astrophysical sources (Winter, 2006)
Particle physics applications … of flavor ratios
Constraining 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? 8 8 (Winter, 2006) R: 10% Mattereffects
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) 1-a a #7 b H M L ? 1-b (Maltoni, Winter, 2008; see also Beacom et al 2002+2003; Lipari et al 2007; …)
Scenario identification (Maltoni, Winter, 2008) 99% CLallowed regions(present data) R Some informationeven if only ~ 10 useful events!(Pion beam source;L: no of eventsobserved in #1)
Generalized source • 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 • 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 • 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 • 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 • 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? ? Preliminary (Huber, Lindner, Schwetz, Winter, in prep.)