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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: AAAAA A A A
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2 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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3 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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4 Different messengers Shock accelerated protons lead to p, , fluxes p: Cosmic rays: affected by magnetic fields (Teresa Montaruli, NOW 2008) : Photons: easily absorbed/scattered : Neutrinos: direct path
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5 Different source types Model-independent constraint: E max < 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)
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Motivation (this talk) What can we learn from neutrinos coming from astrophysical sources about neutrino properties? Especially: Neutrino flavor mixing and decays
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The sources Generic cosmic accelerator
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8 From Fermi shock acceleration to production Example: Active galaxy (Halzen, Venice 2009)
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9 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+1 determined by spectral index s of injection Determined by particle‘s minimum energy E min =m c 2 (~ (E min ) 2 B )
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10 Pion photoproduction (Photon energy in nucleon rest frame) (Mücke, Rachen, Engel, Protheroe, Stanev, 2008; SOPHIA) Resonant production Multi-pion production Different characteristics (energy loss of protons) Power law injection spectrum from Fermi shock acc.
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11 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 losses Solid: with losses
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The fluxes Single source versus diffuse flux versus stacking
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13 Neutrinos from a single source Example: GRBs observed by BATSE Applies to other sources in atmospheric BG-free regime as well … Conclusion: Most likely no significant statistics with only one source! (Guetta et al, astro-ph/0302524)
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14 Diffuse flux (e.g. AGNs) Advantage: optimal statistics (signal) Disadvantage: Backgrounds (e.g. atmospheric, cosmogenic) (Becker, arXiv:0710.1557) Single source spectrum Source distribution in redshift, luminosity Comoving volume Decrease with luminosity distance
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15 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) Extrapolate neutrino spectrum event by event
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Flavor composition and propagation Neutrino flavor mixing
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17 Astrophysical neutrino sources produce certain 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-dissociation of heavy nulcei NB: Do not distinguish between neutrinos and antineutrinos Flavor composition at the source (Idealized)
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18 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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19 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)
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The detection Neutrino telescopes
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21 High-E cosmic neutrinos detected with neutrino telescopes Example: IceCube at south pole Detector material: ~ 1 km 3 antarctic ice (1 million m 3 ) Status 2008: 40 of 80 Strings IceCube http://icecube.wisc.edu/
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22 Neutrino astronomy in the Mediterranean: Example ANTARES http://antares.in2p3.fr/
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23 Different event types Muon tracks from Effective area dominated! (interactions do not have do be within detector) Relatively low threshold Electromagnetic showers (cascades) from e Effective 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
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Flavor ratios … and their limitations
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25 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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26 Applications of flavor ratios Can be sensitive to flavor mixing, neutrino properies Example: Neutron beam Many recent works in literature (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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27 The limitations Flavor ratios depend on energy if energy losses of muons important Distributions of sources or uncertainties within one source Unbalanced statistics: More useful muon tracks than showers (Lipari, Lusignoli, Meloni, 2007; see also: Kachelriess, Tomas, 2006, 2007)
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Complementarity to long- baseline experiments
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29 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 TargetSelection, Focusing Pions Decay tunnel Absorber Neutrinos Reactor experiments Beams, Superbeams Neutrino factory
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30 Reactor experiment: Double Chooz ~ Identical Detectors, L ~ 1.1 km (Source: S. Peeters, NOW 2008) Start: 2009?
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31 Running experiment in the US for the determination of the atmospheric osc. parameters Uses pion decays Beam experiment: MINOS Ferndetektor: 5400 t Near detector: 980 t 735 km Beam line (Protons) Source: MINOS
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32 Narrow band superbeams Off-axis technology to suppress backgrounds Beam spectrum more narrow Examples: T2K NO A T2K beam OA 1 degree OA 2 degrees OA 3 degrees (hep-ex/0106019)
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33 Oscillation probability of interest to measure 13, CP, mass hierachy (in A) Appearance channels (Cervera et al. 2000; Akhmedov et al., 2004) Almost zero for narrow band superbeams
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34 Flavor ratios: Approximations Astro sources for current best-fit values: Superbeams: (Source: hep-ph/0604191)
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35 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) Smallest sensitivity
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36 SB-Reactor-Astrophysical Complementary information for specific best-fit point: Curves intersect in only one point! (Winter, 2006)
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37 Octant complementarity In principle, one can resolve the 23 octant with astrophysical sources (Winter, 2006)
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Particle physics applications … of flavor ratios
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39 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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40 Earlier MH measurement? (Winter, 2006) R: 10% Matter effects 8 8
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41 Decay scenarios 2 3 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 #7 a 1-a 1-b b
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42 R Scenario identification Some information even if only ~ 10 useful events! (Pion beam source; L: no of events observed in #1) 99% CL allowed regions (present data) (Maltoni, Winter, 2008)
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43 Generalized source Define (f e :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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44 Unknown source/diff. flux Cumulative flux (X marginalized X<=X max ) (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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45 Synergies with terrestrial exps Pion beam, 100 muon tracks, only m 1 stable Double Chooz + Astrophysical, only R measured! Independent of flavor composition at source! (Maltoni, Winter, 2008)
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46 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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47 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.) ?
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