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

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

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 )

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

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)

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

8 From Fermi shock acceleration to production Example: Active galaxy (Halzen, Venice 2009)

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: ) 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 )

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.

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: ) Dashed: no losses Solid: with losses

The fluxes Single source versus diffuse flux versus stacking

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/ )

14 Diffuse flux (e.g. AGNs)  Advantage: optimal statistics (signal)  Disadvantage: Backgrounds (e.g. atmospheric, cosmogenic) (Becker, arXiv: ) Single source spectrum Source distribution in redshift, luminosity Comoving volume Decrease with luminosity distance

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/ ; from BATSE satellite data) Extrapolate neutrino spectrum event by event

Flavor composition and propagation Neutrino flavor mixing

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)

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/ ; see also: Kachelriess, Tomas, 2006, 2007; Lipari et al, 2007 for more refined calcs)

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: , and references therein)

The detection Neutrino telescopes

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

22 Neutrino astronomy in the Mediterranean: Example ANTARES

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/ ; many others)   e e   

Flavor ratios … and their limitations

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!

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 ; 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)

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)

Complementarity to long- baseline experiments

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

30 Reactor experiment: Double Chooz ~ Identical Detectors, L ~ 1.1 km (Source: S. Peeters, NOW 2008) Start: 2009?

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

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/ )

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

34 Flavor ratios: Approximations  Astro sources for current best-fit values:  Superbeams: (Source: hep-ph/ )

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

36 SB-Reactor-Astrophysical  Complementary information for specific best-fit point: Curves intersect in only one point! (Winter, 2006)

37 Octant complementarity  In principle, one can resolve the  23 octant with astrophysical sources (Winter, 2006)

Particle physics applications … of flavor ratios

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)

40 Earlier MH measurement? (Winter, 2006) R: 10% Matter effects 8 8

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 ; Lipari et al 2007; …) H ? LM #7 a 1-a 1-b b

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)

43 Generalized source  Define (f e :f  :f  )=(X:1-X:0) at source (no  in flux) (Maltoni, Winter, 2008) X=0: Muon damped source X=1/3: Pion beam source X=1: Neutron beam source

44 Unknown source/diff. flux  Cumulative flux (X marginalized X<=X max ) (Maltoni, Winter, 2008) X<=1/3: Cosmic accelerator with arbitrary pion/muon cooling X<=1: Any source without  production

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)

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)

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.) ?