1. Neutrino phenomenology Lecture 3: Aspects of neutrino astrophysics Winter school Schladming 2010 “Masses and constants” 02.03.2010 Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAA A A A

2. 2 Contents (overall)  Lecture 1: Testing neutrino mass and flavor mixing  Lecture 2: Precision physics with neutrinos  Lecture 3: Aspects of neutrino astrophysics

3. 3 Contents (lecture 3)  Introduction/repetition  Solar oscillations (varying matter density)  Neutrinos from cosmic accelerators … and the determination of „other“ neutrino properties:  The sources  The fluxes  Flavor composition and propagation  Detection  Flavor ratios  Compementarity to Long baseline searches?  Test of „other“ new physics properties Example: Neutrino lifetime  Summary

4. 4 Nobel prize 2002 "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos“  Raymond Davis Jr detected over 30 years 2.000 neutrinos from the Sun  Evidence for nuclear fusion in the Sun‘s interior!  Masatoshi Koshiba detected on 23.02.1987 twelve of the 10.000.000.000.000.000 (10 16 ) neutrinos, which passed his detector, from an extragalactic supernova explosion.  Birth of neutrino astronomy

5. Repetition

6. 6 Standard Solar Model  Neutrinos are produced as electron neutrinos at the source, in the deep interior of the Sun  Neutrinos propagate to the surface of the Sun and leave it  The neutrinos loose coherence on the way to the Earth, i.e., propagate as mass eigenstates pp-fusion chainNeutrino spectra

7. 7 Matter effects (MSW)  Ordinary matter: electrons, but no ,   Coherent forward scattering in matter: Net effect on electron flavor  Matter effects proportional to electron density n e and baseline  Hamiltonian in matter (matrix form, two flavors): Y: electron fraction ~ 0.5 (electrons per nucleon) (Wolfenstein, 1978; Mikheyev, Smirnov, 1985)

8. 8 Parameter mapping  In vacuum:  In matter:

9. Neutrino oscillations in the Sun

10. 10 Constant vs. varying matter density  For constant matter density: H is the Hamiltonian in constant density  For varying matter density: time-dep. Schrödinger equation (H explicitely time-dependent!) Transition amplitudes;  x : mixture   and  

11. 11 Adiabatic limit  Use transformation: … and insert into time-dep. SE […]  Adiabatic limit:  Matter density varies slowly enough such that differential equation system decouples! Amplitudes of mass eigenstates in matter

12. 12 Propagation in the Sun  Neutrino production as e (fusion) at high n e  Neutrino propagates as mass eigenstate in matter (DE decoupled);  : phase factor from propagation  In the Sun: n e (r) ~ n e (0) exp(-r/r 0 ) (r 0 ~ R sun /10); therefore density drops to zero!  Detection as electron flavor: Disappearance of solar neutrinos!

13. 13 Solar oscillations  In practice: A >> 1 only for E >> 1 MeV  For E << 1 MeV: vacuum oscillations Galbiati, Neutrino 2008 Averaged vacuum oscillations: P ee =1-0.5 sin 2 2  Adiabatic MSW limit: P ee =sin 2  ~ 0.3 Standard prediction

14. 14 Some additional comments … on stellar environments  How do we know that the solar neutrino flux is correct?  SNO neutral current measurement  Why are supernova neutrinos so different?  Neutrino densities so high that neutrino-self interactions  Leads to funny „collective“ effects, as gyroscope B. Dasgupta

15. Neutrinos from cosmic accelerators

16. 16 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 )

17. 17 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

18. 18 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; version from M. Boratav) (?)

19. The sources Generic cosmic accelerator

20. 20 From Fermi shock acceleration to production Example: Active galaxy (Halzen, Venice 2009)

21. 21 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 )

22. 22 Pion photoproduction (Photon energy in nucleon rest frame) (Mücke, Rachen, Engel, Protheroe, Stanev, 2008; SOPHIA) Resonant production, direct production Multi-pion production Different characteristics (energy loss of protons) Power law injection spectrum from Fermi shock acc.

23. 23 Pion photoproduction (2)  Often used:  (1232)-resonance approximation  In practice: this resonance hardly ever dominates for charged pions. Example: GRB  The neutrino fluxes from the  -approximation are underestimated by a factor > 2.4 (if norm. to photons from  0 ) (Hümmer, Rüger, Spanier, Winter, 2010)

24. 24 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

25. The fluxes Single source versus diffuse flux versus stacking

26. 26 Neutrinos from a point 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)

27. 27 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

28. 28 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

29. Flavor composition and propagation Neutrino flavor mixing

30. 30  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)

31. 31 Pion beam source (more realistic) (Hümmer, Rüger, Spanier, Winter, 2010; see also Lipari, Lusignoli, Meloni, 2007) Nominal line 1:2 Neutron decays Kinematics of weak decays: muon helicity!

32. 32 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)

33. 33 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)

34. The detection Neutrino telescopes

35. 35  High-E cosmic neutrinos detected with neutrino telescopes  Example: IceCube at south pole Detector material: ~ 1 km 3 antarctic ice (1 million m 3 )  Short before completion IceCube http://icecube.wisc.edu/

36. 36 Neutrino astronomy in the Mediterranean: Example ANTARES http://antares.in2p3.fr/

37. 37 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   

38. Flavor ratios … and their limitations

39. 39 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!

40. 40 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; Choubey, Rodejohann, 2009; Bustamante, Gago, Pena- Garay, 2010, …) (Kachelriess, Serpico, 2005)

41. Complementarity to long- baseline experiments

42. 42  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

43. 43 Flavor ratios: Approximations  Astro sources for current best-fit values:  Superbeams: (Source: hep-ph/0604191)

44. 44 SB-Reactor-Astrophysical  Complementary information for specific best-fit point: Curves intersect in only one point! (Winter, 2006)

45. Particle properties … from flavor ratios (examples) see Pakvasa, arXiv:0803.1701 for a review of other examples: mass varying neutrinos, quantum decoherence, Lorentz/CPT violation, …

46. 46 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)

47. 47 Neutrino lifetime  Neutrino flux (oscillations averaged):  i (E)=  0 E/m: lab frame lifetime of mass eigenstate i  Strongest bound from SN1987A:  /m > 10 5 s/eV on e  Lifetime refers to mass eigenstates, but flavor eigenstates are observed  Unclear if bound on 1 or 2  Astrophysical neutrinos probably best direct test of neutrino lifetime  Distinguish:  Complete decays: L >>  i (E)  Incomplete decays: L <~  i (E)

48. 48 R Complete decays  Using the observables R and S, some complete decay scenarios can be excluded! 99% CL allowed regions (present data) (Maltoni, Winter, 2008) 1 1 Unstable Stable R

49. 49 Incomplete decays  Decay into 1 with  /m ~ 0.1: Bhattacharya, Choubey, Gandhi, Watanabe, 2009

50. 50 Summary and conclusions  Matter effects in the Sun tests  Neutrino oscillations in vacuum  MSW effect  Standard solar model  The observation of astrophysical neutrinos is important for  Identification of cosmic ray accelerators  Test of source properties  Test of neutrino properties  Literature: e.g. Giunti, Kim: Fundamentals of neutrino physics and astrophysics, Oxford, 2007

51. 51 Limitations of flavor ratios  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)

52. 52 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

53. 53 Neutrino decays on cosmological distances?  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