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Neutrino phenomenology Lecture 3: Aspects of neutrino astrophysics

Neutrino phenomenology Lecture 3: Aspects of neutrino astrophysics. Winter school Schladming 2010 “Masses and constants” 02.03.2010 Walter Winter Universität Würzburg. n. TexPoint fonts used in EMF: A A A A A A A A. Contents (overall). Lecture 1: Testing neutrino mass and flavor mixing

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Neutrino phenomenology Lecture 3: Aspects of neutrino astrophysics

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  1. Neutrino phenomenologyLecture 3: Aspects of neutrino astrophysics Winter school Schladming 2010 “Masses and constants” 02.03.2010Walter Winter Universität Würzburg n TexPoint fonts used in EMF: AAAAAAAA

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

  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 propertiesExample: Neutrino lifetime • Summary

  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 detectedon 23.02.1987 twelve of the 10.000.000.000.000.000 (1016) neutrinos, which passed his detector, from an extragalactic supernovaexplosion. • Birth of neutrino astronomy

  5. Repetition

  6. Standard Solar n 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 chain Neutrino spectra

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

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

  9. Neutrino oscillations in the Sun

  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; yx: mixture ym and yt

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

  12. Propagation in the Sun • Neutrino production as ne (fusion) at high ne • Neutrino propagates as mass eigenstate in matter (DE decoupled); x: phase factor from propagation • In the Sun: ne(r) ~ ne(0) exp(-r/r0) (r0 ~ Rsun/10); therefore density drops to zero! • Detection as electron flavor: Disappearance of solarneutrinos!

  13. Solar oscillations • In practice: A >> 1 only for E >> 1 MeV • For E << 1 MeV: vacuum oscillations Averaged vacuumoscillations:Pee=1-0.5 sin22q AdiabaticMSW limit:Pee=sin2q ~ 0.3 Standardprediction Galbiati, Neutrino 2008

  14. Some additional comments… on stellar environments • How do we know that the solarneutrino 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. 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. 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)

  18. 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; version from M. Boratav)

  19. The sources Generic cosmic accelerator

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

  21. 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)

  22. Pion photoproduction Powerlaw injection spectrumfrom Fermishock acc. Multi-pionproduction Differentcharacteristics(energy lossof protons) (Photon energy in nucleon rest frame) Resonant production,direct production (Mücke, Rachen, Engel, Protheroe, Stanev, 2008; SOPHIA)

  23. Pion photoproduction (2) • Often used: D(1232)-resonance approximation • In practice: this resonance hardly ever dominates for charged pions. Example: GRB • The neutrino fluxes from the D-approximation are underestimated by a factor > 2.4 (if norm. to photons from p0) (Hümmer, Rüger, Spanier, Winter, 2010)

  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“ Dashed:no lossesSolid:with losses (example from Reynoso, Romero, arXiv:0811.1383)

  25. The fluxes Single source versus diffuse flux versusstacking

  26. Neutrinos from a point 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)

  27. 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

  28. 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)

  29. Flavor composition and propagation Neutrino flavor mixing

  30. 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

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

  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. 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)

  34. The detection Neutrino telescopes

  35. IceCube • High-E cosmic neutrinos detected with neutrino telescopes • Example: IceCube at south poleDetector material: ~ 1 km3antarctic ice (1 million m3) • Short before completion http://icecube.wisc.edu/

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

  37. 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)

  38. Flavor ratios … and their limitations

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

  41. Complementarity to long-baseline experiments

  42. 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)

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

  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. 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)

  47. Neutrino lifetime • Neutrino flux (oscillations averaged):ti(E)=t0 E/m: lab frame lifetime of mass eigenstate ni • Strongest bound from SN1987A: t/m > 105 s/eV on ne • Lifetime refers to mass eigenstates, but flavor eigenstates are observed • Unclear if bound on n1 or n2 • Astrophysical neutrinos probably best direct test of neutrino lifetime • Distinguish: • Complete decays: L >> ti(E) • Incomplete decays: L <~ ti(E)

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

  49. Incomplete decays • Decay into n1 with t/m ~ 0.1: Bhattacharya, Choubey, Gandhi, Watanabe, 2009

  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

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