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Neutrino physics Lecture 3: Neutrino astrophysics

Neutrino physics Lecture 3: Neutrino astrophysics. Herbstschule für Hochenergiephysik Maria Laach 04-14.09.2012 Walter Winter Universität Würzburg. TexPoint fonts used in EMF: A A A A A A A A. Contents. Introduction: Neutrinos and the sources of the UHECR Simulation of sources

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Neutrino physics Lecture 3: Neutrino astrophysics

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  1. Neutrino physicsLecture 3: Neutrino astrophysics Herbstschule für Hochenergiephysik Maria Laach 04-14.09.2012 Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAAAAA

  2. Contents • Introduction:Neutrinos and the sources of the UHECR • Simulation of sources • Example:Neutrinos from Gamma-Ray Bursts (GRBs) • Neutrino oscillations in the Sun (if time) • Summary and conclusions

  3. 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

  4. Neutrinos and the sources of the UHECR

  5. Neutrinos as cosmic messengers Physics of astrophysical neutrino sources = physics ofcosmic ray sources

  6. galactic extragalactic Evidence for proton acceleration, hints for neutrino production • Observation of cosmic rays: need to accelerate protons/hadrons somewhere • The same sources should produce neutrinos: • in the source (pp, pg interactions) • Proton (E > 6 1010 GeV) on CMB  GZK cutoff + cosmogenic neutrino flux UHECR(heavy?) In the source:Ep,max up to 1012 GeV? GZKcutoff?

  7. Cosmic ray source(illustrative proton-only scenario, pg interactions) If neutrons can escape:Source of cosmic rays Neutrinos produced inratio (ne:nm:nt)=(1:2:0) Delta resonance approximation: Cosmogenic neutrinos p+/p0 determines ratio between neutrinos and high-E gamma-rays High energetic gamma-rays;typically cascade down to lower E Cosmic messengers

  8. The two paradigms for extragalactic sources:AGNs and GRBs • Active Galactic Nuclei (AGN blazars) • Relativistic jets ejected from central engine (black hole?) • Continuous emission, with time-variability • Gamma-Ray Bursts (GRBs): transients • Relativistically expanding fireball/jet • Neutrino production e. g. in prompt phase(Waxman, Bahcall, 1997) Nature 484 (2012) 351

  9. Neutrino emission in GRBs Prompt phasecollision of shocks: dominant ns? (Source: SWIFT)

  10. Neutrino detection:Neutrino telescopes • Example: IceCube at South PoleDetector material: ~ 1 km3 antarctic ice • Completed 2010/11 (86 strings) • Recent data releases, based on parts of the detector: • Point sources IC-40 [IC-22]arXiv:1012.2137, arXiv:1104.0075 • GRB stacking analysis IC-40+IC-59Nature 484 (2012) 351 • Cascade detection IC-22arXiv:1101.1692 • Have not seen anything (yet) • What does that mean? • Are the models too simple? • Which parts of the parameter space does IceCube actually test? • Particle physics reason? http://icecube.wisc.edu/ http://antares.in2p3.fr/

  11. Simulation of sources

  12. Different interaction processes Resonances Differentcharacteristics(energy lossof protons;energy dep.cross sec.) Dres. Multi-pionproduction er (Photon energy in nucleon rest frame) Direct(t-channel)production (Mücke, Rachen, Engel, Protheroe, Stanev, 2008; SOPHIA;Ph.D. thesis Rachen)

  13. Source simulation: pg(particle physics) • D(1232)-resonance approximation: • Limitations: • No p- production; cannot predict p+/ p- ratio (Glashow resonance!) • High energy processes affect spectral shape (X-sec. dependence!) • Low energy processes (t-channel) enhance charged pion production • Solutions: • SOPHIA: most accurate description of physicsMücke, Rachen, Engel, Protheroe, Stanev, 2000Limitations: Monte Carlo, slow; helicity dep. muon decays! • Parameterizations based on SOPHIA • Kelner, Aharonian, 2008Fast, but no intermediate muons, pions (cooling cannot be included) • Hümmer, Rüger, Spanier, Winter, ApJ 721 (2010) 630Fast (~1000 x SOPHIA), including secondaries and accurate p+/ p- ratios • Engine of the NeuCosmA („Neutrinos from Cosmic Accelerators“) software+ time-dependent codes from:Hümmer, Rüger, Spanier, Winter, ApJ 721 (2010) 630

  14. “Minimal“ (top down) n model Q(E) [GeV-1 cm-3 s-1] per time frameN(E) [GeV-1 cm-3] steady spectrum Dashed arrows: include cooling and escape Input: B‘ Opticallythinto neutrons from: Baerwald, Hümmer, Winter,Astropart. Phys. 35 (2012) 508

  15. Kinetic equations • Energy losses in continuous limit:b(E)=-E t-1lossQ(E,t) [GeV-1 cm-3 s-1] injection per time frameN(E,t) [GeV-1 cm-3] particle spectrum including spectral effects • For neutrinos: dN/dt = 0 (steady state) • Simple case: No energy losses b=0 Injection Energy losses Escape often: tesc ~ R

  16. Typical source models • Protons typically injected with power law (Fermi shock acceleration!) • Target photon field typically: • Put in by hand (e.g. obs. spectrum: GRBs) • Thermal target photon field • From synchrotron radiation of co-accelerated electrons/positrons (AGN-like) • From a more complicated combination of radiation processes ?

  17. Peculiarity for neutrinos: Secondary cooling Example: GRB Decay/cooling: charged m, p, K • Secondary spectra (m, p, K) loss-steepend above critical energy • E‘c depends on particle physics only (m, t0), and B‘ • Leads to characteristic flavor composition and shape • Very robust prediction for sources? [e.g. any additional radiation processes mainly affecting the primaries will not affect the flavor composition] • The only way to directly measure B‘? nm Pile-up effect Flavor ratio! Spectralsplit E‘c E‘c E‘c Adiabatic Baerwald, Hümmer, Winter,Astropart. Phys. 35 (2012) 508; also: Kashti, Waxman, 2005; Lipari et al, 2007

  18. Example:Neutrinos from GRBs

  19. The “magic“ triangle g Satellite experiments(burst-by-burst) Model-dependent prediction GRB stacking(next slides) Partly common fudgefactors: how many GRBsare actually observable?Baryonic loading? … ?(energy budget, CR “leakage“, quasi-diffuse extrapolation, …) Robust connectionif CRs only escape as neutrons produced in pg interactions CR n Neutrino telescopes (burst-by-burst or diffuse) CR experiments (diffuse)

  20. g GRB stacking n (Source: IceCube) • Idea: Use multi-messenger approach • Predict neutrino flux fromobserved photon fluxesevent by event (Source: NASA) Coincidence! Neutrino observations(e.g. IceCube, …) GRB gamma-ray observations(e.g. Fermi GBM, Swift, etc) Observed:broken power law(Band function) (Example: IceCube, arXiv:1101.1448) E-2 injection

  21. Gamma-ray burst fireball model:IC-40 data meet generic bounds • Generic flux based on the assumption that GRBs are the sources of (highest energetic) cosmic rays(Waxman, Bahcall, 1999; Waxman, 2003; spec. bursts:Guetta et al, 2003) Nature 484 (2012) 351 IC-40+59 stacking limit • Does IceCube really rule out the paradigm that GRBs are the sources of the ultra-high energy cosmic rays?

  22. IceCube method …normalization • Connection g-rays – neutrinos • Optical thickness to pg interactions:[in principle, lpg ~ 1/(ngs); need estimates for ng, which contains the size of the acceleration region] ½ (charged pions) x¼ (energy per lepton) Energy in protons Energy in neutrinos Fraction of p energyconverted into pions fp Energy in electrons/photons (Description in arXiv:0907.2227; see also Guetta et al, astro-ph/0302524; Waxman, Bahcall, astro-ph/9701231)

  23. IceCube method … spectral shape • Example: 3-ag 3-bg 3-ag+2 First break frombreak in photon spectrum(here: E-1 E-2 in photons) Second break frompion cooling (simplified)

  24. Revision of neutrino flux predictions Analytical recomputationof IceCube method (CFB): cfp: corrections to pion production efficiency cS: secondary cooling and energy-dependenceof proton mean free path(see also Li, 2012, PRD) G ~ 1000 G ~ 200 Comparison with numerics: WB D-approx: simplified pg Full pg: all interactions, K, …[adiabatic cooling included] (Baerwald, Hümmer, Winter, Phys. Rev. D83 (2011) 067303;Astropart. Phys. 35 (2012) 508; PRL, arXiv:1112.1076)

  25. Consequences for IC-40 analysis • Differential limit illustrates interplay with detector response • Shape of prediction used to compute sensitivity limit • Peaks at higher energies IceCube @ n2012:observed two events~ PeV energies from GRBs? (Hümmer, Baerwald, Winter, Phys. Rev. Lett. 108 (2012) 231101)

  26. Systematics in aggregated fluxes • z ~ 1 “typical“ redshift of a GRB • Neutrino flux overestimated if z ~ 2 assumed(dep. on method) • Peak contribution in a region of low statistics • Systematical error on quasi-diffuse flux (90% CL) ~ 50% for 117 bursts, [as used in IC-40 analysis] Weight function:contr. to total flux Distribution of GRBsfollowing star form. rate (strongevolutioncase) 10000 bursts (Baerwald, Hümmer, Winter, Astropart. Phys. 35 (2012) 508)

  27. Quasi-diffuse prediction • Numerical fireball model cannot be ruled out with IC40+59 for same parameters, bursts, assumptions • Peak at higher energy![optimization of future exps?] “Astrophysical uncertainties“:tv: 0.001s … 0.1sG: 200 …500a: 1.8 … 2.2ee/eB: 0.1 … 10 (Hümmer, Baerwald, Winter, Phys. Rev. Lett. 108 (2012) 231101)

  28. Comparison of methods/models from Fig. 3 of Hümmer et al, arXiv:1112.1076, PRL;origin of target photons not specified from Fig. 3 of Nature 484 (2012) 351; uncertainties from Guetta, Spada, Waxman, Astrophys. J. 559 (2001) 2001:target photons from synchrotron emission/inverse Compton completely model-independent (large collision radii allowed): He et al, Astrophys. J. 752 (2012) 29 (P. Baerwald)

  29. Particle physics depletion/reason:Neutrino decay? Decay hypothesis: n2 and n3 decay with lifetimes compatible with SN 1987A bound • Reliable conclusions from astrophysical neutrino flux bounds require cascade (ne) measurements! (from: Baerwald, Bustamante, Winter, 2012)

  30. Neutrinos-cosmic rays n CR • If charged p and n produced together: • GRB not exclusive sources of UHECR? CR leakage? Consequences for (diffuse) neutrino fluxes Fit to UHECR spectrum (Ahlers, Gonzalez-Garcia, Halzen, Astropart. Phys. 35 (2011) 87)

  31. Neutrino oscillations in the Sun

  32. 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

  33. 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!

  34. 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!

  35. 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 Borexino, PRL 108 (2012) 051302

  36. 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

  37. Summary Are GRBs the sources of the UHECR? • Gamma-rays versus neutrinos • Revised model calculations release pressure on fireball model calculations • Baryonic loading will be finally constrained (at least in “conventional“ internal shock models) • Neutrinos versus cosmic rays • Cosmic ray escape as neutrons under tension • Cosmic ray leakage? • Not the only sources of the UHECR? • Solar neutrinos: MSW effect credible thanks to Borexino g n CR

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