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Magnetic field and flavor effects on the neutrino fluxes from cosmic accelerators

Magnetic field and flavor effects on the neutrino fluxes from cosmic accelerators. WIN 2011 January 31-February 5, 2011 Cape Town , South Africa Walter Winter Universität Würzburg. TexPoint fonts used in EMF: A A A A A A A A. Contents. Introduction

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Magnetic field and flavor effects on the neutrino fluxes from cosmic accelerators

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  1. Magnetic field and flavor effects on the neutrino fluxes from cosmic accelerators WIN 2011 January 31-February 5, 2011Cape Town, South Africa Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAAAAA

  2. Contents • Introduction • Simulation of sources, a self-consistent approach • Neutrino propagation and detection;flavor ratios • On gamma-ray burst (GRB) neutrino fluxes • Summary

  3. Neutrino production in astrophysical sources max. center-of-mass energy ~ 103 TeV(for 1021 eV protons) Example: Active galaxy(Halzen, Venice 2009)

  4. Neutrino detection: IceCube • Example: IceCube at South PoleDetector material: ~ 1 km3antarctic ice • Completed 2010/11 (86 strings) • Recent data releases, based on parts of the detector: • Point sources IC-40arXiv:1012.2137 • GRB stacking analysis IC-40arXiv:1101.1448 • Cascade detection IC-22arXiv:1101.1692 http://icecube.wisc.edu/

  5. Example: GRB stacking (Source: IceCube) • Idea: Use multi-messenger approach • Predict neutrino flux fromobserved photon fluxesevent by event • Good signal over background ratio (atmospheric background), moderate statistics (Source: NASA) Coincidence! Neutrino observations(e.g. IceCube, …) GRB gamma-ray observations(e.g. Fermi GBM, Swift, etc) (Example: IceCube, arXiv:1101.1448)

  6. IC-40 data meet generic bounds (arXiv:1101.1448) • Generic flux based on the following assumptions:- GRBs are the sources of (highest energetic) cosmic rays- Fraction of energy the protons loose in pion production ~ 20%(Waxman, Bahcall, 1999; Waxman, 2003) What do such bounds actually mean more generically? Limit IC-40 stacking limit Fraction of p energy lost into pion production(related to optical thicknessof pg/ng interactions) Baryonic loading(ratio between protons andelectrons/positrons in the jet) X

  7. When do we expect a n signal?[some personal comments] • Unclear if specific sources lead to neutrino production; spectral energy distribution can be often described by leptonic processes as well (e.g. inverse Compton scattering, …) • However: whereever cosmic rays are produced, neutrinos should be produced as well (pg, pp!) • There are a number of additional candidates, e.g. • „Hidden“ sources (e.g. „slow jet supernovae“ without gamma-ray counterpart)(Razzaque, Meszaros, Waxman, 2004; Ando, Beacom, 2005; Razzaque, Meszaros, 2005; Razzaque, Smirnov, 2009) • Large fraction of Fermi-LAT unidentified sources? • From the neutrino point of view: „Fishing in the dark blue sea“? Looking at the wrong places? • Need for tailor-made neutrino-specific approaches?

  8. Simulation of sources

  9. Meson photoproduction • Often used: D(1232)-resonance approximation • Limitations: • No p- production; cannot predict p+/ p- ratio (affects neutrino/antineutrino) • High energy processes affect spectral shape • Low energy processes (t-channel) enhance charged pion production • Charged pion production underestimated compared to p0 production by factor of 2.4 (independent of input spectra!) • Solutions: • SOPHIA: most accurate description of physicsMücke, Rachen, Engel, Protheroe, Stanev, 2000Limitations: Often slow, difficult to handle; helicity dep. muon decays! • Parameterizations based on SOPHIA • Kelner, Aharonian, 2008Fast, but no intermediate muons, pions (cooling cannot be included) • Hümmer, Rüger, Spanier, Winter, 2010Fast (~3000 x SOPHIA), including secondaries and accurate p+/ p- ratios; also individual contributions of different processes (allows for comparison with D-resonance!) • Engine of the NeuCosmA („Neutrinos from Cosmic Accelerators“) software from:Hümmer, Rüger, Spanier, Winter, ApJ 721 (2010) 630 T=10 eV

  10. NeuCosmA key ingredients(„Neutrinos from Cosmic Accelerators“) • What it can do so far: • Photohadronics based on SOPHIA(Hümmer, Rüger, Spanier, Winter, 2010) • Weak decays incl. helicity dependence of muons(Lipari, Lusignoli, Meloni, 2007) • Cooling and escape • Potential applications: • Parameter space studies • Flavor ratio predictions • Time-dependent AGN simulations etc. (photohadronics) • Monte Carlo sampling of diffuse fluxes • Stacking analysis with measured target photon fields • Fits (need accurate description!) • … Kinematics ofweak decays: muon helicity! from: Hümmer, Rüger, Spanier, Winter, ApJ 721 (2010) 630

  11. A self-consistent approach • 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) • Requires few model parameters, mainly • Purpose: describe wide parameter ranges with a simple model; minimal set of assumptions for n!? ?

  12. Model summary Dashed arrows: include cooling and escape Dashed arrow: Steady stateBalances injection with energy losses and escapeQ(E) [GeV-1 cm-3 s-1] per time frameN(E) [GeV-1 cm-3] steady spectrum Opticallythinto neutrons Injection Energy losses Escape Hümmer, Maltoni, Winter, Yaguna, Astropart. Phys. 34 (2010) 205

  13. An example (1) a=2, B=103 G, R=109.6 km • Meson production described by(summed over a number of interaction types) • Only product normalization enters in pion spectra as long as synchrotron or adiabatic cooling dominate • Maximal energy of primaries (e, p) by balancing energy loss and acceleration rate Maximum energy: e, p Hümmer, Maltoni, Winter, Yaguna, 2010

  14. An example (2) a=2, B=103 G, R=109.6 km • Secondary spectra (m, p, K) become loss-steepend above a critical energy • Ec depends on particle physics only (m, t0), and B • Leads to characteristic flavor composition • Any additional cooling processes mainly affecting the primaries will not affect the flavor composition • Flavor ratios most robust predicition for sources? Cooling: charged m, p, K Ec Ec Ec Hümmer, Maltoni, Winter, Yaguna, 2010

  15. An example (3) a=2, B=103 G, R=109.6 km m cooling break Synchrotroncooling Spectralsplit p cooling break Pile-up effect Flavor ratio! Pile-upeffect Slope:a/2 Hümmer, Maltoni, Winter, Yaguna, 2010

  16. The Hillas plot • Hillas (necessary) condition for highest energetic cosmic rays (h: acc. eff.) • Protons, 1020 eV, h=1: • We interpret R and B as parameters in bulk frame • High bulk Lorentz factors G relax this condition! Hillas 1984; version adopted from M. Boratav

  17. Flavor composition at the source(Idealized – energy independent) • 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)at high E: Muons loose energy before they decay • Muon beam source (1:1:0)Cooled muons pile up at lower energies (also: heavy flavor decays) • Neutron beam source (1:0:0)Neutron decays from pg(also possible: photo-dissociationof heavy nuclei) • At the source: Use ratio ne/nm (nus+antinus added)

  18. However: flavor composition is energy dependent! Pion beam Muon beam muon damped Energywindowwith largeflux for classification Typicallyn beamfor low E(from pg) Pion beam muon damped Undefined(mixed source) Behaviorfor smallfluxes undefined (from Hümmer, Maltoni, Winter, Yaguna, 2010; see also: Kashti, Waxman, 2005; Kachelriess, Tomas, 2006, 2007; Lipari et al, 2007)

  19. Parameter space scan • All relevant regions recovered • GRBs: in our model a=4 to reproduce pion spectra; pion beam  muon damped (confirmsKashti, Waxman, 2005) • Some dependence on injection index a=2 Hümmer, Maltoni, Winter, Yaguna, 2010

  20. Neutrino propagation and detection

  21. 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)

  22. Which sources can specific data constrain best? • Constrain individual fluxes after flavor mixing with existing data Point sources IC-40arXiv:1012.2137 Energy flux density PRELIMINARY (work in preparation)

  23. Measuring flavor? • In principle, flavor information can be obtained from different event topologies: • Muon tracks - nm • Cascades (showers) – CC: ne, nt, NC: all flavors • Glashow resonance: ne • Double bang/lollipop: nt (Learned, Pakvasa, 1995; Beacom et al, 2003) • In practice, the first (?) IceCube „flavor“ analysis appeared recently – IC-22 cascades (arXiv:1101.1692)Flavor contributions to cascades for E-2 extragalatic test flux (after cuts): • Electron neutrinos 40% • Tau neutrinos 45% • Muon neutrinos 15% • Electron and tau neutrinos detected with comparable efficiencies • Neutral current showers are a moderate background t nt

  24. Flavor ratios at detector • At the detector: define observables which • take into account the unknown flux normalization • take into account the detector properties • Example: Muon tracks to showersDo not need to differentiate between electromagnetic and hadronic showers! • Flavor ratios have recently been discussed for many particle physics applications (for flavor 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; Esmaili, Farzan, 2009; Bustamante, Gago, Pena-Garay, 2010; Mehta, Winter, 2011…)

  25. Parameter uncertainties • Basic dependencerecovered afterflavor mixing • However: mixing parameter knowledge ~ 2015 (Daya Bay, T2K, etc) required Hümmer, Maltoni, Winter, Yaguna, 2010

  26. New physics in R? Energy dependenceflavor comp. source Energy dep.new physics (Example: [invisible] neutrino decay) 1 Stable state 1 Unstable state Mehta, Winter, arXiv:1101.2673

  27. Which sources are most useful? • Most useful:Sources for which different flavor compositions are present; requires substantial B • Some dependence on new physics effect aL=108 GeV No of decayscenarios which canbe identified Mehta, Winter, arXiv:1101.2673

  28. On GRB neutrino fluxes

  29. Waxman-Bahcall, reproduced • Difference to above: target photon field ~ observed photon field used • Reproduced original WB flux with similar assumptions • Additional charged pion production channels included,also p-! broken power law(Band function) p decays only ~ factor 6 Baerwald, Hümmer, Winter, arXiv:1009.4010

  30. Fluxes before flavor mixing ne nm Baerwald, Hümmer, Winter, arXiv:1009.4010

  31. After flavor mixing Consequences: • Different flux shape • Can double peak structure be used? • How reliable is stacking analysis from IC-40? • Different normalization • Expect actually more neutrinos than in original estimates • Baryonic loading x fpstronger constrained? • GRBs not the sourcesof highest energetic CR? (full scale) (full scale) Baerwald, Hümmer, Winter, arXiv:1009.4010; see also: Murase, Nagataki, 2005; Kashti, Waxman, 2005; Lipari, Lusignoli, Meloni, 2007

  32. Summary • Particle production, flavor, and magnetic field effects change the shape of astrophysical neutrino fluxes • Description of the „known“ (particle physics) components should be as accurate as possible for data analysis • Flavor ratios, though difficult to measure, are interesting because • they may be the only way to directly measure B (astrophysics) • they are useful for new physics searches (particle physics) • they are relatively robust with respect to the cooling and escape processes of the primaries (e, p, g) • However: flavor ratios should be interpreted as energy-dependent quantities • The flux shape and flavor ratio of a point source can be predicted in a self-consistent way if the astrophysical parameters can be estimated, such as from a multi-messenger observation (R: from time variability, B: from energy equipartition, a: from spectral shape)

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