1. Constraints on Non- Acceleration Models  A comment on extragalactic magnetic fields  Top-down models  Avoiding the GZK “cut-off”: The Z-burst and new physics  Summary Günter Sigl GReCO, Institut d’Astrophysique de Paris, CNRS et Fédération de Recherche Astroparticule et Cosmologie, Université Paris 7 http://www2.iap.fr/users/sigl/homepage.html

2. Observer immersed in fields of ~ 10 -11 Gauss. Sources of density ~10 -5 Mpc -3 assumed to follow baryon density. Filling factors of magnetic fields from the large scale structure simulation. Some results on propagation in structured extragalactic magnetic fields Scenarios of extragalactic magnetic fields using large scale structure simulations with magnetic fields followed passively and normalized to a few micro Gauss in galaxy clusters. Sigl, Miniati, Ensslin, Phys.Rev.D 68 (2003) 043002; astro-ph/0309695; astro-ph/0401084.

3. The spectrum in the magnetized source scenario shows a pronounced GZK cut-off (spectrum shown is for AGASA acceptance). Deflection in magnetized structures surrounding the sources lead to off-sets of arrival direction from source direction up to >10 degrees up to 10 20 eV in our simulations. This is contrast to Dolag et al., JETP Lett. 79 (2004) 719.  Particle astronomy not necessarily possible, especially for nuclei !

4. Spectra and Composition of Fluxes from Single Discrete Sources considerably depend on Source Magnetization, especially for Sources within a few Mpc Source in the center; weakly magnetized observer modelled as a sphere shown in white at 3.3 Mpc distance. Sigl, astro-ph/0405549 Generalization to Heavy Nuclei: Structured Fields and Individual Sources

5. With field = blue Without field = red Injection spectrum = horizontal line Iron primaries Composition for iron primaries

6. Ultra-High Energy Cosmic Rays and the Connection to  -ray and Neutrino Astrophysics accelerated protons interact: => energy fluences in  -rays and neutrinos are comparable due to isospin symmetry. The neutrino spectrum is unmodified, whereas  -rays pile up below the pair production threshold on the CMB at a few 10 14 eV. The Universe acts as a calorimeter for the total injected electromagnetic energy above the pair threshold. This constrains the neutrino fluxes.

7. A possible acceleration site associated with shocks in hot spots of active galaxies

8. The total injected electromagnetic energy is constrained by the diffuse  -ray flux measured by EGRET in the MeV – 100 GeV regime Neutrino flux upper limit for opaque sources determined by EGRET bound Neutrino flux upper limit for transparent sources more strongly constrained by primary cosmic ray flux at 10 18 – 10 19 eV (Waxman-Bahcall; Mannheim-Protheroe- Rachen)

11. Top-Down Scenarios Decay of early Universe relics of masses ≥10 12 GeV Benchmark estimate of required decay rate: This is not a big number!

12. 1.) long-lived massive free particles (“WIMPZILLA” dark matter)  Fine tuning problem of normalizing Ω X /t X to observed flux.  predicted  -ray domination probably inconsistent with data. But for cosmic strings (or necklaces) the Higgs-Kibble mechanism yields 2.) particles released from topological defects  Fine tuning problem of normalizing to observed flux.  Fine tuning problem only by few orders of magnitude if  Absorption in radio background can lead to nucleon domination. Two types of Top-Down scenarios

13. Topological defects are unavoidable products of phase transitions associated with symmetry change 1.) Iron: Bloch wall Examples: 2.) breaking of gauge symmetries in the early Universe ~1 defect per causal horizon (Higgs-Kibble mechanism) in Grand Unified Theories (GUTs) this implies magnetic monopole production which would overclose the Universe. This was one of the motivations that INFLATION was invented. => particle and/or defect creation must occur during reheating after inflation. Microwave background anisotropies implies scale H inflation ~10 13 GeV. => natural scale for relics to explain ultra-high energy cosmic rays!

14. Flux calculations in Top-Down scenarios a) Assume mode of X-particle decay in GUTs c) fold in injection history and solve the transport equations for propagation b) Determine hadronic quark fragmentation spectrum extrapolated from accelerator data within QCD: modified leading log approximation (Dokshitzer et al.) with and without supersymmetry versus older approximations (Hill). More detailed calculations by Kachelriess, Berezinsky, Toldra, Sarkar, Barbot, Drees: results not drastically different. Fold in meson decay spectra into neutrinos and  -rays to obtain injection spectra for nucleons, neutrinos, and QCD SUSY-QCD

15. The X-particle decay cascade

16. At the highest energies fluxes in increasing order are: nucleons,  -rays, neutrinos, neutralinos.

17. A typical example: Reduced estimate of extragalactic  -ray background limits extragalactic top-down contribution to highest energy cosmic rays. Semikoz, Sigl, JCAP 0404 (2004) 003

18. Future neutrino flux sensitivities and top-down models Semikoz, Sigl, JCAP 0404 (2004) 003

19. Farrar, Biermannradio-loud quasars~1% Virmani et al.radio-loud quasars~0.1% Tinyakov, TkachevBL-Lac objects~10 -4 G.S. et al.radio-loud quasars~10% Correlations with extragalactic Sources Surprise: Deflection seems dominated by our Galaxy. Sources in direction of voids? BL-Lac distances poorly known: Are they consistent with UHECR energies ? Tinyakov, Tkachev, Astropart.Phys. 18 (2002) 165 Tinyakov, Tkachev, hep-ph/0212223

20. 1.) Neutrino primaries but Standard Model interaction probability in atmosphere is ~10 -5.  resonant (Z0) secondary production on massive relic neutrinos: needs extreme parameters and huge neutrino fluxes. 2.) New heavy neutral (SUSY) hadron X 0 : m(X 0 ) > m N increases GZK threshold. but basically ruled out by constraints from accelerator experiments. 3.) New weakly interacting light (keV-MeV) neutral particle electromagnetic coupling small enough to avoid GZK effect; hadronic coupling large enough to allow normal air showers: very tough to do. In all cases: more potential sources, BUT charged primary to be accelerated to even higher energies.  strong interactions above ~1TeV: only moderate neutrino fluxes required. Avoiding the GZK Cutoff If correlated sources turn out to be farther away than allowed by pion production, one can only think of 4 possibilities: 4.) Lorentz symmetry violations.

21. The Z-burst mechanism: Relevant neutrino interactions

23. The Z-burst mechanism: Sources emitting neutrinos and  -rays Sources with constant comoving luminosity density up to z=3, with E -2  -ray injection up to 100 TeV of energy fluence equal to neutrinos, m ν =0.5eV, B=10 -9 G. Kalashev, Kuzmin, Semikoz, Sigl, PRD 65 (2002) 103003

24. The Z-burst mechanism: Exclusive neutrino emitters Sources with comoving luminosity proportional to (1+z) 0 up to z=3, m ν =0.33eV, B=10 -9 G. Semikoz, Sigl, JCAP 0404 (2004) 003

25. For homogeneous relic neutrinos GLUE+FORTE2003 upper limits on neutrino flux above 10 20 eV imply (see figure). Cosmological data including WMAP imply Solar and atmospheric neutrino oscillations indicate near degeneracy at this scale For such masses local relic neutrino overdensities are < 10 on Mpc scales. This is considerably smaller than UHECR loss lengths => required UHE Neutrino flux not significantly reduced by clustering. Even for pure neutrino emitters it is now excluded that the Z-burst contributes significantly to UHECRs

26. Probes of Neutrino Interactions beyond the Standard Model Note: For primary energies around 10 20 eV:  Center of mass energies for collisions with relic backgrounds ~100 MeV – 100 GeV ―> physics well understood  Center of mass energies for collisions with nucleons in the atmosphere ~100 TeV – 1 PeV ―> probes physics beyond reach of accelerators Example: microscopic black hole production in scenarios with a TeV string scale: For neutrino-nucleon scattering with n=1,…,7 extra dimensions, from top to bottom Standard Model cross section Feng, Shapere, PRL 88 (2002) 021303 This increase is not sufficient to explain the highest energy cosmic rays, but can be probed with deeply penetrating showers.

27. However, the neutrino flux from pion-production of extra-galactic trans-GZK cosmic rays allows to put limits on the neutrino-nucleon cross section: Future experiments will either close the window down to the Standard Model cross section, discover higher cross sections, or find sources beyond the cosmogenic flux. How to disentangle new sources and new cross sections? Comparison of this N  - (“cosmogenic”) flux with the non-observation of horizontal air showers results in the present upper limit about 10 3 above the Standard Model cross section. Ringwald, Tu, PLB 525 (2002) 135

28. Solution: Compare rates of different types of neutrino-induced showers Deeply penetrating (horizontal) Earth-skimming upgoing Figure from Cusumano

29. Telescope Array HiRes (mono) Fly’s Eye Feng et al., PRL 88 (2002) 161102 Earth-skimming τ-neutrinos Air-shower probability per τ-neutrino at 10 20 eV for 10 18 eV (1) and 10 19 eV (2) threshold energy for space-based detection. Effective aperture for τ-leptons. Tau-flux ~8.5x10 -4 x τ-neutrino flux independent of σ νN for ground-based detectors. Kusenko, Weiler, PRL 88 (2002) 121104 Comparison of earth-skimming and horizontal shower rates allows to measure the neutrino-nucleon cross section in the 100 TeV range.

30. Sensitivities of LHC and the Pierre Auger project to microscopic black hole production in neutrino-nucleon scattering Ringwald, Tu, PLB 525 (2002) 135 LHC much more sensitive than Auger, but Auger could “scoop” LHC M D = fundamental gravity scale; M bh min = minimal black hole mass

31. Sensitivities of future neutrino telescopes to microscopic black hole production in neutrino-nucleon scattering Ringwald, Kowalski, Tu, PLB 529 (2002) 1 Contained events: Rate ~ Volume Through-going events: Rate ~ Area

32. Conclusions1 1.) Deflection in extragalactic magnetic fields is currently hard to quantify. Sources are likely immersed in magnetic fields of fractions of a microGauss. Such fields can strongly modify spectra and composition even if cosmic rays arrive within a few degrees from the source direction. Extragalactic magnetic fields will therefore play a prominent role in interpretation of future data.

33. Conclusions2 6.) There are many potential high energy neutrino sources including speculative ones. But the only guaranteed ones are due to pion production of primary cosmic rays known to exist: Galactic neutrinos from hadronic interactions up to ~10 16 eV and “cosmogenic” neutrinos around 10 19 eV from photopion production. Flux uncertainties stem from uncertainties in cosmic ray source distribution and evolution. 7.) The highest neutrino fluxes above 10 19 eV are predicted by top-down models, the Z-burst, and cosmic ray sources with power increasing with redshift. However, extragalactic top-down models and the Z-burst are unlikely to considerably contribute to ultra-high energy cosmic rays. 5.) Pion-production establishes a very important link between the physics of high energy cosmic rays on the one hand, and  -ray and neutrino astrophysics on the other hand. All three of these fields should be considered together.

34. Conclusions3 9.) The coming 3-5 years promise an about 100-fold increase of ultra-high energy cosmic ray data due to experiments that are either under construction or in the proposal stage. This will constrain primary cosmic ray flux models. 8.) At energies above ~10 18 eV, the center-of mass energies are above a TeV and thus beyond the reach of accelerator experiments. Especially in the neutrino sector, where Standard Model cross sections are small, this probes potentially new physics beyond the electroweak scale.