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Inferring neutrino cross sections above 10 19 eV

Inferring neutrino cross sections above 10 19 eV. Workshop on Exotic Physics with Neutrino Telescopes Uppsala, Sweden, September 20-22, 2006. based on SPR, A. Irimia and T. J. Weiler, Phys. Rev. D73: 083003, 2006. Why ultrahigh energy neutrinos?. Neutrinos point back to their cosmic sources

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Inferring neutrino cross sections above 10 19 eV

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  1. Inferring neutrino cross sections above 1019 eV Workshop on Exotic Physics with Neutrino Telescopes Uppsala, Sweden, September 20-22, 2006 based on SPR, A. Irimia and T. J. Weiler, Phys. Rev. D73: 083003, 2006

  2. Why ultrahigh energy neutrinos? • Neutrinos point back to their cosmic sources • Above GZK energy (~ 5 x 1019 eV), they may be the only propagating primaries • Neutrinos are little affected by the ambient matter: carry information about the central engine • Neutrinos carry a quantum number that cosmic rays and photons do not have: flavor • Travel over cosmic distances allows studies of their fundamental properties: stability, pseudo-Dirac mass patterns • Extreme energies allow studies of neutrino cross sections beyond the reach of terrestrial accelerators

  3. -N cross section: extrapolations to low-x K. Kutak and J. Kwiecinski, Eur. Phys. J. C29:521, 2003 E. M. Henley and J. Jalilian-Marian, Phys. Rev. D73:094004, 2006 L. A. Anchordoqui, A. M. Cooper-Sarkar, D. Hooper and S. Sarkar, Phys. Rev. D74:043008, 2004

  4. -N cross section: new physics thresholds Black Hole production p-brane production J. L. Feng and A. D. Shapere, Phys. Rev. Lett. 88:021303, 2002 L. A. Anchordoqui, J. L. Feng and H. Goldberg, Phys. Lett. B535:302, 2002 EW instanton effects Exchange of KK modes F. Bezrukov et al., Phys. Rev. D68:036005, 2003 and Phys. Lett. B574:75, 2003 • Ringwald, • Phys. Lett. B555:227, 2003 T. Han and D. Hooper, Phys. Lett. B582:21, 2004 M. Kachelriess and M. Plümacher, Phys. Rev. D62:103006, 2000

  5. -N cross section bounds HERA experiments: in the lab E = 52 TeV ~ 2 10-34 cm2 Using RICE data I. Kravchenko et al., Phys Rev. D73:082002, 2006 V. Barger, P. Huber and D. Marfatia, hep-ph/0606311

  6. Fluorescence detectors • Two types of events: • Neutrino-induced Horizontal Air-Showers (HAS): NC 20% energy transfer and ~44% smaller cross section: only CC e • Neutrino-induced Upgoing Air-Showers (UAS): decay: 64% hadrons (2/3 E into shower), 18% electrons (1/3 E into shower), 18% muons • Two types of experiments: • Ground-based: HiRes, Auger • Space-based: EUSO, OWL  UAS  e HAS

  7. Inference of the -N cross section at UHE • Ratio HAS/UAS • HAS: atmosphere is a low density medium: Rate / • UAS: Earth opaque for E > PeV → only Earth-skimming neutrinos • ! process / 1/ • More complicated dependence due to the ! shower process in the atmosphere A. Kusenko and T. J. Weiler, Phys. Rev. Lett. 88:161101, 2002

  8. Improvements • Inclusion of energy dependences of the  energy losses in the Earth and of the  lifetime in the atmosphere (for UAS) • Inelasticity of →  : <y>=0.2 (for UAS) • Distinction between  propagation in rock and water (for UAS) SPR, A. Irimia and T. J. Weiler, Phys. Rev. D73: 083003, 2006

  9. Improvements • Constraints from shower development and identification • Minimum projected length of the shower track: lmin • Minimum column density beyond the point of shower initiation (for the shower to develop in brightness): dmin • Maximum column density (after which shower particles are below threshold for excitation of N2 molecules): dmax • Too-thin altitude beyond which the signal becomes imperceptible: zthin SPR, A. Irimia and T. J. Weiler, Phys. Rev. D73: 083003, 2006

  10. Fly’s Eye 320 EeV event • For EUSO, each pixel is a map of km2 : lmin = 5, 10 km • dmin = 300-400 g/cm2 • dmax = 1200-1500 g/cm2 • zthin = 3 h = 24 km (z) = 0 e-z/h D. J. Bird et al., Astrophys. J. 441:144, 1995 SPR, A. Irimia and T. J. Weiler, Phys. Rev. D73: 083003, 2006

  11. Improvements • Corrections from Earth curvature (for UAS) • (1020 eV) = 4900 km ~ REarth = 6371 km • Curvature-corrected altitude is increased • Curvature-corrected angle with respect to horizon is increased Overall effect → overestimate the air density for shower development SPR, A. Irimia and T. J. Weiler, Phys. Rev. D73: 083003, 2006

  12. Improvements • Effects of a cloud layer • Simplified model: infinitely thin layer with infinite optical depth • The constraints depend on whether the detector is space-based or ground-based: straightforward implementation for UAS⊗Gand HAS⊗S • Critical altitude for UAS below which • clouds obscure detector for UAS⊗G • clouds have no effect for UAS⊗S SPR, A. Irimia and T. J. Weiler, Phys. Rev. D73: 083003, 2006

  13. Cloudless case lmin = 10 km lmin = 5 km ocean Eth = 1019 eV land Eth = 5 1019 eV ocean land SPR, A. Irimia and T. J. Weiler, Phys. Rev. D73: 083003, 2006

  14. Cloudy case lmin = 5 km zcloud = 2 km ground-based space-based ocean Eth = 1019 eV land Eth = 5 1019 eV ocean land SPR, A. Irimia and T. J. Weiler, Phys. Rev. D73: 083003, 2006

  15. Other dependences for space detectors Eth = 1019 eV Eth = 5 1019 eV lmin = 5 km ocean E = 1020 eV dotted: without Earth-curvature dashed: with Earth-curvature thick: zcloud = 4 km thin: zcloud = 12 km Dependence of Acc on cloud altitude (dmax, dmin, lmin) = solid: (0 g/cm2, 105 g/cm2, 0 km) dashed: (300 g/cm2, 1500 g/cm2, 5 km) dotted: (300 g/cm2, 1500 g/cm2, 10 km) dash-dotted: (400 g/cm2, 1200 g/cm2, 10 km) Dependence of Acc on dmin, dmax , lmin SPR, A. Irimia and T. J. Weiler, Phys. Rev. D73: 083003, 2006

  16. Prospects 25600 km2 EUSO FOV 170000 km2 L. A. Anchordoqui, A. M. Cooper-Sarkar, D. Hooper and S. Sarkar, Phys. Rev. D74:043008, 2004

  17. Conclusions • Comparison of HAS and UAS rates in neutrino observatories may allow us to infer a neutrino-nucleon cross section different from the commonly used extrapolation at ultra high energies • We have presented a mostly analytic and detailed extension of Kusenko and Weiler’s idea for ground- and space-based detectors • Included in the calculation are the dependences of the acceptances on the initial neutrino energy, trigger threshold, composition of the Earth, several shower parameters, cloud layers of arbitrary altitude and Earth’s curvature effects • Our calculation is valid for the energy range ~1018-1021 eV • We can establish the “no-lose theorem”: acceptances are robust regardless of the cross section value • Odds: we assume • to know the flavor ratio at the detector • a small NC/CC ratio • inelasticities as in the SM

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