GRAVITON ENHANCED UHE NEUTRINO CROSS-SECTIONS AND GIANT AIR SHOWERS

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Abstract
The origin of the highest energy cosmic ray showers is a long standing puzzle. In models where the neutrino–proton cross-section rises to typical hadronic values at energies above 1020 eV, the neutrino becomes a candidate for the primary that initiates these showers. Large extra dimension, low scale gravity models suggest just such a strong neutrino interaction possibility. This raises a further question: are the characteristics of observed showers consistent with a neutrino origin? We simulate neutrino induced showers and compare them to proton-induced showers and to data. The comparison includes the study of starting depth, profile with depth, lateral particle distribution at ground and muon lateral distribution at ground level. Our comparison applies to any model of a strongly interacting, neutral particle with an energy transfer per collision of order 10% similar to the neutrino model studied here. We find that for cross-sections above 20 mb there are regions of parameter space where the two types of showers are nearly indistinguishable. We conclude that the neutrino candidate hypothesis cannot presently be ruled out on the basis of shower characteristics.