The Strategy of Discrimination between Flavors for Detection of Cosmogenic Neutrinos

We propose a new method to identify flavors of ultra high energy cosmic neutrinos. Energy loss of leptons in matter provides important informations for the detection of neutrinos originated from high energy astrophysical sources. 50 years ago, Askaryan proposed to detect Cherenkov signals by radio wave from the negative charge excess of particle showers. The theory of Cherenkov pulses with Fraunhofer approximation was widely studied in the past two decades. However, at high energies or for high density materials, electromagnetic shower should be elongated due to the Landau-Pomeranchuck-Migdal (LPM) effect. As such the standard Fraunhofer approximation ceases to be valid when the distance between the shower and the detector becomes comparable with the shower length. We have performed Monte Carlo simulations recently to investigate this regime based on the finite-difference time-domain (FDTD) method, and modified time domain integration method. In this work, we adopt the deduced relationship between the radio signal and the cascade development profile to investigate its implication to lepton signatures. Our method provides a straightforward technique to identify the neutrino flavor through the detected Cherenkov signals.