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We have found a radio-wave-reflection effect in rock salt for the detection of ultra-high energy neutrinos (UHEν's) which are expected to be generated in Greisen, Zatsepin, and Kuzmin (GZK) processes in the universe. When an UHEν interacts with rock salt or ice as a detection medium, a shower is generated. That shower is formed by hadronic and electromagnetic avalanche processes. The energy of the UHEν shower converts to thermal energy through ionization processes. Consequently, the temperature rises along the shower produced by the UHEν. The refractive index of the medium rises with temperature. The irregularity of the refractive index in the medium leads to a reflection of radio waves. This reflection effect combined with the long attenuation length of radio waves in rock salt and ice would yield a new method to detect UHEν's. We measured the phase of the reflected radio wave under irradiation with an electron beam on ice and rock salt powder. The measured phase showed excellent consistence with the power reflection fraction which was measured directly. A model taking into account the temperature change explained the phase and the amplitude of the reflected wave. Therefore the reflection mechanism was confirmed. The power reflection fraction was compared with that calculated with the Fresnel equations, the ratio between the measured result and that obtained with the Fresnel equations in ice was larger than that of rock salt. [ABSTRACT FROM AUTHOR]

An ultra-high-energy neutrino (UHEν) gives temperature rise along the hadronic and electromagnetic shower when it enters into rock salt or ice. Permittivities of them arise with respect the temperatures at ionization processes of the UHEν shower. It is expected by Fresnel's formula that radio wave reflects at the irregularity of the permittivity in the medium. We had found the radio wave reflection effect in rock salt. The reflection effect and long attenuation length of radio wave in rock salt and ice would yield a new UHEν detection method. An experiment for ice was performed to study the reflection effect. A coaxial tube was filled with rock salt powder or ice. Open end of the coaxial tube was irradiated by a 2 MeV electron beam. Radio wave of 435 MHz was introduced to the coaxial tube. We measured the reflection wave from the open end. We found the radio wave reflection effect due to electron beam irradiation in ice as well as in rock salt. [ABSTRACT FROM AUTHOR]

We had found radio-wave-reflection effect in rock salt for detection of an ultra-high energy neutrino (UHEν) which is generated in GZK processes in the universe. When an UHEν interacts with rock salt or ice as a detection medium, the energy converts to a thermal energy. Consequently, a temperature gives rise along an UHEν shower at the interaction location. The permittivity arises with respect to the temperature at ionization processes of the UHEν shower which is composed of hadronic and electromagnetic multiplication processes. The irregularity of the refractive index in the medium for radio wave rises to a reflection. The reflection effect with a long attenuation length of radio wave in rock salt and ice would yield a new method to detect UHEν. They could be used for detection media in which the UHEν interacts with. We could find a huge amount of rock salt or ice over 50 Gt in a natural rock salt formation or Antarctic ice sheet. Radio wave transmitted into the medium generated by a radar system could be reflected by the irregularity of the refractive index at the shower. Receiving the reflected radio wave yields information about the UHEν. [ABSTRACT FROM AUTHOR]