NTA: Towards Nu_Tau Astronomy Up the Hawaiian Mountains
George Wei-Shu Hou

Neutrinos from living (Sun) and dying (SN1987A) stars have been detected underground since decades, but recently, PeV (!) energy astrophysical neutrinos have been reported by the IceCube Collaboration. This opens up a new era of Neutrino Astronomy, if one can point back to the sources. The challenge now is to have higher event rate with much better pointing accuracy. By separating tau conversion from tau shower, the Earth-skimming Nu_Tau method allows for huge target mass and detection volume simultaneously, and feasibility has already been demonstrated by Ashra-1 operating up Mauna Loa on Hawaii Island. In part motivated by the IceCube events, a new observatory, Neutrino Telescope Array (NTA), is being planned. It consists of 3+1 site stations watching for Cherenkov pulses from Mauna Loa, Mauna Kea, and Hualalai, with a central station capable of detecting fluorescence from air showers. Sensitivity is > 100 km3 water equivalent, with pointing accuracy < 0.2 deg for PeV-EeV neutrinos that is almost background-free. With design based on Ashra-1 experience, the goal is for clear discovery and identification of astronomical Nu_Tau sources.