1. George W.S. Hou & M.A. Huang Center for Cosmology and Particle Astrophysics Department of Physics, National Taiwan University, 1, Sec. 4, Roosevelt Rd.,Taipei, 106,TAIWAN http://www.hep1.phys.ntu.edu.tw hou@phys.ntu.edu.tw & huangmh@phys.ntu.edu.tw ? Window of new techniques for observing Neutrinos Conventional detectors such as SK have difficulty to expand target volume, maximum energy ~ 10 15 eV. UHECR detector such as Auger array also detect, energy threshold is high ~ 10 18 eV. Alternative approach  Use mountain as target and shield.  Use atmosphere as calorimeter, measured air shower initiated by the decay of .  appearance Only   can be seen, observation such event prove  to  oscillation seen by SK. VHE Neutrino Telescope Workshop Mar. 21-23, 2002, Taipei, Taiwan, http://hep1.phys.ntu.edu.tw/VHENTW Potential site: Hawaii Big Island  Good weather & Less artificial light  Mt. Hualalai provide a good view of Mt. Loa and situated in the dryer west side of island.  Mt. Loa provide long base line, ~ 90 km wide and 4 km high. Slice along this line   : Conversion efficiency Blue : No dE/dX Red: dE/dX Abstract We study the expected performance of building a neutrino telescope, which targets at energy greater than 10^14 eV utilizing a mountain to interact with neutrinos. The telescope's efficiency in converting neutrinos into leptons is first examined. Then using a potential site on the Big Island of Hawaii, we estimate the acceptance of the proposed detector. The neutrino flux limit at event rate 0.3/year/half decade of energy is estimated to be comparable to that of AMANDA neutrino flux limit at above 10^16 eV. astro-ph/0204145  Detection mechanism similar to  -ray imaging Chrenkov telescope. Cherenkov light image on a 8x8 MAPMT  EUSO type compact detector (Fresnel lens + MAPMT)  Tentative international collaboration: NTU, Taiwan U. Paris, French U. Palermo, Italy U. Hawaii, USA RIKEN, Japan Euso prototype 40cm diameter Fresnel lens, assembled in RIKEN, Japan (Kawasaki et al., 2001, 27th ICRC, 893) Field of view of telescope Azimuth angle: from south to east. Zenith angle: from 86.9º to 91.5º Acceptance Select field of view, count mountain- passing events only! Effective solid angle is Cerenkov light cone,  c ~ 5 º. Effective area: area where tau decay and initiate shower. Consider conversion efficiency Over 1 km 2 sr! Assuming sensitivity is the flux which produce 0.3 events/year* per half decade of energy. * Calendar year, consider 10% duty cycle. Sky coverage From field of view and operation from 12/2003 to 12/2007; 20% duty time Optical detector operate in moonless and cloudless night, typical duty cycle 10%. Galactic center is visible! Conclusions: Hualalai site provide acceptance > 1km 2 sr and good weather condition. Chance to explore MPR limits and set similar upper limit as AMANDA-B10 at higher energy. Nearby point source could be detected, AGN and galactic center could be good candidate for such point source. Earth skimming and Near Horizon shower are being studied. Acceptance will be updated.