A new small array of cherenkov detectors is deployed in Tehran, 1200 m above sea level. This array contains of four tanks full of distilled water with diameter of 60 cm and height of 120 cm. The effective area of each tank is about 0.6 . They are used to detect the air showers and to record the arrival time of the secondary particles. We have collected about 200000 EAS in 1894 h of observation time from nov-2005 to Feb-2006. We find zenith and azimuth distribution of EAS with this array. A distribution with n=5.70.1 was obtained for zenith angle and a West-East asymmetry has been observed in the azimuthal distribution of EAS of cosmic rays because of the magnetic field of the Earth. This asymmetry is about 1%. Since this tank of distilled water is cheaper and more available than Scintillators it is preferable to use them instead of Scintillators in our future larger array. Result of data analysis and computer simulation with CORSIKA code is presented in this paper.

Proceedings of the 30th International Cosmic Ray Conference; Rogelio Caballero, Juan Carlos D'Olivo, Gustavo Medina-Tanco, Lukas Nellen, Federico A. Sánchez, José F. Valdés-Galicia (eds.); Universidad Nacional Autónoma de México, Mexico City, Mexico, 2008; Vol. 5 (HE part 2), pages 909-912