Study of the Shadows of the Moon and the Sun with VHE Cosmic Rays
/ Authors
R. Atkins, W. Benbow, D. Berley, M. Chen, D. Coyne, R. Delay, B. Dingus, D. Dorfan, R. Ellsworth, D. Evans
and 33 more authors
A. Falcone, L. Fleysher, R. Fleysher, G.Gisler, J. Goodman, T. Haines, C. Hoffman, S. Hugenberger, L. Kelley, I. Leonor, J. Macri, M. McConnell, J. McCullough, J. Mcenery, R. Miller, A. Mincer, M. Morales, P. Némethy, J. Ryan, M. Schneider, B. Shen, A. Shoup, G. Sinnis, A. Smith, G. Sullivan, T. Thompson, O. Tumer, K. Wang, M. Wascko, S. Westerhoff, D. Williams, T. Yang, G. Yodh
/ Abstract
Milagrito, a prototype for the Milagro detector, operated for 15 months in 1997-8 and collected 8.9 billion events. It was the first extensive air shower (EAS) array sensitive to showers intiated by primaries with energy below 1 TeV. The shadows of the sun and moon observed with cosmic rays can be used to study systematic pointing shifts and measure the angular resolution of EAS arrays. Below a few TeV, the paths of cosmic rays coming toward the earth are bent by the helio- and geo-magnetic fields. This is expected to distort and displace the shadows of the sun and the moon. The moon shadow, offset from the nominal (undeflected) position, has been observed with high statistical significance in Milagrito. This can be used to establish energy calibrations, as well as to search for the anti-matter content of the VHE cosmic ray flux. The shadow of the sun has also been observed with high significance.