Measurement of the radial distribution of Cherenkov light generated by TeV γ-ray air showers

Abstract

Using air showers induced by TeV γ-rays from Mrk 501, the radial distribution of Cherenkov light is investigated. The shower geometry is reconstructed from the stereoscopic shower images obtained with the telescopes of the HEGRA IACT system. With the core position known to better than 10 m, the light yield as a function of the distance to the shower axis is derived by comparing event-by-event the image intensities measured in the different telescopes. We observe a change in the shape of the light pool with shower energy, and with zenith angle. Data are well reproduced by Monte-Carlo air shower simulations.

On the optimum spacing of stereoscopic imaging atmospheric Cherenkov telescopes

“…Over the last years, the quality of these simulations has improved significantly, both concerning the reliability of the shower simulation [7] and concerning the details of the simulation of the telescopes and their readout (see, e.g, [8]). Simulations have been tested extensively, and key characteristics, such as the radial distribution of Cherenkov light in the light pool, have been verified experimentally [9]. Nevertheless, a direct experimental verification of the dependence of the performance of IACT systems on the intertelescope distance would be highly desirable.…”

Lateral Density Distributions of Cherenkov Photons at Different Altitudes

“…The higher the observation altitude, the more Cherenkov photons were generated by primary incident γ-rays with various energies before a hump formed. The differences in the photon density decreased as the distance from the shower core increased (Aharonian & Akhperjanian, 1999). After a hump was formed, the photon densities determined at three observation altitudes were nearly identical.…”