Asymmetries observed in giant air showers using water Cherenkov detectors

Evidence of azimuthal asymmetries in the time structure and signal size has been found in non-vertical showers as a function of zenith angle. These asymmetries arise because of the different paths traveled by particles in the upper and lower sides of the plane perpendicular to the shower axis to reach detectors at the same axial distances. The shower particles are differentially attenuated as they traverse the atmosphere. Furthermore, most particles are not propagating strictly in the shower direction but are on average going away from the axis. This geometrical projection effect also contributes to the final asymmetry. These novel observations must be understood for parameterisation of the lateral distribution function. Additionally, the asymmetry in time distributions offers a new possibility for the determination of the mass composition because its magnitude is strongly dependent on the fraction of electromagnetic signal at the observation level. The asymmetries found in data collected from the Engineering Array of the Auger Observatory will be compared with Monte Carlo data.

Note:

Talk given at 28th International Cosmic Ray Conferences (ICRC 2003), Tsukuba, Japan, 31 Jul - 7 Aug 2003

talk: Tsukuba 2003/07/31
cosmic radiation: primary
showers: air
Cherenkov counter: water
angular distribution: asymmetry
spatial distribution: parametrization
data analysis method
numerical calculations: Monte Carlo
interpretation of experiments

References(2)

Figures(4)

AIRES: A system for air shower simulations

S.J. Sciutto
(
- La Plata U.
)

e-Print:
- astro-ph/9911331
•
DOI:
- 10.13140/RG.2.2.12566.40002

- Phys.Atom.Nucl. 1993 56