Detector efficiency and exposure of Tunka-Rex for cosmic-ray air showers

Abstract

Tunka-Rex (Tunka Radio Extension) is an antenna array for cosmic-ray detection located in Siberia. Previous studies of cosmic rays with Tunka-Rex have shown high precision in determining the energy of the primary particle and the possibility to reconstruct the depth of the shower maximum. The next step is the reconstruction of the mass composition and the energy spectrum of cosmic rays. One of the main problems appearing within this task is to estimate the detection efficiency of the instrument, and the exposure of the observations. The detection efficiency depends on properties of the primary cosmic rays, such as energy and arrival direction, as well as on many parameters of the instrument: density of the array, efficiency of the receiving antennas, signal-detection threshold, data-acquisition acceptance, and trigger properties. More than that, the configuration of detector changes with time. During the measurements some parts of the detector can provide corrupted data or sometimes do not operate. All these features should be taken into account for an estimation of the detection efficiency. For each energy and arrival direction we estimate the detection probability and effective area of the instrument. To estimate the detection probability of a shower we use a simple Monte Carlo model, which predicts the size of the footprint of the radio emission as function of the primary energy and arrival direction (taking into account the geometry of Earth's magnetic field). Combining these approaches we calculate the event statistics and exposure for each run. This is the first accurate study of the exposure for irregular large-scale radio arrays taking into account most important features of detection, which will be used for the measurement of primary cosmic-ray spectra with Tunka-Rex.

Current Status and New Challenges of The Tunka Radio Extension

“…• Comparing the energy scales of the Tunka-133 and KASCADE-Grande instruments with its radio extensions [17]. • Development of an aperture and exposure model [14] and utilizing this model for the reconstruction of the mean shower maximum as function of energy [7]. Let us begin with the integral for area I.…”

“…It works sufficiently well only in the intermediate range of zenith angles. Comparisons of the model against the hybrid observations with TAIGA detectors as well as detailed description of the model can be found in [14].…”

Present status and prospects of the Tunka Radio Extension

“…• Development model describing aperture and exposure [26] and application of this model for the reconstruction the mean shower maximum as function of primary energy [21].…”

“…Using the efficiency model developed for Tunka-Rex [26], we applied efficiency cuts on the reconstructed events and reconstructed mean shower maximum as a function of a primary energy ( Fig. (4), left).…”

Tunka Advanced Instrument for cosmic rays and Gamma Astronomy

“…Besides this, Tunka-Rex actively uses machine learning techniques [34,35] and develops methods for reconstruction of inclined events [36]. Since Tunka-Rex features absolute energy calibration, it (and radio in general) can serve as a good tool for cross-check of systematics in the energy spectrum [37,38].…”