Abstract
The extremely low flux of ultra-high energy cosmic rays (UHECR) makes their direct observation by orbital experiments practically impossible. For this reason all current and planned UHECR experiments detect cosmic rays indirectly by observing the extensive air showers (EAS) initiated by cosmic ray particles in the atmosphere. The world largest statistics of the ultra-high energy EAS events is recorded by the networks of surface stations. In this paper we consider a novel approach for reconstruction of the arrival direction of the primary particle based on the deep convolutional neural network. The latter is using raw time-resolved signals of the set of the adjacent trigger stations as an input. The Telescope Array (TA) Surface Detector (SD) is an array of 507 stations, each containing two layers plastic scintillator with an area of 3 m2. The training of the model is performed with the Monte-Carlo dataset. It is shown that within the Monte-Carlo simulations, the new approach yields better resolution than the traditional reconstruction method based on the fitting of the EAS front. The details of the network architecture and its optimization for this particular task are discussed.
Highlights
The extremely low flux of ultra-high energy cosmic rays (UHECR) makes their direct observation by orbital experiments practically impossible
The paper is organised as follows: in Section 2 we briefly review the standard reconstruction procedure of UHECR properties used in Telescope Array (TA) Surface Detector (SD) and describe a new method to enhance this reconstruction by means of the convolutional neural network (CNN)
One may see that both the bias and the width of the distribution are smaller for the CNN reconstruction than the standard method
Summary
The extremely low flux of ultra-high energy cosmic rays (UHECR) makes their direct observation by orbital experiments practically impossible. Though being weakly dependent on UHECR source model and composition the large and intermediate scale anisotropy approach can give only a general picture of what real sources could be [20,21,22] These results are more demanding for an accuracy of the UHECR energy reconstruction than the accuracy of reconstruction of events arrival directions. Among the results of these methods application are HiRes evidence of small fraction of UHECR from BL Lacs [23, 24] as well as a recent Auger result on starburst galaxies [25] Another approach is based on the study of events auto-correlation at small angles and search for spatial doublets or triplets of events the present results on auto-correlation are consistent with the isotropic distribution of events, the lower limits on the density of the UHECR sources are established [26, 27]. The improvement in experiment’s angular resolution may boost the analyses of this kind, while the simultaneous improvement in energy resolution may be required
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