A novel trigger algorithm for wide-field-of-view imaging atmospheric Cherenkov technique experiments

The high-altitude detection of astronomical radiation (HADAR) experiment is a new Cherenkov observation technique with a wide field of view (FoV), aimed at observing the prompt emissions of γ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma$$\end{document}-ray bursts (GRBs). The bottleneck for this type of experiment can be found in determining how to reject the high rate of night-sky background (NSB) noise from random stars. In this work, we propose a novel method for rejecting noise, which considers the spatial properties of GRBs and the temporal characteristics of Cherenkov radiation. In space coordinates, the map between the celestial sphere and the fired photomultiplier tubes (PMTs) on the telescope’s camera can be expressed as f(δ(i,j))=δ′(i′,j′)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$f(\delta (i,j))= \delta ^\prime (i^\prime ,j^\prime )$$\end{document}, which means that a limited number of PMTs is selected from one direction. On the temporal scale, a 20-ns time window was selected based on the knowledge of Cherenkov radiation. This allowed integration of the NSB for a short time interval. Consequently, the angular resolution and effective area at 100 GeV in the HADAR experiment were obtained as 0.2∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ$$\end{document} and 104\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$10^4$$\end{document} m2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^2$$\end{document}, respectively. This method can be applied to all wide-FoV experiments.