Application of deep learning methods combined with physical background in wide field of view imaging atmospheric Cherenkov telescopes

The High Altitude Detection of Astronomical Radiation(HADAR)experiment,which was constructed in Tibet,China,combines the wide-angle advantages of traditional EAS array detectors with the high-sensitivity advantages of focused Cherenkov detectors.Its objective is to observe transient sources such as gamma-ray bursts and the counterparts of gravitational waves.This study aims to utilize the latest AI technology to enhance the sensitivity of HADAR experiments.Training datasets and models with distinctive creativity were constructed by incorporating the relevant physical theories for various applications.These models can determine the type,energy,and direction of the incident particles after careful design.We obtained a background identification accuracy of 98.6%,a relative energy reconstruction error of 10.0%,and an angular resolution of 0.22°in a test dataset at 10 TeV.These findings demonstrate the significant potential for enhancing the precision and dependability of detector data analysis in astrophysical research.By using deep learning techniques,the HADAR experiment’s observational sensitivity to the Crab Nebula has surpassed that of MAGIC and H.E.S.S.at energies below 0.5 TeV and remains competitive with conventional narrow-field Cherenkov telescopes at higher energies.In addition,our experiment offers a new approach for dealing with strongly connected,scattered data.

Study on the Performance of the GRANDProto300 Particle Detector Array by Simulation

The Giant Radio Array for Neutrino Detection(GRAND)is a proposed large-scale observatory designed to detect cosmic rays,gamma-rays,and neutrinos with energies exceeding 100 Pe V.The GRANDProto300 experiment is proposed as the early stage of the GRAND project,consisting of a hybrid array of radio antennas and scintillator detectors.The latter,as a mature and traditional detector,is used to cross-check the nature of the candidate events selected from radio observations.In this study,we developed a simulation software called G4GRANDProto300,based on the Geant4 software package,to optimize the spacing of the scintillator detector array and to investigate its effective area.The analysis was conducted at various zenith angles under different detector spacings,including 300,500,600,700,and 900 m.Our results indicate that,for large zenith angles used to search for cosmic-ray in the GRAND project,the optimized effective area is with a detector spacing of 500 m.The G4GRANDProto300 software that we developed could be used to further optimize the layout of the particle detector array in future work.

Prospects for the detection rate of very-high-energyγ-ray emissions from shortγ-ray bursts with the HADAR experiment

The observation of short gamma ray bursts(SGRBs)in the TeV energy range plays an important role in understanding the radiation mechanism and probing potential new physics,such as Lorentz invariance violation(LIV).However,no SGRBs have been observed in this energy range owing to the short duration of SGRBs and the weakness of current experiments.New experiments with new technology are required to detect the very high energy(VHE)emission of SGRBs.In this study,we simulate the VHE γ-ray emissions from SGRBs and calculate the annu-al detection rate with the High Altitude Detection of Astronomical Radiation(HADAR)experiment.First,a set of pseudo-SGRB samples is generated and checked using the observations of the Fermi-GBM,Fermi-LAT,and Swift-BAT measurements.The annual detection rate is calculated from these SGRB samples based on the performance of the HADAR instrument.As a result,the HADAR experiment can detect 0.5 SGRBs per year if the spectral break-off of γ-rays caused by the internal absorption and Klein-Nishina(KN)effect is larger than 100 GeV.For a GRB090510-like GRB in HADAR's view,it should be possible to detect approximately 2000 photons considering the internal absorption and KN effect.With a time delay assumption due to LIV effects,a simulated light curve of GRB090510 has evident energy dependence.We hope that the HADAR experiment can perform SGRB observa-tions and test our calculations in the future.

Chapter 6 Multimessenger Physics

Combining observations of multi-messengers help in boosting the sensitivity of astrophysical source searches,and probe various aspects of the source physics.In this chapter we discuss how LHAASO observations of very high energy(VHE)gamma rays in combination with telescopes for the other messengers can help in solving the origins of VHE neutrinos and galactic and extragalactic cosmic rays.

Testing and analysis of the plastic scintillator units for LHAASO-ED

Background A total of 5195 electromagnetic particle detectors(EDs)are used in the 1-square-kilometer extensive air shower array(KM2A),which is a subarray of the Large High Altitude Air Shower Observatory(LHAASO).Purpose As the detection sensitive medium of the EDs,more than 20,000 plastic scintillator units(BC-408),produced by Saint-Gobain,are used in LHAASO.It is important to monitor the light output of the scintillator units among the units.Method To improve the efficiency,a sampling inspection scheme(misjudgment rate of less than 5%)was designed,and a batch test system was developed.Ten units of scintillator units can be measured at a time.The test system selects the single muon events of cosmic rays to measure the light output values of the plastic scintillator units.Results The measurement has an uncertainty of less than 2%.By pretest calibration,the difference between different channels can be eliminated.The calibration was implemented approximately every 3 months,and the test system had been running stably for 28 months.By measuring the ratio of the signals of selected far and near probe events,the changes in the quality of different batches of plastic scintillator units can be demonstrated.Conclusions The test system realized accurate measurement of the light output,and all batches satisfied the requirements of the experiment.