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.

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.

Lateral distribution of EAS muons measured for the primary cosmic ray energy around 100 TeV

The muonic component of the extensive air showers (EAS) is of great importance for the astroparticle physics. It carries the information about the properties of primary cosmic ray (CR) particles, such as their mass, and electromagnetic and hadronic nature. It provides a sensitive test for the hadronic interaction models, which are inevitable for describing the cascade shower development of cosmic rays in EAS experiments. The YangBaJing Hybrid Array (YBJ-HA) experiment has been in operation since the end of 2016. Surface detectors are used for the measurements of primary energy, angular direction and core position of a shower event, while underground muon detectors are used for measuring the density of muons at various locations. Using the data obtained by the YBJ-HA experiment,this work reports the first measurement of the lateral muon distribution for the primary cosmic ray energy in the 100TeV region. The punch-through effect is evaluated via MC simulation.

Anaphthalimide-based fluorescent probe for mercapto-containing compounds

A polarity-sensitive fluorescent probe MNP was rationally designed and synthesized with naphthalimide as the fluorophore and maleimide as the receptor for thiols. MNP is weakly fluorescent due to the photoinduced electron-transfer （PET） from the fluorophore to the receptor, and it displays evidently solvatochromic UV-vis and fluorescence spectra： the emission shifted from 495 nm in n-hexane to 545 nm in phosphate buffer solution. Michael addition reaction between thiols and the maleimide in MNP inhibited the PET process, which led to about eight-fold fluorescence enhancement. In addition, MNP showed highly sensitivity to rnercapto-containing proteins and it could detect as low as 20.4 μg/mL of BSA in PBS. MNP has potential in fluorescent imaging of thiols in living cells.

100 TeV diffuse γ-rays observation by YangBaJing Hybrid Array

Purpose Cosmic rays up to PeV energy are believed to be generated in our galaxy.γ-rays at 100TeV energies are important probe to identify PeVtrons.Besides,γ-rays contain additional information on the propagation of the galactic cosmic rays.Methods Diffuseγ-rays originating from the Galactic plane from 20 to 200 TeV region are studied with early 160-day data collected by YangBaJing Hybrid Array(YBJ-HA),which is a hybrid array and consists of scintillation detectors and underground muon detectors.All-distance equi-zenith angle and time-swapping methods are used to analyze the number ofγ-rays excess.Result and conclusion Because of no significant observation onγ-ray emission,Helene's method is adopted to derive the 90%confidence level upper limits on the flux of diffuse galacticγ-rays.And the limit to the ratio of the flux ofγ-rays to CRs is obtained at the order of 10^(-4),which is the current best result at these energies.

Electron and positron spectra in three-dimensional spatial-dependent propagation model

The spatial-dependent propagation(SDP)model has been demonstrated to account for the spectral hardening of both primary and secondary Cosmic Rays(CRs)nuclei above about 200 GV.In this work,we further apply this model to the latest AMS-02 observations of electrons and positrons.To investigate the effect of different propagation models,both homogeneous diffusion and SDP are compared.In contrast to the homogeneous diffusion,SDP brings about harder spectra of background CRs and thus enhances background electron and positron fluxes above tens of GeV.Thereby,the SDP model could better reproduce both electron and positron energy spectra when introducing a local pulsar.The influence of the background source distribution is also investigated,where both axisymmetric and spiral distributions are compared.We find that considering the spiral distribution leads to a larger contribution of positrons for energies above multi-GeV than the axisymmetric distribution.In the SDP model,when including a spiral distribution of sources,the all-electron spectrum above TeV energies is thus naturally described.In the meantime,the estimated anisotropies in the all-electrons spectrum show that in contrary to the homogeneous diffusion model,the anisotropy under SDP is well below the observational limits set by the Fermi-LAT experiment,even when considering a local source.