Geometry and optics calibration of WFCTA prototype telescopes using star light

Introduction to Large High Altitude Air Shower Observatory (LHAASO)

The LHAASO~J2018+3651 region is one of the brightest sources in the sky at TeV energies. Photons with energies up to ∼0.27 PeV from this region have been detected with the Large High Altitude Air Shower Observatory (LHAASO) and here we present a detailed study of this region using more data from LHAASO. This analysis resolves the region into six sources: LHAASO~J2018+3641, LHAASO~J2019+3649, LHAASO~J2021+3657, LHAASO~J2016+3712, LHAASO~J2013+3610 and LHAASO~J2028+3655. An investigation of the morphology and spectrum for LHAASO~J2018+3641, LHAASO~J2019+3649 and LHAASO~J2021+3657 are the focus and we find that the spectrum above TeV deviates significantly from a single power-law, and is best described by a power-law with exponential cutoff. The three sources may be associated with PSR~J2021+3651 and its X-ray pulsar wind nebula. Additionally, LHAASO~J2016+3712 is tentatively associated with the evolved supernova remnant CTB 87.

The Large High Altitude Air Shower Observatory (LHAASO) is a hybrid extensive air shower (EAS) array with an area of about 1 𝑘𝑚2 at an altitude of 4410 m a.s.l. in Sichuan province, China. It contains three sub-detectors: 1 𝑘𝑚2 array (KM2A) composed of 5195 electromagnetic particle detectors (ED) and muon detectors (MD); water Cerenkov detector array (WCDA) and 18 Wide Field-of-view Cerenkov Telescope Array (WFCTA). One of the main scientific goals is measuring the individual energy spectra of cosmic rays from ~30 TeV to a couple of EeV. The construction of the whole observatory will be completed by the end of 2021. In this paper, a new energy reconstruction method and result based on KM2A simulated nuclei events will be shown.

Status of LHAASO updates from ARGO-YBJ

As part of the Large High Altitude Air Shower Observatory (LHAASO) project in China, ENDA-64—an extension of the original electron‒neutron detector array (ENDA) consisting of 16 detectors to 64 detectors—has been put into operation. The new array is intended for studying extensive air showers (EAS’s) at energies above 1 PeV and reconstructing the primary energy spectrum and chemical composition of cosmic rays. A prototype of the ENDA cluster has been fabricated on the territory of the Institute for Nuclear Research of the Russian Academy of Sciences in Moscow (ENDA-INR). The paper describes a program developed for fast simulation of the array response. The results obtained using the developed program, the Geant4 simulation software, and experimental data are compared.

The aim of the Large High Altitude Air Shower Observatory (LHAASO), supported by IHEP of the Chinese Academy of Sciences, is a multipurpose project with a complex detectors array for high energy gamma ray and cosmic ray detection. The Wide Field of view Cherenkov Telescope Array (WFCTA), as one of the components of the LHAASO project, aim to tag each primary particle that causes an air shower. The WFCTA is a portable telescope array used to detect cosmic ray spectra. The design of the readout electronics of the WFCTA is described in this paper Sixteen photomultiplier tubes (PMTs), together with their readout electronics are integrated into a single sub-cluster. To maintain good resolution and linearity over a wide dynamic range, a dual-gain amplification configuration on an analog board is used The digital board contains two 16channel 14-bit, 50 Msps analog-to-digital converters (ADC) and its power consumption, noise level, and relative deviation are all tested.

The detection of very high-energy neutrinos by IceCube experiment supports the existence of a comparable gamma-ray counterpart from the same cosmic accelerators. Under the likely assumption that the sources of these particles are of extragalactic origin, the emitted photon flux would be significantly absorbed during its propagation over cosmic distances. However, in the presence of photon mixing with ultra-light axion-like-particles (ALPs), this expectation would be strongly modified. Notably, photon-ALP conversions in the host galaxy would produce an ALP flux which propagates unimpeded in the extragalactic space. Then, the back-conversion of ALPs in the Galactic magnetic field leads to a diffuse high-energy photon flux. In this context, the recent detection of the diffuse high-energy photon flux by the Large High Altitude Air Shower Observatory (LHAASO) allows us to exclude at the 95% CL an ALP-photon coupling g_{agamma } > rsim 3.9–7.8 times 10^{-11}~mathrm {GeV^{-1}} for m_{a}lesssim 4times 10^{-7}~textrm{eV}, depending on the assumptions on the magnetic fields and on the original gamma-ray spectrum. This new bound is complementary with other ALP constraints from very-high-energy gamma-ray experiments and sensitivities of future experiments.

Status of the large high altitude air shower observatory project

The ARGO-YBJ detector, a RPC carpet array at the high altitude of 4300 m has been stably operated since 2007. As a multi-purpose experiment the physics topics of ARGO-YBJ covers the VHE gamma-ray astronomy, cosmic ray physics and solar physics. Results of these experimental studies are reviewed. And as a future extension project, the Large High Altitude Air Shower Observatory (LHAASO) is introduced, some research and development of detectors are described.

We investigate the extinction coefficients of the surface atmospheric aerosol over the Large High Altitude Air Shower Observatory (LHAASO), located at the Haizi Mountain, Daocheng County, China. To this end, we utilize the Longtin model, Mie scattering theory, and experimental data obtained by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). Our theoretical calculations show that the total extinction coefficients of the atmospheric aerosol at the wavelength of 200–500 nm are inversely proportional to the laser wavelength, and influenced by the wind speed. From July 2015 to October 2016, the extinction coefficient of the surface atmospheric aerosols at 532 nm wavelength reached 0.04 km−1 with no wind, while it increased to 0.1 km−1 with gusts. In this period, the extinction coefficients of the surface atmospheric aerosol at 532 nm wavelength, obtained by the CALIPSO, change from 0.01 to 0.07 km−1, which is less than the values obtained the theoretical calculation and larger than the average of Tibetan Plateau in 2006−2016. These calculations and experimental evidence provide important arguments to the model of atmospheric aerosol to be applied in the calibration of LHAASO. Our results suggest that the extinction coefficients over LHAASO require further study, including research on the size distribution, shape, concentration of aerosols particles, wind dependence, relative humidity dependence, etc.

Based on 42 months of observations by the Large High Altitude Air Shower Observatory(LHAASO), we report on the active behavior of the blazar Mrk 501, which exhibited several high states during this period. The most dramatic flare occurred between MJD 59334 and MJD 59348, reaching 62% of the Crab Nebula flux (> 1 TeV). The global spectral energy distribution (SED) of Mrk 501 above 1 TeV is well described by a power-law model with an exponential cutoff, yielding a power-law index of 𝛼 = 2.18 ± 0.04 and a cutoff energy of 𝐸cut = 9.51 ± 1.44 TeV. Ongoing studies focus on multi-wavelength correlations and broadband spectral modeling to further understand the underlying physical mechanisms driving these phenomena. LHAASO's all-weather capability and high duty cycle provide critical continuous data for such investigations.

The Large High Altitude Air Shower Observatory (LHAASO) is a mega-scale dual-task facility designed to study cosmic rays and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula>-rays. Online computing system of LHAASO supports its online operation and computation. Physical phenomena such as cosmic rays occur unpredictably and therefore require the online computing system to run uninterruptedly. LHAASO is large and the environment is harsh, so the online computing system is subject to failure. Once a system fails, maintenance personnel are required to quickly analyze the cause of the failure and repair it. The fault detection and diagnosis software (FADD) is designed to quickly detect and analyze system faults. The software implements comprehensive monitoring of each component of LHAASO’s online computing system (computing nodes, switches, and data flow software) and collects real-time status information. When a fault occurs, FADD can quickly analyze the cause of the fault and provide alarm information to the on-call staff as soon as possible. In addition, it can also analyze historical data within a specified period and generate data reports as needed. FADD is designed to fully consider the characteristics of large-scale high-energy physics experiments and satisfy the requirements of high throughput and high efficiency by using a distributed architecture. The software consists of the following layers: information collection layer, data analysis layer, and result layer, and contains metrics detection software, fault monitoring module, fault diagnosis module, and other functional modules. FADD has been applied to LHAASO and can diagnose operational faults quickly and accurately, helping to reduce the burden on maintenance personnel.

The Large High Altitude Air Shower Observatory (LHAASO) experiment, fully operational since July 2021, is a cutting-edge facility for detecting cosmic rays and gamma rays across a wide energy range. This paper offers an overview of the current status and recent significant scientific achievements of the LHAASO collaboration. These include the gamma-ray astronomy, charged cosmic ray physics and new physics.

The Water Cherenkov Detector Array (WCDA) is one of the core detectors in the Large High Altitude Air Shower Observatory (LHAASO), and it consists of 3600 photomultiplier tubes (PMTs). Both high resolution time and charge measurement are required over a large dynamic range from 1 photoelectron (P.E.) to 4000 P.E. The prototype of an analogue front-end Application Specific Integrated Circuit (ASIC) fabricated using Global Foundry 0.35 μm CMOS technology is designed to read out the PMT signal in the WCDA. This ASIC employs leading edge discrimination and an (RC)4 shaping structure. Combined with the following Time-to-Digital Converter (TDC) and Analog-to-Digital Converter (ADC), both the arrival time and charge of the PMT signal can be measured. Initial test results indicate that time resolution is better than 350 ps and charge resolution is better than 10% at 1 P.E. and better than 1% with large input signals (300 P.E. to 4000 P.E.). Besides, this ASIC has a good channel-to-channel isolation of more than 84 dB and the temperature dependency of charge measurement is less than 5% in the range 0–50°C.

Context. The first Large High Altitude Air Shower Observatory (LHAASO) catalog presents six enigmatic ultra-high-energy (UHE) γ-ray sources with lonely &gt; 25 TeV emission being detected, which are indicated as 1LHAASO: J0007+5659u, J0206+4302u, J0212+4254u, J0216+4237u, J1740+0948u, and J1959+1129u. No counterparts of the six sources have been observed except two energetic pulsars, PSR J0218+4232 and PSR J1740+1000. Among them, 1LHAASO: J0206+4302u, J0212+4254u, and J0216+4237u are connected on the significance map and constitute a dumbbell-like structure. They are close in position and show a similar spectral shape, suggesting a physical association among them. Aims. To explain the origin of the six LHAASO sources, especially the intriguing dumbbell-like structure, we conducted leptonic and hadronic modeling research according to our multiwavelength and multimessenger study. For the dumbbell-like structure, models with traveling pulsar wind nebulae (PWNe) were considered. Methods. The multiwavelength and multimessenger study was based on the Fermi-LAT, Swift-XRT, Planck, CfA 12CO survey, and IceCube neutrino datasets. In the traveling PWN modeling research, we assumed an isotropic and homogeneous diffusion condition and discussed the influence of the diffusion coefficient, distance, and proper motion velocity. Results. We do not discover any counterparts in the multiwavelength and multimessenger study except the two known pulsars. The traveling PWN modeling attempt with a single PWN appears to be implausible for explaining the dumbbell-like structure, as the diffusion coefficient needs to be much lower than the Bohm limit. We also explored a double traveling PWNe model, and it could account for the results of the LHAASO observations. However, the probability of the occurrence of this explanation is significantly lower than that of a conventional triple PWNe explanation. Furthermore, according to our model, the only known pulsar, PSR J0218+4232, is unlikely to be associated with the dumbbell-like structure in an isotropic and homogeneous diffusion environment. The expected teraelectronvolt emission of this pulsar is far from explaining even the eastern part of the structure.