The study of high-energy gamma-ray emission from gamma-ray bursts(GRBs)involves complex synchrotron radiation and synchrotron self-Compton(SSC)scattering mechanisms with multiple parameters exhibiting a wide distribut...The study of high-energy gamma-ray emission from gamma-ray bursts(GRBs)involves complex synchrotron radiation and synchrotron self-Compton(SSC)scattering mechanisms with multiple parameters exhibiting a wide distribution.Recent advancements in GRB research,particularly the observation of very high energy(VHE,>100 Ge V)radiation,have ushered in a new era of multiwavelength exploration,offering fresh perspectives and limitations for understanding GRB radiation mechanisms.This study aimed to leverage VHE observations to refine constraints on synchrotron+SSC radiation from electrons accelerated by forward shocks.By analyzing two external environments—the uniform interstellar medium and stratified stellar wind medium,we conducted spectral and variability fitting for five specific bursts(GRB 180720B,GRB 190114C,GRB 190829A,GRB 201216C,and GRB 221009A)to identify the optimal parameters characterizing these events.A comparative analysis of model parameter distributions with and without VHE radiation observations reveals that the magnetic energy equipartition factorεBis more concentrated with VHE emissions.This suggests that VHE emissions may offer greater constraints on this microphysical parameter.Additionally,we found that the energy budget between VHE and ke V–Me Vγ-ray emissions under the SSC radiation exhibits an almost linear relationship,which may serve as a tool to differentiate radiation mechanisms.We anticipate future statistical analyses of additional VHE bursts to validate our findings.展开更多
With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence...With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence,the Sun and Moon would have some impacts on the observation of gamma-ray sources,which have not been taken into account in previous analysis.In this paper,the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is estimated.The tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some period.The absorption of very high energy gamma rays by sunlight is estimated with detailed method and some useful conclusions are achieved.The main influence is the block of the Sun and Moon on gamma rays and the shadow on the cosmic ray background.The influence is investigated considering the detector angular resolution and some strategies on data analysis are proposed to avoid the underestimation of the gamma-ray emission.展开更多
By accurately measuring composition and energy spectrum of cosmic ray,the origin problem of so called“knee”region(energy>one PeV)can be solved.However,up to the present,the results of the spectrum in the knee reg...By accurately measuring composition and energy spectrum of cosmic ray,the origin problem of so called“knee”region(energy>one PeV)can be solved.However,up to the present,the results of the spectrum in the knee region obtained by several previous experiments have shown obvious differences,so they cannot give effective evidence for judging the theoretical models on the origin of the knee.Recently,the Large High Altitude Air Shower Observatory(LHAASO)has reported several major breakthroughs and important results in astro-particle physics field.Relying on its advantages of wide-sky survey,high altitude location and large area detector arrays,the research content of LHAASO experiment mainly includes ultra high-energy gamma-ray astronomy,measurement of cosmic ray spectra in the knee region,searching for dark matter and new phenomena of particle physics at higher energy.The electron and thermal neutron detector(EN-Detector)is a new scintillator detector which applies thermal neutron detection technology to measure cosmic ray extensive air shower(EAS).This technology is an extension of LHAASO.The EN-Detector Array(ENDA)can highly efficiently measure thermal neutrons generated by secondary hadrons so called“skeleton”of EAS.In this paper,we perform the optimization of ENDA configuration,and obtain expectations on the ENDA results,including thermal neutron distribution,trigger efficiency and capability of cosmic ray composition separation.The obtained real data results are consistent with those by the Monte Carlo simulation.展开更多
In the first part of this Chapter the present state of knowledge from the observations of cosmic rays between 10^(13) and 10^(20) eV is summarized.This is not intended to be a complete review,but rather a broad overvi...In the first part of this Chapter the present state of knowledge from the observations of cosmic rays between 10^(13) and 10^(20) eV is summarized.This is not intended to be a complete review,but rather a broad overview of the relevant processes involving cosmic rays,including the astrophysical environments in which they take place.This overview mainly concerns experimental results and phenomenological aspects of their interpretation,therefore experiments’description is not given but references to the vast bibliography are provided in the text.Some attempt is made to address the most popular explanations offered by theoretical models.The second part is devoted to the description of the LHAASO performance and of its capability to provide a response to several open questions,still unanswered,concerning cosmic rays above 10^(13) eV,highlighting which major steps forward in this field could be taken from LHAASO observations.展开更多
The reconstruction of muon energies is crucial for the data analysis of neutrino experiments using large water Cherenkov detectors,but the resolution for muon energy reconstruction using traditional methods is poor.He...The reconstruction of muon energies is crucial for the data analysis of neutrino experiments using large water Cherenkov detectors,but the resolution for muon energy reconstruction using traditional methods is poor.Here,we propose a revised approach to remove noisy optical modules along the track produced by the propagation of muons through water.The number of photons on the optical modules is first corrected by the attenuation properties of light in water.Then the difference in time between the observed optical modules and the expected ones is determined based on the geometry of the triggered optical modules.Finally,the standard of correction is measured by the ratio of photon number before and after correction.Optical modules selection conditions were optimized according to these parameters,with most noisy optical modules successfully removed,improving the resolution of muon energy reconstruction.展开更多
The large array of imaging atmospheric Cherenkov telescopes(LACT)is a planned array of 32 Cherenkov telescopes,each featuring 6-m diameter mirrors,to be constructed at the LHAASO site.This study focused on optimizing ...The large array of imaging atmospheric Cherenkov telescopes(LACT)is a planned array of 32 Cherenkov telescopes,each featuring 6-m diameter mirrors,to be constructed at the LHAASO site.This study focused on optimizing the array layout and analyzing the performance of LACT.Two observation modes were examined:large zenith angle observations for ultra-high energy events and small zenith angle observations for lower energy thresholds.For large zenith angles(60°),simulations indicate that an 8-telescope subarray can achieve an effective area of 3km^(2)with excellent angular resolution.For small zenith angles,we optimized the layout of 4-telescope cells and the full 32-telescope array.The energy threshold of the full array is approximately 200 GeV,which is particularly crucial for studying transient phenomena such as gamma-ray bursts(GRBs)and active galactic nuclei(AGNs).This study provides essential guidance for finalizing the LACT layout design and estimating performance under various observational conditions.It also highlights the potential of LACT for conducting deep observations of ultra-high energyγ-ray sources,performing morphological studies of PeVatrons,and advancing time-domainγ-ray astronomy.展开更多
In this paper,we report the detection of the very-high-energy(VHE,100 GeV<E<100 TeV)and ultra-high-energy(UHE,E>100 TeV)y-ray emissions from the direction of the young star-forming region W43,observed by the ...In this paper,we report the detection of the very-high-energy(VHE,100 GeV<E<100 TeV)and ultra-high-energy(UHE,E>100 TeV)y-ray emissions from the direction of the young star-forming region W43,observed by the Large High Altitude Air Shower Observation(LHAASO).The extendedγ-ray source was detected with a significance of~16σby KM2A and~17σby WCDA,respectively.The angular extension of this y-ray source is about 0.5 degrees,corresponding to a physical size of about 50pc.We discuss the origin of theγ-ray emission and possible cosmic ray acceleration in the W43 region using multi-wavelength data.Our findings suggest that W43 is likely another young star cluster capable of accelerating cosmic rays(CRs)to at least several hundred TeV.展开更多
We report the detection of an extended very-high-energy(VHE)γ-ray source coincident with the location of middle-aged(62.4 kyr)pulsar PSR J0248+6021,by using the LHAASO-WCDA data of live 796 d and LHAASO-KM2A data of ...We report the detection of an extended very-high-energy(VHE)γ-ray source coincident with the location of middle-aged(62.4 kyr)pulsar PSR J0248+6021,by using the LHAASO-WCDA data of live 796 d and LHAASO-KM2A data of live 1216d.A significant excess of y-ray induced showers is observed both by WCDA in energy bands of 1-25 TeV and KM2A in energy bands of>25 TeV with 7.3σand 13.5σ,respectively.The best-fit position derived through WCDA data is R.A.=42.06°±0.12°and Dec.=60.24°±0.13°with an extension of 0.69°±0.15°and that of the KM2A data is R.A.=42.29°±0.13°and Dec.=60.38°±0.07°with an extension of 0.37°±0.07°.No clear extended multiwavelength counterpart of this LHAASO source has been found from the radio band to the GeV band.The most plausible explanation of the VHEγ-ray emission is the inverse Compton process of highly relativistic electrons and positrons injected by the pulsar.These electrons/positrons are hypothesized to be either confined within the pulsar wind nebula or to have already escaped into the interstellar medium,forming a pulsar halo.展开更多
We report a dedicated study of the newly discovered extended UHEγ-ray source 1LHAASO J0056+6346u.Analyzing 979 d of LHAASO-WCDA data and 1389 d of LHAASO-KM2A data,we observed a significant excess ofγ-ray events wit...We report a dedicated study of the newly discovered extended UHEγ-ray source 1LHAASO J0056+6346u.Analyzing 979 d of LHAASO-WCDA data and 1389 d of LHAASO-KM2A data,we observed a significant excess ofγ-ray events with both WCDA and KM2A.Assuming a point power-law source with a fixed spectral index,the significance maps reveal excesses of 12.65σ,22.18σ,and 10.24σin the energy ranges of 1-25,25-100,and>100 TeV,respectively.We use a 3D likelihood algorithm to derive the morphological and spectral parameters,and the source is detected with significances of 13.72σby WCDA and 25.27σby KM2A.The best-fit positions derived from WCDA and KM2A data are(R.A.=13.96°±0.09°,Decl.=63.92°±0.05°)and(R.A.=14.00°±0.05°,Decl.=63.79°±0.02°),respectively.The angular size(r_(39))of 1LHAASO J0056+6346u is 0.34°±0.04°at 1-25 TeV and 0.24°±0.02°at>25 TeV.The differential flux of this UHEγ-ray source can be described by an exponential cutoff power-law function:(2.67±0.25)×10^(-15)(E/20 TeV)^((-1.97±0.10))e^(-E/(55.1±7.2)TeV)TeV^(-1)cm^(-2)s^(-1).To explore potential sources ofγ-ray emission,we investigated the gas distribution around 1LHAASO J0056+6346u.1LHAASO J0056+6346u is likely to be a TeV PWN powered by an unknown pulsar,which would naturally explain both its spatial and spectral properties.Another explanation is that this UHEγ-ray source might be associated with gas content illuminated by a nearby CR accelerator,possibly the SNR candidate G124.0+1.4.展开更多
The ultra-high-energy(UHE)gamma-ray source 1LHAASO J0007+7303u is positionally associated with the composite SNR CTA1 that is located at high Galactic Latitude b≈10.5°.This provides a rare opportunity to spatial...The ultra-high-energy(UHE)gamma-ray source 1LHAASO J0007+7303u is positionally associated with the composite SNR CTA1 that is located at high Galactic Latitude b≈10.5°.This provides a rare opportunity to spatially resolve the component of the pulsar wind nebula(PWN)and supernova remnant(SNR)at UHE.This paper conducted a dedicated data analysis of 1LHAASO J0007+7303u using the data collected from December 2019 to July 2023.This source is well detected with significances of 21σand 17σat 8-100 TeV and>100 TeV,respectively.The corresponding extensions are determined to be 0.23°±0.03°and 0.17°±0.03°.The emission is proposed to originate from the relativistic electrons accelerated within the PWN of PSR J0007+7303.The energy spectrum is well described by a power-law with an exponential cutoff function dN/dE=(42.4±4.1)(E/20TeV)^(-2.31+0.11)exp(-E/(110±25Tev))TeV-1 cm^(-2)s^(-1)in the energy range from 8 to 300 TeV,implying a steady-state parent electron spectrum dN_(e)/dE_(e)∝(E_(e)/100TeV)^(-3.13±0.16)exp[(-E_(e)/(373±70TeV))^(2)]at energies above≈50 TeV.The cutoff energy of the electron spectrum is roughly equal to the expected current maximum energy of particles accelerated at the PWN terminal shock.Combining the X-ray and gamma-ray emission,the current space-averaged magnetic field can be limited to≈4.5μG.To satisfy the multi-wavelength spectrum and the y-ray extensions,the transport of relativistic particles within the PWN is likely dominated by the advection process under the free-expansion phase assumption.展开更多
The Water Cherenkov Detector Array(WCDA) is a major component of the Large High Altitude Air Shower Array Observatory(LHAASO), a new generation cosmic-ray experiment with unprecedented sensitivity, currently under con...The Water Cherenkov Detector Array(WCDA) is a major component of the Large High Altitude Air Shower Array Observatory(LHAASO), a new generation cosmic-ray experiment with unprecedented sensitivity, currently under construction. WCDA is aimed at the study of TeV γ-rays. In order to evaluate the prospects of searching for TeV γ-ray sources with WCDA, we present a projection of the one-year sensitivity of WCDA to TeV γ-ray sources from TeVCat using an all-sky approach. Out of 128 TeVCat sources observable by WCDA up to a zenith angle of 45°, we estimate that 42 would be detectable in one year of observations at a median energy of 1 TeV. Most of them are Galactic sources, and the extragalactic sources are Active Galactic Nuclei(AGN).展开更多
The tiny modification of dispersion relation induced by Lorentz violation(LV)is an essential topic in quantum gravity(QG)theories,which can be magnified into significant effects when dealing with astrophysical observa...The tiny modification of dispersion relation induced by Lorentz violation(LV)is an essential topic in quantum gravity(QG)theories,which can be magnified into significant effects when dealing with astrophysical observations at high energies and long propagation distances.LV would lead to photon decay at high energies;therefore,observations of high-energy photons could constrain LV or even QG theories.The Large High Altitude Air Shower Observatory(LHAASO)is the most sensitive gamma-array instrument currently operating above 100 TeV.Recently,LHAASO reported the detection of 12 sources above 100 TeV with maximum photon energy exceeding 1 PeV.According to these observations,the most stringent restriction is achieved in this study,i.e.,limiting the LV energy scale to 1.7×10^(33) eV,which is over 139,000 times that of the Planck energy,and achieving an improvement of approximately 1.9 orders of magnitude over previous limits.展开更多
The Galactic plane serves as a natural laboratory for exploring high-energy astrophysical processes,where cosmic rays are accelerated,propagate,and interact with other components in the interstellar medium(ISM).With i...The Galactic plane serves as a natural laboratory for exploring high-energy astrophysical processes,where cosmic rays are accelerated,propagate,and interact with other components in the interstellar medium(ISM).With its unprecedented sensitivity and extensive energy coverage,the Large High Altitude Air Shower Observatory(LHAASO) has opened a new era of Galactic gamma-ray astronomy,especially in the ultra-high-energy(UHE) domain.The recent “Galactic Mini Survey” conducted by LHAASO provides an unprecedented view of UHE gamma-ray sources within the Milky Way.展开更多
I.EXECUTIVE SUMMARY next-generation,high-intensity electron-positron collider"Higgs factory",such as the Circular Electron-Positron Collider(CEPC),is among the highest priorities for the global high-energy c...I.EXECUTIVE SUMMARY next-generation,high-intensity electron-positron collider"Higgs factory",such as the Circular Electron-Positron Collider(CEPC),is among the highest priorities for the global high-energy collider physics community.The CEPC can provide unprecedented opportunities for making fundamental discoveries and providing decisive insights in the quest for a"New Standard Model(SM)"of nature's fundamental interactions.The CEPC could:·Identify the origin of matter,especially the mechanism related to the first-order phase transition in the early Universe,which could produce a detectable gravitational wave signal.展开更多
We report the detection of aγ-ray bubble spanning at least 100deg2 in ultra-high energy(UHE)up to a few PeV in the direction of the star-forming region Cygnus X,implying the presence super PeVatron(s)accelerating pro...We report the detection of aγ-ray bubble spanning at least 100deg2 in ultra-high energy(UHE)up to a few PeV in the direction of the star-forming region Cygnus X,implying the presence super PeVatron(s)accelerating protons to at least 10 PeV.A log-parabola form with the photon indexΓ(E)=(2.71±0.02)+(0.11±0.02)×log10(E/10 TeV)is found fitting the gamma-ray energy spectrum of the bubble well.UHE sources,“hot spots”correlated with very massive molecular clouds,and a quasi-spherical amorphousγ-ray emitter with a sharp central brightening are observed in the bubble.In the core of~0.5°,spatially associating with a region containing massive OB association(Cygnus OB2)and a microquasar(Cygnus X-3),as well as previously reported multi-TeV sources,an enhanced concentration of UHEγ-rays is observed with 2 photons at energies above 1 PeV.The general feature of the bubble,the morphology,and the energy spectrum,are reasonably reproduced by the assumption of a particle accelerator in the core,continuously injecting protons into the ambient medium.展开更多
The Large High Altitude Air Shower Observatory(LHAASO)(Fig.1)is located at Mt.Haizi(4410 m a.s.l.,600 g/cm^(2),29°21'27.56"N,100°08'19.66"E)in Daocheng,Sichuan province,P.R.China.LHAASO con...The Large High Altitude Air Shower Observatory(LHAASO)(Fig.1)is located at Mt.Haizi(4410 m a.s.l.,600 g/cm^(2),29°21'27.56"N,100°08'19.66"E)in Daocheng,Sichuan province,P.R.China.LHAASO consists of 1.3 km^(2) array(KM2A)of electromagnetic particle detectors(ED)and muon detectors(MD),a water Cherenkov detector array(WCDA)with a total active area of 78,000 m^(2),18 wide field-of-view air Cherenkov telescopes(WFCTA)and a newly proposed electron-neutron detector array(ENDA)covering 10,000 m^(2).Each detector is synchronized with all the other through a clock synchronization network based on the White Rabbit protocol.The observatory includes an IT center which comprises the data acquisition system and trigger system,the data analysis facility.In this Chapter,all the above-mentioned components of LHAASO as well as infrastructure are described.展开更多
Purpose The LHAASO project collects trillions of cosmic ray events every year,generating about 10 PB of raw data annually,which brings big challenges for data processing platform.Method The LHAASO data processing plat...Purpose The LHAASO project collects trillions of cosmic ray events every year,generating about 10 PB of raw data annually,which brings big challenges for data processing platform.Method The LHAASO data processing platform is built to handle such a large amount of data,which is composed of some subsystems such as data transfer,data storage,high throughput computing and metadata management.Results and conclusions The platform was under construction since 2018 and has been working well since 2021.In this paper,the details of the design,implementation and performance of the data processing platform are presented.展开更多
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).Purpo...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.展开更多
Background Silicon photomultiplier tube(SiPM)has been widely applied in high energy physics experiments.The wide field of view Cherenkov telescope array of Large High Altitude Air Shower Observatory(LHAASO)consists of...Background Silicon photomultiplier tube(SiPM)has been widely applied in high energy physics experiments.The wide field of view Cherenkov telescope array of Large High Altitude Air Shower Observatory(LHAASO)consists of 12 arrays of SiPMs.Each of the array includes 32*32 pixels.Large Array of imaging atmospheric Cherenkov Telescopes(LACT),the next generation of particle astrophysics experiment,will also adopt SiPM arrays.Purpose LACT will located at a high altitude,leading to a significant operating temperature variation of the SiPM.Since the gain of SiPM is temperature-sensitive,in order to keep it stable,compensation for the gain is necessary by adjusting the bias voltage of SiPM.Methods The compensation circuit provides the bias voltage of SiPM by using a high-voltage output Digital-to-Analog Converter and several high-voltage output amplifiers.To reduce the temperature drift of the gain,the compensation circuit adjust the bias voltage of SiPM according to the operating temperature.Results The compensation circuit supplies SiPM with an adjustable bias voltage from 0 to 80 V,and the adjustment step is 1.22 mV.When the output voltage of the compensation circuit is 64 V,the voltage ripple is 2.59 mV,and the temperature drift is 0.17 mV/℃.In the temperature range from−20 to 30℃,the compensation circuit reduces the gain temperature drift of SiPM to within 2%.展开更多
A sub-array of the Large High Altitude Air Shower Observatory(LHAASO),KM2A is mainly designed to observe a large fraction of the northern sky to hunt for γ-ray sources at energies above 10 TeV.Even though the detecto...A sub-array of the Large High Altitude Air Shower Observatory(LHAASO),KM2A is mainly designed to observe a large fraction of the northern sky to hunt for γ-ray sources at energies above 10 TeV.Even though the detector construction is still underway,half of the KM2A array has been operating stably since the end of 2019.In this paper,we present the KM2A data analysis pipeline and the first observation of the Crab Nebula,a standard candle in very high energy γ-ray astronomy.We detect γ-ray signals from the Crab Nebula in both energy ranges of 10-100 TeV and>100 TeV with high significance,by analyzing the KM2A data of 136 live days between December 2019 and May 2020.With the observations,we test the detector performance,including angular resolution,pointing accuracy and cosmic-ray background rejection power.The energy spectrum of the Crab Nebula in the energy range 10-250 TeV fits well with a single power-law function dN/dE=(1.13±0.05stat±0.08sys)×10^(-14).(E/20 TeV)-309±0.06stat±0.02syscm^(-2) s^(-1) TeV^(-1).It is consistent with previous measurements by other experiments.This opens a new window of γ-ray astronomy above 0.1 PeV through which new ultrahigh-energy γ-ray phenomena,such as cosmic PeVatrons,might be discovered.展开更多
基金supported by the National Natural Science Foundation of China(NSFC,grant Nos.12275279 and 12405124)the China Postdoctoral Science Foundation(No.2023M730423)Horizontal research project in natural sciences(No.H20230120)。
文摘The study of high-energy gamma-ray emission from gamma-ray bursts(GRBs)involves complex synchrotron radiation and synchrotron self-Compton(SSC)scattering mechanisms with multiple parameters exhibiting a wide distribution.Recent advancements in GRB research,particularly the observation of very high energy(VHE,>100 Ge V)radiation,have ushered in a new era of multiwavelength exploration,offering fresh perspectives and limitations for understanding GRB radiation mechanisms.This study aimed to leverage VHE observations to refine constraints on synchrotron+SSC radiation from electrons accelerated by forward shocks.By analyzing two external environments—the uniform interstellar medium and stratified stellar wind medium,we conducted spectral and variability fitting for five specific bursts(GRB 180720B,GRB 190114C,GRB 190829A,GRB 201216C,and GRB 221009A)to identify the optimal parameters characterizing these events.A comparative analysis of model parameter distributions with and without VHE radiation observations reveals that the magnetic energy equipartition factorεBis more concentrated with VHE emissions.This suggests that VHE emissions may offer greater constraints on this microphysical parameter.Additionally,we found that the energy budget between VHE and ke V–Me Vγ-ray emissions under the SSC radiation exhibits an almost linear relationship,which may serve as a tool to differentiate radiation mechanisms.We anticipate future statistical analyses of additional VHE bursts to validate our findings.
基金supported by the National Natural Science Foundation of China under grant Nos.12393854,12022502 and 12263007by the High-level Talent Support program of Yunnan Province。
文摘With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence,the Sun and Moon would have some impacts on the observation of gamma-ray sources,which have not been taken into account in previous analysis.In this paper,the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is estimated.The tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some period.The absorption of very high energy gamma rays by sunlight is estimated with detailed method and some useful conclusions are achieved.The main influence is the block of the Sun and Moon on gamma rays and the shadow on the cosmic ray background.The influence is investigated considering the detector angular resolution and some strategies on data analysis are proposed to avoid the underestimation of the gamma-ray emission.
基金This work was supported by the National Natural Science Foundation of China(NSFC,Nos.12320101005,12373105,U2031103,12205244,and 11963004)Hebei Natural Science Foundation(No.A2019207004).
文摘By accurately measuring composition and energy spectrum of cosmic ray,the origin problem of so called“knee”region(energy>one PeV)can be solved.However,up to the present,the results of the spectrum in the knee region obtained by several previous experiments have shown obvious differences,so they cannot give effective evidence for judging the theoretical models on the origin of the knee.Recently,the Large High Altitude Air Shower Observatory(LHAASO)has reported several major breakthroughs and important results in astro-particle physics field.Relying on its advantages of wide-sky survey,high altitude location and large area detector arrays,the research content of LHAASO experiment mainly includes ultra high-energy gamma-ray astronomy,measurement of cosmic ray spectra in the knee region,searching for dark matter and new phenomena of particle physics at higher energy.The electron and thermal neutron detector(EN-Detector)is a new scintillator detector which applies thermal neutron detection technology to measure cosmic ray extensive air shower(EAS).This technology is an extension of LHAASO.The EN-Detector Array(ENDA)can highly efficiently measure thermal neutrons generated by secondary hadrons so called“skeleton”of EAS.In this paper,we perform the optimization of ENDA configuration,and obtain expectations on the ENDA results,including thermal neutron distribution,trigger efficiency and capability of cosmic ray composition separation.The obtained real data results are consistent with those by the Monte Carlo simulation.
基金Supported by the National Key R&D Program of China(2018YFA0404203)the International Scholarship Program of the MOST of China(G2021166002L)+1 种基金National Natural Science Foundation of China(NSFC)(12147208,U2031103,U1931204)the Science and Technology Department of Sichuan Province(2021YFSY0031)。
文摘In the first part of this Chapter the present state of knowledge from the observations of cosmic rays between 10^(13) and 10^(20) eV is summarized.This is not intended to be a complete review,but rather a broad overview of the relevant processes involving cosmic rays,including the astrophysical environments in which they take place.This overview mainly concerns experimental results and phenomenological aspects of their interpretation,therefore experiments’description is not given but references to the vast bibliography are provided in the text.Some attempt is made to address the most popular explanations offered by theoretical models.The second part is devoted to the description of the LHAASO performance and of its capability to provide a response to several open questions,still unanswered,concerning cosmic rays above 10^(13) eV,highlighting which major steps forward in this field could be taken from LHAASO observations.
基金supported by Institute of High Energy Physics (E25156U110)the Sichuan Department of Science and Technology (2023YFSY0014).
文摘The reconstruction of muon energies is crucial for the data analysis of neutrino experiments using large water Cherenkov detectors,but the resolution for muon energy reconstruction using traditional methods is poor.Here,we propose a revised approach to remove noisy optical modules along the track produced by the propagation of muons through water.The number of photons on the optical modules is first corrected by the attenuation properties of light in water.Then the difference in time between the observed optical modules and the expected ones is determined based on the geometry of the triggered optical modules.Finally,the standard of correction is measured by the ratio of photon number before and after correction.Optical modules selection conditions were optimized according to these parameters,with most noisy optical modules successfully removed,improving the resolution of muon energy reconstruction.
基金supported by the National Nature Science Foundation of China(12041305)the National Youth Thousand Talents Program in China,and the Sichuan Science and Technology Department,Institute of High Energy Physics(2023YFSY0014,E25156U1)+4 种基金supported by the Sichuan Province Science Foundation for Distin-guished Young Scholars(2022JDJQ0043)the Sichuan Science and Technology Department(2023YFSY0014)the Xiejialin Foundation of IHEP(E2546IU2)the National Natural Science Foundation of China(12261141691)the Innovation Project of IHEP(E25451U2)。
文摘The large array of imaging atmospheric Cherenkov telescopes(LACT)is a planned array of 32 Cherenkov telescopes,each featuring 6-m diameter mirrors,to be constructed at the LHAASO site.This study focused on optimizing the array layout and analyzing the performance of LACT.Two observation modes were examined:large zenith angle observations for ultra-high energy events and small zenith angle observations for lower energy thresholds.For large zenith angles(60°),simulations indicate that an 8-telescope subarray can achieve an effective area of 3km^(2)with excellent angular resolution.For small zenith angles,we optimized the layout of 4-telescope cells and the full 32-telescope array.The energy threshold of the full array is approximately 200 GeV,which is particularly crucial for studying transient phenomena such as gamma-ray bursts(GRBs)and active galactic nuclei(AGNs).This study provides essential guidance for finalizing the LACT layout design and estimating performance under various observational conditions.It also highlights the potential of LACT for conducting deep observations of ultra-high energyγ-ray sources,performing morphological studies of PeVatrons,and advancing time-domainγ-ray astronomy.
基金supported by the National Natural Science Foundation of China(Grant Nos.12393854,12175121,12393851,12393852,12393853,12205314,12105301,12305120,12261160362,12105294,U1931201,12375107,and 12173039)the Department of Science and Technology of Sichuan Province,China(Grant No.24NSFSC2319)+2 种基金Project for Young Scientists in Basic Research of Chinese Academy of Sciences(Grant No.YSBR-061)in Thailand by the National Science and Technology Development Agency(NSTDA)the National Research Council of Thailand(NRCT)under the High-Potential Research Team Grant Program(Grant No.N42A650868)。
文摘In this paper,we report the detection of the very-high-energy(VHE,100 GeV<E<100 TeV)and ultra-high-energy(UHE,E>100 TeV)y-ray emissions from the direction of the young star-forming region W43,observed by the Large High Altitude Air Shower Observation(LHAASO).The extendedγ-ray source was detected with a significance of~16σby KM2A and~17σby WCDA,respectively.The angular extension of this y-ray source is about 0.5 degrees,corresponding to a physical size of about 50pc.We discuss the origin of theγ-ray emission and possible cosmic ray acceleration in the W43 region using multi-wavelength data.Our findings suggest that W43 is likely another young star cluster capable of accelerating cosmic rays(CRs)to at least several hundred TeV.
基金supported by the National Natural Science Foundation of China(Grant Nos.12393854,12393851,12393852,12393853,12205314,12105301,12305120,12261160362,12105294,U1931201,12375107,and 12173039)the Department of Science and Technology of Sichuan Province,China(Grant No.24NSFSC2319)+2 种基金the Project for Young Scientists in Basic Research of Chinese Academy of Sciences(Grant No.YSBR-061)in Thailand by the National Science and Technology Development Agency(NSTDA)the National Research Council of Thailand(NRCT)under the High-Potential Research Team Grant Program(Grant No.N42A650868)。
文摘We report the detection of an extended very-high-energy(VHE)γ-ray source coincident with the location of middle-aged(62.4 kyr)pulsar PSR J0248+6021,by using the LHAASO-WCDA data of live 796 d and LHAASO-KM2A data of live 1216d.A significant excess of y-ray induced showers is observed both by WCDA in energy bands of 1-25 TeV and KM2A in energy bands of>25 TeV with 7.3σand 13.5σ,respectively.The best-fit position derived through WCDA data is R.A.=42.06°±0.12°and Dec.=60.24°±0.13°with an extension of 0.69°±0.15°and that of the KM2A data is R.A.=42.29°±0.13°and Dec.=60.38°±0.07°with an extension of 0.37°±0.07°.No clear extended multiwavelength counterpart of this LHAASO source has been found from the radio band to the GeV band.The most plausible explanation of the VHEγ-ray emission is the inverse Compton process of highly relativistic electrons and positrons injected by the pulsar.These electrons/positrons are hypothesized to be either confined within the pulsar wind nebula or to have already escaped into the interstellar medium,forming a pulsar halo.
基金supported by the National Natural Science Foundation of China(Grant Nos.12393854,12393851,12393852,12393853,12205314,12105301,12305120,12261160362,12105294,U1931201,12375107,and 12173039)the Department of Science and Technology of Sichuan Province,China(Grant Nos.24NSFSC2319,and 2024NSFSC0449)+5 种基金the Project for Young Scientists in Basic Research of Chinese Academy of Sciences(Grant No.YSBR-061)in Thailand by the National Science and Technology Development Agency(NSTDA)the National Research Council of Thailand(NRCT)under the High-Potential Research Team Grant Program(Grant No.N42A650868)supported by the National Key R&D Program of China(Grant Nos.2023YFA1608000,and 2017YFA0402701)the CAS Key Research Program of Frontier Sciences(Grant No.QYZDJ-SSW-SLH047)used data from the Canadian Galactic Plane Survey,a Canadian project with international partners,supported by the Natural Sciences and Engineering Research Council。
文摘We report a dedicated study of the newly discovered extended UHEγ-ray source 1LHAASO J0056+6346u.Analyzing 979 d of LHAASO-WCDA data and 1389 d of LHAASO-KM2A data,we observed a significant excess ofγ-ray events with both WCDA and KM2A.Assuming a point power-law source with a fixed spectral index,the significance maps reveal excesses of 12.65σ,22.18σ,and 10.24σin the energy ranges of 1-25,25-100,and>100 TeV,respectively.We use a 3D likelihood algorithm to derive the morphological and spectral parameters,and the source is detected with significances of 13.72σby WCDA and 25.27σby KM2A.The best-fit positions derived from WCDA and KM2A data are(R.A.=13.96°±0.09°,Decl.=63.92°±0.05°)and(R.A.=14.00°±0.05°,Decl.=63.79°±0.02°),respectively.The angular size(r_(39))of 1LHAASO J0056+6346u is 0.34°±0.04°at 1-25 TeV and 0.24°±0.02°at>25 TeV.The differential flux of this UHEγ-ray source can be described by an exponential cutoff power-law function:(2.67±0.25)×10^(-15)(E/20 TeV)^((-1.97±0.10))e^(-E/(55.1±7.2)TeV)TeV^(-1)cm^(-2)s^(-1).To explore potential sources ofγ-ray emission,we investigated the gas distribution around 1LHAASO J0056+6346u.1LHAASO J0056+6346u is likely to be a TeV PWN powered by an unknown pulsar,which would naturally explain both its spatial and spectral properties.Another explanation is that this UHEγ-ray source might be associated with gas content illuminated by a nearby CR accelerator,possibly the SNR candidate G124.0+1.4.
基金in China by the National Natural Science Foundation of China(Grant Nos.12393851,12393854,12393852,12393853,12022502,12205314,12105301,12261160362,12105294,U1931201,and 2024NSFJQ0060)in Thailand by the National Science and Technology Development Agency(NSTDA)the National Research Council of Thailand(NRCT)under the High-Potential Research Team Grant Program(Grant No.N42A650868)。
文摘The ultra-high-energy(UHE)gamma-ray source 1LHAASO J0007+7303u is positionally associated with the composite SNR CTA1 that is located at high Galactic Latitude b≈10.5°.This provides a rare opportunity to spatially resolve the component of the pulsar wind nebula(PWN)and supernova remnant(SNR)at UHE.This paper conducted a dedicated data analysis of 1LHAASO J0007+7303u using the data collected from December 2019 to July 2023.This source is well detected with significances of 21σand 17σat 8-100 TeV and>100 TeV,respectively.The corresponding extensions are determined to be 0.23°±0.03°and 0.17°±0.03°.The emission is proposed to originate from the relativistic electrons accelerated within the PWN of PSR J0007+7303.The energy spectrum is well described by a power-law with an exponential cutoff function dN/dE=(42.4±4.1)(E/20TeV)^(-2.31+0.11)exp(-E/(110±25Tev))TeV-1 cm^(-2)s^(-1)in the energy range from 8 to 300 TeV,implying a steady-state parent electron spectrum dN_(e)/dE_(e)∝(E_(e)/100TeV)^(-3.13±0.16)exp[(-E_(e)/(373±70TeV))^(2)]at energies above≈50 TeV.The cutoff energy of the electron spectrum is roughly equal to the expected current maximum energy of particles accelerated at the PWN terminal shock.Combining the X-ray and gamma-ray emission,the current space-averaged magnetic field can be limited to≈4.5μG.To satisfy the multi-wavelength spectrum and the y-ray extensions,the transport of relativistic particles within the PWN is likely dominated by the advection process under the free-expansion phase assumption.
基金Supported by National Natural Science Foundation of China(11761141001,11635011,11873005)The LHAASO project is supported by the National Key R&D Program of China(2018YFA0404200),the Chinese Academy of Sciences,the Key Laboratory of Particle Astrophysics,IHEP,CAS。
文摘The Water Cherenkov Detector Array(WCDA) is a major component of the Large High Altitude Air Shower Array Observatory(LHAASO), a new generation cosmic-ray experiment with unprecedented sensitivity, currently under construction. WCDA is aimed at the study of TeV γ-rays. In order to evaluate the prospects of searching for TeV γ-ray sources with WCDA, we present a projection of the one-year sensitivity of WCDA to TeV γ-ray sources from TeVCat using an all-sky approach. Out of 128 TeVCat sources observable by WCDA up to a zenith angle of 45°, we estimate that 42 would be detectable in one year of observations at a median energy of 1 TeV. Most of them are Galactic sources, and the extragalactic sources are Active Galactic Nuclei(AGN).
基金Supported in China by National Key R&D program of China(2018YFA0404201)National Science Foundation of China(NSFC)(12022502)。
文摘The tiny modification of dispersion relation induced by Lorentz violation(LV)is an essential topic in quantum gravity(QG)theories,which can be magnified into significant effects when dealing with astrophysical observations at high energies and long propagation distances.LV would lead to photon decay at high energies;therefore,observations of high-energy photons could constrain LV or even QG theories.The Large High Altitude Air Shower Observatory(LHAASO)is the most sensitive gamma-array instrument currently operating above 100 TeV.Recently,LHAASO reported the detection of 12 sources above 100 TeV with maximum photon energy exceeding 1 PeV.According to these observations,the most stringent restriction is achieved in this study,i.e.,limiting the LV energy scale to 1.7×10^(33) eV,which is over 139,000 times that of the Planck energy,and achieving an improvement of approximately 1.9 orders of magnitude over previous limits.
文摘The Galactic plane serves as a natural laboratory for exploring high-energy astrophysical processes,where cosmic rays are accelerated,propagate,and interact with other components in the interstellar medium(ISM).With its unprecedented sensitivity and extensive energy coverage,the Large High Altitude Air Shower Observatory(LHAASO) has opened a new era of Galactic gamma-ray astronomy,especially in the ultra-high-energy(UHE) domain.The recent “Galactic Mini Survey” conducted by LHAASO provides an unprecedented view of UHE gamma-ray sources within the Milky Way.
基金the Natural Science Foundation of China(NSFC)(11905162,12035008,12075097,12075123,12090060,12090064,12105248,12135006,12175039,12205227,12205312,12205387,12205171,12235008,12321005,12235001,12305094,12305115,12335005,12375091,12375094,12375096,11975129,12375194,12447167,12475094,12475101,12475106,12475111,12425506,12375101,12405119,12405101,12505121,12135007,12175218,12075213,12335005,12175243,12533001,12125503,12305103,12505120,12575099,12505122,12342502,12575106,12147214,W2432006,W2441004)the National Key R&D Program of China(2024YFA1610603)+22 种基金the China Postdoctoral Science Foundation(2023M732255,2025M773403,GZC20231613)the Natural Science Foundation of Jiangsu Province(BK20210201)the Natural Science Foundation of Henan(Distinguished Young Scholars of Henan Province)(242300421046)the Natural Science Foundation of Sichuan Province(2025ZNSFSC0880)the Guangdong Major Project of Basic and Applied Basic Research(2020B0301030008)the Department of Science and Technology of Shandong province(tsqn202312052,2024HWYQ-005)the Startup Research Fund of Henan Academy of Sciences(20251820001)the Excellent Young Talents Program of Wuhan University of Technology(40122102)the research program of the Wuhan University of Technology(3120625397,2020IB024)the Fundamental Research Funds for the Central Universities(JZ2023HGTB0222,WUT:2022IVA052)the Excellent Scholar Project of Southeast University(Class A)the Big Data Computing Center of Southeast University,National Science and Technology Council,the Ministry of Education(Higher Education Sprout Project NTU-114L104022-1)the Center for Theoretical Sciences of Taiwan,and Vietnam National Foundation for Science and Technology Development(NAFOSTED)(103.01-2023.50)the Research Office of the University of the Witwatersrand and South African Department of Science and Innovation through the SA-CERN programthe self-determined research funds of Central China Normal University from the colleges'basic research and operation of MOE(CCNU24AI003)SJTU Double First Class start-up fund(WF220442604)the Innovation Capability Support Program of Shaanxi(2021KJXX-47)the Slovenian Research Agency under the research core funding No.P1-0035,the research grants J1-3013,N1-0253,CONICET,ANPCyT under project(PICT-2021-00374)Higher Education Sprout Project(NTU-114L104022-1)KIAS Individual Grants(PG086002)at the Korea Institute for Advanced Study,FAPESP(2021/09547-9)the Slovenian Research Agency under the research core funding(P1-0035)research grants J1-3013,N1-0253the bilateral project Proteus PR-12696/Projet 50194VC。
文摘I.EXECUTIVE SUMMARY next-generation,high-intensity electron-positron collider"Higgs factory",such as the Circular Electron-Positron Collider(CEPC),is among the highest priorities for the global high-energy collider physics community.The CEPC can provide unprecedented opportunities for making fundamental discoveries and providing decisive insights in the quest for a"New Standard Model(SM)"of nature's fundamental interactions.The CEPC could:·Identify the origin of matter,especially the mechanism related to the first-order phase transition in the early Universe,which could produce a detectable gravitational wave signal.
基金supported in China by the National Key R&D Program of China(2018YFA0404201,2018YFA0404202,2018YFA0404203,and 2018YFA0404204)the National Natural Science Foundation of China(12105294,12022502,12261160362,12205314,U1931201,and U2031105)+1 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences(2022010)in Thailand by the National Science and Technology Development Agency(NSTDA)and National Research Council of Thailand(NRCT):High-Potential Research Team Grant Program(N42A650868).
文摘We report the detection of aγ-ray bubble spanning at least 100deg2 in ultra-high energy(UHE)up to a few PeV in the direction of the star-forming region Cygnus X,implying the presence super PeVatron(s)accelerating protons to at least 10 PeV.A log-parabola form with the photon indexΓ(E)=(2.71±0.02)+(0.11±0.02)×log10(E/10 TeV)is found fitting the gamma-ray energy spectrum of the bubble well.UHE sources,“hot spots”correlated with very massive molecular clouds,and a quasi-spherical amorphousγ-ray emitter with a sharp central brightening are observed in the bubble.In the core of~0.5°,spatially associating with a region containing massive OB association(Cygnus OB2)and a microquasar(Cygnus X-3),as well as previously reported multi-TeV sources,an enhanced concentration of UHEγ-rays is observed with 2 photons at energies above 1 PeV.The general feature of the bubble,the morphology,and the energy spectrum,are reasonably reproduced by the assumption of a particle accelerator in the core,continuously injecting protons into the ambient medium.
基金Supported by National Natural Science Foundation in China(NSFC)(U2031103,U1831208,11805209,11775233)NSFC for Distinguished Young Scholars(12025502)+1 种基金the Science and Technology Department of Sichuan Province(2021YFSY0031)the International Partnership Program of Chinese Academy of Sciences(113111KYSB20170055)。
文摘The Large High Altitude Air Shower Observatory(LHAASO)(Fig.1)is located at Mt.Haizi(4410 m a.s.l.,600 g/cm^(2),29°21'27.56"N,100°08'19.66"E)in Daocheng,Sichuan province,P.R.China.LHAASO consists of 1.3 km^(2) array(KM2A)of electromagnetic particle detectors(ED)and muon detectors(MD),a water Cherenkov detector array(WCDA)with a total active area of 78,000 m^(2),18 wide field-of-view air Cherenkov telescopes(WFCTA)and a newly proposed electron-neutron detector array(ENDA)covering 10,000 m^(2).Each detector is synchronized with all the other through a clock synchronization network based on the White Rabbit protocol.The observatory includes an IT center which comprises the data acquisition system and trigger system,the data analysis facility.In this Chapter,all the above-mentioned components of LHAASO as well as infrastructure are described.
基金supported by National Nature Science Foundation of China(GrantNos.12075268,12175255,12175258,12105300)the Chinese Academy of Science,Institute of High Energy Physics.
文摘Purpose The LHAASO project collects trillions of cosmic ray events every year,generating about 10 PB of raw data annually,which brings big challenges for data processing platform.Method The LHAASO data processing platform is built to handle such a large amount of data,which is composed of some subsystems such as data transfer,data storage,high throughput computing and metadata management.Results and conclusions The platform was under construction since 2018 and has been working well since 2021.In this paper,the details of the design,implementation and performance of the data processing platform are presented.
基金Thiswork is supported byNationalKeyR&Dpro-gram of China under the grant 2018YFA0404201by the National Nat-ural Science Foundation of China(Grant Nos.11805209,12022502)the Chinese Academy of Science,Institute of High Energy Physics.
文摘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.
文摘Background Silicon photomultiplier tube(SiPM)has been widely applied in high energy physics experiments.The wide field of view Cherenkov telescope array of Large High Altitude Air Shower Observatory(LHAASO)consists of 12 arrays of SiPMs.Each of the array includes 32*32 pixels.Large Array of imaging atmospheric Cherenkov Telescopes(LACT),the next generation of particle astrophysics experiment,will also adopt SiPM arrays.Purpose LACT will located at a high altitude,leading to a significant operating temperature variation of the SiPM.Since the gain of SiPM is temperature-sensitive,in order to keep it stable,compensation for the gain is necessary by adjusting the bias voltage of SiPM.Methods The compensation circuit provides the bias voltage of SiPM by using a high-voltage output Digital-to-Analog Converter and several high-voltage output amplifiers.To reduce the temperature drift of the gain,the compensation circuit adjust the bias voltage of SiPM according to the operating temperature.Results The compensation circuit supplies SiPM with an adjustable bias voltage from 0 to 80 V,and the adjustment step is 1.22 mV.When the output voltage of the compensation circuit is 64 V,the voltage ripple is 2.59 mV,and the temperature drift is 0.17 mV/℃.In the temperature range from−20 to 30℃,the compensation circuit reduces the gain temperature drift of SiPM to within 2%.
基金Supported in China by National Key R&D program of China under the grants(2018YF A0404201.2018YFA0404202.2018YF A0404203)by NSFC(12022502,190527,135011,11761141001.U1931112,11775131,U1931201,11905043,U1931108)by NSFSPC(ZR2019MA014),and in Thailand by RTA6280002 from Thailand Science Research and Innovation。
文摘A sub-array of the Large High Altitude Air Shower Observatory(LHAASO),KM2A is mainly designed to observe a large fraction of the northern sky to hunt for γ-ray sources at energies above 10 TeV.Even though the detector construction is still underway,half of the KM2A array has been operating stably since the end of 2019.In this paper,we present the KM2A data analysis pipeline and the first observation of the Crab Nebula,a standard candle in very high energy γ-ray astronomy.We detect γ-ray signals from the Crab Nebula in both energy ranges of 10-100 TeV and>100 TeV with high significance,by analyzing the KM2A data of 136 live days between December 2019 and May 2020.With the observations,we test the detector performance,including angular resolution,pointing accuracy and cosmic-ray background rejection power.The energy spectrum of the Crab Nebula in the energy range 10-250 TeV fits well with a single power-law function dN/dE=(1.13±0.05stat±0.08sys)×10^(-14).(E/20 TeV)-309±0.06stat±0.02syscm^(-2) s^(-1) TeV^(-1).It is consistent with previous measurements by other experiments.This opens a new window of γ-ray astronomy above 0.1 PeV through which new ultrahigh-energy γ-ray phenomena,such as cosmic PeVatrons,might be discovered.
