Browsing by Author "Danzengluobu"

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    Absolute calibration of LHAASO WFCTA camera based on LED
    (2022-01-01) Aharonian F.; An Q.; Axikegu; Bai L.X.; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Cai H.; Cai J.T.; Cao Z.; Cao Z.; Chang J.; Chang J.F.; Chen B.M.; Chen E.S.; Chen J.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen X.L.; Chen Y.; Cheng N.; Cheng Y.D.; Cui S.W.; Cui X.H.; Cui Y.D.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; della Volpe D.; Piazzoli B.D.E.; Dong X.J.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fan Z.X.; Fang J.; Fang K.; Feng C.F.; Feng L.; Feng S.H.; Feng Y.L.; Fu Y.T.; Gan H.Y.; Gao B.; Gao C.D.; Gao L.Q.; Gao Q.; Gao W.; Ge M.M.; Geng L.S.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo J.G.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; He H.H.; He H.N.; He J.C.; He S.L.; He X.B.; He Y.; Heller M.; Hor Y.K.; Hou C.; Hu H.B.; Hu S.; Hu S.C.; Hu X.J.; Huang D.H.; Huang Q.L.; Huang W.H.; Huang X.T.; Huang X.Y.; Huang Z.C.; Ji F.; Ji X.L.; Jia H.Y.; Jiang K.; Jiang Z.J.; Jin C.; Ke T.; Kuleshov D.; Levochkin K.; Li B.B.; Li C.; Li C.; Li F.; Mahidol University
    The main scientific goal of the LHAASO WFCTA experiment is to measure the cosmic ray energy spectra and composition from 10 TeV to 1 EeV. Cherenkov photons in the extensive air shower measured by the SiPM camera of Cherenkov telescopes can be used to reconstruct the cosmic ray energy. The absolute calibration of the camera is a crucial step to achieve the accurate measurement of the cosmic ray energy spectrum. A multi-wavelength cylindrical illuminator based on LEDs is developed and mounted inside the telescope to calibrate and monitor the camera, and the illuminator's stability is better than 0.5% under the temperature variation from -26 to 26 °C. A portable probe with a single photoelectron resolution of 21.6% is developed. After calibration by National Institute of Metrology, China (NIM), the probe is taken to the LHAASO site to measure the absolute photon density of the cylindrical illuminator inside the telescope. Based on the illuminator with known photon density, the photon conversion factor of the camera can be calibrated, and the overall calibration uncertainty is less than 2.6%.
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    An Enigmatic PeVatron in an Area around H ii Region G35.6−0.5
    (2025-01-20) Cao Z.; Aharonian F.; Axikegu; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Bian W.; Bukevich A.V.; Cao Q.; Cao W.Y.; Cao Z.; Chang J.; Chang J.F.; Chen A.M.; Chen B.Q.; Chen E.S.; Chen H.X.; Chen L.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen Y.; Cheng N.; Cheng Y.D.; Chu M.C.; Cui M.Y.; Cui S.W.; Cui X.H.; Cui Y.D.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; Dong X.Q.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fang J.; Fang J.H.; Fang K.; Feng C.F.; Feng H.; Feng L.; Feng S.H.; Feng X.T.; Feng Y.; Feng Y.L.; Gabici S.; Gao B.; Gao C.D.; Gao Q.; Gao W.; Gao W.K.; Ge M.M.; Ge T.T.; Geng L.S.; Giacinti G.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo J.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; Hannuksela O.A.; Hasan M.; He H.H.; He H.N.; He J.Y.; He Y.; Hor Y.K.; Hou B.W.; Hou C.; Hou X.; Hu H.B.; Hu Q.; Hu S.C.; Huang C.; Huang D.H.; Huang T.Q.; Huang W.J.; Huang X.T.; Huang X.Y.; Huang Y.; Huang Y.Y.; Ji X.L.; Jia H.Y.; Jia K.; Jiang H.B.; Jiang K.; Cao Z.; Mahidol University
    Identifying Galactic PeVatrons (PeV particle accelerators) from ultrahigh-energy (UHE, >100 TeV) γ-ray sources plays a crucial role in revealing the origin of Galactic cosmic rays. The UHE source 1LHAASO J1857+0203u is suggested to be associated with HESS J1858+020, which may be attributed to the possible PeVatron candidate supernova remnant (SNR) G35.6−0.4 or H ii region G35.6−0.5. We perform detailed analysis on the very-high-energy and UHE γ-ray emissions toward this region with data from the Large High Altitude Air Shower Observatory (LHAASO). 1LHAASO J1857+0203u is detected with a significance of 11.6σ above 100 TeV, indicating the presence of a PeVatron. It has an extent of ∼0 . ° 18 with a power-law (PL) spectral index of ∼2.5 at 1-25 TeV and pointlike emission with a PL spectral index of ∼3.2 above 25 TeV. Using archival CO and H i data, we identify some molecular and atomic clouds that may be associated with the TeV γ-ray emissions. Our modeling indicates that the TeV γ-ray emissions are unlikely to arise from clouds illuminated by the protons that escaped from SNR G35.6−0.4. In the scenario in which H ii region G35.6−0.5 could accelerate particles to the UHE band, the observed GeV-TeV γ-ray emission could be well explained by a hadronic model with a PL spectral index of ∼2.0 and cutoff energy of ∼450 TeV. However, an origin in an evolved pulsar wind nebula cannot be ruled out.
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    An ultrahigh-energy γ-ray bubble powered by a super PeVatron
    (2024-01-01) Cao Z.; Aharonian F.; An Q.; Axikegu; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Cai J.T.; Cao Q.; Cao W.Y.; Cao Z.; Chang J.; Chang J.F.; Chen A.M.; Chen E.S.; Chen L.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen Y.; Cheng N.; Cheng Y.D.; Cui M.Y.; Cui S.W.; Cui X.H.; Cui Y.D.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; della Volpe D.; Dong X.Q.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fang J.; Fang K.; Feng C.F.; Feng L.; Feng S.H.; Feng X.T.; Feng Y.L.; Gabici S.; Gao B.; Gao C.D.; Gao L.Q.; Gao Q.; Gao W.; Gao W.K.; Ge M.M.; Geng L.S.; Giacinti G.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; He H.H.; He H.N.; He J.Y.; He X.B.; He Y.; Heller M.; Hor Y.K.; Hou B.W.; Hou C.; Hou X.; Hu H.B.; Hu Q.; Hu S.C.; Huang D.H.; Huang T.Q.; Huang W.J.; Huang X.T.; Huang X.Y.; Huang Y.; Huang Z.C.; Ji X.L.; Jia H.Y.; Jia K.; Jiang K.; Jiang X.W.; Jiang Z.J.; Jin M.; Kang M.M.; Ke T.; Kuleshov D.; Kurinov K.; Li B.B.; Li C.; Cao Z.; Mahidol University
    We report the detection of a γ-ray bubble spanning at least 100 deg2 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 index Γ(E)=(2.71±0.02)+(0.11±0.02)×log10(E/10TeV) 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 amorphous γ-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 UHE γ-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.
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    Broadband γ-Ray Spectrum of Supernova Remnant Cassiopeia A
    (2025-03-20) Cao Z.; Aharonian F.; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Bian W.; Bukevich A.V.; Cai C.M.; Cao W.Y.; Cao Z.; Chang J.; Chang J.F.; Chen A.M.; Chen E.S.; Chen H.X.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen X.B.; Chen X.J.; Chen Y.; Cheng N.; Cheng Y.D.; Chu M.C.; Cui M.Y.; Cui S.W.; Cui X.H.; Cui Y.D.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; Diao Y.X.; Dong X.Q.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fang J.; Fang J.H.; Fang K.; Feng C.F.; Feng H.; Feng L.; Feng S.H.; Feng X.T.; Feng Y.; Feng Y.L.; Gabici S.; Gao B.; Gao C.D.; Gao Q.; Gao W.; Gao W.K.; Ge M.M.; Ge T.T.; Geng L.S.; Giacinti G.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo J.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; Hannuksela O.A.; Hasan M.; He H.H.; He H.N.; He J.Y.; He X.Y.; He Y.; ndez-Cadena S.H.; Hor Y.K.; Hou B.W.; Hou C.; Hou X.; Hu H.B.; Hu S.C.; Huang C.; Huang D.H.; Huang J.J.; Huang T.Q.; Huang W.J.; Huang X.T.; Huang X.Y.; Huang Y.; Huang Y.Y.; Ji X.L.; Jia H.Y.; Jia K.; Cao Z.; Mahidol University
    The core-collapse supernova remnant (SNR) Cassiopeia A (Cas A) is one of the brightest galactic radio sources with an angular radius of ~2.5 ¢ . Although no extension of this source has been detected in the γ-ray band, using more than 1000 days of LHAASO data above ∼0.8 TeV, we find that its spectrum is significantly softer than those obtained with Imaging Air Cherenkov Telescopes (IACTs), and its flux near ∼1 TeV is about 2 times higher. In combination with analyses of more than 16 yr of Fermi-LAT data covering 0.1 GeV–1 TeV, we find that the spectrum above 30 GeV deviates significantly from a single power law and is best described by a smoothly broken power law with a spectral index of 1.90 ± 0.15stat (3.41 ± 0.19stat) below (above) a break energy of 0.63 ± 0.21stat TeV. Given differences in the angular resolution of LHAASO-WCDA and IACTs, TeV γ-ray emission detected with LHAASO may have a significant contribution from regions surrounding the SNR illuminated by particles accelerated earlier, which, however, are treated as background by IACTs. Detailed modeling can be used to constrain the acceleration processes of TeV particles in the early stage of SNR evolution.
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    Calibration of the air shower energy scale of the water and air Cherenkov techniques in the LHAASO experiment
    (2021-09-15) F. Aharonian; Q. An; Axikegu; L. X. Bai; Y. X. Bai; Y. W. Bao; D. Bastieri; X. J. Bi; Y. J. Bi; H. Cai; J. T. Cai; Zhen Cao; Zhe Cao; J. Chang; J. F. Chang; B. M. Chen; E. S. Chen; J. Chen; Liang Chen; Liang Chen; Long Chen; M. J. Chen; M. L. Chen; Q. H. Chen; S. H. Chen; S. Z. Chen; T. L. Chen; X. L. Chen; Y. Chen; N. Cheng; Y. D. Cheng; S. W. Cui; X. H. Cui; Y. D. Cui; B. Z. Dai; H. L. Dai; Z. G. Dai; Danzengluobu; D. Della Volpe; B. D.Ettorre Piazzoli; X. J. Dong; K. K. Duan; J. H. Fan; Y. Z. Fan; Z. X. Fan; J. Fang; K. Fang; C. F. Feng; L. Feng; S. H. Feng; Y. L. Feng; B. Gao; C. D. Gao; L. Q. Gao; Q. Gao; W. Gao; M. M. Ge; L. S. Geng; G. H. Gong; Q. B. Gou; M. H. Gu; F. L. Guo; J. G. Guo; X. L. Guo; Y. Q. Guo; Y. Y. Guo; Y. A. Han; H. H. He; H. N. He; J. C. He; S. L. He; X. B. He; Y. He; M. Heller; Y. K. Hor; C. Hou; H. B. Hu; S. Hu; S. C. Hu; X. J. Hu; D. H. Huang; Q. L. Huang; W. H. Huang; X. T. Huang; X. Y. Huang; Z. C. Huang; F. Ji; X. L. Ji; H. Y. Jia; K. Jiang; Z. J. Jiang; C. Jin; T. Ke; D. Kuleshov; K. Levochkin; B. B. Li; Cong Li; Cheng Li; F. Li; H. B. Li; State Key Laboratory of Particle Detection & Electronics; Nanjing University; Shanghai Astronomical Observatory Chinese Academy of Sciences; Institute for Nuclear Research of the Russian Academy of Sciences; Shandong University; Wuhan University; Yunnan University; Institute of High Energy Physics Chinese Academy of Science; University of Chinese Academy of Sciences; Guangzhou University; Tsinghua University; Sun Yat-Sen University; University of Science and Technology of China; Zhengzhou University; Dublin Institute for Advanced Studies; Università degli Studi di Napoli Federico II; Sichuan University; National Astronomical Observatories Chinese Academy of Sciences; Max-Planck-Institut für Kernphysik; Southwest Jiaotong University; Purple Mountain Observatory Chinese Academy of Sciences; Université de Genève; Hebei Normal University; Tibet University; TIANFU Cosmic Ray Research Center
    The Wide Field-of-View Cherenkov Telescope Array (WFCTA) and the Water Cherenkov Detector Array (WCDA) of LHAASO are designed to work in combination for measuring the energy spectra of the cosmic ray species over a very wide energy range from a few TeV to 10 PeV. The energy calibration can be achieved with a proven technique of measuring the westward shift of the Moon shadow cast by galactic cosmic rays due to the geomagnetic field. This deflection angle Δ is inversely proportional to the cosmic ray rigidity. The precise measurement of the shifts by WCDA allows us to calibrate its energy scale for energies as high as 35 TeV. Through a set of commonly triggered events, the energy scales can be propagated to WFCTA. The energies of the events can be derived both by WCDA-1 and WFCTA with the median energies 23.4±0.1±1.3 TeV and (21.9±0.1 TeV), respectively, which are consistent within uncertainties. In addition, the propagation of the energy scale is also validated by the Moon shadow based on the same data selection criteria of the commonly triggered events. This paper reports, for the first time, an observational measurement of the absolute energy scale of the primary cosmic rays generating showers observed by air Cherenkov telescopes.
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    Constraining the Cosmic-Ray Energy Based on Observations of Nearby Galaxy Clusters by LHAASO
    (2025-03-20) Cao Z.; Aharonian F.; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Bian W.; Bukevich A.V.; Cai C.M.; Cao W.Y.; Cao Z.; Chang J.; Chang J.F.; Chen A.M.; Chen E.S.; Chen H.X.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen X.B.; Chen X.J.; Chen Y.; Cheng N.; Cheng Y.D.; Chu M.C.; Cui M.Y.; Cui S.W.; Cui X.H.; Cui Y.D.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; Diao Y.X.; Dong X.Q.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fang J.; Fang J.H.; Fang K.; Feng C.F.; Feng H.; Feng L.; Feng S.H.; Feng X.T.; Feng Y.; Feng Y.L.; Gabici S.; Gao B.; Gao C.D.; Gao Q.; Gao W.; Gao W.K.; Ge M.M.; Ge T.T.; Geng L.S.; Giacinti G.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo J.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; Hannuksela O.A.; Hasan M.; He H.H.; He H.N.; He J.Y.; He X.Y.; He Y.; Hernández-Cadena S.; Hor Y.K.; Hou B.W.; Hou C.; Hou X.; Hu H.B.; Hu S.C.; Huang C.; Huang D.H.; Huang J.J.; Huang T.Q.; Huang W.J.; Huang X.T.; Huang X.Y.; Huang Y.; Huang Y.Y.; Ji X.L.; Jia H.Y.; Jia K.; Cao Z.; Mahidol University
    Galaxy clusters act as reservoirs of high-energy cosmic rays (CRs). As CRs propagate through the intracluster medium, they generate diffuse γ-rays detectable by arrays such as LHAASO. These γ-rays result from proton-proton (pp) collisions of very high-energy cosmic rays or inverse Compton (IC) scattering of positron-electron pairs created by pγ interactions of ultra-high-energy cosmic rays (UHECRs). We analyzed diffuse γ-ray emission from the Coma, Perseus, and Virgo clusters using LHAASO data. Diffuse emission was modeled as a disk of radius R500 for each cluster while accounting for point sources. No significant diffuse emission was detected, yielding 95% confidence level (C.L.) upper limits on the γ-ray flux: for WCDA (1-25 TeV) and KM2A (>25 TeV), less than (49.4, 13.7, 54.0) and (1.34, 1.14, 0.40) × 10−14 ph cm−2 s−1 for Coma, Perseus, and Virgo, respectively. The γ-ray upper limits can be used to derive model-independent constraints on the integral energy of cosmic ray protons above 10 TeV (corresponding to the LHAASO observational range >1 TeV under the pp scenario) to be less than (1.96, 0.59, 0.08) × 1061 erg. The absence of detectable annuli/ring-like structures, indicative of cluster accretion or merging shocks, imposes further constraints on models in which the UHECRs are accelerated in the merging shocks of galaxy clusters.
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    Constraints on Heavy Decaying Dark Matter from 570 Days of LHAASO Observations
    (2022-12-23) Cao Z.; Aharonian F.; An Q.; Axikegu; Bai L.X.; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Cai J.T.; Cao Z.; Chang J.; Chang J.F.; Chen E.S.; Chen L.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen Y.; Cheng H.L.; Cheng N.; Cheng Y.D.; Cui S.W.; Cui X.H.; Cui Y.D.; D'Ettorre Piazzoli B.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; Della Volpe D.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fan Z.X.; Fang J.; Fang K.; Feng C.F.; Feng L.; Feng S.H.; Feng X.T.; Feng Y.L.; Gao B.; Gao C.D.; Gao L.Q.; Gao Q.; Gao W.; Gao W.K.; Ge M.M.; Geng L.S.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo J.G.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; He H.H.; He H.N.; He S.L.; He X.B.; He Y.; Heller M.; Hor Y.K.; Hou C.; Hou X.; Hu H.B.; Hu Q.; Hu S.; Hu S.C.; Hu X.J.; Huang D.H.; Huang W.H.; Huang X.T.; Huang X.Y.; Huang Y.; Huang Z.C.; Ji X.L.; Jia H.Y.; Jia K.; Jiang K.; Jiang Z.J.; Jin M.; Kang M.M.; Ke T.; Kuleshov D.; Levochkin K.; Li B.B.; Li C.; Li C.; Li F.; Li H.B.; Mahidol University
    The kilometer square array (KM2A) of the large high altitude air shower observatory (LHAASO) aims at surveying the northern γ-ray sky at energies above 10 TeV with unprecedented sensitivity. γ-ray observations have long been one of the most powerful tools for dark matter searches, as, e.g., high-energy γ rays could be produced by the decays of heavy dark matter particles. In this Letter, we present the first dark matter analysis with LHAASO-KM2A, using the first 340 days of data from 1/2-KM2A and 230 days of data from 3/4-KM2A. Several regions of interest are used to search for a signal and account for the residual cosmic-ray background after γ/hadron separation. We find no excess of dark matter signals, and thus place some of the strongest γ-ray constraints on the lifetime of heavy dark matter particles with mass between 105 and 109 GeV. Our results with LHAASO are robust, and have important implications for dark matter interpretations of the diffuse astrophysical high-energy neutrino emission.
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    Constraints on Ultraheavy Dark Matter Properties from Dwarf Spheroidal Galaxies with LHAASO Observations
    (2024-08-09) Cao Z.; Aharonian F.; An Q.; Axikegu; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Cai J.T.; Cao Q.; Cao W.Y.; Cao Z.; Chang J.; Chang J.F.; Chen A.M.; Chen E.S.; Chen L.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen Y.; Cheng N.; Cheng Y.D.; Cui M.Y.; Cui S.W.; Cui X.H.; Cui Y.D.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; Della Volpe D.; Dong X.Q.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fang J.; Fang K.; Feng C.F.; Feng L.; Feng S.H.; Feng X.T.; Feng Y.L.; Gabici S.; Gao B.; Gao C.D.; Gao L.Q.; Gao Q.; Gao W.; Gao W.K.; Ge M.M.; Geng L.S.; Giacinti G.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; He H.H.; He H.N.; He J.Y.; He X.B.; He Y.; Heller M.; Hor Y.K.; Hou B.W.; Hou C.; Hou X.; Hu H.B.; Hu Q.; Hu S.C.; Huang D.H.; Huang T.Q.; Huang W.J.; Huang X.T.; Huang X.Y.; Huang Y.; Huang Z.C.; Ji X.L.; Jia H.Y.; Jia K.; Jiang K.; Jiang X.W.; Jiang Z.J.; Jin M.; Kang M.M.; Ke T.; Kuleshov D.; Kurinov K.; Li B.B.; Li C.; Cao Z.; Mahidol University
    In this Letter we try to search for signals generated by ultraheavy dark matter at the Large High Altitude Air Shower Observatory (LHAASO) data. We look for possible γ rays by dark matter annihilation or decay from 16 dwarf spheroidal galaxies in the field of view of the LHAASO. Dwarf spheroidal galaxies are among the most promising targets for indirect detection of dark matter that have low fluxes of astrophysical γ-ray background while having large amount of dark matter. By analyzing more than 700 days of observational data at LHAASO, no significant dark matter signal from 1 TeV to 1 EeV is detected. Accordingly we derive the most stringent constraints on the ultraheavy dark matter annihilation cross section up to EeV. The constraints on the lifetime of dark matter in decay mode are also derived.
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    Construction and on-site performance of the LHAASO WFCTA camera
    (2021-07-01) F. Aharonian; Q. An; Axikegu; L. X. Bai; Y. X. Bai; Y. W. Bao; D. Bastieri; X. J. Bi; Y. J. Bi; H. Cai; J. T. Cai; Z. Cao; Z. Cao; J. Chang; J. F. Chang; X. C. Chang; B. M. Chen; J. Chen; L. Chen; L. Chen; L. Chen; M. J. Chen; M. L. Chen; Q. H. Chen; S. H. Chen; S. Z. Chen; T. L. Chen; X. L. Chen; Y. Chen; N. Cheng; Y. D. Cheng; S. W. Cui; X. H. Cui; Y. D. Cui; B. Z. Dai; H. L. Dai; Z. G. Dai; Danzengluobu; D. della Volpe; B. D’Ettorre Piazzoli; X. J. Dong; J. H. Fan; Y. Z. Fan; Z. X. Fan; J. Fang; K. Fang; C. F. Feng; L. Feng; S. H. Feng; Y. L. Feng; B. Gao; C. D. Gao; Q. Gao; W. Gao; M. M. Ge; L. S. Geng; G. H. Gong; Q. B. Gou; M. H. Gu; J. G. Guo; X. L. Guo; Y. Q. Guo; Y. Y. Guo; Y. A. Han; H. H. He; H. N. He; J. C. He; S. L. He; X. B. He; Y. He; M. Heller; Y. K. Hor; C. Hou; X. Hou; H. B. Hu; S. Hu; S. C. Hu; X. J. Hu; D. H. Huang; Q. L. Huang; W. H. Huang; X. T. Huang; Z. C. Huang; F. Ji; X. L. Ji; H. Y. Jia; K. Jiang; Z. J. Jiang; C. Jin; D. Kuleshov; K. Levochkin; B. B. Li; C. Li; C. Li; F. Li; H. B. Li; H. C. Li; H. Y. Li; J. Li; K. Li; State Key Laboratory of Particle Detection & Electronics; Nanjing University; Shanghai Astronomical Observatory Chinese Academy of Sciences; Institute for Nuclear Research of the Russian Academy of Sciences; Shandong University; Wuhan University; Yunnan University; Institute of High Energy Physics Chinese Academy of Science; University of Chinese Academy of Sciences; Guangzhou University; Tsinghua University; Sun Yat-Sen University; University of Science and Technology of China; Zhengzhou University; Dublin Institute for Advanced Studies; Università degli Studi di Napoli Federico II; Sichuan University; National Astronomical Observatories Chinese Academy of Sciences; Max-Planck-Institut für Kernphysik; Southwest Jiaotong University; Purple Mountain Observatory Chinese Academy of Sciences; Université de Genève; Hebei Normal University; Tibet University; TIANFU Cosmic Ray Research Center
    The focal plane camera is the core component of the Wide Field-of-view Cherenkov/fluorescence Telescope Array (WFCTA) of the Large High-Altitude Air Shower Observatory (LHAASO). Because of the capability of working under moonlight without aging, silicon photomultipliers (SiPM) have been proven to be not only an alternative but also an improvement to conventional photomultiplier tubes (PMT) in this application. Eighteen SiPM-based cameras with square light funnels have been built for WFCTA. The telescopes have collected more than 100 million cosmic ray events and preliminary results indicate that these cameras are capable of working under moonlight. The characteristics of the light funnels and SiPMs pose challenges (e.g. dynamic range, dark count rate, assembly techniques). In this paper, we present the design features, manufacturing techniques and performances of these cameras. Finally, the test facilities, the test methods and results of SiPMs in the cameras are reported here.
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    Corrigendum to “Performance test of the electromagnetic particle detectors for the LHAASO experiment” [Nucl. Instrum. Methods Phys. Res. A 1001 (2021) 165193] (Nuclear Inst. and Methods in Physics Research, A (2021) 1001, (S0168900221001777), (10.1016/j.nima.2021.165193))
    (2022-01-11) Aharonian F.; An Q.; Axikegu; Bai L.X.; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Cai H.; Cai J.T.; Cao Z.; Chang J.; Chang J.F.; Chang X.C.; Chen B.M.; Chen J.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen X.L.; Chen Y.; Cheng N.; Cheng Y.D.; Cui S.W.; Cui X.H.; Cui Y.D.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; della Volpe D.; Piazzoli B.D.E.; Dong X.J.; Fan J.H.; Fan Y.Z.; Fan Z.X.; Fang J.; Fang K.; Feng C.F.; Feng L.; Feng S.H.; Feng Y.L.; Gao B.; Gao C.D.; Gao Q.; Gao W.; Ge M.M.; Geng L.S.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo J.G.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; He H.H.; He H.N.; He J.C.; He S.L.; He X.B.; He Y.; Heller M.; Hor Y.K.; Hou C.; Hou X.; Hu H.B.; Hu S.; Hu S.C.; Hu X.J.; Huang D.H.; Huang Q.L.; Huang W.H.; Huang X.T.; Huang Z.C.; Ji F.; Ji X.L.; Jia H.Y.; Jia K.; Jiang K.; Jiang Z.J.; Jin C.; Kuleshov D.; Levochkin K.; Li B.; Li B.B.; Li C.; Li F.; Li H.; Li H.B.; Li H.C.; Li H.Y.; Li J.; Li K.; Li W.L.; Mahidol University
    The authors regret < (1) In the abstract: “[Formula presented] charge resolution for single particle of 18.5% and [Formula presented]” change to “[Formula presented]charge resolution for single particle of 22.2% and [Formula presented]” (2) Fig. 11 shows distribution of charge resolution of 4362EDs, this figure should be replaced with the followed figure. [Figure presented] (3) In the conclusion: “The charge resolution for single-track events of all tested EDs is about 18.5%”. – change to – “The charge resolution for single-track events of all tested EDs is about 22.2%”. >. The authors would like to apologize for any inconvenience caused. We are sorry that there is a mistake in the paper of “Performance test of the electromagnetic particle detectors for the LHAASO experiment”. That is the figure 11 was submitted by mistake. During the ED's performance test, the definition of charge resolution of single particle developed a little bit which brought confusions. In the beginning, we define [Formula presented], where MPV is the maximum of the fitted function. Then we use [Formula presented], however it is relate to the range of spectrum. Finally, we use [Formula presented], where, [Formula presented] using a Gaussian approximation in the paper. Figures of the charge resolution with these definitions were stored in the same directory. Thus, a wrong figure was uploaded during the paper submission. We are very sorry that our negligence causing inconvenience to everyone.
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    Data quality control system and long-term performance monitor of LHAASO-KM2A
    (2025-01-01) Cao Z.; Aharonian F.; Axikegu; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Bian W.; Bukevich A.V.; Cao Q.; Cao W.Y.; Cao Z.; Chang J.; Chang J.F.; Chen A.M.; Chen E.S.; Chen H.X.; Chen L.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen Y.; Cheng N.; Cheng Y.D.; Cui M.Y.; Cui S.W.; Cui X.H.; Cui Y.D.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; Dong X.Q.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fang J.; Fang J.H.; Fang K.; Feng C.F.; Feng H.; Feng L.; Feng S.H.; Feng X.T.; Feng Y.; Feng Y.L.; Gabici S.; Gao B.; Gao C.D.; Gao Q.; Gao W.; Gao W.K.; Ge M.M.; Geng L.S.; Giacinti G.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; Hasan M.; He H.H.; He H.N.; He J.Y.; He Y.; Hor Y.K.; Hou B.W.; Hou C.; Hou X.; Hu H.B.; Hu Q.; Hu S.C.; Huang D.H.; Huang T.Q.; Huang W.J.; Huang X.T.; Huang X.Y.; Huang Y.; Ji X.L.; Jia H.Y.; Jia K.; Jiang K.; Jiang X.W.; Jiang Z.J.; Jin M.; Kang M.M.; Karpikov I.; Kuleshov D.; Kurinov K.; Li B.B.; Cao Z.; Mahidol University
    The KM2A is the largest sub-array of the Large High Altitude Air Shower Observatory (LHAASO). It consists of 5216 electromagnetic particle detectors (EDs) and 1188 muon detectors (MDs). The data recorded by the EDs and MDs are used to reconstruct primary information of cosmic-ray and gamma-ray showers. To ensure the reliability of the LHAASO-KM2A data, a three-level quality control system has been established. It is used to monitor the status of detector units, stability of reconstructed parameters and the performance of the array based on observations of the Crab Nebula and Moon shadow. This paper will introduce the control system and its application on the LHAASO-KM2A data collected from August 2021 to July 2023. During this period, the pointing and angular resolution of the array were stable. From the observations of the Moon shadow and Crab Nebula, the results achieved using the two methods are consistent with each other. For example, according to the observation of the Crab Nebula with KM2A at energies from 25 TeV to 100 TeV, the time averaged pointing errors are estimated to be −0.003°±0.005° and 0.001°±0.006° in the R.A. and Dec directions, respectively.
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    Deep view of composite SNR CTA1 with LHAASO in γ-rays up to 300 TeV
    (2025-07-01) Cao Z.; Aharonian F.; Axikegu; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Bian W.; Bukevich A.V.; Cao Q.; Cao W.Y.; Cao Z.; Chang J.; Chang J.F.; Chen A.M.; Chen E.S.; Chen H.X.; Chen L.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen Y.; Cheng N.; Cheng Y.D.; Chu M.C.; Cui M.Y.; Cui S.W.; Cui X.H.; Cui Y.D.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; Dong X.Q.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fang J.; Fang J.H.; Fang K.; Feng C.F.; Feng H.; Feng L.; Feng S.H.; Feng X.T.; Feng Y.; Feng Y.L.; Gabici S.; Gao B.; Gao C.D.; Gao Q.; Gao W.; Gao W.K.; Ge M.M.; Ge T.T.; Geng L.S.; Giacinti G.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo J.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; Hannuksela O.A.; Hasan M.; He H.H.; He H.N.; He J.Y.; He Y.; Hor Y.K.; Hou B.W.; Hou C.; Hou X.; Hu H.B.; Hu Q.; Hu S.C.; Huang C.; Huang D.H.; Huang T.Q.; Huang W.J.; Huang X.T.; Huang X.Y.; Huang Y.; Huang Y.Y.; Ji X.L.; Jia H.Y.; Jia K.; Jiang H.B.; Jiang K.; Jiang X.W.; Cao Z.; Mahidol University
    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 21σ and 17σ at 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)(E20TeV)−2.31±0.11exp(−E110±25TeV) TeV−1 cm−2 s−1 in the energy range from 8 to 300 TeV, implying a steady-state parent electron spectrum dNe/dEe∝(Ee100TeV)−3.13±0.16exp[(−Ee373±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 ≈ 4.5 µG. To satisfy the multi-wavelength spectrum and the γ-ray extensions, the transport of relativistic particles within the PWN is likely dominated by the advection process under the free-expansion phase assumption.
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    Design and Implementation of a Portable Laser Calibration System for LHAASO-WFCTA
    (2024-09-27) Yuan G.; Sun Q.; Jin M.; Xia J.; Liu J.; Min Z.; Zhu F.; Chen L.; Wang Y.; Liu Y.; Zhang Y.; Cao Z.; Aharonian F.; An Q.; Axikegu; Bai L.X.; Bai Y.X.; Bai L.X.; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Cai H.; Cai J.T.; Cao Z.; Chang J.; Chang J.F.; Chen B.M.; Chen E.S.; Chen J.; Chen L.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen X.L.; Chen Y.; Cheng N.; Cheng Y.D.; Cui S.W.; Cui X.H.; Cui Y.D.; D’Ettorre Piazzoli B.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; della Volpe D.; Dong X.J.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fan Z.X.; Fang J.; Fang K.; Feng C.F.; Feng L.; Feng S.H.; Feng Y.L.; Gao B.; Gao C.D.; Gao L.Q.; Gao Q.; Gao W.; Ge M.M.; Geng L.S.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo J.G.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; He H.H.; He H.N.; He J.C.; He S.L.; He X.B.; He Y.; Heller M.; Hor Y.K.; Hou C.; Hu H.B.; Hu S.; Hu S.C.; Hu X.J.; Huang D.H.; Huang Q.L.; Huang W.H.; Huang X.T.; Huang X.Y.; Huang Z.C.; Ji F.; Yuan G.; Mahidol University
    The Wide Field of View Cherenkov Telescope Array (WFCTA), situated in the harsh environment of Daocheng, is established to investigate ultrahigh energy cosmic rays. To enhance the calibration of WFCTA, a portable laser calibration system has been developed, which provides specified energy and direction of the YAG laser. Special designs, including power system, north calibration, and rotating system, have been implemented to ensure the proper functioning of the portable laser calibration system. The aluminum alloy of the entire frame and the vibration damper provide robust anti-impact ability and safety during transportation to different observation locations. A temperature control facility has been employed to meet the operational temperature requirement of electronic equipment. Various sensors have been utilized to monitor environmental parameters, the energy of YAG laser pulses, azimuth and pitch angles, and other parameters in real-time. The auto-control program is communicated wirelessly to avoid any manual interference with the system. The field experiment results have confirmed the reliability of the system and its ability to meet the calibration requirements of WFCTA.
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    Detection of Very High-energy Gamma-Ray Emission from the Radio Galaxy M87 with LHAASO
    (2024-11-01) Cao Z.; Aharonian F.; Axikegu; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Bian W.; Bukevich A.V.; Cao Q.; Cao W.Y.; Cao Z.; Chang J.; Chang J.F.; Chen A.M.; Chen E.S.; Chen H.X.; Chen L.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen Y.; Cheng N.; Cheng Y.D.; Chu M.C.; Cui M.Y.; Cui S.W.; Cui X.H.; Cui Y.D.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; Dong X.Q.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fang J.; Fang J.H.; Fang K.; Feng C.F.; Feng H.; Feng L.; Feng S.H.; Feng X.T.; Feng Y.; Feng Y.L.; Gabici S.; Gao B.; Gao C.D.; Gao Q.; Gao W.; Gao W.K.; Ge M.M.; Ge T.T.; Geng L.S.; Giacinti G.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo J.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; Hannuksela O.A.; Hasan M.; He H.H.; He H.N.; He J.Y.; He Y.; Hor Y.K.; Hou B.W.; Hou C.; Hou X.; Hu H.B.; Hu Q.; Hu S.C.; Huang C.; Huang D.H.; Huang T.Q.; Huang W.J.; Huang X.T.; Huang X.Y.; Huang Y.; Huang Y.Y.; Ji X.L.; Jia H.Y.; Jia K.; Jiang H.B.; Jiang K.; Jiang X.W.; Cao Z.; Mahidol University
    The nearby radio galaxy M87 is a very high-energy (VHE) gamma-ray emitter established by observations with ground-based gamma-ray detectors. Here we report the long-term monitoring of M87 from 2021 to 2024 with the Large High Altitude Air Shower Observatory (LHAASO). M87 has been detected by LHAASO with a statistical significance ∼ 9σ. The observed energy spectrum extends to 20 TeV, with a possible hardening at ∼20 TeV and then a clear softening at higher energies. Assuming that the intrinsic spectrum is described by a single power law up to 20 TeV, a tight upper bound on the extragalactic background light intensity is obtained. A strong VHE flare lasting 8 days, with a rise time of τ r rise = 1.05 ± 0.49 days and decay time of τ d decay = 2.17 ± 0.58 days, was found in early 2022. A possible GeV flare is seen also in Fermi Large Area Telescope data during the VHE flare period. The variability time as short as 1 day seen in the LHAASO data suggests a compact emission region with a size of ∼3 × 1015 δ cm (δ being the Doppler factor of the emitting region), corresponding to a few Schwarzschild radii of the central supermassive black hole in M87. The continuous monitoring of the source reveals a duty cycle of ∼1% for VHE flares with a flux above 10−11 erg cm−2 s−1.
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    Discovery of a New Gamma-Ray Source, LHAASO J0341+5258, with Emission up to 200 TeV
    (2021-08-10) Zhen Cao; F. Aharonian; Q. An; Axikegu; L. X. Bai; Y. X. Bai; Y. W. Bao; D. Bastieri; X. J. Bi; Y. J. Bi; H. Cai; J. T. Cai; Zhe Cao; J. Chang; J. F. Chang; B. M. Chen; E. S. Chen; J. Chen; Liang Chen; Liang Chen; Long Chen; M. J. Chen; M. L. Chen; Q. H. Chen; S. H. Chen; S. Z. Chen; T. L. Chen; X. L. Chen; Y. Chen; N. Cheng; Y. D. Cheng; S. W. Cui; X. H. Cui; Y. D. Cui; B. D'Ettorre Piazzoli; B. Z. Dai; H. L. Dai; Z. G. Dai; Danzengluobu; D. Della Volpe; X. J. Dong; K. K. Duan; J. H. Fan; Y. Z. Fan; Z. X. Fan; J. Fang; K. Fang; C. F. Feng; L. Feng; S. H. Feng; Y. L. Feng; B. Gao; C. D. Gao; L. Q. Gao; Q. Gao; W. Gao; M. M. Ge; L. S. Geng; G. H. Gong; Q. B. Gou; M. H. Gu; F. L. Guo; J. G. Guo; X. L. Guo; Y. Q. Guo; Y. Y. Guo; Y. A. Han; H. H. He; H. N. He; J. C. He; S. L. He; X. B. He; Y. He; M. Heller; Y. K. Hor; C. Hou; H. B. Hu; S. Hu; S. C. Hu; X. J. Hu; D. H. Huang; Q. L. Huang; W. H. Huang; X. T. Huang; X. Y. Huang; Z. C. Huang; F. Ji; X. L. Ji; H. Y. Jia; K. Jiang; Z. J. Jiang; C. Jin; T. Ke; D. Kuleshov; K. Levochkin; B. B. Li; Cheng Li; Cong Li; F. Li; H. B. Li; State Key Laboratory of Particle Detection & Electronics; Nanjing University; Shanghai Astronomical Observatory Chinese Academy of Sciences; Institute for Nuclear Research of the Russian Academy of Sciences; Shandong University; Wuhan University; Yunnan University; Institute of High Energy Physics Chinese Academy of Science; University of Chinese Academy of Sciences; Guangzhou University; Tsinghua University; Sun Yat-Sen University; University of Science and Technology of China; Zhengzhou University; Dublin Institute for Advanced Studies; Università degli Studi di Napoli Federico II; Sichuan University; National Astronomical Observatories Chinese Academy of Sciences; Max-Planck-Institut für Kernphysik; Southwest Jiaotong University; Purple Mountain Observatory Chinese Academy of Sciences; Hebei Normal University; Tibet University; Universit'e de Gen ve; TIANFU Cosmic Ray Research Center
    We report the discovery of a new unidentified extended γ-ray source in the Galactic plane named LHAASO J0341+5258 with a pretrial significance of 8.2 standard deviations above 25 TeV. The best-fit position is R.A. = 55. 34 0. 11 and decl. = 52. 97 0. 07. The angular size of LHAASO J0341+5258 is 0. 29 0. 06stat 0. 02sys. The flux above 25 TeV is about 20% of the flux of the Crab Nebula. Although a power-law fit of the spectrum from 10 to 200 TeV with the photon index α = 2.98 0.19stat 0.02sys is not excluded, the LHAASO data together with the flux upper limit at 10 GeV set by the Fermi-LAT observation, indicate a noticeable steepening of an initially hard power-law spectrum with a cutoff at ≈50 TeV. We briefly discuss the origin of ultra-high-energy gamma rays. The lack of an energetic pulsar and a young supernova remnant inside or in the vicinity of LHAASO J0341+5258 challenge, but do not exclude, both the leptonic and hadronic scenarios of gamma-ray production.
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    Discovery of Very High Energy Gamma-Ray Emissions from the Low-luminosity AGN NGC 4278 by LHAASO
    (2024-08-01) Cao Z.; Aharonian F.; Axikegu; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Bian W.; Bukevich A.V.; Cao Q.; Cao W.Y.; Cao Z.; Chang J.; Chang J.F.; Chen A.M.; Chen E.S.; Chen H.X.; Chen L.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen Y.; Cheng N.; Cheng Y.D.; Cui M.Y.; Cui S.W.; Cui X.H.; Cui Y.D.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; Dong X.Q.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fang J.; Fang J.H.; Fang K.; Feng C.F.; Feng H.; Feng L.; Feng S.H.; Feng X.T.; Feng Y.; Feng Y.L.; Gabici S.; Gao B.; Gao C.D.; Gao Q.; Gao W.; Gao W.K.; Ge M.M.; Geng L.S.; Giacinti G.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; Hasan M.; He H.H.; He H.N.; He J.Y.; He Y.; Hor Y.K.; Hou B.W.; Hou C.; Hou X.; Hu H.B.; Hu Q.; Hu S.C.; Huang D.H.; Huang T.Q.; Huang W.J.; Huang X.T.; Huang X.Y.; Huang Y.; Ji X.L.; Jia H.Y.; Jia K.; Jiang K.; Jiang X.W.; Jiang Z.J.; Jin M.; Kang M.M.; Karpikov I.; Kuleshov D.; Kurinov K.; Li B.B.; Cao Z.; Mahidol University
    The first source catalog of the Large High Altitude Air Shower Observatory (LHAASO) reported the detection of a very high energy gamma-ray source, 1LHAASO J1219+2915. This Letter presents a further detailed study of the spectral and temporal behavior of this pointlike source. The best-fit position of the TeV source (R.A. = 185.°05 ± 0.°04, decl. = 29.°25 ± 0.°03) is compatible with NGC 4278 within ∼0.°03. Variation analysis shows an indication of variability on a timescale of a few months in the TeV band, which is consistent with low-frequency observations. Based on these observations, we report the detection of TeV γ-ray emissions from this low-luminosity active galactic nucleus. The observation by LHAASO's Water Cherenkov Detector Array during the active period has a significance level of 8.8σ with a best-fit photon spectral index Γ = 2.56 ± 0.14 and a flux f1-10 TeV = (7.0 ± 1.1sta ± 0.35syst) × 10−13 photons cm−2 s−1, or approximately 5% of the Crab Nebula. The discovery of VHE gamma-ray emission from NGC 4278 indicates that compact, weak radio jets can efficiently accelerate particles and emit TeV photons.
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    A dynamic range extension system for LHAASO WCDA-1
    (2021-12-01) F. Aharonian; Q. An; Axikegu; L. X. Bai; Y. X. Bai; Y. W. Bao; D. Bastieri; X. J. Bi; Y. J. Bi; H. Cai; J. T. Cai; Z. Cao; Z. Cao; J. Chang; J. F. Chang; X. C. Chang; B. M. Chen; J. Chen; L. Chen; L. Chen; L. Chen; M. J. Chen; M. L. Chen; Q. H. Chen; S. H. Chen; S. Z. Chen; T. L. Chen; X. L. Chen; Y. Chen; N. Cheng; Y. D. Cheng; S. W. Cui; X. H. Cui; Y. D. Cui; B. Z. Dai; H. L. Dai; Z. G. Dai; Danzengluobu; D. della Volpe; B. D’Ettorre Piazzoli; X. J. Dong; J. H. Fan; Y. Z. Fan; Z. X. Fan; J. Fang; K. Fang; C. F. Feng; L. Feng; S. H. Feng; Y. L. Feng; B. Gao; C. D. Gao; Q. Gao; W. Gao; M. M. Ge; L. S. Geng; G. H. Gong; Q. B. Gou; M. H. Gu; J. G. Guo; X. L. Guo; Y. Q. Guo; Y. Y. Guo; Y. A. Han; H. H. He; H. N. He; J. C. He; S. L. He; X. B. He; Y. He; M. Heller; Y. K. Hor; C. Hou; X. Hou; H. B. Hu; S. Hu; S. C. Hu; X. J. Hu; D. H. Huang; Q. L. Huang; W. H. Huang; X. T. Huang; Y. Huang; Z. C. Huang; F. Ji; X. L. Ji; H. Y. Jia; K. Jiang; Z. J. Jiang; C. Jin; D. Kuleshov; K. Levochkin; B. B. Li; C. Li; C. Li; F. Li; H. B. Li; H. C. Li; H. Y. Li; J. Li; State Key Laboratory of Particle Detection & Electronics; Nanjing University; Shanghai Astronomical Observatory Chinese Academy of Sciences; Institute for Nuclear Research of the Russian Academy of Sciences; Shandong University; Wuhan University; Yunnan University; Institute of High Energy Physics Chinese Academy of Science; University of Chinese Academy of Sciences; Guangzhou University; Tsinghua University; Sun Yat-Sen University; University of Science and Technology of China; Zhengzhou University; Dublin Institute for Advanced Studies; Università degli Studi di Napoli Federico II; Sichuan University; National Astronomical Observatories Chinese Academy of Sciences; Max-Planck-Institut für Kernphysik; Southwest Jiaotong University; Purple Mountain Observatory Chinese Academy of Sciences; Université de Genève; Hebei Normal University; Tibet University; TIANFU Cosmic Ray Research Center
    Purpose: The main scientific goal of LHAASO-WCDA is to survey gamma-ray sources with energy from 100 GeV to 30 TeV. To observe high-energy shower events, especially to measure the energy spectrum of cosmic rays from 100 TeV to 10 PeV, a dynamic range extension system (WCDA++) is designed to use a 1.5-inch PMT with a dynamic range of four orders of magnitude for each cell in WCDA-1. Method: The dynamic range is extended by using these PMTs to measure the effective charge density in the core region of air shower events, which is an important parameter for identifying the composition of primary particles. Result and Conclusion: The system has been running for more than one year. In this paper, the details of the design and performance of WCDA++ are presented.
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    Evidence for particle acceleration approaching PeV energies in the W51 complex
    (2024-01-01) Cao Z.; Aharonian F.; Axikegu; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Bian W.; Bukevich A.V.; Cao Q.; Cao W.Y.; Cao Z.; Chang J.; Chang J.F.; Chen A.M.; Chen E.S.; Chen H.X.; Chen L.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen Y.; Cheng N.; Cheng Y.D.; Cui M.Y.; Cui S.W.; Cui X.H.; Cui Y.D.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; Dong X.Q.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fang J.; Fang J.H.; Fang K.; Feng C.F.; Feng H.; Feng L.; Feng S.H.; Feng X.T.; Feng Y.; Feng Y.L.; Gabici S.; Gao B.; Gao C.D.; Gao Q.; Gao W.; Gao W.K.; Ge M.M.; Geng L.S.; Giacinti G.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; Hasan M.; He H.H.; He H.N.; He J.Y.; He Y.; Hor Y.K.; Hou B.W.; Hou C.; Hou X.; Hu H.B.; Hu Q.; Hu S.C.; Huang D.H.; Huang T.Q.; Huang W.J.; Huang X.T.; Huang X.Y.; Huang Y.; Ji X.L.; Jia H.Y.; Jia K.; Jiang K.; Jiang X.W.; Jiang Z.J.; Jin M.; Kang M.M.; Karpikov I.; Kuleshov D.; Kurinov K.; Li B.B.; Cao Z.; Mahidol University
    The γ-ray emission from the W51 complex is widely acknowledged to be attributed to the interaction between the cosmic rays (CRs) accelerated by the shock of supernova remnant (SNR) W51C and the dense molecular clouds in the adjacent star-forming region, W51B. However, the maximum acceleration capability of W51C for CRs remains elusive. Based on observations conducted with the Large High Altitude Air Shower Observatory (LHAASO), we report a significant detection of γ rays emanating from the W51 complex, with energies from 2 to 200 TeV. The LHAASO measurements, for the first time, extend the γ-ray emission from the W51 complex beyond 100 TeV and reveal a significant spectrum bending at tens of TeV. By combining the “π0-decay bump” featured data from Fermi-LAT, the broadband γ-ray spectrum of the W51 region can be well-characterized by a simple pp-collision model. The observed spectral bending feature suggests an exponential cutoff at ∼400 TeV or a power-law break at ∼200 TeV in the CR proton spectrum, most likely providing the first evidence of SNRs serving as CR accelerators approaching the PeV regime. Additionally, two young star clusters within W51B could also be theoretically viable to produce the most energetic γ rays observed by LHAASO. Our findings strongly support the presence of extreme CR accelerators within the W51 complex and provide new insights into the origin of Galactic CRs.
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    Exploring Lorentz Invariance Violation from Ultrahigh-Energy γ Rays Observed by LHAASO
    (2022-02-04) Cao Z.; Aharonian F.; An Q.; Axikegu; Bai L.X.; Bai Y.X.; Bao Y.W.; Bastieri D.; Bi X.J.; Bi Y.J.; Cai H.; Cai J.T.; Cao Z.; Chang J.; Chang J.F.; Chen B.M.; Chen E.S.; Chen J.; Chen L.; Chen L.; Chen M.J.; Chen M.L.; Chen Q.H.; Chen S.H.; Chen S.Z.; Chen T.L.; Chen X.L.; Chen Y.; Cheng N.; Cheng Y.D.; Cui S.W.; Cui X.H.; Cui Y.D.; Piazzoli B.D.E.; Dai B.Z.; Dai H.L.; Dai Z.G.; Danzengluobu; Della Volpe D.; Dong X.J.; Duan K.K.; Fan J.H.; Fan Y.Z.; Fan Z.X.; Fang J.; Fang K.; Feng C.F.; Feng L.; Feng S.H.; Feng Y.L.; Gao B.; Gao C.D.; Gao L.Q.; Gao Q.; Gao W.; Ge M.M.; Geng L.S.; Gong G.H.; Gou Q.B.; Gu M.H.; Guo F.L.; Guo J.G.; Guo X.L.; Guo Y.Q.; Guo Y.Y.; Han Y.A.; He H.H.; He H.N.; He J.C.; He S.L.; He X.B.; He Y.; Heller M.; Hor Y.K.; Hou C.; Hou X.; Hu H.B.; Hu S.; Hu S.C.; Hu X.J.; Huang D.H.; Huang Q.L.; Huang W.H.; Huang X.T.; Huang X.Y.; Huang Z.C.; Ji F.; Ji X.L.; Jia H.Y.; Jiang K.; Jiang Z.J.; Jin C.; Ke T.; Kuleshov D.; Levochkin K.; Li B.B.; Li C.; Li C.; Li F.; Li H.B.; Mahidol University
    Recently, the LHAASO Collaboration published the detection of 12 ultrahigh-energy γ-ray sources above 100 TeV, with the highest energy photon reaching 1.4 PeV. The first detection of PeV γ rays from astrophysical sources may provide a very sensitive probe of the effect of the Lorentz invariance violation (LIV), which results in decay of high-energy γ rays in the superluminal scenario and hence a sharp cutoff of the energy spectrum. Two highest energy sources are studied in this work. No signature of the existence of the LIV is found in their energy spectra, and the lower limits on the LIV energy scale are derived. Our results show that the first-order LIV energy scale should be higher than about 105 times the Planck scale MPl and that the second-order LIV scale is >10-3MPl. Both limits improve by at least one order of magnitude the previous results.
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    Extended Very-High-Energy Gamma-Ray Emission Surrounding PSR J0622+3749 Observed by LHAASO-KM2A
    (2021-06-18) F. Aharonian; Q. An; Axikegu; L. X. Bai; Y. X. Bai; Y. W. Bao; D. Bastieri; X. J. Bi; Y. J. Bi; H. Cai; J. T. Cai; Z. Cao; Z. Cao; J. Chang; J. F. Chang; X. C. Chang; B. M. Chen; J. Chen; L. Chen; L. Chen; L. Chen; M. J. Chen; M. L. Chen; Q. H. Chen; S. H. Chen; S. Z. Chen; T. L. Chen; X. L. Chen; Y. Chen; N. Cheng; Y. D. Cheng; S. W. Cui; X. H. Cui; Y. D. Cui; B. Z. Dai; H. L. Dai; Z. G. Dai; Danzengluobu; D. Della Volpe; B. D'Ettorre Piazzoli; X. J. Dong; J. H. Fan; Y. Z. Fan; Z. X. Fan; J. Fang; K. Fang; C. F. Feng; L. Feng; S. H. Feng; Y. L. Feng; B. Gao; C. D. Gao; Q. Gao; W. Gao; M. M. Ge; L. S. Geng; G. H. Gong; Q. B. Gou; M. H. Gu; J. G. Guo; X. L. Guo; Y. Q. Guo; Y. Y. Guo; Y. A. Han; H. H. He; H. N. He; J. C. He; S. L. He; X. B. He; Y. He; M. Heller; Y. K. Hor; C. Hou; X. Hou; H. B. Hu; S. Hu; S. C. Hu; X. J. Hu; D. H. Huang; Q. L. Huang; W. H. Huang; X. T. Huang; Z. C. Huang; F. Ji; X. L. Ji; H. Y. Jia; K. Jiang; Z. J. Jiang; C. Jin; D. Kuleshov; K. Levochkin; B. B. Li; C. Li; C. Li; F. Li; H. B. Li; H. C. Li; H. Y. Li; J. Li; K. Li; State Key Laboratory of Particle Detection & Electronics; Nanjing University; Shanghai Astronomical Observatory Chinese Academy of Sciences; Institute for Nuclear Research of the Russian Academy of Sciences; Shandong University; Wuhan University; Yunnan University; Institute of High Energy Physics Chinese Academy of Science; University of Chinese Academy of Sciences; Guangzhou University; Tsinghua University; Sun Yat-Sen University; University of Science and Technology of China; Zhengzhou University; Dublin Institute for Advanced Studies; Università degli Studi di Napoli Federico II; Sichuan University; National Astronomical Observatories Chinese Academy of Sciences; Max-Planck-Institut für Kernphysik; Southwest Jiaotong University; Purple Mountain Observatory Chinese Academy of Sciences; Université de Genève; Hebei Normal University; Tibet University; TIANFU Cosmic Ray Research Center
    We report the discovery of an extended very-high-energy (VHE) gamma-ray source around the location of the middle-aged (207.8 kyr) pulsar PSR J0622+3749 with the Large High-Altitude Air Shower Observatory (LHAASO). The source is detected with a significance of 8.2σ for E>25 TeV assuming a Gaussian template. The best-fit location is (right ascension, declination) =(95.47°±0.11°,37.92°±0.09°), and the extension is 0.40°±0.07°. The energy spectrum can be described by a power-law spectrum with an index of -2.92±0.17stat±0.02sys. No clear extended multiwavelength counterpart of the LHAASO source has been found from the radio to sub-TeV bands. The LHAASO observations are consistent with the scenario that VHE electrons escaped from the pulsar, diffused in the interstellar medium, and scattered the interstellar radiation field. If interpreted as the pulsar halo scenario, the diffusion coefficient, inferred for electrons with median energies of ∼160 TeV, is consistent with those obtained from the extended halos around Geminga and Monogem and much smaller than that derived from cosmic ray secondaries. The LHAASO discovery of this source thus likely enriches the class of so-called pulsar halos and confirms that high-energy particles generally diffuse very slowly in the disturbed medium around pulsars.