Measurements of All-Particle Energy Spectrum and Mean Logarithmic Mass of Cosmic Rays from 0.3 to 30 PeV with LHAASO-KM2A

We present the measurements of all-particle energy spectrum and mean logarithmic mass of cosmic rays in the energy range of 0.3-30 PeV using data collected from LHAASO-KM2A between September 2021 and December 2022, which is based on a nearly composition-independent energy reconstruction method, achieving unprecedented accuracy. Our analysis reveals the position of the knee at 3.67±0.05±0.15  PeV. Below the knee, the spectral index is found to be -2.7413±0.0004±0.0050, while above the knee, it is -3.128±0.005±0.027, with the sharpness of the transition measured with a statistical error of 2%. The mean logarithmic mass of cosmic rays is almost heavier than helium in the whole measured energy range. It decreases from 1.7 at 0.3 PeV to 1.3 at 3 PeV, representing a 24% decline following a power law with an index of -0.1200±0.0003±0.0341. This is equivalent to an increase in abundance of light components. Above the knee, the mean logarithmic mass exhibits a power law trend towards heavier components, which is reversal to the behavior observed in the all-particle energy spectrum. Additionally, the knee position and the change in power-law index are approximately the same. These findings suggest that the knee observed in the all-particle spectrum corresponds to the knee of the light component, rather than the medium-heavy components.

Measurement of Ultra-High-Energy Diffuse Gamma-Ray Emission of the Galactic Plane from 10 TeV to 1 PeV with LHAASO-KM2A

The diffuse Galactic γ-ray emission, mainly produced via interactions between cosmic rays and the interstellar medium and/or radiation field, is a very important probe of the distribution, propagation, and interaction of cosmic rays in the Milky Way. In this Letter, we report the measurements of diffuse γ rays from the Galactic plane between 10 TeV and 1 PeV energies, with the square kilometer array of the Large High Altitude Air Shower Observatory (LHAASO). Diffuse emissions from the inner (15°10  TeV). The energy spectrum in the inner Galaxy regions can be described by a power-law function with an index of -2.99±0.04, which is different from the curved spectrum as expected from hadronic interactions between locally measured cosmic rays and the line-of-sight integrated gas content. Furthermore, the measured flux is higher by a factor of ∼3 than the prediction. A similar spectrum with an index of -2.99±0.07 is found in the outer Galaxy region, and the absolute flux for 10≲E≲60  TeV is again higher than the prediction for hadronic cosmic ray interactions. The latitude distributions of the diffuse emission are consistent with the gas distribution, while the longitude distributions show clear deviation from the gas distribution. The LHAASO measurements imply that either additional emission sources exist or cosmic ray intensities have spatial variations.

A tera-electron volt afterglow from a narrow jet in an extremely bright gamma-ray burst

Some gamma-ray bursts (GRBs) have a tera-electron volt (TeV) afterglow, but the early onset of this has not been observed. We report observations with the Large High Altitude Air Shower Observatory of the bright GRB 221009A, which serendipitously occurred within the instrument field of view. More than 64,000 photons >0.2 TeV were detected within the first 3000 seconds. The TeV flux began several minutes after the GRB trigger, then rose to a peak about 10 seconds later. This was followed by a decay phase, which became more rapid ~650 seconds after the peak. We interpret the emission using a model of a relativistic jet with half-opening angle ~0.8°. This is consistent with the core of a structured jet and could explain the high isotropic energy of this GRB.

Constraints on Heavy Decaying Dark Matter from 570 Days of LHAASO Observations

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 10^{5} and 10^{9}  GeV. Our results with LHAASO are robust, and have important implications for dark matter interpretations of the diffuse astrophysical high-energy neutrino emission.

[Predictive value of prognostic inflammatory and tumor score in intrahepatic cholangiocarcinoma]

Objective: To compare and analyze the predictive value of different inflammatory factors and tumor markers in intrahepatic cholangiocarcinoma and to develop a new and effective preoperative prognostic scoring system. Methods: 102 and 72 cases with intrahepatic cholangiocarcinoma who underwent radical surgery in Tianjin Medical University Cancer Institute and Hospital and the Affiliated Hospital of Weifang Medical University were selected as the experimental group and the validation group, respectively. Clinicopathological and follow-up data were collected. Cox proportional-hazards model was used to analyze the predictive value of different prognostic markers. The relationship between prognostic markers and clinicopathological data was analyzed by rank sum test, χ² or Fisher's exact test. Results: Among the direct inflammatory factors, tumor markers and combined inflammatory factors, prognostic inflammatory index (PII), carbohydrate antigen (CA) 19-9 and systemic inflammation score (SIS) were the most significant predictive factors for postoperative survival outcomes in patients with intrahepatic cholangiocarcinoma. The prognostic inflammatory and tumor score (PITS) was proposed as a new prognostic scoring system for intrahepatic cholangiocarcinoma. PII and CA19-9 were included into the scoring criteria for prognostic stratification of patients. PITS was an independent predictor of tumor-free survival and overall survival in patients with intrahepatic cholangiocarcinoma. Patients with high-grade PITS had later tumor grade and higher frequency of vascular invasion. Conclusion: PITS is highly effective prognostic scoring system for patients with intrahepatic cholangiocarcinoma. In addition, PITS is recommended for preoperative prognostic stratification in patients with intrahepatic cholangiocarcinoma.

Exploring Lorentz Invariance Violation from Ultrahigh-Energy γ Rays Observed by LHAASO

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 10^{5} times the Planck scale M_{Pl} and that the second-order LIV scale is >10^{-3}M_{Pl}. Both limits improve by at least one order of magnitude the previous results.

Peta-electron volt gamma-ray emission from the Crab Nebula

The Crab Nebula is a bright source of gamma rays powered by the Crab Pulsar's rotational energy through the formation and termination of a relativistic electron-positron wind. We report the detection of gamma rays from this source with energies from 5 × 10^-4 to 1.1 peta-electron volts with a spectrum showing gradual steepening over three energy decades. The ultrahigh-energy photons imply the presence of a peta-electron volt electron accelerator (a pevatron) in the nebula, with an acceleration rate exceeding 15% of the theoretical limit. We constrain the pevatron's size between 0.025 and 0.1 parsecs and the magnetic field to ≈110 microgauss. The production rate of peta-electron volt electrons, 2.5 × 10³⁶ ergs per second, constitutes 0.5% of the pulsar spin-down luminosity, although we cannot exclude a contribution of peta-electron volt protons to the production of the highest-energy gamma rays.

Extended Very-High-Energy Gamma-Ray Emission Surrounding PSR J0622+3749 Observed by LHAASO-KM2A

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±0.17_{stat}±0.02_{sys}. 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.

Ultrahigh-energy photons up to 1.4 petaelectronvolts from 12 γ-ray Galactic sources

The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 10¹⁵ electronvolts) indicates the existence of the so-called PeVatrons-cosmic-ray factories that accelerate particles to PeV energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays¹. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) γ radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref. ²). Although γ-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane^3-6, unbiased identification and in-depth exploration of PeVatrons requires detection of γ-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy γ-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy γ-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators.

Variable dimensionality from mononuclear and trinuclear to one and two dimensions: a series of copper(II) compounds with 4,4'-dipyridine dioxide

Reaction of 4,4'-dipyridine dioxide (dpdo) and CuCl(2).6H(2)O in aqueous solution gave an adduct [Cu(H(2)O)(6)]Cl(2).2dpdo.2H(2)O 1, which has a hydrogen-bonded three-dimensional network. While substituting CuCl(2).6H(2)O with Cu(ClO(4))(2).6H(2)O, three pseudopolymorphs, namely, [Cu(dpdo)(6)][ClO(4)](2) 2, [Cu(3)(dpdo)(8)(H(2)O)(6)][ClO(4)](6).2dpdo.6H(2)O 3, and [Cu(dpdo)(H(2)O)(4)][ClO(4)](2).2dpdo 4, were isolated. 2 consists of a mononuclear copper coordinated with six terminal dpdo ligands. Adjacent mononuclear units are overlapped through pi-pi stacking of pyridine rings to give a 2D sheet with a triangular channel. 3 forms a trinuclear cluster bridged by two dpdo molecules. The solvate and terminal dpdo molecules are interwoven through hydrogen bonding and pi-pi stacking to lead to a rectangular channel with a dimensionality of 12.98 A x 13.44 A. 4 has a one-dimensional chain structure bridged by dpdo. Two solvate dpdo ligands link these chains through hydrogen bonding to generate two sets of three-dimensional networks which are interwoven through a common conjunctive point [Cu(H(2)O)(4)](2+), yielding a three-dimensional open framework with triangular channels. ClO(4)(-) anions are included within these channels in 2-4 through weak C-H...O hydrogen bonding. The introduction of the second spacer, 4,4'-bipyridine, generated a 2D architecture [Cu(dpdo)(4,4'-bipy)][ClO(4)](2).2H(2)O.dpdo 5, which is constructed by 4,4'-bipy and 4,4'-dpdo simultaneously, exhibiting a large channel with approximate dimensionality 11.1 A x 12.6 A, in which solvate 4,4'-dpdo ligand and perchlorate anions are accommodated.

Structures and magnetism of two novel heptanuclear lanthanide-centered trigonal prismatic clusters: [LnCu6(mu 3-OH)3(HL)2(L)4](ClO4)2.25H2O (Ln = La, Tb; H2L = iminodiacetic acid)

The new heteronuclear iminodiacetic acid (H2L) complexes [LnCu6(mu 3-OH)3(HL)2(L)4](ClO4)(2).25H2O with Ln = La (1) and Tb (2) have been prepared in aqueous solution and characterized by single-crystal X-ray diffraction to be isomorphous (crystallographic data for 1 and 2: hexagonal, P63/m; a = b = 12.6425(14) A, c = 24.541(5) A, Z = 2 (1); a = b = 12.5802(9) A, c = 24.285(4) A, Z = 2 (2)). Ln3+ was found to be located in the center of the trigonal prismatic cage formed by six Cu2+ ions, with a tricapped trigonal prismatic coordination environment of nine O atoms. The magnetic properties of complexes 1 and 2 have been studied. The results indicate the presence of ferromagnetic couplings between Tb3+ and Cu2+ in compound 2.