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A precision measurement of the nitrogen flux with rigidity (momentum per unit charge) from 2.2 GV to 3.3 TV based on $2.2\times {10}^6$ events is presented. The detailed rigidity dependence of the nitrogen flux spectral index is presented for the first time. The spectral index rapidly hardens at high rigidities and becomes identical to the spectral indices of primary He, C, and O cosmic rays above $\sim 700\mathrm{GV}$. We observed that the nitrogen flux ${\mathrm{\Phi }}_{\mathrm{N}}$ can be presented as the sum of its primary component ${\mathrm{\Phi }}_{\mathrm{N}}^P$ and secondary component ${\mathrm{\Phi }}_{\mathrm{N}}^S$, ${\mathrm{\Phi }}_{\mathrm{N}}={\mathrm{\Phi }}_{\mathrm{N}}^P+{\mathrm{\Phi }}_{\mathrm{N}}^S$, and we found ${\mathrm{\Phi }}_{\mathrm{N}}$ is well described by the weighted sum of the oxygen flux ${\mathrm{\Phi }}_{\mathrm{O}}$ (primary cosmic rays) and the boron flux ${\mathrm{\Phi }}_{\mathrm{B}}$ (secondary cosmic rays), with ${\mathrm{\Phi }}_{\mathrm{N}}^P=(0.090\pm 0.002)\times {\mathrm{\Phi }}_{\mathrm{O}}$ and ${\mathrm{\Phi }}_{\mathrm{N}}^S=(0.62\pm 0.02)\times {\mathrm{\Phi }}_{\mathrm{B}}$ over the entire rigidity range. This corresponds to a change of the contribution of the secondary cosmic ray component in the nitrogen flux from 70% at a few GV to $<30\%$ above 1 TV.

A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on $6.8\times {10}^6$ positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to $\sim 250\mathrm{GeV}$, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.

We present high-statistics, precision measurements of the detailed time and energy dependence of the primary cosmic-ray electron flux and positron flux over 79 Bartels rotations from May 2011 to May 2017 in the energy range from 1 to 50 GeV. For the first time, the charge-sign dependent modulation during solar maximum has been investigated in detail by leptons alone. Based on $23.5\times {10}^6$ events, we report the observation of short-term structures on the timescale of months coincident in both the electron flux and the positron flux. These structures are not visible in the $e^{+}/e^{-}$ flux ratio. The precision measurements across the solar polarity reversal show that the ratio exhibits a smooth transition over $830\pm 30$ days from one value to another. The midpoint of the transition shows an energy dependent delay relative to the reversal and changes by $260\pm 30$ days from 1 to 6 GeV.

The diffuse Galactic $\gamma$-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 $\gamma$ 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 ($15°<l<125°$, $|b|<5°$) and outer ($125°<l<235°$, $|b|<5°$) Galactic plane are detected with $29.1\sigma$ and $12.7\sigma$ significance, respectively. The outer Galactic plane diffuse emission is detected for the first time in the very- to ultra-high-energy domain ($E>10\mathrm{TeV}$). The energy spectrum in the inner Galaxy regions can be described by a power-law function with an index of $-2.99\pm 0.04$, 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 $\sim 3$ than the prediction. A similar spectrum with an index of $-2.99\pm 0.07$ is found in the outer Galaxy region, and the absolute flux for $10\lesssim E\lesssim 60\mathrm{TeV}$ 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.

The evolution of the in-plane magnetic anisotropies in Fe${}_3$O${}_4$/GaAs(100) and Fe${}_3$O${}_4$/MgO/GaAs(100) hybrid spintronic structures has been studied by magneto-optical Kerr effect and ferromagnetic resonance (FMR). The surface and volume contributions to the in-plane cubic and uniaxial anisotropies have been distinguished in Fe${}_3$O${}_4$/GaAs by fitting the anisotropy constants, measured by FMR, as a function of the magnetic film thickness. It was found that interfacial chemical bonding rather than strain relaxation plays the dominant role in causing the unexpected uniaxial magnetic anisotropy (UMA) in Fe${}_3$O${}_4$ films grown directly on the GaAs surfaces. In contrast, after MgO barrier insertion, FMR results show that the UMA is greatly reduced, and strain relaxation is found to be the main origin of the UMA in Fe${}_3$O${}_4$/MgO/GaAs structures.

We present the first search for the leptonic decays $D^{*+}\to e^{+}{\nu }_e$ and $D^{*+}\to {\mu }^{+}{\nu }_{\mu }$ by analyzing a data sample of electron-positron collisions recorded with the BESIII detector at center-of-mass energies between 4.178 and 4.226 GeV, corresponding to an integrated luminosity of $6.32{\mathrm{fb}}^{-1}$. No significant signal is observed. The upper limits on the branching fractions for $D^{*+}\to e^{+}{\nu }_e$ and $D^{*+}\to {\mu }^{+}{\nu }_{\mu }$ are set to be $1.1\times {10}^{-5}$ and $4.3\times {10}^{-6}$ at 90% confidence level, respectively.

We report the observation of new properties of primary cosmic rays He, C, and O measured in the rigidity (momentum/charge) range 2 GV to 3 TV with $90\times {10}^6$ helium, $8.4\times {10}^6$ carbon, and $7.0\times {10}^6$ oxygen nuclei collected by the Alpha Magnetic Spectrometer (AMS) during the first five years of operation. Above 60 GV, these three spectra have identical rigidity dependence. They all deviate from a single power law above 200 GV and harden in an identical way.

A precision measurement by AMS of the positron fraction in primary cosmic rays in the energy range from 0.5 to 500 GeV based on 10.9 million positron and electron events is presented. This measurement extends the energy range of our previous observation and increases its precision. The new results show, for the first time, that above $\sim 200\mathrm{GeV}$ the positron fraction no longer exhibits an increase with energy.

Recently, the LHAASO Collaboration published the detection of 12 ultrahigh-energy $\gamma$-ray sources above 100 TeV, with the highest energy photon reaching 1.4 PeV. The first detection of PeV $\gamma$ 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 $\gamma$ 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 $M_{\mathrm{Pl}}$ and that the second-order LIV scale is $>{10}^{-3}{M}_{\mathrm{Pl}}$. Both limits improve by at least one order of magnitude the previous results.

The kilometer square array (KM2A) of the large high altitude air shower observatory (LHAASO) aims at surveying the northern $\gamma$-ray sky at energies above 10 TeV with unprecedented sensitivity. $\gamma$-ray observations have long been one of the most powerful tools for dark matter searches, as, e.g., high-energy $\gamma$ 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 $\gamma /\text{hadron}$ separation. We find no excess of dark matter signals, and thus place some of the strongest $\gamma$-ray constraints on the lifetime of heavy dark matter particles with mass between ${10}^5$ and ${10}^9\mathrm{GeV}$. Our results with LHAASO are robust, and have important implications for dark matter interpretations of the diffuse astrophysical high-energy neutrino emission.

We report the observation of new properties of primary cosmic rays, neon (Ne), magnesium (Mg), and silicon (Si), measured in the rigidity range 2.15 GV to 3.0 TV with $1.8\times {10}^6\mathrm{Ne}$, $2.2\times {10}^6\mathrm{Mg}$, and $1.6\times {10}^6\mathrm{Si}$ nuclei collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. The Ne and Mg spectra have identical rigidity dependence above 3.65 GV. The three spectra have identical rigidity dependence above 86.5 GV, deviate from a single power law above 200 GV, and harden in an identical way. Unexpectedly, above 86.5 GV the rigidity dependence of primary cosmic rays Ne, Mg, and Si spectra is different from the rigidity dependence of primary cosmic rays He, C, and O. This shows that the Ne, Mg, and Si and He, C, and O are two different classes of primary cosmic rays.

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 $\mathrm{\Delta }$ 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 $23.4\pm 0.1\pm 1.3\mathrm{TeV}$ and ($21.9\pm 0.1\mathrm{TeV}$), 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.

Precision measurements of cosmic ray positrons are presented up to 1 TeV based on 1.9 million positrons collected by the Alpha Magnetic Spectrometer on the International Space Station. The positron flux exhibits complex energy dependence. Its distinctive properties are (a) a significant excess starting from $25.2\pm 1.8\mathrm{GeV}$ compared to the lower-energy, power-law trend, (b) a sharp dropoff above $284_{-64}^{+91}\mathrm{GeV}$, (c) in the entire energy range the positron flux is well described by the sum of a term associated with the positrons produced in the collision of cosmic rays, which dominates at low energies, and a new source term of positrons, which dominates at high energies, and (d) a finite energy cutoff of the source term of $E_s=810_{-180}^{+310}\mathrm{GeV}$ is established with a significance of more than $4\sigma$. These experimental data on cosmic ray positrons show that, at high energies, they predominantly originate either from dark matter annihilation or from other astrophysical sources.

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 $\mathrm{J}0622+3749$ with the Large High-Altitude Air Shower Observatory (LHAASO). The source is detected with a significance of $8.2\sigma$ for $E>25\mathrm{TeV}$ assuming a Gaussian template. The best-fit location is (right ascension, declination) $=(95.47°\pm 0.11°,37.92°\pm 0.09°)$, and the extension is $0.40°\pm 0.07°$. The energy spectrum can be described by a power-law spectrum with an index of $-2.92\pm {0.17}_{\mathrm{stat}}\pm {0.02}_{\mathrm{sys}}$. 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 $\sim 160\mathrm{TeV}$, 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.

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.

In the Large High Altitude Air Shower Observatory (LHAASO), the square kilometer array, with 5249 electromagnetic particle detectors (EDs) and 1188 muon detectors, is deployed to explore the gamma-ray sources above 30 TeV with unprecedented sensitivity and to measure primary cosmic rays in the energy range from 10 TeV to 100 PeV. The energetic particles produced by extensive air showers can serve as a continuously available source for calibration of the numerous EDs over a large area. In this study, the detector untriggered probability is first proposed to estimate the particle density at different distances from the shower core and distinguish the characteristic single-particle signal detected by each ED. This method uses science data directly, and does not require prior knowledge of the cosmic-ray elemental composition or hadronic interaction model. Experimental results show that this self-calibration can be used to determine the number of particles detected by each ED with an accuracy better than 2% within a time scale of hours, which is adequate to meet the physics requirements of the LHAASO experiment. With this high efficiency and accuracy, this calibration also provides an ideal method to monitor the detector performance throughout an expected lifetime of $>10\mathrm{years}$.

We report on the observation of new properties of secondary cosmic rays Li, Be, and B measured in the rigidity (momentum per unit charge) range 1.9 GV to 3.3 TV with a total of $5.4\times {10}^6$ nuclei collected by AMS during the first five years of operation aboard the International Space Station. The Li and B fluxes have an identical rigidity dependence above 7 GV and all three fluxes have an identical rigidity dependence above 30 GV with the $\mathrm{Li}/\mathrm{Be}$ flux ratio of $2.0\pm 0.1$. The three fluxes deviate from a single power law above 200 GV in an identical way. This behavior of secondary cosmic rays has also been observed in the AMS measurement of primary cosmic rays He, C, and O but the rigidity dependences of primary cosmic rays and of secondary cosmic rays are distinctly different. In particular, above 200 GV, the secondary cosmic rays harden more than the primary cosmic rays.

Precision measurements by the Alpha Magnetic Spectrometer on the International Space Station of the primary cosmic-ray electron flux in the range 0.5 to 700 GeV and the positron flux in the range 0.5 to 500 GeV are presented. The electron flux and the positron flux each require a description beyond a single power-law spectrum. Both the electron flux and the positron flux change their behavior at $\sim 30\mathrm{GeV}$ but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. The determination of the differing behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.

A precision measurement by AMS of the antiproton flux and the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 GV is presented based on $3.49\times 10^5$ antiproton events and $2.42\times 10^9$ proton events. The fluxes and flux ratios of charged elementary particles in cosmic rays are also presented. In the absolute rigidity range $\sim 60$ to $\sim 500\mathrm{GV}$, the antiproton $\overline{p}$, proton $p$, and positron $e^{+}$ fluxes are found to have nearly identical rigidity dependence and the electron $e^{-}$ flux exhibits a different rigidity dependence. Below 60 GV, the ($\overline{p}/p$), ($\overline{p}/e^{+}$), and ($p/e^{+}$) flux ratios each reaches a maximum. From $\sim 60$ to $\sim 500\mathrm{GV}$, the ($\overline{p}/p$), ($\overline{p}/e^{+}$), and ($p/e^{+}$) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.

Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of ${}^3\mathrm{He}$ and ${}^4\mathrm{He}$ fluxes are presented. The measurements are based on 100 million ${}^4\mathrm{He}$ nuclei in the rigidity range from 2.1 to 21 GV and 18 million ${}^3\mathrm{He}$ from 1.9 to 15 GV collected from May 2011 to November 2017. We observed that the ${}^3\mathrm{He}$ and ${}^4\mathrm{He}$ fluxes exhibit nearly identical variations with time. The relative magnitude of the variations decreases with increasing rigidity. The rigidity dependence of the ${}^3\mathrm{He}/{}^4\mathrm{He}$ flux ratio is measured for the first time. Below 4 GV, the ${}^3\mathrm{He}/{}^4\mathrm{He}$ flux ratio was found to have a significant long-term time dependence. Above 4 GV, the ${}^3\mathrm{He}/{}^4\mathrm{He}$ flux ratio was found to be time independent, and its rigidity dependence is well described by a single power law $\propto R^{\mathrm{\Delta }}$ with $\mathrm{\Delta }=-0.294\pm 0.004$. Unexpectedly, this value is in agreement with the B/O and B/C spectral indices at high energies.