分类： 物理学 >> 核物理学 分类： 天文学 >> 天文仪器与技术 分类： 材料科学 >> 材料科学（综合） 提交时间： 2023-12-15
Pei-Yi Feng
Xi-Lei Sun
Zheng-Hua An
Yong Deng
Cheng-Er Wang
Huang Jiang
Jun-Jie Li
Da-Li Zhang
Xin-Qiao Li
Shao-Lin Xiong
Chao Zheng
Ke Gong
Sheng Yang
Xiao-Jing Liu
Min Gao
Xiang-Yang Wen
Ya-Qing liu
Yan-Bing Xu
Xiao-Yun Zhao
Jia-Cong Liu
摘要： The GECAM series of satellites utilizes LaBr3(Ce), LaBr3(Ce,Sr), and NaI(Tl) crystals as sensitive materials for gamma-ray detectors (GRDs). To investigate the non-linearity in the detection of low-energy gamma rays and address the errors in the calibration of the E-C relationship, comprehensive tests and comparative studies of the three aforementioned crystals were conducted using Compton electrons, radioactive sources, and monoenergetic X-rays. The non-linearity test results of the Compton electrons and X-rays demonstrated substantial differences, with all three crystals presenting a higher non-linearity for X/-rays than for Compton electrons. Despite the LaBr3(Ce) and LaBr3(Ce,Sr) crystals having higher absolute light yields, they exhibited a noticeable non-linear decrease in the light yield, especially at energies below 400 keV. The NaI(Tl) crystal demonstrated an excess light output in the 6200 keV range, reaching a maximum excess of 9.2% at 30 keV in the X-ray testing and up to 15.5% at 14 keV during Compton electron testing, indicating a significant advantage in the detection of low-energy gamma rays. Furthermore, we explored the underlying causes of the observed non-linearity in these crystals. This study not only elucidates the detector responses of GECAM, but also initiates a comprehensive investigation of the non-linearity of domestically produced lanthanum bromide and sodium iodide crystals.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
TiPei Li
ShaoLin Xiong
ShuangNan Zhang
FangJun Lu
LiMing Song
XueLei Cao
Zhi Chang
Gang Chen
Li Chen
TianXiang Chen
Yong Chen
YiBao Chen
YuPeng Chen
Wei Cui
WeiWei Cui
JingKang Deng
YongWei Dong
YuanYuan Du
MinXue Fu
GuanHua Gao
摘要： Finding the electromagnetic (EM) counterpart of binary compact star merger, especially the binary neutron star (BNS) merger, is critically important for gravitational wave (GW) astronomy, osmology and fundamental physics. On Aug. 17, 2017, Advanced LIGO and Fermi/GBM independently triggered the first BNS merger, GW170817, and its high energy EM counterpart, GRB 170817A, respectively, resulting in a global observation campaign covering gamma-ray, X-ray, UV, optical, IR, radio as well as neutrinos. The High Energy X-ray telescope (HE) onboard Insight-HXMT (Hard X-ray Modulation Telescope) is the unique high-energy gamma-ray telescope that monitored the entire GW localization area and especially the optical counterpart (SSS17a/AT2017gfo) with very large collection area (~1000 cm2) and microsecond time resolution in 0.2-5 MeV. In addition, Insight-HXMT quickly implemented a Target of Opportunity (ToO) observation to scan the GW localization area for potential X-ray emission from the GW source. Although Insight-HXMT did not detect any significant high energy (0.2-5 MeV) radiation from GW170817, its observation helped to confirm the nexpected weak and soft nature of GRB 170817A. Meanwhile, Insight-HXMT/HE provides one of the most stringent constraints (~10-7 to 10-6 erg/cm2/s) for both GRB170817A and any other possible precursor or extended emissions in 0.2-5 MeV, which help us to better understand the properties of EM radiation from this BNS merger. Therefore the observation of Insight-HXMT constitutes an important chapter in the full context of multi-wavelength and multi-messenger observation of this historical GW event.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： We study natural supersymmetry in the Generalized Minimal Supergravity (GmSUGRA).For the parameter space with low energy electroweak fine-tuning measures less than 50, we are left with only the Z-pole, Higgs-pole and Higgsino LSP scenarios for dark matter (DM). We perform the focused scans for such parameter space and find that it satisfies various phenomenological constraints and is compatible with the current direct detection bound on neutralino DM reported by the LUX experiment. Such parameter space also has solutions with correct DM relic density besides the solutions with DM relic density smaller or larger than 5 WMAP9 bounds. We present five benchmark points as examples. In these benchmark points, gluino and the first two generations of squarks are heavier than 2 TeV, stop ˜t1,2 are in the mass range [1, 2] TeV, while sleptons are lighter than 1 TeV. Some part of the parameter space can explain the muon anomalous magnetic moment within 3 as well. We also perform the collider study of such solutions by implementing and comparing with relevant studies done by the ATLAS and CMS Collaborations. We find that the points with Higgsino dominant ˜ 02/ ˜ ±1 mass upto 300 GeV are excluded in Z-pole scenario while for Higgs-pole scenario, the points with ˜ 02 mass up to 460 GeV are excluded. We also notice that the Higgsino LSP points in our present scans are beyond the reach of present LHC searches. Next, we show that for both the Z-pole and Higgs-pole scenarios, the points with electroweak fine-tuning measure around 20 do still survive.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： The AMS-02 has measured the cosmic ray electron (plus positron) spectrum up to ∼TeV with an unprecedent precision. The spectrum can be well described by a power law without any obvious features above 10 GeV. The satellite instrument Dark Matter Particle Explorer (DAMPE), which was launched a year ago, will measure the electron spectrum up to 10 TeV with a high energy resolution. The cosmic electrons beyond TeV may be attributed to few local cosmic ray sources, such as supernova remnants. Therefore, spectral features, such as cutoff and bumps, can be expected at high energies. In this work we give a careful study on the perspective of the electron spectrum beyond TeV. We first examine our astrophysical source models on the latest leptonic data of AMS-02 to give a self-consistent picture. Then we focus on the discussion about the candidate sources which could be electron contributors above TeV. Depending on the properties of the local sources (especially on the nature of Vela), DAMPE may detect interesting features in the electron spectrum above TeV in the future.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： We study the dynamic changes of electron energy distribution (EED) through systematically analysing the quasi-simultaneous spectral energy distributions (SEDs) of the flat spectrum radio quasar 3C 279 in different states. With Markov chain Monte Carlo (MCMC) technique we model fourteen SEDs of 3C 279 using a leptonic model with a three-parameter log-parabola electron energy distribution (EED). The 14 SEDs can be satisfactorily fitted with the one-zone leptonic model. The observed γ rays in 13 states are attributed to Compton scattering of external infrared photons from a surrounding dusty torus. The curved γ-ray spectrum observed during 2-8 April 2014 is well explained by the external Compton of dust radiation. It is found that there is a clear positive correlation between the curvature parameter b of the EED and the electron peak energy γ′pk. No clear correlation between b and the synchrotron peak frequency νs is found, due to the varied product of Doppler factor and fluid magnetic field from state to state. We interpret the correlation of b−γ′pk in a stochastic acceleration scenario. This positive correlation is in agreement with the prediction in the stage when the balance between acceleration and radiative cooling of the electrons is nearly established in the case of the turbulence spectral index q=2.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： We study the possibility that the long term red timing-noise in pulsars originates from the evolution of the magnetic inclination angle χ. The braking torque under consideration is a combination of the dipole radiation and the current loss. We find that the evolution of χ can give rise to extra cubic and fourth-order polynomial terms in the timing residuals. These two terms are determined by the efficiency of the dipole radiation, the relative electric-current density in the pulsar tube and χ. The following observation facts can be explained with this model: a) young pulsars have positive ν¨; b) old pulsars can have both positive and negative ν¨; c) the absolute values of ν¨ are proportional to −ν˙; d) the absolute values of the braking indices are proportional to the characteristic ages of pulsars. If the evolution of χ is purely due to rotation kinematics, then it can not explain the pulsars with braking index less than 3, and thus the intrinsic change of the magnetic field is needed in this case. Comparing the model with observations, we conclude that the drift direction of χ might oscillate many times during the lifetime of a pulsar. The evolution of χ is not sufficient to explain the rotation behavior of the Crab pulsar, because the observed χand χ˙ are inconsistent with the values indicated from the timing residuals using this model.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： Newly born magnetars are promising sources for gravitational wave (GW) detection due to their ultra-strong magnetic fields and high spin frequencies. Within the scenario of a growing tilt angle between the star's spin and magnetic axis, due to the effect of internal viscosity, we obtain improved estimates of the stochastic gravitational wave backgrounds (SGWBs) from magnetic deformation of newly born magnetars. We find that the GW background spectra contributed by the magnetars with ultra-strong toroidal magnetic fields of 10^{17} G could roughly be divided into four segments. Most notably, in contrast to the background spectra calculated by assuming constant tilt angles \chi=\pi/2, the background radiation above 1000 Hz are seriously suppressed. However, the background radiation at the frequency band \sim100-1000 Hz are moderately enhanced, depending on the strengths of the dipole magnetic fields. We suggest that if all newly born magnetars indeed have toroidal magnetic fields of 10^{17} G, the produced SGWBs should show sharp variations with the observed frequency at several tens to about 100 hertz. If these features could be observed through sophisticated detection of the SGWB using the proposed Einstein Telescope, it will provide us a direct evidence of the tilt angle evolutions and further some deep understandings about the properties of newly born magnetars.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： We re-estimate the surface magnetic fields of neutron stars (NSs) in Be X-ray binaries (BeXBs) with different models of torque, improved beyond Klus et al. (2014). In particular, a new torque model (Dai \& Li 2006) is applied to three models of magnetosphere radius. Unlike the previous models, the new torque model does not lead to divergent results for any fastness parameter. The inferred surface magnetic fields of these NSs for the two compressed magnetosphere models are much higher than that for the uncompressed magnetosphere model. The new torque model using the compressed-magnetosphere radius (Shi, Zhang \& Li 2014) leads to unique solutions near spin equilibrium in all cases, unlike other models that usually give two branches of solutions. Although our conclusions are still affected by the simplistic assumptions about the magnetosphere radius calculations, we show several groups of possible surface magnetic field values with our new models when the interaction between the magnetosphere and the infalling accretion plasma is considered. The estimated surface magnetic fields for NSs BeXBs in the Large Magellanic Cloud, the Small Magellanic Cloud and the Milk Way are between the quantum critical field and the maximum "virial" value by the spin equilibrium condition.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： Precise spectra of 3C 279 in the 0.5-70 keV range, obtained during two epochs of \emph{Swift} and \emph{NuSTAR} observations, are analyzed using a near-equipartition model. We apply a one-zone leptonic model with a three-parameter log-parabola electron energy distribution (EED) to fit the \emph{Swift} and \emph{NuSTAR} X-ray data, as well as simultaneous optical and \emph{Fermi}-LAT γ-ray data. The Markov Chain Monte Carlo (MCMC) technique is used to search the high-dimensional parameter space and evaluate the uncertainties on model parameters. We show that the two spectra can be successfully fit in near-equipartition conditions, defined by the ratio of the energy density of relativistic electrons to magnetic field ζe being close to unity. In both spectra, the observed X-rays are dominated by synchrotron-self Compton photons, and the observed γ rays are dominated by Compton scattering of external infrared photons from a surrounding dusty torus. Model parameters are well constrained. From the low state to the high state, both the curvature of the log-parabola width parameter and the synchrotron peak frequency significantly increase. The derived magnetic fields in the two states are nearly identical (∼1\ G), but the Doppler factor in the high state is larger than that in the low state (∼28 versus ∼18). We derive that the gamma-ray emission site takes place outside the broad-line region, at ≳ 0.1 pc from the black hole, but within the dusty torus. Implications for 3C 279 as a source of high-energy cosmic-rays are discussed.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
Xiaoyuan Huang
Anna S. Lamperstorfer
Yue-Lin Sming Tsai
Ming Xu
Qiang Yuan Jin Chang
Yong-Wei Dong
Bing-Liang Hu
Jun-Guang L╱
Le Wang
Bo-Bing Wu
Shuang-Nan Zhang
摘要： HERD is the High Energy cosmic-Radiation Detection instrument proposed to operate onboard China's space station in the 2020s. It is designed to detect energetic cosmic ray nuclei, leptons and photons with a high energy resolution (∼1% for electrons and photons and 20% for nuclei) and a large geometry factor (>3m2sr for electrons and diffuse photons and >2m2sr for nuclei). In this work we discuss the capability of HERD to detect monochromatic γ-ray lines, based on simulations of the detector performance. It is shown that HERD will be one of the most sensitive instruments for monochromatic γ-ray searches at energies between ∼10 to a few hundred GeV. Above hundreds of GeV, Cherenkov telescopes will be more sensitive due to their large effective area. As a specific example, we show that a good portion of the parameter space of a supersymmetric dark matter model can be probed with HERD.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： We model the evolution of the spin frequency's second derivative ν¨ and the braking index n of radio pulsars with simulations within the phenomenological model of their surface magnetic field evolution, which contains a long-term power-law decay modulated by short-term oscillations. For the pulsar PSR B0329+54, a model with three oscillation components can reproduce its ν¨ variation. We show that the "averaged" n is different from the instantaneous n, and its oscillation magnitude decreases abruptly as the time span increases, due to the "averaging" effect. The simulated timing residuals agree with the main features of the reported data. Our model predicts that the averaged ν¨ of PSR B0329+54 will start to decrease rapidly with newer data beyond those used in Hobbs et al.. We further perform Monte Carlo simulations for the distribution of the reported data in |ν¨| and |n| versus characteristic age τc diagrams. It is found that the magnetic field oscillation model with decay index α=0 can reproduce the distributions quite well. Compared with magnetic field decay due to the ambipolar diffusion (α=0.5) and the Hall cascade (α=1.0), the model with no long term decay (α=0) is clearly preferred for old pulsars by the p-values of the two-dimensional Kolmogorov-Smirnov test.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： The AMS-02 collaboration has just released the cosmic antiproton to proton ratio p¯/p with a high precision up to ∼450 GeV. In this work, we calculate the secondary antiprotons generated by cosmic ray interactions with the interstellar medium taking into account the uncertainties from the cosmic ray propagation. The p¯/p ratio predicted by these processes shows some tension with the AMS-02 data in some regions of propagation parameters, but the excess is not significant. We then try to derive upper bounds on the dark matter annihilation cross section from the p¯/p data or signal regions favored by the data. It is shown that the constraint derived by the AMS-02 data is similar to that from Fermi-LAT observations of dwarf galaxies. The signal region for dark matter is usually required mχ∼O(10) TeV and $\left\sim\mathcal{O}(10^{-23})~\cm^3~\sec^{-1}$.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： The precise spectra of Cosmic Ray (CR) electrons and positrons have been published by the measurement of AMS-02. It is reasonable to regard the difference between the electrons and positrons spectra ( △Φ=Φe−−Φe+ ) as being dominated by primary electrons. Noticing that the resulting electron spectrum shows no sign of spectral softening above 20 GeV, which is in contrast with the prediction of standard model. In this work, we generalize the analytic one dimensional two-halo model of diffusion to a three dimensional realistic calculation by implementing a spatial variant diffusion coefficients in DRAGON package. As a result, we can reproduce the spectral hardening of protons observed by several experiments, and predict an excess of high energy primary electrons which agrees with the measurement reasonably well. Unlike the break spectrum obtained for protons, the model calculation predicts a smooth electron excess and thus slightly over predicts the flux from tens of GeV to 100GeV. To understand this issue, further experimental and theoretical studies are necessary.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： Fermi-LAT analyses show that the gamma-ray photon spectral indices Gamma_gamma of a large sample of blazars correlate with the vFv peak synchrotron frequency v_s according to the relation Gamma_gamma = d - k log v_s. The same function, with different constants d and k, also describes the relationship between Gamma_gamma and peak Compton frequency v_C. This behavior is derived analytically using an equipartition blazar model with a log-parabola description of the electron energy distribution (EED). In the Thomson regime, k = k_EC = 3b/4 for external Compton processes and k = k_SSC = 9b/16 for synchrotron self-Compton (SSC) processes, where b is the log-parabola width parameter of the EED. The BL Lac object Mrk 501 is fit with a synchrotron/SSC model given by the log-parabola EED, and is best fit away from equipartition. Corrections are made to the spectral-index diagrams for a low-energy power-law EED and departures from equipartition, as constrained by absolute jet power. Analytic expressions are compared with numerical values derived from self-Compton and external Compton scattered gamma-ray spectra from Ly alpha broad-line region and IR target photons. The Gamma_gamma vs. v_s behavior in the model depends strongly on b, with progressively and predictably weaker dependences on gamma-ray detection range, variability time, and isotropic gamma-ray luminosity. Implications for blazar unification and blazars as ultra-high energy cosmic-ray sources are presented. Arguments by Ghisellini et al. (2014) that the jet power exceeds the accretion luminosity depend on the doubtful assumption that we are viewing at the Doppler angle.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： The gamma-ray excess observed by the Fermi-LAT in the Galactic Center can be interpreted by the dark matter annihilation to bb¯ via a light pseudoscalar in the NMSSM. It is interesting to note that the corresponding singlet scalar is useful to achieve a strongly first order phase transition required by the electroweak baryogenesis. In this paper, we investigate the possibility that the NMSSM model can simultaneously accommodate these two issues. The phase transition strength can be characterized by the vacua energy gap at zero temperature and be sufficiently enhanced by the tree-level effect in the NMSSM. We find that the annihilation of Singlino/Higgsino DM particles occurring close to the light pseudoscalar resonance is favored by the galactic center excess and the observed DM relic density, and a resulting small κ/λ and a negative Aκ can also lead to a successful strongly first order electroweak phase transition.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： We study the prospect of dark matter (DM) searches in the monojet channel at future pp colliders with center-of-mass energies of 33, 50, and 100~TeV. We consider a class of simplified models in which a vector boson connecting DM particles to quarks is introduced. Comparing with studies in the effective field theory, the present framework gives more reasonable production rates and kinematics of the DM signatures. We estimate the sensitivities of future colliders with an integrated luminosity of 3 ab−1 to the DM-induced monojet signature and show the parameter space that can be explored. The constraints from direct and indirect DM detection experiments are compared with the future collider sensitivities. We find that the future collider detection will be much more sensitive than the indirect detection for the vector interaction, and have better sensitivities than those of the direct detection by several orders of magnitude for the axial vector interaction.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
LIU Jin-Sheng
HUANG Jing
CHEN Ding
ZHZNG Ying
ZHAI Liu-Ming
CHEN Xu
HU Xiao-Bin
LIN Yu-Hui
ZHANG Xue-Yao
FENG Cun-Feng
JIA Huan-Yu
ZHOU Xun-Xiu
ANZENGLUOBU
CHEN Tian-Lu
LI Hai-Jin
LIU Mao-Yuan
YUAN Ai-Fang
摘要： Aiming at the observation of cosmic-ray chemical composition at the "knee" energy region, we have been developinga new type air-shower core detector (YAC, Yangbajing Air shower Core detector array) to be set up at Yangbajing (90.522∘ E, 30.102∘ N, 4300 m above sea level, atmospheric depth: 606 g/m2) in Tibet, China. YAC works together with the Tibet air-shower array (Tibet-III) and an underground water cherenkov muon detector array (MD) as a hybrid experiment. Each YAC detector unit consists of lead plates of 3.5 cm thick and a scintillation counter which detects the burst size induced by high energy particles in the air-shower cores. The burst size can be measured from 1 MIP (Minimum Ionization Particle) to 106 MIPs. The first phase of this experiment, named "YAC-I", consists of 16 YAC detectors each having the size 40 cm × 50 cm and distributing in a grid with an effective area of 10 m2. YAC-I is used to check hadronic interaction models. The second phase of the experiment, called "YAC-II", consists of 124 YAC detectors with coverage about 500 m2. The inner 100 detectors of 80 cm × 50 cm each are deployed in a 10 × 10 matrix from with a 1.9 m separation and the outer 24 detectors of 100 cm × 50 cm each are distributed around them to reject non-core events whose shower cores are far from the YAC-II array. YAC-II is used to study the primary cosmic-ray composition, in particular, to obtain the energy spectra of proton, helium and iron nuclei between 5×1013 eV and 1016 eV covering the "knee" and also being connected with direct observations at energies around 100 TeV. We present the design and performance of YAC-II in this paper.
分类： 物理学 >> 核物理学 提交时间： 2016-09-02
摘要： The maximum frequency of gravitational waves (GWs) detectable with traditional pulsar timing methods is set by the Nyquist frequency (fNy) of the observation. Beyond this frequency, GWs leave no temporal-correlated signals; instead, they appear as white noise in the timing residuals. The variance of the GW-induced white noise is a function of the position of the pulsars relative to the GW source. By observing this unique functional form in the timing data, we propose that we can detect GWs of frequency > fNy (super-Nyquist frequency GWs; SNFGWs). We demonstrate the feasibility of the proposed method with simulated timing data. Using a selected dataset from the Parkes Pulsar Timing Array data release 1 and the North American Nanohertz Observatory for Gravitational Waves publicly available datasets, we try to detect the signals from single SNFGW sources. The result is consistent with no GW detection with 65.5\% probability. An all-sky map of the sensitivity of the selected pulsar timing array to single SNFGW sources is generated, and the position of the GW source where the selected pulsar timing array is most sensitive to is λs=−0.82, βs=−1.03 (rad); the corresponding minimum GW strain is h=6.31×10−11 at f=1×10−5 Hz.
分类： 物理学 >> 核物理学 提交时间： 2016-09-01
摘要： Context: The LIGO consortium announced the first direct detection of gravitation wave event GW150914 from two merging black holes; however the nature of the black holes are still not clear. Aims: We study whether electromagnetic radiation can be detected from merging stellar mass black binaries like GW150914. Methods: We briefly investigate the possible growth and merging processes of the two stellar mass black holes in the merging event of GW150914 detected by aLIGO, as clocked by a distant external observer. Our main results are: (1) The description of the black hole growth using stationary metric of a pre-existing black hole predicts strong electromagnetic radiation from merging black holes, which is inconsistent with GW150914; (2) Only gravitational wave radiation can be produced in the coalescence of two black holes such as that in the GW150914 event, if the black hole growth is described using time-dependent metric considering the influence of the in-falling matter onto a pre-existing black hole, as clocked by a distant external observer. Conclusions: Future high sensitivity detections of gravitational waves from merging black holes might be used to probe matter distribution and space-time geometry in the vicinity of the horizon. Perhaps the GW150914-like events can be identified with traditional astronomy observations only if the black holes are embedded in extremely dense medium before their final merge, when very strong electromagnetic radiation is produced and can escape from the system.
分类： 物理学 >> 核物理学 提交时间： 2016-08-31
摘要： A new air-shower core-detector array (YAC : Yangbajing Air-shower Core-detector array) has been developed to measure the primary cosmic-ray composition at the "knee" energies in Tibet, China, focusing mainly on the light components. The prototype experiment (YAC-I) consisting of 16 detectors has been constructed and operated at Yangbajing (4300 m a.s.l.) in Tibet since May 2009. YAC-I is installed in the Tibet-III AS array and operates together. In this paper, we performed a Monte Carlo simulation to check the sensitivity of YAC-I+Tibet-III array to the cosmic-ray light component of cosmic rays around the knee energies, taking account of the observation conditions of actual YAC-I+Tibet-III array. The selection of light component from others was made by use of an artificial neural network (ANN). The simulation shows that the light-component spectrum estimated by our methods can well reproduce the input ones within 10\% error, and there will be about 30\% systematic errors mostly induced by the primary and interaction models used. It is found that the full-scale YAC and the Tibet-III array is powerful to study the cosmic-ray composition, in particular, to obtain the energy spectra of protons and helium nuclei around the knee energies.
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