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Register a new userThe Knee of the Cosmic Hydrogen and Helium Spectrum below 1 PeV Measured by ARGO-YBJ and a Cherenkov Telescope of LHAASO
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The measurement of cosmic ray energy spectra, in particular for individual species, is an essential approach in finding their origin. Locating the knees of the spectra is an important part of the approach and has yet to be achieved. Here we report a measurement of the mixed Hydrogen and Helium spectrum using the combination of the ARGO-YBJ experiment and of a prototype Cherenkov telescope for the LHAASO experiment. A knee feature at 640+/-87 TeV, with a clear steepening of the spectrum, is observed. This gives fundamental inputs to galactic cosmic ray acceleration models.
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Large High Altitude Air Shower Observatory(LHAASO) is a composite cosmic ray observatory consisting of three detector arrays: kilometer square array (KM2A) which includes the electromagnetic detector array and muon detector array, water Cherenkov detector array (WCDA) and wide field of view Cherenkov telescope array (WFCTA). One of the main scientific objectives of LHAASO is to precisely measure the cosmic rays energy spectrum of individual components from 1014 eV to 1018 eV. The hybrid observation will be employed by LHAASO experiment, in which the lateral and longitudinal distributions of the extensive air shower can be observed simultaneously. Thus many kinds of parameters can be used for primary nuclei identification. In this paper, high purity cosmic ray simulation samples of light nuclei component are obtained through Multi-Variable Analysis. The apertures of 1/4 LHAASO array for pure proton and mixed proton and helium (H&He) samples are 900 m2Sr and 1800 m2Sr respectively. A prospect of proton and H&He spectra from 100 TeV to 4 PeV is discussed.
In this paper we report on the observation of the anisotropy of cosmic ray arrival direction at different angular scales with ARGO-YBJ. Evidence of new few-degree excesses throughout the sky region 195$^{circ}leq$ R.A. $leq$ 315$^{circ}$ is presented for the first time. We report also on the measurement of the light-component (p+He) spectrum of primary cosmic rays in the range 5 - 200 TeV.
The combined measurement of the cosmic ray (CR) energy spectrum and anisotropy in their arrival direction distribution needs the knowledge of the elemental composition of the radiation to discriminate between different origin and propagation models. Important information on the CR mass composition can be obtained studying the EAS muon content through the measurement of the CR rate at different zenith angles. In this paper we report on the observation of the anisotropy of galactic CRs at different angular scales with the ARGO-YBJ experiment. We report also on the study of the primary CR rate for different zenith angles. The light component (p+He) has been selected and its energy spectrum measured in the energy range (5 - 200) TeV for quasi-vertical events. With this analysis for the first time a ground-based measurement of the CR spectrum overlaps data obtained with direct methods for more than one energy decade, thus providing a solid anchorage to the CR spectrum measurements carried out by EAS arrays in the knee region. Finally, a preliminary study of the non-attenuated shower component at a zenith angle $theta >$ 70$^{circ}$ (through the observation of the so-called horizantal air showers) is presented.
The ARGO-YBJ detector, located at high altitude in the Cosmic Ray Observatory of Yangbajing in Tibet (4300 m asl, about 600 g/cm2 of atmospheric depth) provides the opportunity to study, with unprecedented resolution, the cosmic ray physics in the primary energy region between 10^{12} and 10^{16} eV. The preliminary results of the measurement of all-particle and light-component (i.e. protons and helium) energy spectra between approximately 5 TeV and 5 PeV are reported and discussed. The study of such energy region is particularly interesting because not only it allows a better understanding of the so called knee of the energy spectrum and of its origin, but also provides a powerful cross-check among very different experimental techniques. The comparison between direct measurements by balloons/satellites and the results by surface detectors, implying the knowledge of shower development in the atmosphere, also allows to test the hadronic interaction models currently used for understanding particle and cosmic ray physics up the highest energies.
The ARGO-YBJ experiment is a full coverage air shower detector operated at the Yangbajing International Cosmic Ray Observatory. The detector has been in stable data taking in its full configuration since November 2007 to February 2013. The high altitude and the high segmentation and spacetime resolution offer the possibility to explore the cosmic ray energy spectrum in a very wide range, from a few TeV up to the PeV region. The high segmentation allows a detailed measurement of the lateral distribution, which can be used in order to discriminate showers produced by light and heavy elements. In this work we present the measurement of the cosmic ray light component spectrum in the energy range 3-3000 TeV. The analysis has been carried out by using a two-dimensional unfolding method based on the Bayes theorem.
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