Component Of Cosmic Rays Research Articles

Recent research progress in <italic>γ</italic>-ray-bright supernova remnants

With the observations of the ground-based and space γ -ray telescopes, the study on the origin of cosmic rays (CRs) has been deepened. As sources of CRs below the “knee” energy, the sample of supernova remnants (SNRs) with GeV-TeV γ -ray emission is being enlarged, getting to show some statistical properties in flux, spectra, etc. Appreciable observational and theoretical efforts have been made to investigate the radiation mechanisms of the γ -ray emission from SNRs and, especially, the hadronic interaction between SNRs and molecular clouds (MCs) so as to verify the scenario that relativistic protons, as the main component of CRs, can be produced by the SNR shocks. The detection of characteristic π0 -decay bump at 70 MeV in SNRs W44 and IC 443 marks a great progress in this regard. There are essentially two types of models explaining the hadronic γ -ray emission: direct proton-MC collision at the SNR shocks and MC “illumination” by escaped protons. A lot of work still need to do, such as systematic researches with a larger sample of γ -ray emitting SNRs, reasonable model calculation of the SNR emission in γ -rays together with other wavelengths, investigation of the molecular environment of SNRs, and even basic distinguishing of hardronic/leptonic property of the γ -ray emission. In this article, we will briefly summarize the present status of the above-mentioned studies.

Fermi-LAT observations of the Sagittarius B complex

Aims. We use 5 years of Fermi-LAT data towards the Galactic-centre giant molecular cloud complex, Sagittarius B, to test questions of how well-mixed the Galactic component of cosmic rays are and what the level of the cosmic-ray sea in different parts of the Galaxy is. Methods. We use dust-opacity maps from the Planck satellite to obtain independent methods for background subtraction and an estimate for the mass of the region. We then present high-quality spectra of gamma-ray emission from 0.3 to 30 GeV and obtain an estimate of the cosmic-ray spectrum from the region. Results. We obtain an estimate of the mass of the region of $1.5 \pm 0.2 \times 10^7~\rm M_{\odot}$ using the Planck data, which agrees well with molecular-line-derived estimates for the same region. We find the the gamma-ray flux from this region is fitted well with a cosmic-ray spectrum that is the same as is observed locally, with evidence of a small over-density at intermediate (1-10 GeV) energies. Conclusions. We conclude that the gamma-ray and cosmic-ray spectrum in the region can be well-fitted using a local cosmic-ray spectrum.

Solar modulation of GCR electrons over the 23rd solar minimum with PAMELA

The satellite-borne PAMELA experiment has been continuously collecting data since 15th June 2006, when it was launched from the Baikonur cosmodrome to detect the charged component of cosmic rays over a wide energy range and with unprecedented statistics. The apparatus design is particularly suited for particle and antiparticle identification. The PAMELA experiment has measured the electron spectrum at Earth in great detail, extending up to about 100 GeV and down to about 200 MeV. The galactic cosmic ray electron spectra for 2007 and 2009, i.e. measured during the A<0 solar minimum of solar cycle 23, are presented. These fluxes provide important information for the study of charge dependent solar modulation effects.

Cosmic rays: the spectrum and chemical composition from 1010 to 1020 eV

The production of energetic particles in the universe remains one of the great mysteries of modern science. The mechanisms of acceleration in astrophysical sources and the details about the propagation through the galactic and extragalactic media are still to be defined. In recent years, the cosmic ray flux has been measured with high precision in the energy range from 1010 to 1020.5 eV by several experiments using different techniques. In some energy ranges, it has been possible to determine the flux of individual elements (hydrogen to iron nuclei). This paper explores an astrophysical scenario in which only our Galaxy and the radio galaxy Cen A produce all particles measured on Earth in the energy range from 1010 to 1020.5 eV . Data from AMS-02, CREAM, KASCADE, KASCADE-Grande and the Pierre Auger Observatories are considered. The model developed here is compared to the total and if available to the individual particle flux of the experiments considered.The flux of each element as determined by AMS-02, CREAM, KASCADE and KASCADE-Grande and the mass sensitivity parameter Xmax measured by the Pierre Auger Observatory above 10^ eV are also explored within the framework of the model. The transition from 1016 to 1018 eV is carefully analyzed. It is shown that the flux measured in this energy range suggest the existence of an extra component of cosmic rays yet to be understood.

Current status of the MONICA experiment to study the ionic composition of solar cosmic rays

The current status of the MONICA experiment to study fluxes of cosmic ray ions from H to Ni in the energy range of 10–300 MeV in the vicinity of the Earth is described. The main scientific objective of the MONICA experiment is to measure the ionic and isotope compositions and energy spectra of solar cosmic rays for individual solar events, and to study the time evolution of these characteristics. The MONICA experiment will also allow us to investigate the ionic and isotope compositions of the anomalous cosmic ray component, galactic cosmic rays, and fluxes of nuclei in the Earth’s radiation belt. Ion fluxes will be observed using the MONICA large-aperture multilayer semiconductor spectrometer telescope on board a spacecraft in a circumterrestrial polar orbit with an altitude on the order of 600 km. This will enable us to measure the charges of ions with energies over 10 MeV/nucleon by using the Earth’s magnetic field as a charge separator. The geometric factor of the instrument is 100 cm2 sr; its angular resolution is 1°.

The GAMMA-400 experiment: Status and prospects

The development of the GAMMA-400 γ-ray telescope continues. The GAMMA-400 is designed to measure fluxes of γ-rays and the electron-positron cosmic-ray component possibly associated with annihilation or decay of dark matter particles; and to search for and study in detail discrete γ-ray sources, to measure the energy spectra of Galactic and extragalactic diffuse γ-rays, and to study γ-ray bursts and γ-rays from the active Sun. The energy range for measuring γ-rays and electrons (positrons) is from 100 MeV to 3000 GeV. For 100-GeV γ-rays, the γ-ray telescope has an angular resolution of ∼0.01°, an energy resolution of ∼1%, and a proton rejection factor of ∼5 × 105. The GAMMA-400 will be installed onboard the Russian Space Observatory.

Sensitivity of YAC to measure the light-component spectrum of primary cosmic rays at the ‘knee’ energies

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 the 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 the actual YAC-I+Tibet-III array. The selection of light component from others was made by use of an artificial neural network. 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.

Performance of the AMS-02 Electromagnetic Calorimeter in Space

AMS-02(Alpha Magnetic Spectrometer) is an high energy particle detector developed to operate on the International Space Station. AMS-02 was installed on ISS on May 2011 and is expected to operate for 10-20 years collecting about 160-320 billions of events. The main goals of the experiment are the detection of primordial antimatter and dark matter by studying spectra and flux of different cosmic ray components (protons, electrons, nuclei, positrons, antiprotons, gamma rays, etc) in the high energy range (1-2000 GeV). Identification of electrons, positrons and photons is provided by the Electromagnetic Calorimeter (ECAL), a fine grained lead-scintillating fibers sampling calorimeter that allows for a precise three-dimensional imaging of the longitudinal and lateral shower development. It provides an excellent reconstruction of electromagnetic shower energy and a highly efficient rejection of the hadronic background. Thanks to the 3D shower reconstruction capability, ECAL allows a stand-alone determination of the incoming particle direction, with unprecedented angular resolution. As a result, ECAL is able to identify high energy photons coming from galactic or extragalactic sources.

Cosmic ray origins in supernova blast waves

We extend the self-similar solution derived by Chevalier for a Sedov blast wave accelerating cosmic rays (CR) to show that the Galactic CR population can be divided into (A) CR with energies above ∼200 GeV released upstream during CR acceleration by supernova remnants (SNR), (B) CR advected into the interior of the SNR during expansion and then released from the SNR at the end of its life to provide the Galactic CR component below ∼200 GeV. The intersection between the two populations may correspond to a measured change in the Galactic CR spectral index at this energy.

Measuring and Test Workbenches of Experimental Complex NEVOD

The measuring and test automated workbenches used to maintain the health of existing and commissioning of new detectors of the unique scientific facility “Experimental complex NEVOD” are described. The structure of workbenches and their main characteristics are presented. Workbenches include standard high-precision instruments manufactured by Tektronix, CAEN, Aktakom, and specially designed components and modules. Procedures of measurements and tests are carried out in automatic mode under control of computer. Management programs of workbenches are written on the basis of original methods, allowing to obtain reliable and complete information on the status and characteristics of the components of physical systems. Calibration of equipment is carried out through registration of various components of cosmic rays.

Space γ-observatory GAMMA-400 Current Status and Perspectives

GAMMA-400 γ-ray telescope is designed to measure fluxes of γ-rays and the electron–positron cosmic ray component possibly generated in annihilation or decay of dark matter particles; to search for and study in detail discrete γ-ray sources, to examine the energy spectra of Galactic and extragalactic diffuse γ-rays, to study γ-ray bursts and γ-rays from the active Sun. GAMMA-400 consists of plastic scintillation anticoincidence top and lateral detectors, converter-tracker, plastic scintillation detectors for the time-of-flight system (TOF), two-part calorimeter (CC1 and CC2), plastic scintillation lateral detectors of calorimeter, plastic scintillation detectors of calorimeter, and neutron detector. The converter-tracker consists of 13 layers of double (x, y) silicon strip coordinate detectors (pitch of 0.08mm). The first three and final one layers are without tungsten while the middle nine layers are interleaved with nine tungsten conversion foils. The thickness of CC1 and CC2 is 2 X0 (0.1λ0) and 23 X0 (1.1λ0) respectively (where X0 is radiation length and λ0 is nuclear interaction one). The total calorimeter thickness is 25 X0 or 1.2λ0 for vertical incident particles registration and 54 X0 or 2.5λ0 for laterally incident ones.The energy range for γ-rays and electrons (positrons) registration in the main aperture is from ∼0.1GeV to ∼3.0 TeV. The γ-ray telescope main aperture angular and energy resolutions are respectively ∼0.01 and ∼1% for 102 GeV γ-quanta, the proton rejection factor is ∼5×105. The first three strip layers without tungsten provide the registration of γ-rays down to ∼20 MeV in the main aperture. Also this aperture allows investigating high energy light nuclei fluxes characteristics.Electrons, positrons, light nuclei and gamma-quanta will also register from the lateral directions due to special aperture configuration. Lateral aperture energy resolution is the same as for main aperture for electrons, positrons, light nuclei and gamma-quanta in energy range E>1.0GeV. But using lateral aperture it is possible to detect low-energy gammas in the ranges 0.2 − 10 MeV and 10 MeV – 1.0GeV with energy resolution 8% − 2% and 2% correspondingly accordingly to GAMMA-400 “Technical Project” stage results. Angular resolution in the lateral aperture provides only for low-energy gamma-quanta from non-stationary events (GRB, solar flares and so on) due segments of CC2 count rate analysis.GAMMA-400 γ-ray telescope will be installed onboard the Russian Space Observatory GAMMA-400. The lifetime of the space observatory will be at least seven years. The launch of the space observatory is scheduled for the early 2020s.

Method of Incident Low-Energy Gamma-Ray Direction Reconstruction in GAMMA-400 Gamma-Ray Space Telescope

Gamma-telescope GAMMA-400 is designed to measure fluxes of γ-rays and the electron–positron cosmic ray component possibly associated with dark matter particles annihilation or decay; and to search for and study in detail discrete γ-ray sources, to investigate the energy spectra of Galactic and extragalactic diffuse γ-rays, and to study γ-ray bursts (GRB) and γ-rays from the active Sun. GAMMA-400 gamma-ray space-based telescope scientific goals require fine angular resolution. GAMMA-400 is the pair production telescope. In the converter-tracker the incident gamma-quantum convert into electron-positron pair in the tungsten layer and then the tracks are registered by silicon-strip position-sensitive detectors. Multiple scattering processes become a significant obstacle in the incident gamma direction reconstruction for energies below several GeV. The method of utilising this process to improve the resolution is proposed in the presented work.

Cosmic-ray world with gamma-ray astronomy: a wealth on information, an even more open issue

Since from their discovery in 1912, Cosmic-Rays (CRs) are one of the most debated issues of the high energy astrophysics. Their origin is still a fundamental problem and is the subject of very intense research. Until now, the best candidate sources of Galactic CR component are Supernova Remnants (SNRs) but final proof for the origin of CRs up to the knee can only be obtained through two fundamental signatures, the detection of a clear gamma-ray signature of π 0 decay in Galactic sources and the identification of sources emitting a photon spectrum up to PeV energies. Both indications are quite difficult to obtain. The two gamma-ray satellites, AGILE and Fermi, together with ground telescopes operating in the TeV energy range (HESS, VERITAS and MAGIC), collected a great amount of data from SNRs. In spite of the recent discovery of the neutral pion spectral signature in the SNR W44 spectrum by AGILE (and confirmed by Fermi-LAT), all gamma-ray data collected at GeV and TeV energies for several young and middle-aged SNRs provide interesting challenges to current theoretical models. The emerging view from gamma-ray and particle detection is intriguing and lead to revisit the CR-SNR paradigm, considering also the contribution of other kind of sources.

Bounds on the origin of extragalactic ultrahigh energy cosmic rays from the IceCube neutrino observations

We study general implications of the IceCube observations in the energy range from ${10}^{6}\text{ }\text{ }\mathrm{GeV}$ to ${10}^{10}\text{ }\text{ }\mathrm{GeV}$ for the origin of extragalactic ultrahigh energy cosmic rays assuming that high energy neutrinos are generated by the photomeson production of protons in the extragalactic universe. The PeV-energy neutrino flux observed by IceCube gives strong bounds on the photomeson-production optical depth of protons in their sources and the intensity of the proton component of extragalactic cosmic rays. The neutrino flux implies that extragalactic cosmic-ray sources should have the optical depth greater than $\ensuremath{\sim}0.01$ and contribute to more than a few percent of the observed bulk of cosmic rays at 10 PeV. If the spectrum of cosmic rays from these extragalactic sources extends well beyond 1 EeV, the neutrino flux indicates that extragalactic cosmic rays are dominant in the observed total cosmic-ray flux at 1 EeV and above, favoring the dip transition model of cosmic rays. The cosmic-ray sources are also required to be efficient neutrino emitters with the optical depth close to unity in this case. The highest energy cosmic-ray ($\ensuremath{\sim}{10}^{11}\text{ }\text{ }\mathrm{GeV}$) sources should not be strongly evolved with redshift to account for the IceCube observations, suggesting that any cosmic-ray radiation scenarios involving distant powerful astronomical objects with strong cosmological evolution are strongly disfavored. These considerations conclude that none of the known extragalactic astronomical objects can be simultaneously a source of both PeV and trans-EeV energy cosmic rays. We also discuss a possible effect of cosmic-ray propagation in magnetized intergalactic space to the connection between the observed total cosmic-ray flux and neutrino flux.

Material discrimination using scattering and stopping of cosmic ray muons and electrons: Differentiating heavier from lighter metals as well as low-atomic weight materials

Reported is a new method to apply cosmic-ray tomography in a manner that can detect and characterize not only dense assemblages of heavy nuclei (like Special Nuclear Materials, SNM) but also assemblages of medium- and light-atomic-mass materials (such as metal parts, conventional explosives, and organic materials). Characterization may enable discrimination between permitted contents in commerce and contraband (explosives, illegal drugs, and the like). Our Multi-Mode Passive Detection System (MMPDS) relies primarily on the muon component of cosmic rays to interrogate Volumes of Interest (VOI). Muons, highly energetic and massive, pass essentially un-scattered through materials of light atomic mass and are only weakly scattered by conventional metals used in industry. Substantial scattering and absorption only occur when muons encounter sufficient thicknesses of heavy elements characteristic of lead and SNM. Electrons are appreciably scattered by light elements and stopped by sufficient thicknesses of materials containing medium-atomic-mass elements (mostly metals). Data include simulations based upon GEANT and measurements in the HMT (Half Muon Tracker) detector in Poway, CA and a package scanner in both Poway and Socorro NM. A key aspect of the present work is development of a useful parameter, designated the “stopping power” of a sample. The low-density regime, comprising organic materials up to aluminum, is characterized using very little scattering but a strong variation in stopping power. The medium-to-high density regime shows a larger variation in scattering than in stopping power. The detection of emitted gamma rays is another useful signature of some materials.

Recent developments in cosmic ray physics

The search for a theory of the origin of cosmic rays that may be considered as a standard, agreeable model is still ongoing. On one hand, much circumstantial evidence exists of the fact that supernovae in our Galaxy play a crucial role in producing the bulk of cosmic rays observed on Earth. On the other hand, important questions about their ability to accelerate particles up to the knee remain unanswered. The common interpretation of the knee as a feature coinciding with the maximum energy of the light component of cosmic rays and a transition to a gradually heavier mass composition is mainly based on KASCADE results. Some recent data appear to question this finding: YAC1 – Tibet Array and ARGO-YBJ find a flux reduction in the light component at ∼ 700 TeV, appreciably below the knee. Whether the maximum energy of light nuclei is as high as 3000 TeV or rather as low as a few hundred TeV has very important consequences on the supernova remnant paradigm for the origin of cosmic rays, as well on the crucial issue of the transition from Galactic to extragalactic cosmic rays. In such a complex phenomenological situation, it is important to have a clear picture of what is really known and what is not. Here I will discuss some solid and less solid aspects of the theory (or theories) for the origin of cosmic rays and the implications for future searches in this field.

Neutrino signatures of the origins of cosmic rays

The intensity of extraterrestrial neutrinos discovered by IceCube [M. G. Aartsen et al. (IceCube Collaboration), Science 342 (2013) 1242856] is in reasonable agreement with predictions of neutrinos from the jets of active galactic nuclei due to pion production by accelerated protons [K. Mannheim, Astropart. Phys. 3 (1995) 295]. The observed deficit of Glashow-resonance events at 6.3 PeV could result from the suppression of events with energies larger than PeV due to the presence of a strong “big blue bump” radiation field in flat-spectrum radio quasars. The total neutrino spectrum could exhibit a two-component structure in which the sub-PeV component is dominated by the jets from AGN with high accretion rates and another component peaking at EeV energies due to those with low accretion rates. Each component of the neutrino spectrum should carry the energy flux that corresponds to its relative contribution to the extragalactic gamma ray background. The arrival directions should correlate with known sources, and a simple test shows that the PeV events can indeed be explained by known blazars with prominent radio jets. If a Galactic component of cosmic rays with energies per nucleon above knee energies exists, as air shower array data seem to indicate, the neutrinos due to pion production from these sources are also detectable, pinpointing them an energies where gamma-ray observations are not yet possible.

ANTIPROTONS PRODUCED IN SUPERNOVA REMNANTS

We present the energy spectrum of antiproton cosmic ray (CR) component calculated on the basis of the nonlinear kinetic model of CR production in supernova remnants (SNR). The model includes reacceleration of already existing in interstellar medium antiprotons as well as creation of antiprotons in nuclear collisions of accelerated protons with gas nuclei and their subsequent acceleration by SNR shock. It is shown that antiprotons production in SNRs produces considerable effect in their resultant energy spectrum making it essentially flatter above 10 GeV so that the spectrum at TeV-energies increases by a factor of five. Calculated antiproton spectrum is well consistent with the PAMELA data, which correspond to energies below 100 GeV. As a consistency check we have also calculated within the same model the energy spectra of secondary nuclei and show that the measured boron-to-carbon ratio is consistent with the significant SNR contribution.

Indirect searches for dark matter

Abstract The indirect detection of particle dark matter (DM) is based on the search for anomalous components in cosmic rays (CRs) due to the annihilation of DM pairs in the galactic halo, on the top of the standard astrophysical production. We revise here the most recent results on the DM searches for γ -rays, antiprotons, antideuterons and positrons in CRs.

Energy, altitude, and mass dependence of steepness of the lateral distribution function of electrons and muons in extensive air showers

In the present work, the energy and mass dependence of the steepness of the lateral distribution function of electrons and muons (η) are investigated. Based on a CORSIKA simulation, different characteristics of η for proton, helium, oxygen, and iron primaries in the energy range 1014–1017eV are presented. It is found that η is a mass sensitive parameter, and its potential as a mass discrimination parameter between light and heavy primaries is studied. Moreover, the altitude dependence of η for KASCADE and Auger experiments (110 and 1400m) is discussed. It is shown that the Auger experiment is potentially more effective for applying this parameter as a mass discriminator between light and heavy cosmic ray components, especially at high energies.