Composition Of Primary Cosmic Rays Research Articles

Estimation of the PCR mass composition in the energy range 1017–1019 eV on the basis of multicomponent analysis of the characteristics of EASs detected at the Yakutsk array

The characteristics of longitudinal and radial extensive air shower development derived from the results of detection of the charged particle flux and Cherenkov light in extensive air showers at the Yakutsk array. To estimate the primary cosmic ray composition, a combination of the parameters Xmax and ρ600 and the database simulated using the CORSIKA code (QGSJET model) for showers generated by five types of nuclei (p, He, C, Si, Fe) in the energy range 1017–1019 eV were used. Application of the multicomponent method made it possible to divide the showers into three groups (p + He), C, and (Si + Fe) and estimate their percentage. The error in identifying nuclei in the energy range 1017–1018 eV does not exceed 30%.

Andyrchy facility for detection of cosmic rays

The Andyrchy facility was created for studying the energy spectrum and nuclear composition of primary cosmic rays in the region of a knee in the cosmic-ray spectrum. The position of this facility above the Baksan underground scintillation telescope allows simultaneous detection of electron-photon and high-energy muon components of extensive air showers. The parameters of this facility also allow it to be used for solving a number of other problems of cosmic-ray physics. Data since 1996 have been collected for several physical problems. The facility is described, and its performance characteristics are presented.

10.1007/s11450-008-2007-6

The RUNJOB balloon-born emulsion chamber experiments have been carried out for investigating the composition and energy spectra of primary cosmic rays at energies 10-1000 TeV/nucleon. On the data of the treatment of RUNJOB` X-ray emulsion chambers exposed since 1995 to 1999 year about 50 % proton tracks were identified. In remained half of the events from proton group the one charged primary tracks were not found in the search area determined with high accuracy by the triangulation method using the several background heavy tracks. Considered methodical reasons in this paper could not explain this experimental result. The one from the probable physical reasons that is the neutrons in cosmic ray flux does not explain it too.

Hadronic interactions and extensive air showers

Understanding hadronic multiparticle production is important for deriving the composition and energy spectrum of primary cosmic rays from air shower measurements at high energy. In this article, predictions of hadronic interaction models are discussed, emphasizing uncertainties and constraints due to model assumptions and accelerator measurements. The sensitivity of shower observables to model predictions is illustrated by considering two representative examples, the electron/muon shower size at different detection altitudes and the longitudinal shower profile, and the need for measuring several observables of each shower is stressed.

Reconstruction of energy spectra of elemental groups with KASCADE: Sensitivity to hadronic interaction models

The electron and muon number of extensive air showers (EAS) measured at ground level are the main observables of the detector array of the KASCADE experiment. The two-dimensional frequency distribution of these observables is used for reconstructing the energy spectra of five elemental groups representing the chemical composition of primary cosmic rays in the energy range from 1015 eV to 1017 eV. The results of the presented unfolding analysis depend crucially on simulations of EAS, and therefore on the hadronic interaction models used for their generation. As it turns out, the results for the individual energy spectra show to be sensitive to the characteristics of the interaction model used. Furthermore, none of the models discussed (QGSJet and SIBYLL) is capable to describe the data consistently over the whole measurement range with discrepancies appearing in different energy regions.

Mass composition of primary cosmic rays at energies of 1–1000 PeV according to data of experiment “Pamir”

Experimental data obtained with X-ray emulsion chambers by the "Pamir" collaboration are compared with calculations using the code MC0 of the quark-gluon-string model. The best fit to the experimental data is attained assuming that the primary cosmic ray (PCR) mass composition in the PCR energy range 10 15 –10 17 eV becomes slowly enriched with heavy nuclei, so that the proton fraction decreases from 33% at E 0 = 10 15 eV to 20% at E 0 = 10 17 eV . To bring model calculations in agreement with experimental data at PCR energy E 0 = 10 17 – 10 18 eV it is necessary to assume a rapid increase of the proton fraction in PCR composition and a possible change of slope exponent of the PCR energy integral spectrum from γ = 2.05 to γ = 1.65 .

A new study on the energy spectrum and composition of primary cosmic rays at energies ∼ 10 14–10 16 eV using the GRAPES-3 array at Ooty

Data collected with the 250-detector air shower array and the 560 m 2 area tracking muon detector, operated at Ooty in southern India by the GRAPES collaboration, have been analyzed to study the shape of the energy spectrum and the composition around the knee . It is shown that muon multiplicity distributions, observed with the highly modular muon detector, permit a relatively more reliable measurement of the composition of the primary flux which then helps in a more accurate reconstruction of the energy spectrum from the observed shower size spectrum. Some preliminary results are presented here.

UNDERGROUND MUON ENERGY SPECTRA WITH THE MACRO TRD

The MACRO detector was located in the Hall B of the Gran Sasso underground Laboratories under an average rock overburden of 3700 hg/cm2. A TRD composed by three identical modules, covering an horizontal area of 36 m2, was added to the MACRO detector in order to measure the residual energy of muons entering MACRO. This kind of measurement provides a useful tool to study the primary cosmic ray energy spectra and composition, their interactions with the Earth's atmosphere and the propagation of muons inside the rock. The results of the measurement of the energy of single and double muons crossing MACRO will be presented. Our data show that double muons are more energetic than single ones in the rock depth range from 3000 to 6500 hg/cm2. Single muon data confirm the reliability of the models adopted to describe the cosmic ray interactions with the atmosphere and the muon propagation inside the rock.

SELECTION OF THE PRIMARY COSMIC RAY LIGHT COMPONENT WITH ARGO-YBJ

The ARGO-YBJ experiment, currently under construction at the YangBaJing High Altitude Cosmic Ray Laboratory (Tibet, P.R. China, 4300 m a.s.l.), may be upgraded with a large muon detector (~ 2500 m2) both to extend the sensitivity to γ-ray sources to energies ≥ 20 TeV and to perform a cosmic ray primary composition study. In this paper we discuss the capability of the upgraded ARGO-YBJ detector to select the primary cosmic ray light component in the knee energy region.

The water Cherenkov detector array for studies of cosmic rays at the University of Puebla

We describe the design and performance of a hybrid extensive air shower detector array built on the Campus of the University of Puebla ( 19 ∘ N , 90 ∘ W , 800 g / cm 2 ) to measure the energy, arrival direction and composition of primary cosmic rays with energies around 1 PeV, i.e., around the knee of the cosmic ray spectrum. The array consists of 3 water Cherenkov detectors of 1.86 m 2 cross-section and 12 liquid scintillator detectors of 1 m 2 distributed in a square grid with a detector spacing of 20 m over an area of 4000 m 2 . We discuss the calibration and stability of the array for both sets of detectors and report on preliminary measurements and reconstruction of the lateral distributions for the electromagnetic (EM) and muonic components of extensive air showers. We also discuss how the hybrid character of the array can be used to measure mass composition of the primary cosmic rays by estimating the relative contents of muons with respect to the EM component of extensive air showers. This facility is also used to train students interested in the field of cosmic rays.

KASCADE measurements of energy spectra for elemental groups of cosmic rays: Results and open problems

A composition analysis of KASCADE air shower data is performed by means of unfolding the two-dimensional frequency spectrum of electron and muon numbers. Aim of the analysis is the determination of energy spectra for elemental groups representing the chemical composition of primary cosmic rays. Since such an analysis depends crucially on simulations of air showers the two different hadronic interaction models QGSJet and SIBYLL are used for their generation. The resulting primary energy spectra show that the knee in the all particle spectrum is due to a steepening of the spectra of light elements but, also, that neither of the two simulation sets is able to describe the measured data consistently over the whole energy range with discrepancies appearing in different energy regions.

A large area muon tracking detector for ultra-high energy cosmic ray astrophysics—the GRAPES-3 experiment

Certain aspects of ultra-high energy (UHE) cosmic ray astrophysics require correlated studies on the electron and muon components of air showers, namely, the search for cosmic ray sources through γ -ray astronomy and studies on the variation of the nuclear composition of primary cosmic rays with energy. While studies on the electron component provide basic information about the arrival direction and energy, it is the muon component that plays a crucial role in distinguishing primary γ -rays from charged cosmic ray particles and in determining the composition. A large area (560 m 2 ), tracking muon detector of the GRAPES-3 experiment, operating at Ooty in southern India, has been designed for detailed studies on both of these aspects of UHE cosmic ray astrophysics. We present here the details of the muon detector, associated electronics and the data acquisition system. A brief discussion of the potential of the muon detector is presented through simulation studies.

Impact of varying atmospheric profiles on extensive air shower observation: atmospheric density and primary mass reconstruction

The longitudinal profile of extensive air showers is sensitive to the energy and type/mass of the primary particle. One of its characteristics, the atmospheric depth of shower maximum, is often used to reconstruct the elemental composition of primary cosmic rays. In this article, the impact of the atmospheric density profile on the reconstruction of the depth of maximum, as observed in fluorescence light measurements, is investigated. We consider in detail the atmospheric density profile and its time variations at the site of the southern Pierre Auger Observatory, using data that were obtained from meteorological radio soundings. Similar atmospheric effects are expected to be found also at other sites.

The Energy Spectrum and the Chemical Composition of Primary Cosmic Rays with Energies from 1014to 1016eV

We have measured extensive air showers with primary energies above 6 TeV at Mount Chacaltaya in Bolivia. The data were collected by an air shower array called the Minimum Air Shower (MAS) array starting in 2000 March. We applied an equi-intensity analysis method to the extensive air showers extended over the region of their maximum development. We varied the mixture of protons and iron in our simulations and compared these to the data to determine the mixing ratio of protons as a function of the primary energy. Using this, we derived the primary energy spectrum from 1014 to 5 × 1016 eV. Consequently, we conclude that the power-law index of the spectrum changes gradually around 1015.5 eV and that the obtained proton ratio decreases with increasing energy. We directly measured the longitudinal development of air showers generated by primaries with energies around the knee. We found that the average mass number of primary cosmic rays shows a steady increase with energy above 1014.5 eV and that the dominant component around the knee is not protons.

The cosmic ray primary composition in the “knee” region through the EAS electromagnetic and muon measurements at EAS-TOP

The evolution of the cosmic ray primary composition in the energy range 106–107 GeV (i.e. the “knee” region) is studied by means of the e.m. and muon data of the Extensive Air Shower EAS-TOP array (Campo Imperatore, National Gran Sasso Laboratories). The measurement is performed through: (a) the correlated muon number (Nμ) and shower size (Ne) spectra, and (b) the evolution of the average muon numbers and their distributions as a function of the shower size. From analysis (a) the dominance of helium primaries at the knee, and therefore the possibility that the knee itself is due to a break in their energy spectrum (at EkHe=(3.5±0.3)×106 GeV) are deduced. Concerning analysis (b), the measurement accuracies allow the classification in terms of three mass groups: light (p,He), intermediate (CNO), and heavy (Fe). At primary energies E0≈106 GeV the results are consistent with the extrapolations of the data from direct experiments. In the knee region the obtained evolution of the energy spectra leads to: (i) an average steep spectrum of the light mass group (γp,He>3.1), (ii) a spectrum of the intermediate mass group harder than the one of the light component (γCNO≃2.75, possibly bending at EkCNO≈(6–7)×106 GeV), (iii) a constant slope for the spectrum of the heavy primaries (γFe≃2.3–2.7) consistent with the direct measurements. In the investigated energy range, the average primary mass increases from 〈lnA〉=1.6–1.9 at E0≃1.5×106 GeV to 〈lnA〉=2.8–3.1 at E0≃1.5×107 GeV. The result supports the standard acceleration and propagation models of galactic cosmic rays that predict rigidity dependent cut-offs for the primary spectra of the different nuclei. The uncertainties connected to the hadronic interaction model (QGSJET in CORSIKA) used for the interpretation are discussed.

Influence of shower fluctuations and primary composition on studies of the shower longitudinal development

We study the influence of shower fluctuations, and the possible presence of different nuclear species in the primary cosmic ray spectrum, on the experimental determination of both shower energy and the proton air inelastic cross section from studies of the longitudinal development of atmospheric showers in fluorescence experiments. We investigate the potential of track length integral and shower size at maximum as estimators of shower energy. We find that at very high energy (~10^19-10^20 eV) the error of the total energy assignment is dominated by the dependence on the hadronic interaction model, and is of the order of 5%. At lower energy (~10^17-10^18 eV), the uncertainty of the energy determination due to the limited knowledge of the primary cosmic ray composition is more important. The distribution of depth of shower maximum is discussed as a measure of the proton-air cross section. Uncertainties in a possible experimental measurement of this cross section introduced by intrinsic shower fluctuations, the model of hadronic interactions, and the unknown mixture of primary nuclei in the cosmic radiation are numerically evaluated.

The cosmic ray primary composition in the ?knee? region through the EAS electromagnetic and muon measurements at EAS-TOP

The evolution of the cosmic ray primary composition in the energy range 10 6 –10 7 GeV (i.e. the “knee” region) is studied by means of the e.m. and muon data of the Extensive Air Shower EAS-TOP array (Campo Imperatore, National Gran Sasso Laboratories). The measurement is performed through: (a) the correlated muon number ( N μ ) and shower size ( N e ) spectra, and (b) the evolution of the average muon numbers and their distributions as a function of the shower size. From analysis (a) the dominance of helium primaries at the knee, and therefore the possibility that the knee itself is due to a break in their energy spectrum (at E k He =(3.5±0.3)×10 6 GeV) are deduced. Concerning analysis (b), the measurement accuracies allow the classification in terms of three mass groups: light (p,He), intermediate (CNO), and heavy (Fe). At primary energies E 0 ≈10 6 GeV the results are consistent with the extrapolations of the data from direct experiments. In the knee region the obtained evolution of the energy spectra leads to: (i) an average steep spectrum of the light mass group ( γ p,He >3.1), (ii) a spectrum of the intermediate mass group harder than the one of the light component ( γ CNO ≃2.75, possibly bending at E k CNO ≈(6–7)×10 6 GeV), (iii) a constant slope for the spectrum of the heavy primaries ( γ Fe ≃2.3–2.7) consistent with the direct measurements. In the investigated energy range, the average primary mass increases from 〈ln A 〉=1.6–1.9 at E 0 ≃1.5×10 6 GeV to 〈ln A 〉=2.8–3.1 at E 0 ≃1.5×10 7 GeV. The result supports the standard acceleration and propagation models of galactic cosmic rays that predict rigidity dependent cut-offs for the primary spectra of the different nuclei. The uncertainties connected to the hadronic interaction model (QGSJET in CORSIKA) used for the interpretation are discussed.

The ATIC long duration balloon project

Long Duration Balloon (LDB) scientific experiments, launched to circumnavigate the south pole over Antarctica, have particular advantages compared to Shuttle or other Low Earth Orbit (LEO) missions in terms of cost, weight, scientific “duty factor” and work force development. The Advanced Thin Ionization Calorimeter (ATIC) cosmic-ray astrophysics experiment is a good example of a university-based project that takes full advantage of current LDB capability. The ATIC experiment is currently being prepared for its first LDB science flight that will investigate the charge composition and energy spectra of primary cosmic-rays over the energy range from about 10 10 to 10 14 eV. The instrument is built around a fully active, Bismuth–Germanate (BGO) ionization calorimeter to measure the energy deposited by cascades formed by particles interacting in a thick carbon target. A highly segmented silicon matrix, located above the target, provides good incident charge resolution plus rejection of “backscattered” particles from the cascade. Trajectory reconstruction is based on the cascade profile in the BGO calorimeter, plus information from the three pairs of scintillator hodoscope layers in the target section above it. A full evaluation of the experiment was performed during a test flight occurring between 28 December 2000 and 13 January 2001 where ATIC was carried to an altitude of ∼37 km above Antarctica by a ∼850,000 m 3 helium filled balloon for one circumnavigation of the continent. All systems behaved well, the detectors performed as expected, >43 GB of engineering and cosmic-ray event data were returned and these data are now undergoing preliminary data analysis. During the coming 2002–2003 Antarctica summer season, we are preparing for an ATIC science flight with ∼15 to 30 days of data collection in the near-space environment of Long Duration Balloon (LDB) float altitudes.

The ATIC long duration balloon project

Long Duration Balloon (LDB) scientific experiments, launched to circumnavigate the south pole over Antarctica, have particular advantages compared to Shuttle or other Low Earth Orbit (LEO) missions in terms of cost, weight, scientific “duty factor” and work force development. The Advanced Thin Ionization Calorimeter (ATIC) cosmic-ray astrophysics experiment is a good example of a university-based project that takes full advantage of current LDB capability. The ATIC experiment is currently being prepared for its first LDB science flight that will investigate the charge composition and energy spectra of primary cosmic-rays over the energy range from about 10 10 to 10 14 eV. The instrument is built around a fully active, Bismuth–Germanate (BGO) ionization calorimeter to measure the energy deposited by cascades formed by particles interacting in a thick carbon target. A highly segmented silicon matrix, located above the target, provides good incident charge resolution plus rejection of “backscattered” particles from the cascade. Trajectory reconstruction is based on the cascade profile in the BGO calorimeter, plus information from the three pairs of scintillator hodoscope layers in the target section above it. A full evaluation of the experiment was performed during a test flight occurring between 28 December 2000 and 13 January 2001 where ATIC was carried to an altitude of ∼37 km above Antarctica by a ∼850,000 m 3 helium filled balloon for one circumnavigation of the continent. All systems behaved well, the detectors performed as expected, >43 GB of engineering and cosmic-ray event data were returned and these data are now undergoing preliminary data analysis. During the coming 2002–2003 Antarctica summer season, we are preparing for an ATIC science flight with ∼15 to 30 days of data collection in the near-space environment of Long Duration Balloon (LDB) float altitudes.

The cosmic ray primary composition between 10 15 and 10 16 eV from Extensive Air Showers electromagnetic and TeV muon data

The cosmic ray primary composition in the energy range between 10 15 and 10 16 eV, i.e., around the “knee” of the primary spectrum, has been studied through the combined measurements of the EAS-TOP air shower array (2005 m a.s.l., 10 5 m 2 collecting area) and the MACRO underground detector (963 m a.s.l., 3100 m w.e. of minimum rock overburden, 920 m 2 effective area) at the National Gran Sasso Laboratories. The used observables are the air shower size ( N e) measured by EAS-TOP and the muon number ( N μ) recorded by MACRO. The two detectors are separated on average by 1200 m of rock, and located at a respective zenith angle of about 30°. The energy threshold at the surface for muons reaching the MACRO depth is approximately 1.3 TeV. Such muons are produced in the early stages of the shower development and in a kinematic region quite different from the one relevant for the usual N μ− N e studies. The measurement leads to a primary composition becoming heavier at the knee of the primary spectrum, the knee itself resulting from the steepening of the spectrum of a primary light component (p, He) of Δ γ=0.7±0.4 at E 0∼4×10 15 eV. The result confirms the ones reported from the observation of the low energy muons at the surface (typically in the GeV energy range), showing that the conclusions do not depend on the production region kinematics. Thus, the hadronic interaction model used (CORSIKA/QGSJET) provides consistent composition results from data related to secondaries produced in a rapidity region exceeding the central one. Such an evolution of the composition in the knee region supports the “standard” galactic acceleration/propagation models that imply rigidity dependent breaks of the different components, and therefore breaks occurring at lower energies in the spectra of the light nuclei.