Primary Cosmic Ray Flux Research Articles

Estimating the fraction of gamma quanta in the primary cosmic ray flux with energies of ∼1017 eV from the MSU EAS array data

Using data from the MSU EAS array and model calculations, we search for events with abnormally small fractions of muons with energies above 10 GeV in showers with particle numbers of >2 × 107 and zenith angles of <30 degrees. We confirm with good statistical accuracy that the content of gamma quanta in the primary cosmic ray flux can be as high as 2% at energies of ∼1017 eV.

Evaluation of the gamma-quanta fraction in the primary cosmic ray flux with energy about 1017eV according to the EAS MSU array data

Using the data of the EAS MSU array and model calculations we have performed the search of events with abnormally small fraction of muons with energy above 10 GeV in showers with particle numbers greater than 2.107 and with zenith angles less than 30 degrees. The aim of the work – to estimate a fraction of muon-poor showers in which the underground muon detector registered no muons. These events may be identified as showers generated by primary gamma-quanta of ultrahigh energies. With good statistical accuracy we have confirmed our earlier conclusion that the content of gamma-quanta in the primary cosmic ray flux may be as much as 2 % at energies about 1017 eV.

NEVOD-DECOR experiment: results and future

Russian-Italian NEVOD-DECOR experiment on the measurements of the local muon density spectra (LMDS) at various zenith angles gave possibility to obtain information on primary cosmic ray flux and interaction characteristics in a record wide energy range from 1015 to more than 1018 eV. Comparison of the measurement results with CORSIKA-based simulations showed the increase of LMDS slope at PeV energies of primaries (corresponding to the first knee); a trend to a heavier primary mass composition above the knee; indication for a second knee (a further increase of the spectrum slope near 1017 eV). At large zenith angles and high muon densities (corresponding to primary energies around 1018 eV) a considerable excess of muon bundle events in comparison with the expectation based on independent estimates of the primary spectrum and widely used hadron interaction models has been found. In 2011, a new phase of measurements of the energy spectrum of cascade showers initiated by high-energy muons in water and of the energy deposit of muon bundles at various zenith angles and muon multiplicities started. Further plans include the deployment of a traditional EAS array around the NEVOD-DECOR complex.

Flux and Spectra of Primary Cosmic Rays at Yangbajing With the AMS-01 Experiment

利用Alpha Magnetic Spectrometer(AMS)实验对近地空间不同地磁纬度处不同能量原初宇宙线微分能谱的观测,通过积分近似计算和拟合方法,研究得出西藏羊八井地磁纬度处原初宇宙线质子动能在0.44～4.31GeV,4.31～12.38GeV,12.38～199.06GeV区间内的积分流强与拟合能谱函数以及原初宇宙线氦核在刚度区间6.92～14.45GV,14.45～229.9GV的积分流强与拟合能谱函数,为近一步进行羊八井处本底宇宙线流强估算奠定了基础.

The GeV-TeV Galactic gamma-ray diffuse emission

The Galactic gamma-ray diffuse emission is currently observed in the GeV-TeV energy range with unprecedented accuracy by the Fermi satellite. Understanding this component is crucial as it provides a background to many different signals such as extragalactic sources or annihilating dark matter. It is timely to reinvestigate how it is calculated and to assess the various uncertainties which are likely to affect the accuracy of the predictions. The Galactic gamma-ray diffuse emission is mostly produced above a few GeV by the interactions of cosmic ray primaries impinging on the interstellar material. The theoretical error on that component is derived by exploring various potential sources of uncertainty. Particular attention is paid to cosmic ray propagation. Nuclear cross sections, the proton and helium fluxes at the Earth, the Galactic radial profile of supernova remnants and the hydrogen distribution can also severely affect the signal. The propagation of cosmic ray species throughout the Galaxy is described in the framework of a semi-analytic two-zone diffusion/convection model. This allows to convert the constraints set by the boron-to-carbon data into a theoretical uncertainty on the diffuse emission. New deconvolutions of the HI and CO sky maps are also used to get the hydrogen distribution within the Galaxy. The thickness of the cosmic ray diffusive halo is found to have a significant effect on the Galactic gamma-ray diffuse emission while the interplay between diffusion and convection has little influence on the signal. The uncertainties related to nuclear cross sections and to the primary cosmic ray fluxes at the Earth are significant. The radial distribution of supernova remnants along the Galactic plane turns out to be a key ingredient. As expected, the predictions are extremely sensitive to the spatial distribution of hydrogen within the Milky Way.

Study of EAS neutron component temporal structure

The neutron component of Extensive Air Showers (EAS) carries information about the primary cosmic ray flux as well as about parameters of hadronic interactions at ultra- high energies. We present here the data obtained with the Neutron array which is a prototype of a novel type EAS array PRISMA (Stenkin, 2009). The prototype consists of 5 large area scintillator detectors (0.75 m 2 each) placed in the corners and in the center of 5 m side square. The scintillator consisting of an alloy of ZnS(Ag) and 6 LiF is shaped as a thin layer of grains covered with thin transparent plastic film.

An update of the generator of atmospheric muons from parametric formulas (MUPAGE)

We present a new version of the fast generator of atmospheric muons based on parametric formulas (MUPAGE). The parameterization of the deep sea muon flux relies on a primary Cosmic Ray flux and interaction model able to correctly reproduce the flux, the multiplicity distribution, the spatial distance between muons as measured by the underground MACRO experiment [1]. MUPAGE produces the event kinematics of the muon bundle on the surface of a user-defined cylinder, surrounding the virtual detector. The new version improves the possibility to select the total energy of the muons bundle, and the choice of a virtual cylinder of any dimensions. Program title: MUPAGE Catalogue identifier: AEBT_v2_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEBT_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3421 No. of bytes in distributed program, including test data, etc.: 59 308 Distribution format: tar.gz Programming language: C++ Computer: The code has been developed and tested on Pentium M, 2.0 GHz; 2x Intel Xeon Quad Core, 2.33 GHz. Operating system: Scientific Linux 3.x; 4.x; 5.x; Slackware 12.0.0. RAM: 50 MB Supplementary material: The table mentioned in the “Summary of revisions” section, can be obtained here. Classification: 1.1, 11.3 External routines: ROOT ( http://root.cern.ch ) Catalogue identifier of previous version: AEBT_v1_0 Journal reference of previous version: Comput. Phys. Comm. 179 (2008) 915 Does the new version supersede the previous version?: Yes Nature of problem: Fast simulation of atmospheric muon bundles for underwater/ice neutrino telescopes. Solution method: Atmospheric muon events are generated according to parametric formulas [2] giving the flux, the multiplicity, the radial distribution and the energy spectrum. Reasons for new version: We simplified the possible choice of the muon bundle energy, which in the previous version could give a wrong estimation of the equivalent livetime. In addition, in the former version the choice of a virtual cylinder with height much larger than the diameter stopped the program. The problem is now fixed. Summary of revisions: The MUPAGE event generator computes automatically the equivalent livetime corresponding to the number of generated events N gen on the user-defined cylinder ( can ) surrounding the virtual detector. MUPAGE needs some parameters as input (provided by the user in the file dat/parameters.dat ). These parameters refer to the detector configuration, to the medium and to the range of simulation parameters (multiplicity, zenith angle, muon energy), see Table 1 (Supplementary material). In the previous version, the user could change the energy range of each muon in the bundle using Emin and Emax (minimum and maximum of the muon energy at the can level). It has been found that an arbitrary change of these values produces a wrong computation of the livetime. In the new version, these values cannot be changed and have been removed from the data cards. The selection of the energy threshold of the event is now possible with the Ethreshold parameter. It represents the sum of the energy of muons in the same bundle. The default value has been decreased to Ethreshold = 0.001 TeV . The user may now increase the threshold value without any corruption of the livetime computation. A second problem was related to the choice of the can size. The error was due to an uncorrected frame coordinate transformation in the code. MUPAGE produces the muon bundle event kinematics on the surface of the can . If the height was much larger than the can diameter, the program crashed and had to be restarted after increasing the value of MFactor . The new version corrects the error, and this parameter is not necessary anymore. In addition, there is not the need to increase the can radius (using the EnlargedCANr parameter) with a too large value. It is now recommended to define EnlargedCANr equal to Rmax . Restrictions: Water vertical depth range from 1.5 to 5 km w.e.; zenith angle range from 0 to 85 degrees. Additional comments: The program requires the ROOT libraries for the pseudorandom number generator. Running time: Running with the default settings takes only a few seconds.

Proton-air cross section measurement with the ARGO-YBJ cosmic ray experiment

The proton-air cross section in the energy range 1–100 TeV has been measured by the ARGO-YBJ cosmic ray experiment. The analysis is based on the primary cosmic ray flux attenuation for different atmospheric depths (i.e. zenith angles) and exploits the detector capabilities of selecting the shower development stage by means of hit multiplicity, density and lateral profile measurements at ground. The effects of shower fluctuations, the contribution of heavier primaries and the uncertainties of the hadronic interaction models, have been taken into account. The results have been used to estimate the total proton-proton cross section at center-of-mass energies between 70 and 500 GeV, where no accelerator data are currently available.2 MoreReceived 27 April 2009DOI:https://doi.org/10.1103/PhysRevD.80.092004©2009 American Physical Society

Ultra high-energy cosmic ray proton interactions

The recent Auger results suggest that the coincidences of arrival directions with ‘nearby’ AGN, and the HiRes discovery of the GZK cut-off, indicate protons to be at least the strongly dominant component of primary extra galactic cosmic ray flux. The measured longitudinal extensive air shower propagation characteristics, however, indicate at least a mixed composition, if the conventional interaction model is correct. For the present work we assume that the particles are indeed protons and examine the consequences for the high-energy interaction physics. We have found that such a supposition requires strong violation of the so-called Feynman scaling.

Search for the end of the energy spectrum of primary cosmic rays

The experiments on the search for the end of the cosmic-ray energy spectrum with the particle detector array technique and the optical (Čerenkov and/or fluorescence) technique are summarized. In the highest observed energy region, the suppression of the flux above about 6×1019 eV, which corresponds to the so-called ‘Greisen–Zatsepin–Kuz'min (GZK) cutoff energy’, is confirmed by the new results from the High-Resolution Fly's Eye (HiRes) and the Pierre Auger Observatory (Auger). Summarizing the spectra observed from 1014 to 1020 eV with world wide experiments, there is still room for further investigations on the energy scale and the flux of primary cosmic rays. In order to establish the energy scale, it is necessary not only to understand the optical technique further, but also to determine the primary species in the highest energy region. Also, it is important to make more detailed measurements on the energy spectrum in the 1017–1018 eV region. To observe the super-GZK events and the anticipated recovery of the spectrum above the GZK cutoff, the search for the end of cosmic-ray energy spectrum will be continued even after a century since the discovery of cosmic rays in 1912.

Very high energy proton-proton cross section

The recent Pierre Auger Observatory result suggesting a coincidence of extensive air showers arrival directions with ``nearby'' active galactic nuclei and HiRes discovery of the Greisen-Zatsepin-Kuzmin cutoff indicates protons to be only or at least the strongly dominant component of primary extra galactic cosmic ray flux. However, showers initiated by these ultrahigh energy particles developed faster than predicted by the simulation calculations with conventional interaction models. This could be evidence of the substantial increase of the $p$-air cross section. The progress in understanding the proton-proton cross section description allows us to examine this possibility, and eventually reject it as an explanation of the ultrahigh energy cosmic ray ``pure proton'' controversy.

MUons from PArametric formulas: A fast GEnerator of atmospheric [formula omitted]-bundles for neutrino telescopes (MUPAGE)

Atmospheric muons play an important role for neutrino telescopes, because they provide the most abundant source of events for real time monitoring, calibration and tests. On the other side, they also represent the major background source. A fast Monte Carlo generator (called MUPAGE) of atmospheric muon bundles for underwater/ice neutrino telescopes is presented here. MUPAGE is based on parametric formulas [Y. Becherini, A. Margiotta, M. Sioli, M. Spurio, Astrop. Phys. 25 (2006) 1–13; M. Spurio, Nucl. Instr. and Meth. A 567 (2006) 492] obtained from a full Monte Carlo simulation of cosmic ray showers generating muons in bundles, which are propagated down to 5 km w.e. It produces the event kinematics on the surface of a user-defined virtual cylinder, surrounding the detector. The multiplicity of the muons in the bundle, the muon lateral distribution and energy spectrum are simulated according to a specific model of the primary cosmic ray flux, with constraints from measurements of the muon flux obtained in underground experiments. Some examples of application are presented.

High-energy cosmic-ray fluxes in the Earth atmosphere: Calculations vs experiments

A new calculation of the atmospheric fluxes of cosmic-ray hadrons and muons in the energy range 10 – 10 5 GeV has been performed for the set of hadron production models, EPOS 1.6, QGSJET II-03, SIBYLL 2.1, and others that are of interest to cosmic-ray physicists. The fluxes of secondary cosmic rays at several levels in the atmosphere are computed using directly data of the ATIC-2, GAMMA experiments, and the model proposed recently by Zatsepin and Sokolskaya as well as the parameterization of the primary cosmic-ray spectrum by Gaisser and Honda. The calculated energy spectra of the hadrons and muon flux as a function of zenith angle are compared with measurements as well as other calculations. The effect of uncertainties both in the primary cosmic-ray flux and hadronic model predictions on the spectra of atmospheric hadrons and muons is considered.

Atmospheric MUons from PArametric formulas: a fast GEnerator for neutrino telescopes (MUPAGE)

Neutrino telescopes will open, in the next years, new opportunities in observational high energy astrophysics. In these detectors, atmospheric muons from primary cosmic ray interactions in the atmosphere play an important role, because they provide the most abundant source of events for calibration and test. On the other side, they represent the major background source. In this paper a fast Monte Carlo generator (called MUPAGE) of bundles of atmospheric muons for underwater/ice neutrino telescopes is presented. MUPAGE is based on parametric formulas [Y. Becherini, A. Margiotta, M. Sioli, M. Spurio, Astrop. Phys. 25 (2006) 1] obtained from a full Monte Carlo simulation of cosmic ray showers generating muons in bundle, which are propagated down to 5 km w.e. It produces the event kinematics on the surface of a user-defined cylinder, surrounding the virtual detector. The multiplicity of the muons in the bundle, the muon lateral distribution and energy spectrum are simulated according to a specific model of primary cosmic ray flux, with constraints from measurements of the muon flux with underground experiments. As an example of application, the result of the generation of events on a cylindrical surface of ∼1.4 km 2 at a depth of 2450 m of water is presented. Program summary Program title: MUPAGE Catalogue identifier: AEBT_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEBT_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 3534 No. of bytes in distributed program, including test data, etc.: 61 383 Distribution format: tar.gz Programming language: C++ Computer: Pentium M, 2.0 GHz; 2x Intel Xeon Quad Core, 2.33 GHz Operating system: Scientific Linux 3.x; Scientific Linux 4.x; Slackware 12.0.0 RAM: 50 MB Word size: 32 bits Classification: 1.1, 11.3 External routines: The ROOT system ( http://root.cern.ch) Nature of problem: Fast simulation of atmospheric muon bundles for underwater/ice neutrino telescopes. Solution method: Atmospheric muon events are generated according to parametric formulas [1] giving the flux, the multiplicity, the radial distribution and the energy spectrum. Restrictions: Water vertical depth range from 1.5 to 5 km w.e.; zenith angle range from 0 to 85 degrees. Additional comments: The program requires the ROOT libraries for the pseudorandom number generator.

Study of the solar anisotropy of cosmic ray primaries of about 200 GeV energy with the L3+C muon detector

Context. Primary cosmic rays experience multiple deflections in the non-uniform galactic and heliospheric magnetic fields which may generate anisotropies. Aims. A study of anisotropies in the energy range between 100 and 500 GeV is performed. This energy range is not yet well explored.Methods. The L3 detector at the CERN electron-positron collider, LEP, is used for a study of the angular distribution of atmospheric muons with energies above 20 GeV. This distribution is used to investigate the isotropy of the time-dependent intensity of the primary cosmic-ray flux with a Fourier analysis.Results. A small deviation from isotropy at energies around 200 GeV is observed for the second harmonics at the solar frequency. No sidereal anisotropy is found at a level above . The measurements were performed in the years 1999 and 2000. . © 2008 ESO.

Hadronic Interactions Modeling, and the calculation of the inclusive fluxes of atmospheric muons and neutrinos

This work discusses the importance of the modeling of hadronic interactions for the prediction of the atmospheric muon and neutrino fluxes. The calculation requires a precise knowledge of the primary cosmic ray fluxes and of the single particle inclusive energy spectra in hadronic interactions. The present calculations, after taking into account the effects of neutrino oscillations, can describe quite successfully the existing data. The uncertainty in the extrapolation of the prediction to very high energy is dominated by our poor knowledge of the primary cosmic ray spectra, the size of Feynman–scaling violations, and our poor understanding of the properties of charmed particles production. The measurement of the atmospheric muon and neutrino fluxes at very high energy with the future neutrino telescopes could provide an important constraint on the combination of the cosmic ray fluxes and the description of hadronic interactions at high energy.

BESS-Polar experiment: Progress and future prospects

The first scientific flight of the BESS-Polar balloon-borne experiment was successfully carried out in December 2004 from Antarctica with the primary scientific objectives of searching for primordial antiparticles from the universe and making precision measurements of primary cosmic-ray fluxes. During the 8.5 day flight, the newly developed BESS-Polar spectrometer worked well and gathered data from 9 × 10 8 cosmic-ray events, showing its capability for making long-duration science observations. We have already started hardware development for the second experiment, which is expected to be a flight of more than 20 days during the next solar minimum period with the upgraded spectrometer. In this manuscript, progress on and prospects for the BESS-Polar experiment are described.

Nonuniversal spectra of ultrahigh energy cosmic ray primaries and secondaries in a structured universe

Analytical calculations of extragalactic cosmic ray spectra above {approx}10{sup 17} eV are often performed assuming continuous source distributions, giving rise to spectra that depend little on the propagation mode, be it rectilinear or diffusive. We perform trajectory simulations for proton primaries in the probably more realistic case of discrete sources with a density of {approx}10{sup -5} Mpc{sup -3}. We find two considerable nonuniversal effects that depend on source distributions and magnetic fields: First, the primary extragalactic cosmic ray flux can become strongly suppressed below a few 10{sup 18} eV due to partial confinement in magnetic fields surrounding sources. Second, the secondary photon to primary cosmic ray flux ratio between {approx_equal}3x10{sup 18} eV and {approx_equal}10{sup 20} eV decreases with decreasing source density and increasing magnetization. As a consequence, in acceleration scenarios for the origin of highest energy cosmic rays the fraction of secondary photons may be difficult to detect even for experiments such as Pierre Auger. The cosmogenic neutrino flux does not significantly depend on source density and magnetization.

Ultra-high energy cosmic ray investigations by means of EAS muon density measurements

A new approach to investigations of ultra-high energy cosmic rays based on the ground-level measurements of the spectra of local density of EAS muons at various zenith angles is considered. Basic features of the local muon density phenomenology are illustrated using a simple semi-analytical model. It is shown that muon density spectra are sensitive to the spectrum slope, primary composition, and to the features of hadronic interaction. New experimental data on muon bundles at zenith angles from 30° to horizon obtained with the coordinate detector DECOR are compared with CORSIKA-based simulations. It is found that measurements of muon density spectra in inclined EAS give possibility to study characteristics of primary cosmic ray flux in a very wide energy range from 10 15 to 10 19 eV.

Constraints on the fraction of primary gamma rays at ultra-high energies from the muon data of the Yakutsk EAS array

By using data on the total signal and on the muon component of air showers detected at the Yakutsk array, the possible upper limits on the fraction of primary gamma rays at ultra-high energies is analyzed in the framework of the recently suggested event-by-event approach. Upper limits on the photon fraction in the integral flux of primary cosmic rays are derived. At 95% C.L., these limits are 22% for primary energies E 0 > 4 × 1019 eV and 12% for E 0 > 2 × 1019 eV. Despite the presence of muonless events, the data are consistent with the complete absence of photons at least at 95% C.L. The sensitivity of the results to systematic uncertainties, in particular to those of the energy determination for nonphoton primaries, is discussed.