Cosmic Ray Cascades Research Articles

Simulation of radio signals from cosmic-ray cascades in air and ice as observed by in-ice Askaryan radio detectors

Simulation of radio signals from cosmic-ray cascades in air and ice as observed by in-ice Askaryan radio detectors

Top cross section in the LHeC and FCC-he energy range

Predictions of the top-pair production cross section in electron-proton (ep) collisions at the future circular collider hadron-electron (FCC-he) and the large hadron electron collider (LHeC) in the leading order (LO) and the next-to-leading order (NLO) approximations in perturbative quantum chromodynamics (QCD) are presented. Numerical results for the top structure functions and the ratio of structure functions are computed at the renormalization scale μ2=Q2+4mt2 in the collinear generalized double asymptotic scaling (DAS) approach. These results are presented in terms of the effective parameters of the parameterization of F2(x,Q2), where relying on a Froissart-bounded. These quantitative results can be important for future collider experiments at the center-of-mass energy frontier and the improvement of the phenomenological models for the development of the cosmic ray cascades in ultra-high-energy domain. We obtained the uncertainties because of the power-law behavior x−Δ of the collinear parton distribution functions (PDFs), the factorization, and renormalization scales, on the top properties at high inelasticity for the FCC-he center-of-mass (CM) energy at the NLO approximation.

Application of machine learning in cosmic ray particle identification

Machine learning algorithms can learn the rules and patterns of big data through computers, excavate potential information hidden behind the data, and be widely used to solve classification, regression, clustering, and other problems. Firstly, this paper uses CORSIKA software to simulate the process of cosmic ray cascade shower in the atmosphere, generating information such as the initial energy, zenith angle, azimuth angle of cosmic ray particles. Then, this paper uses the Geant4 toolkit to conduct thermal neutron detector response simulation, generating 4000 particles in each of proton, helium, CNO, MgAlSi and iron. Based on the experimental simulation data of thermal neutron detector, this paper constructs machine learning models for identifying cosmic ray particles by using decision tree (DT), random forest (RF) and BP neural network (BP NN) respectively. For each particle, all the machine learning algorithms are used for model training based on the simulation data. The cross grid search method is used to adjust the hyper parameters of each machine learning algorithm. The AUC value and <i>Q</i> quality factor value of each algorithm are used as evaluation indexes for particle composition identification. The AUC value is a general indicator for evaluating algorithm performance in machine learning and the <i>Q</i> quality factor value is an evaluation index commonly used in the field of high energy physics. The Experimental results show that different machine learning models have great influence on particle prediction accuracy, and the random forest cosmic ray particle identification model has sufficient accuracy and generalization capability. In the test, the decision tree algorithm adjusted by cross grid search method is sensitive to the medium components (CNO and MgAlSi). The AUC values of the algorithm are all above 0.95 and the <i>Q</i> quality factor values are all above 6. The random forest algorithm adjusted by the cross grid search method has the best effect on the identification of cosmic ray particles. The AUC values of the algorithm are all more than 0.92 and the <i>Q</i> quality factor values are all more than 4. The BP neural network algorithm is only sensitive to proton and iron. This study provides a new method and selection for identifying and screening the cosmic ray particles and it also provides a new idea for the following measurement of cosmic ray energy spectrum by thermal neutron detector.

Analysis of the Capability of Detection of Extensive Air Showers by Simple Scintillator Detectors

One of the main objectives of the CREDO project is to register cosmic-ray cascades in many distributed detectors in the search for so-called Cosmic-Ray Ensembles (CRE). This requires precise knowledge of the probability of detection of individual Extensive Air Showers (EAS) in a very wide range of energies and an analysis of their correlations. The standard approach based on detailed and extensive simulations is not possible for many such systems; thus, a faster method is developed. Knowing the characteristics of EAS from more general simulations, any required probability is calculated. Such probability depends on particle density at a given point, which is a function of the distance from the centre of the cascade, the energy, mass and the zenith angle of the primary cosmic-ray particle. It is necessary to use proper distribution of the number of secondary particles reaching the ground and their fluctuations. Finally, to calculate the total probability of EAS detection, the primary cosmic-ray spectrum and abundance of various particles in it have to be taken into account. The effective probability can be used to estimate the expected number of EAS events measured by a set of small detectors. In this work, results from several versions of calculations, with different complexity levels, are presented and compared with the first measurement performed with a test detector system. These results confirm that the majority of events observed with this small detector array are caused by cosmic-ray particles with very high energies. Such analysis can be also useful for the design of more effective systems in the future. Slightly larger systems of simple detectors may be used to distinguish cascades initiated by photons from those started from other primary cosmic-ray particles.

Cosmic-ray atmospheric cutoff energies of polar neutron monitors

The atmospheric cutoff, similarly to the geomagnetic cutoff, is the lower energy limit for cosmic ray particles that can reach a given location on the ground and be registered by a detector there, e.g., by a neutron monitor. It is caused by the decreasing intensity of a cosmic-ray cascade in the lower atmosphere. Although the geomagnetic cutoff is higher than atmospheric over the most of the Earth’s surface, the latter is dominant and therefore defines the neutron monitor count rate in the polar regions. The atmospheric cutoff decreases with the altitude, and this provides additional sensitivity of high-altitude polar neutron monitors to low-energy particles, mainly solar energetic protons during the so-called ground-level enhancement events.In this work, we quantitatively estimated the atmospheric cutoff energies for 21 polar neutron monitor stations in conditions without a significant solar energetic particle event. The cutoff value can be as low as about 300 MeV for protons (VOSTOK and DOMC/DOMB stations), which is notably lower than about 430 MeV at sea level. In addition to that, we estimated the worst case scenario of the strongest-ever observed ground-level enhancement event GLE#05, occurred on the 23rd of February, 1956, and showed that the atmospheric cutoff becomes as low as about 100 MeV. In other words, some neutron monitor stations can register particles with energies of even about 100 MeV during an exceptionally strong solar particle event. It is explained by the highly intensive and soft spectrum of the event in its early delayed phase.

Top pair production at ultra-high energies

The top quark, the heaviest quark and, indeed, the heaviest elementary particle known today, constitutes a novel probe of the long-lived medium in quark-gluon phase which, as expected, can be produced even in light nuclei collisions at ultra-high energies. Some distinctive features are considered for particle production in the top sector in ultra-high energy domain. The antitop-top pair production is studied within the quantum chromodynamics and effective field theory approach used for calculations of total partonic cross sections. Predictions for all observables are computed at NNLO in quantum chromodynamics and at LO in effective field theory. These quantitative results can be important for both the future collider experiments at center-of-mass energy frontier and the improvement of the phenomenological models for development of the cosmic ray cascades in ultra-high energy domain. Thus the study allows the better understanding of heavy particle production and emphasizes the exciting interrelation between the high-energy physics on accelerators and ultra-high energy cosmic ray measurements.

Global Characteristics of the Medium Produced in Ultra-High Energy Cosmic Ray Collisions

Estimations of some geometrical and bulk parameters are presented for the matter produced in various type collisions with ultra-high energy cosmic ray (UHECR) particles. Results for multiplicity density at midrapidity, decoupling time, and energy density are discussed for small and larger collision systems. Based on the analytic functions suggested previously elsewhere, estimations for a wide set of space-time quantities are obtained for emission region created in various particle collisions at energies of UHECR. The space particle densities at freeze-out are derived also and allow the possibility of novel features for secondary particle production like Bose-Einstein condensation at least for nuclear interactions with UHECR particles. The estimations obtained for global and geometrical parameters indicate the creation of deconfined quark-gluon matter with large enough volume and lifetime even in light nuclear collisions at UHECR energies. These quantitative results can be important for both the future collider experiments at center-of-mass energy frontier and the improvement of the phenomenological models for development of the cosmic ray cascades in ultra-high energy domain.

Atmospheric impacts of the strongest known solar particle storm of 775 AD

Sporadic solar energetic particle (SEP) events affect the Earth’s atmosphere and environment, in particular leading to depletion of the protective ozone layer in the Earth’s atmosphere, and pose potential technological and even life hazards. The greatest SEP storm known for the last 11 millennia (the Holocene) occurred in 774–775 AD, serving as a likely worst-case scenario being 40–50 times stronger than any directly observed one. Here we present a systematic analysis of the impact such an extreme event can have on the Earth’s atmosphere. Using state-of-the-art cosmic ray cascade and chemistry-climate models, we successfully reproduce the observed variability of cosmogenic isotope 10Be, around 775 AD, in four ice cores from Greenland and Antarctica, thereby validating the models in the assessment of this event. We add to prior conclusions that any nitrate deposition signal from SEP events remains too weak to be detected in ice cores by showing that, even for such an extreme solar storm and sub-annual data resolution, the nitrate deposition signal is indistinguishable from the seasonal cycle. We show that such a severe event is able to perturb the polar stratosphere for at least one year, leading to regional changes in the surface temperature during northern hemisphere winters.

Numerical calculations of cosmic ray cascade in the Earth's atmosphere using different particle interaction models

The interaction of primary cosmic rays with the Earth's atmosphere is investigated using the simulation toolkit GEANT4. Two reference lists of physical processes - QGSP_BIC_HP and FTFP_BERT_HP - are used in the simulations of cosmic ray cascade in the atmosphere. The cosmic ray neutron fluxes are calculated for mean level of solar activity, high geomagnetic latitudes and sea level. The calculated fluxes are compared with the published results of other analogous simulations and with experimental data.

Investigating the Characteristics of Longitudinal Profile of Primary Particles in Extensive Air Showers

One of the characteristics of longitudinal development of extensive air showers is the number of charged particles and depth of shower maximum in extensive air showers as a function of primary energy, which is often used to reconstruct the elemental composition of primary cosmic rays. Studying of extensive air shower characteristics was performed by investigating the longitudinal development parameters depending on Heitler model for different primary particles. The simulation of the number of charged particles and depth of shower maximum (NandXmax) in extensive air showers of particle cascades was performed using AIRES code for SIBYLL hadronic model for different primary particles like electron, positron, gamma quanta and iron nuclei at the energy range 1014-1019eV. The comparison between the simulated longitudinal development ofNandXmaxusing SIBYLL hadronic model with two hadronic models (QGSJET99 ans SIBYLL16) has shown an opportunity for determination of cosmic ray cascade interactions in extensive air showers.

Generalized self-veto probability for atmospheric neutrinos

Neutrino telescopes such as IceCube search for an excess of high energy neutrinos above the steeply falling atmospheric background as one approach to finding extraterrestrial neutrinos. For samples of events selected to start in the detector, the atmospheric background can be reduced to the extent that a neutrino interaction inside the fiducial volume is accompanied by a detectable muon from the same cosmic-ray cascade in which the neutrino was produced. Here we provide an approximate calculation of the veto probability as a function of neutrino energy and zenith angle.

Numerical calculations of cosmic ray cascade in the Earth’s atmosphere – Results for nucleon spectra

The interaction of primary cosmic rays with Earth’s atmosphere is investigated using the simulation toolkit Geant4. The yield functions of atmospheric nucleon fluxes are computed for the energy of primary cosmic ray particles ranging from 0.1 to 104GeV. The model is presented that enables to calculate differential particle fluxes in the atmosphere for given level of solar modulation and geomagnetic latitude. The accuracy of the computations is verified by experimental data taken under various conditions. The calculated particle fluxes can be employed for estimation of the production rates of cosmogenic nuclides in the atmosphere and Earth’s surface, for calculations of cosmic ray exposure dose for the public and soft-error failure rates in the microelectronics.

Fermi LAT observation of quiet gamma-ray emission from the Sun and first solar flares detection

We show the latest results of Fermi-LAT observations of the quiescent Sun during the first 18 months of the mission. During this period the solar activity was at its minimum, hence the solar emission induced by cosmic rays was at its maximum. Two emission components are clearly distinguished: the point-like emission from the solar disk due to the cosmic-ray cascades in the solar atmosphere, and the extended emission due to inverse Compton scattering of cosmic ray electrons on solar photons in the heliosphere. We present the entire analysis, showing spectra and angular profiles of both components and discuss the comparison with models and future plans. Finally we report on Fermi Large Area Telescope (LAT) detection of the first solar flares and discussing the possible emission mechanisms.

FERMILARGE AREA TELESCOPE OBSERVATIONS OF TWO GAMMA-RAY EMISSION COMPONENTS FROM THE QUIESCENT SUN

We report the detection of high-energy gamma rays from the quiescent Sun with the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope (Fermi) during the first 18 months of the mission. These observations correspond to the recent period of low solar activity when the emission induced by cosmic rays is brightest. For the first time, the high statistical significance of the observations allows clear separation of the two components: the point-like emission from the solar disk due to cosmic ray cascades in the solar atmosphere, and extended emission from the inverse Compton scattering of cosmic ray electrons on solar photons in the heliosphere. The observed integral flux (>100 MeV) from the solar disk is (4.6 +/- 0.2 [statistical error] +1.0/-0.8 [systematic error]) x10^{-7} cm^{-2} s^{-1}, which is ~7 times higher than predicted by the "nominal" model of Seckel et al. (1991). In contrast, the observed integral flux (>100 MeV) of the extended emission from a region of 20 deg radius centered on the Sun, but excluding the disk itself, (6.8 +/-0.7 [stat.] +0.5/-0.4 [syst.]) x10^{-7} cm^{-2} s^{-1}, along with the observed spectrum and the angular profile, are in good agreement with the theoretical predictions for the inverse Compton emission.

γ/hadron separation in very-high-energy [formula omitted]-ray astronomy using a multivariate analysis method

In recent years, Imaging Atmospheric Cherenkov Telescopes (IACTs) have discovered a rich diversity of very high energy (VHE, >100 GeV) γ -ray emitters in the sky. These instruments image Cherenkov light emitted by γ -ray induced particle cascades in the atmosphere. Background from the much more numerous cosmic-ray cascades is efficiently reduced by considering the shape of the shower images, and the capability to reduce this background is one of the key aspects that determine the sensitivity of a IACT. In this work we apply a tree classification method to data from the High Energy Stereoscopic System (H.E.S.S.). We show the stability of the method and its capabilities to yield an improved background reduction compared to the H.E.S.S. Standard Analysis.

Erratum: "Inverse Compton Scattering on Solar Photons, Heliospheric Modulation, and Neutrino Astrophysics" ([URL ADDRESS="/cgi-bin/resolve?2006ApJ...652L..65M" STATUS="OKAY"]ApJ, 652, L65 [2006][/URL

We study the inverse Compton scattering of solar photons by Galactic cosmic-ray electrons. We show that the gamma-ray emission from this process is substantial with the maximum flux in the direction of the Sun; the angular distribution of the emission is broad. This previously-neglected foreground should be taken into account in studies of the diffuse Galactic and extragalactic gamma-ray emission. Furthermore, observations by GLAST can be used to monitor the heliosphere and determine the electron spectrum as a function of position from distances as large as Saturn's orbit to close proximity of the Sun, thus enabling unique studies of solar modulation. This paves the way for the determination of other Galactic cosmic-ray species, primarily protons, near the solar surface which will lead to accurate predictions of gamma rays from pp-interactions in the solar atmosphere. These albedo gamma rays will be observable by GLAST, allowing the study of deep atmospheric layers, magnetic field(s), and cosmic-ray cascade development. The latter is necessary to calculate the neutrino flux from pp-interactions at higher energies (>1 TeV). Although this flux is small, it is a "guaranteed flux" in contrast to other astrophysical sources of neutrinos, and may be detectable by km^3 neutrino telescopes of the near future, such as IceCube. Since the solar core is opaque for very high-energy neutrinos, directly studying the mass distribution of the solar core may thus be possible.

Production of 3He in crustal rocks by cosmogenic thermal neutrons

Accurate determination of cosmogenic 3He concentrations in minerals has to account for nucleogenic 3He produced from the reaction of thermalized neutrons with 6Li. Thermal neutrons from the cosmic ray cascade are typically not considered. However, in exposed basalts and granites the flux of cosmogenic thermal neutrons (CTN) is generally 10–200 times higher than the thermal neutron flux produced by (α,n) reactions in the rock, with the absolute values dependent on composition and geographic location. The reaction of CTN with Li can account for 5–50% of the cosmogenic 3He in minerals in typical granitiod rocks, depending on the Li content and distribution, and petrography of the rock, and may be considerably higher in special cases. In basalts this contribution is usually lower (1.5–6%) but may still warrant consideration. The strong depth-dependence of CTN-produced 3He in rock may be used to assess erosion of landforms, similar to CTN-produced 36Cl; however, as 3He is stable it has the potential to extend the useful time range to older surfaces.

The role of charm at ultrahigh energies

Experimental data on cosmic ray cascades with enlarged attenuation lengths (Tien-Shan effect) are discussed in terms of charmed particles production. The obtained values of the charm hadron production cross-section at high energies are presented and confronted with recent accelerator data. The seeming absence of GZK-cutoff is ascribed to the delay of evolution of the cascades with charm in the atmosphere. The important role of large cross section of charm hadron production in the development of inclined showers in the atmosphere at ultrahigh energies is shown.

Inverse Compton Scattering on Solar Photons, Heliospheric Modulation, and Neutrino Astrophysics

We study the inverse Compton scattering of solar photons by Galactic cosmic-ray electrons. We show that the γ-ray emission from this process is substantial, with the maximum flux in the direction of the Sun; the angular distribution of the emission is broad. This previously neglected foreground should be taken into account in studies of the diffuse Galactic and extragalactic γ-ray emission. Furthermore, observations by GLAST can be used to monitor the heliosphere and determine the electron spectrum as a function of position from distances as large as Saturn's orbit to close proximity of the Sun, thus enabling unique studies of solar modulation. This paves the way for the determination of other Galactic cosmic-ray species, primarily protons, near the solar surface, which will lead to accurate predictions of γ-rays from p-p interactions in the solar atmosphere. These albedo γ-rays will be observable by GLAST, allowing the study of deep atmospheric layers, magnetic field(s), and cosmic-ray cascade development. The latter is necessary to calculate the neutrino flux from p-p interactions at higher energies (>1 TeV). Although this flux is small, it is a "guaranteed flux" in contrast to other astrophysical sources of neutrinos and may be detectable by km3 neutrino telescopes of the near future, such as IceCube. Since the solar core is opaque for very high energy neutrinos, directly studying the mass distribution of the solar core may thus be possible.

Charm in cosmic rays (The long-flying component of EAS cores)

Experimental data on cosmic ray cascades with enlarged attenuation lengths (Tien–Shan effect) are presented and analyzed in terms of charm hadroproduction. The very first estimates of charm hadroproduction cross sections from experimental data at high energies are confirmed and compared with recent accelerator results.