Search

We present a summary of recent tests and measurements of hadronic interaction properties with air showers. This report has a special focus on muon density measurements. Several experiments reported deviations between simulated and recorded muon densities in extensive air showers, while others reported no discrepancies. We combine data from eight leading air shower experiments to cover shower energies from PeV to tens of EeV. Data are combined using the z-scale, a unified reference scale based on simulated air showers. Energy-scales of experiments are cross-calibrated. Above 10 PeV, we find a muon deficit in simulated air showers for each of the six considered hadronic interaction models. The deficit is increasing with shower energy. For the models EPOS-LHC and QGSJet-II.04, the slope is found significant at 8 sigma. [ABSTRACT FROM AUTHOR]

The origin and nature of ultrahigh-energy cosmic rays (UHECRs) are one of the most intriguing mysteries in particle astrophysics and astronomy. The two largest observatories, the Pierre Auger Observatory and the Telescope Array Experiment, are steadily observing UHECRs in both hemispheres in order to better understand their origin and associated acceleration mechanisms at the highest energies. We highlight their latest results including on-going upgrades, AugerPrime and TA×4, and then address the requirements for a next-generation observatory. We share recent updates and perspectives for a future ground array of fluorescence detectors, addressing the requirements for a large-area, low-cost detector suitable for measuring the properties of the highest energy cosmic rays with an unprecedented aperture. [ABSTRACT FROM AUTHOR]

The Carpet air shower array of the Baksan Neutrino Observatory is in operation for a long time, and it was modernized more than once. A short review of important results obtained with this array is given, as well as future prospects, since at the moment the new project called Carpet-3 is in progress, using the old array as its basis. The purpose of the new project is to substantially increase the muon detector area (quite soon up to 400 m2 and later up to 600 m2). This improvement will allow one to reach a very good sensitivity to diffuse cosmic photons by selecting muon-poor showers. The energy range where the new experiment will be competitive with other experiments of gamma-ray astronomy is near and below 100 TeV. [ABSTRACT FROM AUTHOR]

The detection of cosmic rays via the electric field (the so-called radio detection) is nowadays a fully operative technique. With the aim of exploring the low-frequency part of the emission spectrum (below 10 MHz), the EXTASIS experiment has been conceived. Located within the CODALEMA experiment at the Nançay radio-observatory, EXTASIS measures the low-frequency emission coming from the extensive air showers created by cosmic rays. Being able to calculate the electric field at low frequency is crucial in order to correctly interpret our results. We present some results from the EXTASIS experiment and discuss the calculation of the low-frequency radio signal. We also present a new formula for the electric field of a particle track within two semi-infinite media (air and soil). [ABSTRACT FROM AUTHOR]

Antenna arrays are beginning to make important contributions to high energy astroparticle physics supported by recent progress in the radio technique for air showers. This article provides an update to my more extensive review published in Prog. Part. Nucl. Phys. 93 (2017) 1. It focuses on current and planned radio arrays for atmospheric particle cascades, and briefly references to a number of evolving prototype experiments in other media, such as ice. While becoming a standard technique for cosmic-ray nuclei today, in future radio detection may drive the field for all type of primary messengers at PeV and EeV energies, including photons and neutrinos. In cosmic-ray physics accuracy becomes increasingly important in addition to high statistics. Various antenna arrays have demonstrated that they can compete in accuracy for the arrival direction, energy and position of the shower maximum with traditional techniques. The combination of antennas and particles detectors in one array is a straightforward way to push the total accuracy for high-energy cosmic rays for low additional cost. In particular the combination of radio and muon detectors will not only enhance the accuracy for the cosmic-ray mass composition, but also increase the gamma-hadron separation and facilitate the search for PeV and EeV photons. Finally, the radio technique can be scaled to large areas providing the huge apertures needed for ultra-high-energy neutrino astronomy. [ABSTRACT FROM AUTHOR]

One of the main objectives of cosmic-ray studies are precise measurements of the energy and chemical composition of particles with extreme energies. Large and sophisticated detectors are used to find events seen as showers starting in the Earth's atmosphere with recorded energies larger than 100 EeV. However, a Cosmic-Ray Ensemble (CRE) developing before reaching the Earth as a bunch of correlated particles may spread over larger areas and requires an extended set of detectors to be discovered. The Cosmic-Ray Extremely Distributed Observatory (CREDO) is a solution to find such phenomena. Even simple detectors measuring the particle arrival time only are useful in this approach, as they are sufficient both to provide candidate CRE events and to determine the direction from which they are arriving. [ABSTRACT FROM AUTHOR]

The LHCb experiment is designed to study flavor physics of b and c quarks. The detector is optimized for the study of identified hadrons produced in the forward direction, which also makes LHCb very interesting for the understanding of cosmic-ray induced air showers. LHCb is analysing proton-proton, protonlead, and lead-lead collisions. As a unique feature, LHCb is also studying beam interactions with noble gases using its SMOG system. We present recent measurements of charmed mesons, which are used to obtain production cross-sections, to constrain the parton PDF, to test pomeron and multi-particle interactions, nuclear and collective effects. These mostly have an indirect impact on the modeling of hadronic interactions. Finally, we present a direct measurement of the anti-proton production in proton collisions with helium gas, which are important for the understanding of AMS-02 and PAMELA data. [ABSTRACT FROM AUTHOR]

Digital archives for nuclear emulsion data of past experiments, such as in cosmic-ray and accelerator physics, is being studied and prepared. Significant progress of HTS, which is an automatic read-out system for tracks recorded in emulsion, is achieving a read-out speed of about 1m2/hour and opens a possibility to read all tracks recorded in emulsion of past experiments. Current status of our first trial with RUNJOB emulsion plates is reported. Till now, the top-most 10 plates had been scanned by HTS and preliminary data is presented. [ABSTRACT FROM AUTHOR]

Cygnus X-3 binary system is a famous object studied over the wide range of electromagnetic spectrum. Early detections of ultra-high energy gamma-rays from Cygnus X-3 by Kiel, Havera Park and then by Akeno triggered the construction of several large air shower detectors. Also, Cygnus X-3 has been proposed to be one of the most powerful sources of charged cosmic ray particles in the Galaxy. The results of twenty-year observations of the Cyg X-3 binary at energies 800 GeV - 85 TeV are presented with images, spectra during periods of flaring activity and at low flux periods. The correlation of TeV flux increases with flaring activity at the lower energy range of X-ray and radio emission from the relativistic jets of Cygnus X-3 is found as well as 4.8-hour orbital modulation of TeV γ-ray intensity. Detected modulation of TeV γ-ray emission with orbit and important characteristics of Cyg X-3 such as the high luminosity of the companion star and the close orbit leads to an efficient generation of γ-ray emission through inverse Compton scattering in this object. The different type variability of very high-energy γ-emission and correlation of radiation activity in the wide energy range can provide essential information on the mechanism of particle production up to very high energies. [ABSTRACT FROM AUTHOR]

The Large High Altitude Air Shower Observatory (LHAASO) is a new hybrid array for very high energy gamma ray astronomy and cosmic ray physics. The KM2A array, one of the main parts of LHAASO, covers an area of 1.3 km2 to observe gamma rays above 10 TeV up to 1 PeV for many sources. A prototype with 1% the size of the whole KM2A has been in stable operation for more than two years. A Monte Carlo simulation program named G4KM2A was developed; based on this work, the trigger rate, hit multiplicity, angular and core reconstruction are compared with KM2A prototype data. Finally, the moon shadow with -6.5 significance was obtained. The G4KM2A simulation results are consistent with KM2A prototype data and can be used for the whole KM2A array in future. [ABSTRACT FROM AUTHOR]

The present point of view on the sources of cosmic rays in Galaxy considers explosions of supernovae as sources of these particles up to energies of 1017 eV. However, the experimental data obtained with Pamela, Fermi, AMS-02 spectrometers requires the existence of nearby sources of cosmic rays at distances less then 1 kpc from the solar system. These sources could explain such experimental data as the growth of the ratio of galactic positrons to electrons with increasing energy, the complex dependence of the exponent of the proton and alpha spectra from the energy of these particles, the appearance of an anomaly component in cosmic rays. We consider active dwarf stars as possible sources of galactic cosmic rays in the energy range up to 1014 eV. These stars produce powerful stellar flares. The generation of high-energy cosmic rays has to be accompanied by high-energy gamma-ray emission. Here we present the SHALON long-term observation data aimed at searching for gamma-ray emission above 800 GeV from active red dwarf stars. The data obtained during more than 10 years observations of the dwarf stars V962 Tau, V780 Tau, V388 Cas and V1589 Cyg were analyzed. The high-energy gamma-ray emission in the TeV energy range, mostly of the flaring type from the sources mentioned above, was detected. This result confirms that active dwarf stars are also the sources of high-energy galactic cosmic rays. [ABSTRACT FROM AUTHOR]

The future space-based GAMMA-400 gamma-ray telescope will be installed on the Navigator platform of the Russian Astrophysical Observatory. A highly elliptical orbit will provide observations for 7-10 years of many regions of the celestial sphere continuously for a long time (~ 100 days). GAMMA-400 will measure gamma-ray fluxes in the energy range from ~ 20 MeV to several TeV and electron + positron fluxes up to ~ 20 TeV. GAMMA-400 will have an excellent separation of gamma rays from the background of cosmic rays and electrons + positrons from protons and an unprecedented angular (~ 0.01° at Eγ = 100 GeV) and energy (~ 1% at Eγ = 100 GeV) resolutions better than for Fermi-LAT, as well as ground-based facilities, by a factor of 5-10. Observations of GAMMA-400 will provide new fundamental data on discrete sources and spectra of gamma-ray emission and electrons + positrons, as well as the nature of dark matter. [ABSTRACT FROM AUTHOR]

Observation of cosmic gamma rays is important in the understanding of high-energy objects or phenomena in the universe. Since 2008, the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope (Fermi-LAT) has surveyed the sub-GeV/GeV gamma-ray sky and achieved high statistics measurements. However, observation at low galactic latitudes remains difficult owing to the lack of angular resolution, and new issues following the operation of Fermi-LAT have arisen. We devised a precise gamma-ray observation project, Gamma-Ray Astro-Imager with Nuclear Emulsion (GRAINE), using balloon-borne emulsion gammaray telescopes to realize high angular resolution, polarization-sensitive, and large-aperture observations in the 10 MeV–100 GeV energy region. Following basic developments on the ground, we performed three balloon-borne experiments with upgraded instruments. In this paper, we present results from the second balloon experiment in 2015, a report on the latest balloon experiment conducted on April 26, 2018, and a recent study on hadronic interactions using proton beams. [ABSTRACT FROM AUTHOR]

Measuring the knees of the cosmic ray spectra for individual species is a very important approach to solve the problem of the origin of ultra high energy galactic cosmic rays. The knee of the iron spectrum is implied to be above 10 PeV from previous experiments, such as ARGO-YBJ and LHAASO-WFCTA. LHAASO is a suitable size for measurements with the required precision. The key is to separate iron nuclei from all cosmic ray samples. In this paper, we identify a couple of variables that are sensitive to the composition of showers recorded by the detector arrays in LHAASO. A multi variate analysis is proposed for the separation. The efficiency and purity of the selection for demanded species are optimized by well configuring the LHAASO array using the LHAASO simulation tools. [ABSTRACT FROM AUTHOR]

The HAWC (High Altitude Water Cherenkov) observatory, located on the slopes of the Sierra Negra volcano in the state of Puebla, Mexico, was designed with the goal of detecting gamma-rays in the Teraelectron- volt energy range. However, most of the air showers that are detected with the observatory, with a rate of ≈ 27 kHz, are of hadronic origin. This makes that, after three years of operations, HAWC has accumulated a very large data set that allows to perform cosmic-ray analysis of high precision. The details of the observatory operation, as well as a selection of recent results in cosmic-ray physics are discussed in this work. [ABSTRACT FROM AUTHOR]

The Alpha Magnetic Spectrometer (AMS-02) is a wide acceptance high-energy physics experiment installed on the International Space Station in May 2011 and operating continuously since then. With a collection rate of approximately 1.7 × 1010 events/year, and the combined identification capabilities of 5 independent detectors, AMS-02 is able to precisely separate cosmic rays light nuclei (1 ≤ Z ≤ 8). Knowledge of the precise rigidity dependence of the light nuclei fluxes is important in understanding the origin, acceleration, and propagation of cosmic rays. AMS-02 collaboration has recently released the precise measurements of the fluxes of light nuclei as a function of rigidity (momentum/charge) in the range between 2 GV and 3 TV. Based on the observed spectral behaviour, the light nuclei can be separated in three distinct families: primaries (hydrogen, helium, carbon, and oxygen), secondaries (lithium, beryllium, and boron), and mixed (nitrogen). Spectral indices of all light nuclei fluxes progressively harden above 100 GV. Primary cosmic ray fluxes have an identical hardening above 60 GV, of about γ = 0.12 ± 0.04. While helium, carbon and oxygen have identical spectral index magnitude, the hydrogen spectral index shows a different magnitude, i.e. the primary-to-primary H/He ratio is well described by a single power law above 45 GV with index -0.077 ± 0.007. Secondary cosmic ray fluxes have identical rigidity dependence above 30 GV. Secondary cosmic rays all harden more than primary species, and together all secondary-to-primary ratios show a hardening difference of 0.13 ± 0.03. Remarkably, the nitrogen flux is well described over the entire rigidity range by the sum of the primary flux equal to 9% of the oxygen flux and the secondary flux equal to 62% of the boron flux. [ABSTRACT FROM AUTHOR]

Using our developed new relativistic viscous hydrodynamics code, we investigate the QGP bulk property from comparison with the ALICE data of Pb+Pb √sNN = 2.76 TeV collisions at the Large Hadron Collider. [ABSTRACT FROM AUTHOR]

We review the phenomenology of relativistic nuclear collisions in the light of ultra-high energy cosmic ray physics. A novel phase of quantum chromodynamics called quark-gluon plasma is expected to appear in nuclear collisions at high energies. The produced hot matter is found to be well-described as a relativistic fluid with small viscosity. We show that the transport coefficient can be quantitatively extracted by comparing theoretical estimations of viscous hydrodynamic models to experimental data. [ABSTRACT FROM AUTHOR]

The main features of the rapidity density distribution of the produced hadrons in multiple particle production in nucleon collisions are; (a) the distribution in the forward region (ȳ ≥ 0) has a shape similar to the Fermi distribution, (b) the distribution in the most forward region reaches almost the maximum rapidity ymax = ln(√s/M) (M : nucleon mass), and (c) the shrinkage of the distribution from the maximum rapidity increases with the incident energy (i.e. violation of Feynman scaling law). These features are possible to be described by the assumptions that; (1) a fireball of the gas (made of nuclear matter, with the temperature Ti and with the shape of the incident nucleon with Lorentz contraction) is produced in the collision, (2) the fireball makes the adiabatic expansion, and (3) the constituent particles of the gas obey the Maxwell-Boltzmann distribution of the temperature Tf in the final state. [ABSTRACT FROM AUTHOR]

We summarize the main features of the hadronic interaction model EPOS, which is used for cosmic ray air shower simulations but also for p-p, p-A, and A-A collisions to be compared with experimental data from LHC and RHIC. [ABSTRACT FROM AUTHOR]

After a brief introduction of parton saturation in hadrons at small Bjorken's x, we recapitulate its phenomenological implications in high-energy particle production, such as longitudinal correlation, particle mulctiplicity, limiting fragmentation and charm quark production, which may have relevance to study of highenergy cosmic ray physics. [ABSTRACT FROM AUTHOR]

High-energy neutrino-nucleus interactions are discussed by considering neutrino-oscillation experiments and ultra-high-energy cosmic neutrino interactions. The largest systematic error for the current neutrino oscillation measurements comes from the neutrino-nucleus interaction part, and its accurate understanding is essential for high-precision neutrino physics, namely for studying CP violation in the lepton sector. Depending on neutrino beam energies, quasi-elastic, resonance, Regge, or/and deep inelastic scattering (DIS) processes contribute to the neutrino cross section. It is desirable to have a code to calculate the neutrino-nucleus cross section in any kinematical range by combining various theoretical descriptions. On the other hand, the IceCube collaboration started obtaining cross section data up to the 1015 eV range, so that it became necessary to understand ultra-high-energy neutrino interactions beyond the artificial lepton-accelerator energy range. For future precise neutrino physics including the CP measurement, it is also necessary to understand accurate nuclear corrections. The current status is explained for nuclear corrections in DIS structure functions. The possibility is also discussed to find gravitational sources within nucleons and nuclei, namely matrix elements of quark-gluon energy-momentum tensor. They could be probed by neutrino interactions without replying on direct ultra-weak "gravitational interactions" with high-intensity neutrino beams, possibly at a future neutrino factory, by using techniques of hadron tomography. [ABSTRACT FROM AUTHOR]

We review recent developments of an event generator JAM microscopic transport model to simulate high energy nuclear collisions, especially at high baryon density regions. Recent developments focus on the collective effects: implementation of nuclear potentials, equation of state (EoS) modified collision term, and dynamical integration of fluid dynamics. With these extensions, we can discuss the EoS dependence of the transverse collective flows. [ABSTRACT FROM AUTHOR]

Transverse single spin asymmetry, AN, of very forward π0 production from polarized p + p collisions provides new information toward an understanding of its production mechanism. AN of forward π0 in the pseudorapidity region of 3 < η < 4 has been described by the partonic structure of the proton in the perturbative QCD framework. However, recent data indicates a potential contribution from not only partonic but also diffractive interactions. In order to provide a new insight on the origin of the AN, we measured the very forward π0 production in the pseudorapidity region of 6 < η from √s = 510 GeV polarized p + p collisions at RHIC in 2017. We report our measurement of the very forward π0 over the transverse momentum range of 0 < pT < 1 GeV/c and the preliminary result. [ABSTRACT FROM AUTHOR]

The very-forward energy production in hadron collisions is of paramount importance for the understanding of ultra-high energy cosmic ray air showers. The CASTOR calorimeter of CMS is located at -6:6 < η < -5:2 in the phase-space where the peak of energy is deposited at LHC. The composition and characteristics of the particles in this phase-space have a determining impact on the formation of air shower cascades. An overview of various energy measurements performed with CASTOR is reported and possible implications for cosmic ray physics are outlined. [ABSTRACT FROM AUTHOR]

We present a new model for generating complete exclusive hadronic final states in high energy collisions involving heavy ions. The model is called Angantyr and is inspired by the old Fritiof model, building on the concept of wounded nucleons. [ABSTRACT FROM AUTHOR]

One of the applications of the hadronic interaction model Sibyll is the simulation of extensive air showers of ultra-high energy cosmic rays. In recent years it has become more and more clear that simulations do not agree with measurements when it comes to observables related to muons in air showers. We discuss the processes in Sibyll that are directly related to muon production in extensive air showers and describe their relation to shower observables. [ABSTRACT FROM AUTHOR]

We discuss in some detail the physics content of the new model, QGSJET-III-01, focusing on major problems related to the treatment of semihard processes in the very high energy limit. A special attention has been payed to the main improvement, compared to the QGSJET-II model, which is related to a phenomenological treatment of leading power corrections corresponding to final parton rescattering off soft gluons. In particular, this allowed us to use a twice smaller separation scale between the soft and hard parton physics, compared to the previous model version, QGSJET-II-04. Preliminary results obtained with the new model are also presented. [ABSTRACT FROM AUTHOR]

Professor Oscar Saavedra San Martin passed away on 8 April 2018 at Bonvicino-Italy. The Organizing Committee of the 20th International Symposium on Very High Energy Cosmic Rays-ISVHECRI-2018, held in Nagoya, Japan decided to pay a tribute to Oscar, born on 29 June, 1940 at LaPaz, Bolivia. During the banquet, a small presentation in honour to Oscar was scheduled in a special section of Wednesday 23 May 2018. His last participation was at the 19th ISVHECRI held in Moscow, Russian Federation, during the period 22-27 August 2016. Oscar joined the BASJE-Bolivian Air Shower Joint Experiment in 1966, a collaboration between Bolivia and Japan. The aim of BASJE was to search for high energy γ's coming mainly from the center of Galaxy, due to the Chacaltaya location. From 1967 to 1968 he served as Director of the Cosmic Ray Laboratory at Chacaltaya following the BASJE experiments. Due to his huge contribution to Bolivian Science, Oscar received in 2009 the Doctor Honoris Causa title and was nominated Scientific Ambassador of his motherland. He gained his Doctorate from Milan University in 1964 and after immigration to Italy was a staff member of Torino University. On his retirement Torino University awarded him the title of Emeritus Professor. [ABSTRACT FROM AUTHOR]

An international cooperation, named Brasil-Japan Collaboration of Chacaltaya Emulsion Chamber Experiment (B-J Collaboration) exposed 2.35 × 108 m2.s, during the period 15thJun, 1962 till 10thMay, 1988. It corresponds to 22 'runs' on Cosmic Rays and in this figure are not included photosensitive material set in the lower part of the two-storied emulsion chamber. Although 3 more 'runs' occurred after 1988, they were not included either, because they were not yet properly measured and because they contain mixed Japanese and Russian films. Chacaltaya Mountain was firstly used in 1947 for 2 meson observations and π - μ decays. It was a wise choice not only for these observations but also for the B-J Collaboration and for the Alpaca Project, running at neighbouring sites. The main results observed by the B-J Collaboration are presented. [ABSTRACT FROM AUTHOR]

Although they are best known for studying astrophysical neutrinos, neutrino telescopes like IceCube can study neutrino interactions, at energies far above those that are accessible at accelerators. In this writeup, I present two IceCube analyses of neutrino interactions at energies far above 1 TeV. The first measures neutrino absorption in the Earth, and, from that determines the neutrino-nucleon cross-section at energies between 6.3 and 980 TeV. We find that the cross-sections are 1.30 +0.21-0.19 (stat.) +0.39-0.43 (syst.) times the Standard Model crosssection. We also present a measurement of neutrino inelasticity, using νμ charged-current interactions that occur within IceCube. We have measured the average inelasticity at energies from 1 TeV to above 100 TeV, and found that it is in agreement with the Standard Model expectations. We have also performed a series of fits to this track sample and a matching cascade sample, to probe aspects of the astrophysical neutrino flux, particularly the flavor ratio. [ABSTRACT FROM AUTHOR]

Results of analysis of experimental data on cascade showers with energies of 0.1 – 10 TeV initiated by muons in the Cherenkov water detector NEVOD are presented. The method of selection and reconstruction of cascade parameters in the volume of the detector is discussed. Experimental distributions of cascade axes in zenith angle and energy spectrum of cascades are obtained. The measured distributions are compared with results of calculations. [ABSTRACT FROM AUTHOR]

The paper presents results on the longitudinal development of air showers of ultra-high energies obtained from radio emission measurements at the Yakutsk array. The energy, the depth of maximum development of individual showers are determined and a statistical analysis of Xmax in order to estimate the fluctuation of air shower development σ(Xmax) in the energy region 1017-1018 eV is performed. It is shown that σ(Xmax) in the energy region 1017-1018 eV is equal to 50-60 g·cm-2, which doesn't contradict with a mixed composition of cosmic rays - protons and helium nuclei. This is also indicated by data of the Xmax value dependence on energy. [ABSTRACT FROM AUTHOR]

Determination of the primary particle mass using air fluorescence or a Cherenkov detector array is one of the most difficult task of experimental cosmic ray studies. The information about the primary particle mass is a compound of the produced particle multiplicity, inelasticity, interaction cross-section and many other parameters, thus it is necessary to compare registered showers with sophisticated Monte-Carlo simulation results. In this work we present results of the studies of at least three possible ways of extrapolating proton- Nucleus and Nucleus-Nucleus cross sections to cosmic ray energies based on the Glauber theory. They are compared with experimental accelerator and cosmic ray data for the proton-air cross section. We also present results of the EAS development with the most popular high-energy interaction models adopted in the CORSIKA program with our cross section extrapolations. The average position of the shower maximum and the width of its distribution are compared with experimental data and some discussion is given. [ABSTRACT FROM AUTHOR]

The experimental technique of fluorescence light measurement is used for indirect observations of cosmic ray particles at very high energies. Extensive Air Showers (EAS) initiated by Extreme Energy Cosmic Rays (EECRs), up to 100 EeV and entering the Earth's atmosphere, are simulated with the CORSIKA package. The influence of different simulation parameters on the EAS characteristics is studied, especially on the longitudinal distribution of charged particles, depth of shower maximum and energy released to the air. By taking the atmospheric scattering of light into account, the number of fluorescence photons, with wavelengths between 300-430 nm, and their arrival time distribution to an ideal space telescope are calculated. [ABSTRACT FROM AUTHOR]

Complex analysis of the Yakutsk array data in order to find air showers produced by photons with energy ≥1018 eV is carried out. On the basis of simulations and experimental data, selection criteria are formed and air showers with characteristics close to those criteria are selected. Using the data an upper limit of the integral photon flux in cosmic radiation of ultra-high energies is obtained. [ABSTRACT FROM AUTHOR]

IceCube is a cubic-kilometer Cherenkov detector in the deep ice at the geographic South Pole. The dominant event yield is produced by penetrating atmospheric muons with energies above several 100 GeV. Due to its large detector volume, IceCube provides unique opportunities to study atmospheric muons with large statistics in detail. Measurements of the energy spectrum and the lateral separation distribution of muons offer insights into hadronic interactions during the air shower development and can be used to test hadronic models. We will present an overview of various measurements of atmospheric muons in IceCube, including the energy spectrum of muons between 10 TeV and 1 PeV. This is used to derive an estimate of the prompt contribution of muons, originating from the decay of heavy (mainly charmed) hadrons and unflavored mesons. We will also present measurements of the lateral separation distributions of TeV muons between 150m and 450m for several initial cosmic ray energies between 1 PeV and 16 PeV. Finally, the angular distribution of atmospheric muons in IceCube will be discussed. [ABSTRACT FROM AUTHOR]

The Yakutsk array has been used to study cosmic rays since 1974. Charged particles such as electrons, positrons and muons are detected, as well as radio signals emitted by air showers. However, the characteristic shower component detected by the array is Cherenkov light. This article briefly reviews recent results from the Yakutsk array group. [ABSTRACT FROM AUTHOR]

The origin of ultra-high energy cosmic rays (UHECRs) has been a long-standing mystery. One of the uncertainties in UHECR observation derives from the hadronic interaction model used for air shower Monte-Carlo (MC) simulations. The number of muons observed at ground level from UHECR induced air showers is expected to depend upon the composition of primary cosmic rays. The MC prediction also depends on hadronic interaction models. One may test the hadronic interaction models by comparing the measured number of muons with the MC prediction. The Telescope Array (TA) is the largest experiment in the northern hemisphere observing UHECR in Utah, USA. It aims to reveal the origin of UHECR by studying the energy spectrum, mass composition and anisotropy of cosmic rays by utilizing an array of surface detectors (SDs) and fluorescence detectors. We studied muon densities in the UHE extensive air showers by analyzing the signal of TA SD stations for highly inclined showers which should have high muon purity. A high muon purity condition is imposed that requires the geometry of the shower and relative position of the given station and implies that muons dominate the signal. On condition that the muons contribute about 65% of the total signal, the number of particles from air showers is typically 1.88 ± 0.08(stat:) ± 0.42(syst:) times larger than the MC prediction with the QGSJET II-03 model for protons. The same feature was also obtained for other hadronic models, such as QGSJET II-04. [ABSTRACT FROM AUTHOR]

The hybrid design of the Pierre Auger Observatory allows for the measurement of a number of properties of extensive air showers initiated by ultra-high energy cosmic rays. By comparing these measurements to predictions from air shower simulations, it is possible to both infer the cosmic ray mass composition and test hadronic interactions beyond the energies reached by accelerators. In this paper, we will present a compilation of results of air shower measurements by the Pierre Auger Observatory which are sensitive to the properties of hadronic interactions and can be used to constrain the hadronic interaction models. The inconsistencies found between the interpretation of different observables with regard to primary composition and between their measurements and simulations show that none of the currently used hadronic interaction models can provide a proper description of air showers and, in particular, of the muon production. [ABSTRACT FROM AUTHOR]

The Telescope Array is the largest hybrid cosmic ray detector in the Northern hemisphere designed to measure primary particles in 4 PeV to 100 EeV range. The main TA detector consists of an air shower array of 507 plastic scintillation counters on a 1.2 km square grid and fluorescence detectors at three stations overlooking the sky above the air shower array. The experiment and its recent measurements - spectrum, composition, and anisotropy - is reviewed. Recently the construction of the TA Low energy Extension (TALE) detector, which consists of an additional fluorescence detector and an infill array, was finished. TALE lowers the energy threshold of TA down to 4 PeV. We are also constructing the TAx4 detector to increase statistics in particular at the highest energies. The current status and the future prospects of these new TAx4 experiments is reported. [ABSTRACT FROM AUTHOR]

In this paper some recent results from the Pierre Auger Collaboration are presented. These are the measurement of the energy spectrum of cosmic rays over a wide range of energies (1017.5 to above 1020 eV), studies of the cosmic-ray mass composition with the fluorescence and surface detector of the Observatory, the observation of a large-scale anisotropy in the arrival direction of cosmic rays above 8 × 1018 eV and indications of anisotropy at intermediate angular scales above 4 × 1019 eV. The astrophysical implications of the spectrum and composition results are also discussed. Finally the progress of the upgrade of the Observatory, AugerPrime is presented. [ABSTRACT FROM AUTHOR]

Uncertainties of the model energy spectra of the most energetic secondary charged mesons are discussed. Computer simulations of the partial energy spectra of the atmospheric vertical muons induced by primary cosmic particles with various fixed energies in terms of hadronic interactions models had been carried out with the help of the CORSIKA package. These partial spectra have been convolved with the contemporary spectra of the primary cosmic particles in the energy range 0.1-10 000 TeV. Results of simulations are compared with the contemporary data of the atmospheric vertical muon flux. Comparison shows that all models underestimate the production of secondary charged π±-mesons (and K±-mesons) by a factor of ~ 1.4 ÷ 2 at the highest energies. This underestimation induces a more rapid development of extensive air showers in the atmosphere and results in uncertainties in estimates of energy and composition of the primary cosmic particles. [ABSTRACT FROM AUTHOR]

The Large Hadron Collider provides collisions of protons and nuclei at the highest energies available in the laboratory. A variety of recent results for minimum-bias pp, p+Pb and Pb+Pb collisions obtained by the ATLAS experiment is presented. For pp collisions they include the total and inelastic cross section, properties of minimum-bias events, underlying event characteristics and measurements of diffractive processes. The results for p+Pb and Pb+Pb collisions that are relevant for cosmic ray studies are also presented. [ABSTRACT FROM AUTHOR]

The atmospheric neutrino flux has been measured by several experiments and its understanding has been improved by comparing with the theoretical predictions in detail. In this paper recent results of the flux measurements will be reviewed and discussed. [ABSTRACT FROM AUTHOR]

It is well known that the correlation of atmospheric neutrinos and muons are simply correlated in the energy region of 1–10 GeV, and used for the test bench of the hadronic interaction model used for the calculation of the atmospheric neutrino flux. However, the correlation becomes unclear for neutrinos in the energy range below 1 GeV, which is important for the study of mass ordering of neutrino and CP phase of the neutrino mass. We extend the study of the correlation to the lower neutrino energies and find that the atmospheric muon flux observed at high altitude shows a good correlation to the atmospheric neutrino flux, and could be used to calibrate the hadronic interaction model. [ABSTRACT FROM AUTHOR]

The Extensive Air Shower (EAS) data collected by the Horizon-10T detector system has numerous events exhibiting the unusual spatial and temporal structure. These are events typically with two to four pulses of tens of ns wide that are present at distances above 300 m from the EAS axis, with these pulses being delayed by hundreds of ns. Each of such pulse groups were registered simultaneously by several detectors separated by up to a km from each other. The detectors brief overview and the analysis of simulated EAS by the CORSIKA software package are given in this article. The analysis indicates that such events with unusual structure cannot be formed by showers with EM and hadronic components only. This indicates a possibility for a new process observation beyond the standard model description in the energy range above ~1018 eV. [ABSTRACT FROM AUTHOR]

A phenomenon of abnormally weak absorption of very high energy cosmic ray hadrons in thick lead blocks is discussed. This phenomenon was first observed in a Tien Shan high altitude experiment to study hadronic cores of extensive air showers (EAS) with a deep ionization calorimeter and encouraged researchers to introduce the hypothesis of the so-called long-flying or penetrating cosmic ray component. A similar effect was detected later with deep uniform lead X-ray emulsion chambers (XREC) at the Pamirs, which we discuss in detail. To establish the nature of the phenomenon we are have carried out dedicated experiments at the Tien Shan and at the Pamirs by exposing two-storey XRECs with large air gaps. According to detailed simulation of the chamber response, these experiments are very sensitive to the production of charmed hadrons in the forward kinematic region and can prove a hypothesis that the phenomenon under study can be explained on the assumption of very high values of charm particle production cross section at 〈ELab〉 ~ 75 TeV in the forward kinematic region at xLab ≳ 0.1 which are near the upper limit of recent results of collider experiments, i.e., σpp→c¯c ~ 8 mb. The same factor makes it possible to fit all the features of the experimental hadron absorption curve observed by means of deep uniform lead XRECs, including its bending at a depth of ~ 70 c.u. [ABSTRACT FROM AUTHOR]