Mass Composition Of Cosmic Rays Research Articles

Studies of ultra-high-energy cosmic rays by the Yakutsk air shower array, based on the Cherenkov light detection technique

The paper presents the results of long-term, continuous observations of the Cherenkov light at the Yakutsk array. The Cherenkov light measurements allow one to reconstruct the longitudinal development of the shower, which is associated with both the model of hadron interactions and the mass composition of cosmic rays. The paper also provides a review of the results that are important for the physics of air showers and the astrophysics of cosmic rays, obtained over a long period of time at the Yakutsk array.

Methods of machine learning for the analysis of cosmic rays mass composition with the KASCADE experiment data

We study the problem of reconstruction of high-energy cosmic rays mass composition from the experimental data of extensive air showers. We develop several machine learning methods for the reconstruction of energy spectra of separate primary nuclei at energies 1–100 PeV, using the public data and Monte-Carlo simulations of the KASCADE experiment from the KCDC platform. We estimate the uncertainties of our methods, including the unfolding procedure, and show that the overall accuracy exceeds that of the method used in the original studies of the KASCADE experiment.

Investigation of ultra-high energy cosmic ray mass composition by the ground based detectors

Investigation of ultra-high energy cosmic ray mass composition by the ground based detectors

Results from recent analysis of KASCADE-Grande data

KASCADE and its extension array of KASCADE-Grande were devoted to measure individual air showers of cosmic rays in the primary energy range of 100 TeV to 1 EeV. The experiment has substantially contributed to investigate the energy spectrum and mass composition of cosmic rays in the transition region from galactic to extragalactic origin of cosmic rays as well as to quantify the characteristics of hadronic interaction models in the air shower development through validity tests using the multi-detector information from KASCADE-Grande. Although the data accumulation was completed in 2013, data analysis is still continuing. Recently, we investigated the reliability of the new hadronic interactions models of the SIBYLL version 2.3d only with the energy spectra from the KASCADE-Grande data. The evolution of the muon content of high energy air showers in the atmosphere is studied as well, using EPOS-LHC, SIBYLL 2.3, QGSJET-II-04 and SIBYLL 2.3c. In this talk, recent results from KASCADE-Grande and the update of the KASCADE Cosmic Ray Data Centre (KCDC) will be discussed.

Probing hadronic interaction models with the hybrid data of the Pierre Auger Observatory

Presently large systematic uncertainties remain in the description of hadronic interactions at ultra-high energies and a fully consistent description of air-shower experimental data is yet to be reached. The amount of data collected by the Pierre Auger Observatory using simultaneously the fluorescence and surface detectors in the energy range 10^{18.5}18.5 -10^{19.0}19.0 eV has provided opportunity to perform a multi-parameter test of model predictions. We apply a global method to simultaneously fit the mass composition of cosmic rays and adjustments to the simulated depth of shower maximum, and hadronic signal at ground level. The best description of the hybrid data is obtained for a deeper scale of simulated depth of shower maximum than predicted by hadronic interaction models tuned to the LHC data. Consequently, the deficit of the simulated hadronic signal at ground level, dominated by muons, is alleviated with respect to the unmodified hadronic interaction models. Because of the size of the adjustments to simulated depth of shower maximum and hadronic signal and the large number of events in the sample, the statistical significance of these assumed adjustments is large, greater than 5\sigma_{stat}σstat, even for the combination of the systematic experimental shifts within 1\sigma_{sys}σsys that are the most favorable for the models.

Cosmic ray mass composition at the knee using azimuthal fluctuations of air shower particles detected at ground by the KASCADE experiment

The presence of hadronic sub-showers causes azimuthal non-uniformity in the particle distributions on the ground in vertical air showers. The LCm parameter, which quantifies the non-uniformity of the signal recorded in detectors located at a given distance on a ring around the shower axis, has been successfully introduced as a gamma/hadron discriminator at PeV energies [23]. In this work, we demonstrate that the LCm parameter can effectively serve as a mass composition discriminator in experiments that employ a compact array of detectors, like KASCADE. We reconstruct the LCm parameter distributions in the energy range lg(E/eV) = [15.0 – 16.0] using measurements from the KASCADE experiment, with intervals of lg(E/eV) = 0.2, which are then fitted with MC templates for five primary nuclei species p, He, C, Si, and Fe considering three hadronic interaction models: QGSjet-II-04, EPOS-LHC and SIBYLL 2.3d. We find that the LCm parameter exhibits minimal dependence on the specific hadronic interaction model considered. The reconstructed fractions of individual species demonstrate a linear decrease in the abundance of protons and He nuclei with increasing energy, while the heavier components become prevalent above the knee as predicted by all three hadronic interaction models. Our findings indicate that the abundance of particle types as a function of energy aligns with different astrophysical models that link the knee to the acceleration and propagation of cosmic rays within the Galaxy. Furthermore, they also demonstrate excellent agreement with three more recent data-driven astrophysical models. These findings suggest that the LCm parameter could be a valuable tool for forthcoming measurements of the LHAASO experiment to enhance our knowledge about the origin and acceleration mechanisms of cosmic rays.

Muon Puzzle in Ultra-High Energy EASs According to Yakutsk Array and Auger Experiment Data

The lateral distribution of particles in extensive air showers from cosmic rays with energy above $10^{17}$ eV registered at the Yakutsk complex array was analyzed. Experimentally measured particle densities were compared to the predictions obtained within frameworks of three ultra-high energy hadron interaction models. The cosmic ray mass composition estimated by the readings of surface-based and underground detectors of the array is consistent with results based on the Cherenkov light lateral distribution data. A comparison was made with the results of direct measurement of the muon component performed at the Pierre Auger Observatory. It is demonstrated that the densities of muon flux measured at Yakutsk array are consistent with results of fluorescent light measurements and disagree with results on muons obtained at the Auger array.

A Method to Estimate the Primary Mass of Ultrahigh-energy Cosmic Rays from Measurements of the Depth of the Shower Maximum and the Muon Content

The origin and mass composition of ultrahigh-energy cosmic rays is one of the big open questions of modern physics. Estimating the mass of ultrahigh-energy cosmic rays always involves the comparison of data with simulations using hadronic interaction models. The state-of-the-art hadronic interaction models, however, fail to agree with each other on the expected depths of the shower maxima, and on the average number of muons produced in air showers initiated by the same primary particles. Thus the interpretation of data in terms of the primary masses of cosmic rays differs depending on which hadronic interaction model is considered as a reference. Good agreement, however, can be found in the implications from hadronic interaction models in the prediction of the change of the average depth of the shower maximum and in the relative change in the number of produced muons as a function of the nuclear mass of the primary cosmic ray. Considering these, a model-independent estimation of the primary mass of ultrahigh-energy cosmic rays can be given in relative terms. In this work we propose a method to estimate the primary mass of ultrahigh-energy cosmic rays from the depth of the shower maximum and the number of muons produced in the shower, utilizing the similarities of modern hadronic interaction models. We discuss a geometric approach that combines the depth of the shower maximum and the number of muons produced in a shower to estimate the mass of the primary particle.

Estimation of the air shower depth of the maximum development by the relative fraction of muons and the composition of cosmic rays in the energy region E0≥5 EeV by Yakutsk array data

The paper presents joint analysis of the characteristics of the electron-photon and Cherenkov components, and muons with a threshold ${ϵ}_{\mathrm{thr}}\ensuremath{\ge}1\text{ }\text{ }\mathrm{GeV}$ and zenith angles less than 60\ifmmode^\circ\else\textdegree\fi{}. The analysis is based on complex data of air shower registration. A quantitative estimation of muons at different distances from the shower axis and the ratio of muons and charged particles at a distance of 600 m are obtained. The empirical relationship found between ${\ensuremath{\rho}}_{\ensuremath{\mu}}(600)/{\ensuremath{\rho}}_{\ensuremath{\mu}+e}(600)$ and the depth of the maximum ${X}_{\mathrm{max}}$ estimated by Cherenkov light data. It allowed to estimate ${X}_{\mathrm{max}}$ in individual showers by fraction of muons ${\ensuremath{\rho}}_{\ensuremath{\mu}}(600)/{\ensuremath{\rho}}_{\ensuremath{\mu}+e}(600)$. From the set of such showers, the dependence of ${X}_{\mathrm{max}}$ on the energy ${E}_{0}$ was found. Mass composition of cosmic rays with highest energies is estimated by comparison of the experimental ${X}_{\mathrm{max}}$ and QGSJetII-04 simulation ${X}_{\mathrm{max}}$ for different primary nuclei. The composition of cosmic rays determined from the muon component of air showers, mainly consists of protons and helium nuclei in the energy range 5--10 EeV. At energies greater than 30 EeV the mass composition is becoming heavier due to CNO and iron nuclei.

Modeling strangeness enhancements to resolve the muon excess in cosmic ray extensive air shower data

Experimental observations of extensive air showers have revealed an excess of the muon content with respect to their theoretical simulations, which we refer to as the muon puzzle. This muon puzzle hampers a precise determination of the ultra-high-energy cosmic ray mass composition. We investigate the potential of producing states of dense quark-gluon matter (which we call fireballs) to resolve the muon puzzle as quantified with data from the Pierre Auger Observatory on the depth of the shower maximum and the number of muons at ground. Adopting a phenomenological fireball model, we find that the inelasticity enhancement associated with the formation of a plasma state is in tension with data on the electromagnetic longitudinal shower development. Instead, we restrict the fireball model to only enhance the strangeness produced in Standard Model hadronic interactions, and dub this model the strangeball model. With an analytic approach based on the Heitler-Matthews model we then find explicit sets of strangeball parameters that resolve the muon puzzle. Constraints from data on shower-to-shower fluctuations of the muon number require strangeness enhancements already at energies accessible to current-generation collider experiments. At Tevatron and LHC energies we estimate 40% of the interactions to produce strangeballs, corresponding to a 5–9% increase of the average fraction of energy retained in the hadronic cascade compared to predictions from current hadronic interaction models. A comparison with relevant measurements of the LHCf and LHCb detectors does not directly exclude this scenario, though the obtained tension with LHCb suggests a stringent test at 14 TeV.

A machine learning approach for mass composition analysis with TALE-SD data

The TALE experiment is a Telescope Array Low-energy Extension constructed to observe cosmic rays with energies down to 1016.5 to clarify the origin of the second knee and the energy of the galactic to extragalactic CRs transition. TALE consists of 10 high-elevation fluorescence detectors and 80 scintillation counters in an area of 21 km2. The key of data interpretation is the mass composition of cosmic rays, and we report on a machine learning approach of mass composition analysis that utilizes waveform data of TALE scintillation counters.

Status of the LHCf experiment

A precise understanding of hadronic interactions is essential to interpreting the mass composition of ultra-high energy cosmic rays from the results of air shower experiments. The Large Hadron Collier forward (LHCf) experiment aims to measure forward neutral particles for validation of hadronic interaction models adopted in air shower simulations. We already published the production cross sections of forward photons and neutrons for proton-proton collisions at √s=13 TeV. Recently, we showed a preliminary result of the energy spectrum of forward η mesons for proton-proton collisions at √s=13 TeV. Moreover, in September 2022, we had another data-taking for proton-proton collisions at √s=13.6 TeV. In data taking, we planned to obtain a number of π0 and η candidates ten times larger for precise measurements and to perform the joint operation with ATLAS Roman pots and zero-degree calorimeters. Thanks to the joint operation with the ATLAS Roman pots, we can measure diffractive mass and neutral particles from diffractive dissociation simultaneously. Furthermore, energy resolution for neutrons is expected to be improved from 40% to 20% by combining the LHCf and the ATLAS zero-degree calorimeters. In this work, we report the status and prospects of the LHCf experiment.

Measurements of Cosmic Ray Mass Composition with the IceCube Neutrino Observatory

The IceCube Neutrino Observatory is a multi-component detector at the South Pole. Besides studying high-energy neutrinos, it is capable of measuring high-energy cosmic rays from PeV to EeV. This energy region is thought to cover the transition from galactic to extragalactic sources of cosmic rays. The observatory consists of the deep in-ice IceCube array, which measures the high-energy (≥500 GeV) muonic component, and the IceTop surface array, which is sensitive to the electromagnetic and low-energy muonic part of an air shower. The primary energy and the mass composition can be measured simultaneously by applying statistical methods including modern machine-learning techniques to reconstruct cosmic ray air showers. In this contribution, we will discuss recent improvements to the reconstruction techniques, the mass composition sensitivity, and an outlook on future improved measurements with the full surface scintillator/radio array to mitigate snow accumulation and measure the air shower maximum Xmax using imaging air-Cherenkov telescopes IceAct.

Cosmic ray mass composition measurement with the TALE hybrid detector

The Telescope Array (TA) located in the State of Utah in the US is the largest ultra-high energy cosmic rays observatory in the northern hemisphere. The Telescope Array Low-energy Extension (TALE) detector was constructed to study the transition of cosmic rays from Galactic to extra-galactic origin. The TALE detector consists of a Fluorescence Detector (FD) station with 10 high elevation telescopes located at the TA Middle Drum FD Station (itself made up of 14 FD telescopes), and a Surface Detector (SD) array made up of 80 scintillation counters, including 40 with 400 m spacing and 40 with 600 m spacing. We have continued stable observation with hybrid mode since 2017. In this contribution, we present the latest result of the cosmic ray mass composition measurement using almost 4 years of TALE hybrid data.

A new network of electric field mills at the Pierre Auger Observatory

The Pierre Auger Observatory is the largest ground-based experiment for the detection of ultra-high energy cosmic rays. In a hybrid approach, many detectors – including radio antennas – observe the extensive air showers induced by cosmic rays. As part of the AugerPrime upgrade, new antennas will be installed on each of the surface-detector stations covering a total area of around 3000 km2. This will allow us to study the mass composition of cosmic rays arriving with large inclination angles.The radio emission of air showers is heavily influenced in the presence of strong atmospheric electric fields during thunderstorm conditions. In that case measured data are difficult to interpret and therefore the atmospheric electric field over the array has to be monitored. We present the design and status of a new network of electric field mills (EFM) that will be used to take on this task. We show how we plan to perform the measurements with an absolute calibration. In addition, the electric-field data will be useful for other studies related to atmospheric electricity.

A Monte Carlo study to check muon numbers in hadronic interaction models observed by the Tibet hybrid experiment (YAC-II + Tibet-III + MD)

The interpretation of the EAS data relies on the employment of hadronic interaction models, which are subject to theoretical and experimental uncertainties that may hamper composition studies of cosmic rays. To check the reliability of such models at the energies relevant for EAS studies, the predictions of the models can be compared with data from air shower observatories. In this regard, the study of the number of muons becomes extremely useful, since they are sensitive to the hadronic interactions that occur in the early phases of the EAS development. In the paper, we propose a Monte Carlo study to test the number of muons in hadronic interaction models by the hybrid experiment (YAC-II + Tibet-III + MD). For an air-shower event, the Tibet air-shower array (Tibet-III) provides the arrival direction and the air-shower size which are interrelated to primary energy, the Yangbajing Air shower Core detector (YAC-II) array measures the high energy electromagnetic particles in the very forward region so as to obtain the characteristic parameters of air-shower cores, at the same time, the underground MDs record the number of high-energy muons above 1 GeV. Since we can select proton events with high accuracy by YAC-II almost independently of the hadronic interaction models, the accompanying number of muons induced by proton events can be fed out. With the unique settle of YAC-II, our results show that the description of muon numbers in different hadronic interaction models can be well systematics-checked to avoid the ambiguity of the primary cosmic-ray mass composition around the knee energy region by the Tibet hybrid experiment (YAC-II + Tibet-III + MD).

Testing effects of Lorentz invariance violation in the propagation of astroparticles with the Pierre Auger Observatory

Lorentz invariance violation (LIV) is often described by dispersion relations of the form E i 2 = m i 2+p i 2+δi,n E 2+n with delta different based on particle type i, with energy E, momentum p and rest mass m. Kinematics and energy thresholds of interactions are modified once the LIV terms become comparable to the squared masses of the particles involved. Thus, the strongest constraints on the LIV coefficients δi,n tend to come from the highest energies. At sufficiently high energies, photons produced by cosmic ray interactions as they propagate through the Universe could be subluminal and unattenuated over cosmological distances. Cosmic ray interactions can also be modified and lead to detectable fingerprints in the energy spectrum and mass composition observed on Earth. The data collected at the Pierre Auger Observatory are therefore possibly sensitive to both the electromagnetic and hadronic sectors of LIV. In this article, we explore these two sectors by comparing the energy spectrum and the composition of cosmic rays and the upper limits on the photon flux from the Pierre Auger Observatory with simulations including LIV. Constraints on LIV parameters depend strongly on the mass composition of cosmic rays at the highest energies. For the electromagnetic sector, while no constraints can be obtained in the absence of protons beyond 1019 eV, we obtain δγ,0 > -10-21, δγ,1 > -10-40 eV-1 and δγ,2 > -10-58 eV-2 in the case of a subdominant proton component up to 1020 eV. For the hadronic sector, we study the best description of the data as a function of LIV coefficients and we derive constraints in the hadronic sector such as δhad,0 < 10-19, δhad,1 < 10-38 eV-1 and δhad,2 < 10-57 eV-2 at 5σ CL.

Particle physics in cosmic rays

The Pierre Auger Observatory is the world’s largest detector of ultra-high energy cosmic rays (UHECRs). It uses an array of fluorescence telescopes and particle detectors at the ground to obtain detailed measurements of the energy spectrum, mass composition and arrival directions of primary cosmic rays (above the energy of [Formula: see text] eV) with accuracy not attainable until now. Observations of extensive air showers performed by the Pierre Auger Observatory can also be used to probe hadronic interactions at high energy, in a kinematic and energy region not accessible by man-made accelerators. Indeed, exploiting Auger data, we reach center-of-mass energies up to 400 TeV, i.e. more than 30 times of those attainable at the Large Hadron Collider (LHC), and explore interactions in the very forward region of phase space on targets of atomic mass of 14. In addition, a precise measurement of the muon component of air showers at the ground is more sensitive to the details of the hadronic interactions along many steps of the cascade development, such as the multiplicity of the secondaries and the fraction of electromagnetic component with respect to the total signal. On the other hand, the intrinsic muon fluctuations mostly depend on the first interaction. In this paper, we overview the new Auger studies exploring the connection between the dynamics of the air shower and the multi-particle production, and how this knowledge can be translated into constraints of the high-energy hadronic models as well as direct measurements, complementary to, and beyond the reach of, accelerator experiments.

Tunka-Grande scintillation array: resent results

Objectives of the TAIGA Astrophysical complex include the study of the flux of charged cosmic rays and diffuse gamma rays with energies above 100 TeV. This complex is located in the Tunka Valley about 50 km from Lake Baikal at the site of the Tunka-133 Cherenkov facility. TAIGA includes the TAIGA-HiSCORE wide-angle Cherenkov array, the network of Imaging Atmospheric Cherenkov Telescopes (TAIGA-IACT), the Tunka-Grande and TAIGA-Muon scintillation arrays. In this work, we present the results of an analysis of the joint events of the Tunka-Grande scintillation array and TAIGA-HiSCORE and Tunka-133 Cherenkov facilities. The results verify sufficient accuracy of the scintillation experiment for the hybrid study of mass composition of cosmic rays and gamma-hadron separation.

Energy Spectrum and Mass Composition of Cosmic Rays from the Data of the Astrophysical Complex TAIGA

Energy Spectrum and Mass Composition of Cosmic Rays from the Data of the Astrophysical Complex TAIGA