Development Of Air Showers Research Articles

Performance study for the photon measurements of the upgraded LHCf calorimeters with Gd2SiO5 (GSO) scintillators

The Large Hadron Collider forward (LHCf) experiment was motivated to understand the hadronic interaction processes relevant to cosmic-ray air shower development. We have developed radiation-hard detectors with the use of Gd2SiO5 (GSO) scintillators for proton-proton √s = 13 TeV collisions. Calibration of such detectors for photon measurement has been completed at the CERN SPS T2-H4 line in 2015 using electron beams of 100–250 GeV and muon beams of 150–250 GeV . After the channel-by-channel absolute energy calibration, the energy resolution of the calorimeters is confirmed to be better than 3% for electrons with energy above 100 GeV . The position dependence of the energy scale of the calorimeters was reduced to the level of 1% after the corrections for scintillator nonuniformity and the shower leakage effect. The position resolution of the new shower imaging detector, a GSO-bar hodoscope interleaved in the calorimeter, was 100 μm for 200 GeV electrons. The experimental results are well explained by Monte Carlo simulations. We have confirmed that the new detectors meet the requirement of the LHCf experiment at √s = 13 TeV.

Open issues in hadronic interactions for air showers

In detailed air shower simulations, the uncertainty in the prediction of shower observables for different primary particles and energies is currently dominated by differences between hadronic interaction models. With the results of the first run of the LHC, the difference between post-LHC model predictions has been reduced to the same level as experimental uncertainties of cosmic ray experiments. At the same time new types of air shower observables, like the muon production depth, have been measured, adding new constraints on hadronic models. Currently no model is able to consistently reproduce all mass composition measurements possible within the Pierre Auger Observatory for instance. Comparing the different models, and with LHC and cosmic ray data, we will show that the remaining open issues in hadronic interactions in air shower development are now in the pion-air interactions and in nuclear effects.

Open issues in hadronic interactions for air showers

In detailed air shower simulations, the uncertainty in the prediction of shower observables for different primary particles and energies is currently dominated by differences between hadronic interaction models. With the results of the first run of the LHC, the difference between post-LHC model predictions has been reduced to the same level as experimental uncertainties of cosmic ray experiments. At the same time new types of air shower observables, like the muon production depth, have been measured, adding new constraints on hadronic models. Currently no model is able to consistently reproduce all mass composition measurements possible within the Pierre Auger Observatory for instance. Comparing the different models, and with LHC and cosmic ray data, we will show that the remaining open issues in hadronic interactions in air shower development are now in the pion-air interactions and in nuclear effects.

CTA Atmospheric Calibration

The main contribution to the systematic uncertainties of Atmospheric Imaging Cherenkov Telescopes (IACTs) currently stems from the uncertainty in the determination of atmospheric properties for a given moment of observation. This technique uses the atmosphere as a calorimeter of gamma-ray induced atmospheric air showers and measures the amount of Cherenkov light collected by large mirrors and focused towards a pixellized camera. Atmospheric conditions affect the measured Cherenkov light yield in several ways: the air-shower development itself, the variation of the Cherenkov angle with altitude and the loss of photons due to scattering and absorption of Cherenkov light. Although IACTs use to be located at astronomical sites, characterized by extremely clear atmospheric conditions, the local atmosphere should be continuously monitored, in terms of molecular density profiles, aerosol extinction profiles, and clouds. Moreover, a general understanding of the site and particularly aerosol climatology is desirable for a robust interpretation of the sensing instruments’ data. Here, the strategy of the Cherenkov Telescope Array (CTA) on atmospheric monitoring is presented, designed to ensure that the related systematic uncertainties are brought down by at least a factor of two with respect to current installations. Additionally, a more intelligent scheduling scheme is aimed at, where source observations are selected using dedicated auxiliary atmospheric monitoring instruments and taking into account the feasibility of a later analysis according to the underlying scientific case. This plan should reduce data loss during offline data selection and enhance the effective duty cycle of the CTA.

Testing of the VENUS 4.12, DPMJET 2.55, QGSJET II-03 and SIBYLL 2.3 hadronic interaction models via help of the atmospheric vertical muon spectra

Uncertainties of the model energy spectra of the most energetic secondary π± -mesons (and K ± -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 interval 102 −107 GeV in terms of the VENUS 4.12, DPMJET 2.55, QGSJET II-03 and SIBYLL 2.3 models had been carried out with help of CORSIKA package. These partial spectra should be convoluted with the contemporary spectra of the primary cosmic particles. Results of simulations are compared with the contemporary atmospheric vertical muon flux data. Comparison shows that all models underestimate production of secondary π± -mesons (and K ± -mesons) by factor of ∼ 2 at the most high energies. This underestimation induces 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.

Results of the LHCf experiment and the forward measurements at the LHC

The Large Hadron Collider is intensively used to test hadronic interaction models used in cosmic-ray physics because its maximum (designed) collision energy √s = 14 TeV corresponds to the interaction of a 1017 eV cosmic-ray proton hitting the atmosphere. In this paper various types of forward experiments at the LHC, where the particles relevant to the air shower development are observed, are reviewed. Recent results of a dedicated experiment for precise forward measurement, the LHC forward, are discussed in detail. A future possibility at the LHC, light ion collisions, is also discussed.

Model-stable universality of the air shower electromagnetic component: An approach to solving the mass composition problem

On the basis of the scaling approach and CORSIKA simulations data the radial scale factor of lateral distribution of electrons in extensive air showers is confirmed as potentially effective primary mass estimator, and its sensitivity to hadronic interaction model is investigated. It is shown that improved composition results both on average and event-by-event basis can be achieved taking into account the universality property of air shower development expressed by the relation between radial scale factor and longitudinal age parameter. The enhancements of such a theoretically motivated tool for the unbiased cosmic ray composition deduction in a wide primary energy range from (multi-)hybrid air shower measurements of nearest future are discussed.

Model-stable universality of the air shower electromagnetic component: An approach to solving the mass composition problem

On the basis of the scaling approach and CORSIKA simulations data the radial scale factor of the lateral distribution of electrons in extensive air showers is confirmed as a potentially effective primary mass estimator, and its sensitivity to hadronic interaction model is investigated. It is shown that improved composition results both on average and event-by-event basis can be achieved taking into account the universality property of air shower development expressed by the relation between the radial scale factor and the longitudinal age parameter. The enhancements of such a theoretically motivated tool for an unbiased cosmic ray composition deduction in a wide primary energy range for current and future (multi-)hybrid air shower measurements are discussed.

Ultraforward particle production from color glass condensate and Lund fragmentation

We present an analysis of data on single inclusive pion production measured by the LHCf collaboration in high-energy proton-proton and proton-nucleus at ultra-forward rapidities, $8.8 \leq\! y\leq \!10.8$. We also analyse forward RHIC data for calibration purposes. Our analysis relies on the use of a Monte Carlo event generator that combines a perturbative description of the elementary scattering process at partonic level based on the hybrid formalism of the Color Glass Condensate with an implementation of hadronization in the framework of the Lund string fragmentation model. This procedure allows us to reach values of the momenta of the produced particles as low as detected experimentally $p_t\sim0.1$ GeV. We achieve a good description of single inclusive spectra of charged particles and neutral pions at RHIC and the LHC respectively, and nuclear modification factors for proton-lead collisions at the LHC. Our results add evidence to the idea that particle production in the domain of very small Bjorken-$x$ is dominated by the saturation effects encoded in the unintegrated gluon distribution of the target. Being forward particle production of key importance in the development of air showers, we stress that this approach allows for a theoretically controlled extrapolation of our results to the scale of ultra-high energy cosmic rays, thus serving as starting point for future works on this topic.

Measurement of the mass composition of ultra-high energy cosmic rays with the Pierre Auger Observatory

The understanding of the nature of ultra-high energy cosmic rays is one of the most intriguing open questions for current and future observatories. With its hybrid design and huge exposure, the Pierre Auger Observatory provides valuable statistical measurements of the chemical composition of cosmic rays with energies above 1017 eV, including the search for neutral primaries such as neutrinos and photons. We report on the most recent results which are based on the accurate measurement of the depth of the shower maximum, Xmax, by the fluorescence telescopes and on the shape of the signals recorded by the water-Cherenkov detectors. The interpretation of these results in terms of mass composition is also discussed related to the hadronic interaction models used to describe the development of air showers.

Latest LHCf physics results

The LHCf experiment is dedicated to the measurement of very forward particle production in the high energy hadron-hadron collisions at LHC, with the aim of improving the cosmic-ray air shower developments models. The detector has taken data in p-p collisions at different center of mass energies, from 900 GeV up to 7 TeV, and in p-Pb collisions at s=5.02 TeV. The results of forward production spectra of neutrons in p-p collisions and π0 in p-Pb collisions, compared with the models most widely used in the High Energy Cosmic Ray physics, are presented in this paper.

First indication of LPM effect in LHCf, an LHC experiment

The Large Hadron Collider forward (LHCf) experiment is dedicated to the measurement of very forward neutral particle production in the high energy hadron-hadron collisions at LHC. The aim of the experiment is to improve the cosmic ray air shower development models and its setup gives an important opportunity to directly measure the Landau Pomeranchunk Migdal (LPM) effect in heavy absorber. This work presents the analysis for LPM effect on data taken in 2010 and 2013 at √ s = 7 TeV and √ s NN = 5.02 TeV respectively. We study the interactions of gamma, mainly produced by π 0 decay, in one of the calorimeter pairs of LHCf. This is composed by 16 Tungsten layers as absorbers and 16 plastic scintillators for energy measurements (Arm2). We use three parameters to describe the mean shower profile with respect the photon mean energy. The results are compared with Epics MonteCarlo simulation with LPM active and inactive models, shows a first evidence of LPM effect.

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.

The hybrid energy spectrum of Telescope Array’s Middle Drum Detector and surface array

The Telescope Array experiment studies ultra high energy cosmic rays using a hybrid detector. Fluorescence telescopes measure the longitudinal development of the extensive air shower generated when a primary cosmic ray particle interacts with the atmosphere. Meanwhile, scintillator detectors measure the lateral distribution of secondary shower particles that hit the ground. The Middle Drum (MD) fluorescence telescope station consists of 14 telescopes from the High Resolution Fly’s Eye (HiRes) experiment, providing a direct link back to the HiRes measurements. Using the scintillator detector data in conjunction with the telescope data improves the geometrical reconstruction of the showers significantly, and hence, provides a more accurate reconstruction of the energy of the primary particle. The Middle Drum hybrid spectrum is presented and compared to that measured by the Middle Drum station in monocular mode. Further, the hybrid data establishes a link between the Middle Drum data and the surface array. A comparison between the Middle Drum hybrid energy spectrum and scintillator Surface Detector (SD) spectrum is also shown.

Relation between hadronic interactions and ultra-high energy extensive air showers

The simulation of hadronic interactions is of fundamental importance for the analysis of extensive air showers. The details of the relation between the measurement of hadronic interactions at accelerators and the impact on the air shower development is very difficult to evaluate. Several possibilities to study this relation are presented here.

The Mass Composition of Ultra-high Energy Cosmic Rays Measured by New Fluorescence Detectors in the Telescope Array Experiment

The longitudinal development of an extensive air shower reaches its maximum at a depth, Xmax, that depends on the species of the primary cosmic ray. Using a technique based on Xmax, we measure the cosmic-ray mass composition from analyses of 3.7 years of monocular mode operations with the newly constructed fluorescence detectors of the Telescope Array experiment. The Xmax analysis shows our data to be consistent with a proton dominant composition at energies above 1018.0eV.

Constraints of hadronic interaction models from the cosmic muon observations

A simple method of the vertical muon energy spectrum simulations has been suggested. These calculations have been carried out in terms of various models of hadronic interactions. The most energetic π ± -mesons and K ± -mesons produced in hadron interactions contribute mainly to this energy spectrum of muons due to the very steep energy spectrum of the primary particles. So, some constraints on the hadronic interaction models may be set from a comparison of calculated results with cosmic data on the vertical muon energy spectrum. This comparison showed that the most energetic secondary particles production is too high in the case of the QGSJET II-04 model and rather low in the case of the QGSJET II-03 model. These conclusion have been supported by the LHC data. The longitudinal development of extensive air showers (EAS), in particular, the depth Xmax of its maximum, is determined by the rate of fragmentation of energy E0 of the primary particle. This rate depends on the interaction cross sections of shower particles, and on the energy spectra of secondary particles are generated in interactions. Obviously, if the probability of particle production with energies close to the energy of the incident particle is high then the development of the cascade slows down. Conversely, in the case of rapid fragmentation of the incident energy cascades develop rather rapidly. The depth Xmax of shower maximum in many studies is the main parameter for determining the composition of primary cosmic radiation (PCR) at ultra-high energies. It should also be noted that in the case of the slow rate of development cascade and hence large values of depth Xmax the lateral distribution of the shower particles at the observation level becomes narrower. Therefore, the values of signals in the surface and underground detectors located at large distances from the shower core are decreased. It must be taken into account when determining the density of muons at large distances from the shower core and the composition of the PCR found from the muon lateral distribution. Studies of the composition and characteristics of the energy spectrum of the PCR are important components of theories of the origin of cosmic rays at ultra-high energies. Interpretation of experimental data on the depth of the shower maximum Xmax and the observed fraction of muons at a fixed distance from the shower core are carried out in terms of different hadronic

Forward hadron production at the LHC

Observations of ultra high energy cosmic rays by extensive air showers rely on correct modeling of hadronic interaction in the forward region at very high energy. Recent new data from the LHC, especially for forward particle production, are important for a precise understanding of air shower development. In this article recent forward production data from p-p, p-Pb, and Pb-Pb collisions at LHC are reviewed.

LHC data on inelastic diffraction and uncertainties in the predictions for longitudinal extensive air shower development

The present status of experimental studies of inelastic diffraction at the Large Hadron Collider is analyzed. The impact of the current uncertainties concerning the diffraction rate on the predicted extensive air shower development is investigated. A relation to studies of the primary composition of ultrahigh energy cosmic rays is illustrated by comparing numerical simulation results to the data of the Telescope Array experiment on the distributions of the shower maximum position.

Spectrum and charge ratio of vertical cosmic ray muons up to momenta of 2.5 TeV/c

The ALEPH detector at LEP has been used to measure the momentum spectrum and charge ratio of vertical cosmic ray muons underground. The sea-level cosmic ray muon spectrum for momenta up to 2.5TeV/c has been obtained by correcting for the overburden of 320m water equivalent (mwe). The results are compared with Monte Carlo models for air shower development in the atmosphere. From the analysis of the spectrum the total flux and the spectral index of the cosmic ray primaries is inferred. The charge ratio suggests a dominantly light composition of cosmic ray primaries with energies in the energy range between 103 and 105GeV.