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Register a new userComparison of AGASA data with CORSIKA simulation
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An interpretation of AGASA (Akeno Giant Air Shower Array) data by comparing the experimental results with the simulated ones by CORSIKA (COsmic Ray SImulation for KASCADE) has been made. General features of the electromagnetic component and low energy muons observed by AGASA can be well reproduced by CORSIKA. The form of the lateral distribution of charged particles agrees well with the experimental one between a few hundred metres and 2000 m from the core, irrespective of the hadronic interaction model studied and the primary composition (proton or iron). It does not depend on the primary energy between 10^17.5 and 10^20 eV as the experiment shows. If we evaluate the particle density measured by scintillators of 5 cm thickness at 600 m from the core (S_0(600), suffix 0 denotes the vertically incident shower) by taking into account the similar conditions as in the experiment, the conversion relation from S_0(600) to the primary energy is expressed as E [eV] = 2.15 x 10^17 x S_0(600)^1.015, within 10% uncertainty among the models and composition used, which suggests the present AGASA conversion factor is the lower limit. Though the form of the muon lateral distribution fits well to the experiment within 1000 m from the core, the absolute values change with hadronic interaction model and primary composition. The slope of the rho_mu(600) (muon density above 1 GeV at 600 m from the core) vs. S_0(600) relation in experiment is flatter than that in simulation of any hadronic model and primary composition. Since the experimental slope is constant from 10^15 eV to 10^19 eV, we need to study this relation in a wide primary energy range to infer the rate of change of chemical composition with energy. keywords: cosmic ray, extensive air shower, simulation, primary energy estimation PACS number ; 96.40.De, 96.40.Pq
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The fluxes of atmospheric muons and neutrinos are calculated by a three dimensional Monte Carlo simulation with the air shower code CORSIKA using the hadronic interaction models DPMJET, VENUS, GHEISHA, and UrQMD. For the simulation of low energy primary particles the original CORSIKA has been extended by a parametrization of the solar modulation and a microscopic calculation of the directional dependence of the geomagnetic cut-off functions. An accurate description for the geography of the Earth has been included by a digital elevation model, tables for the local magnetic field in the atmosphere, and various atmospheric models for different geographic latitudes and annual seasons. CORSIKA is used to calculate atmospheric muon fluxes for different locations and the neutrino fluxes for Kamioka. The results of CORSIKA for the muon fluxes are verified by an extensive comparison with recent measurements. The obtained neutrino fluxes are compared with other calculations and the influence of the hadronic interaction model, the geomagnetic cut-off and the local magnetic field on the neutrino fluxes is investigated.
A new method of a primary cosmic particle energy measurement with the extensive air shower (EAS) technique has been developed by exploiting: a) the joint analysis of the shower size, obtained by the EAS-TOP array, and of the EAS Cherenkov light lateral distribution (LDF), obtained by the QUEST array, and b) simulations based on the CORSIKA code. The method is based on the strict correlation between the size/energy ratio and the steepness of the Cherenkov light lateral distribution and has been compared with a classical one based on the Cherenkov light flux at a fixed distance (175 m) from the EAS core. The independence of the energy measurement both on the mass of primary particle and the hadronic interaction model used for the analysis is shown. Based on this approach the experimental integral intensity of cosmic rays flux with energy more than 3*10^15 eV is obtained with good systematic and statistical accuracy.
The current measurements of the cosmic ray energy spectrum at ultra-high energies ($text{E}>10^{19}$ eV) are characterized by large systematic errors and poor statistics. In addition, the experimental results of the two experiments with the largest published data sets, AGASA and HiRes, appear to be inconsistent with each other, with AGASA seeing an unabated continuation of the energy spectrum even at energies beyond the GZK cutoff energy at $10^{19.6}$ eV. Given the importance of the related astrophysical questions regarding the unknown origin of these highly energetic particles, it is crucial that the extent to which these measurements disagree be well understood. Here we evaluate the consistency of the two measurements for the first time with a model-independent method that accounts for the large statistical and systematic errors of current measurements. We further compare the AGASA and HiRes spectra with the recently presented Auger spectrum. The method directly compares two measurements, bypassing the introduction of theoretical models for the shape of the energy spectrum. The inconsistency between the observations is expressed in terms of a Bayes Factor, a standard statistic defined as the ratio of a separate parent source hypothesis to a single parent source hypothesis. Application to the data shows that the two-parent hypothesis is disfavored. We expand the method to allow comparisons between an experimental flux and that predicted by any model.
We use the SHERPA Monte Carlo generator to simulate the process $e^+e^-rightarrowmbox{hadrons}$ using matrix elements with up to six partons in the final state. Two samples of SHERPA events are generated. In the LO sample, all final states are generated with leading order matrix elements; in the NLO sample, matrix elements for final states with up to four partons are generated at next-to-leading order, while matrix elements for final states with five or six partons are generated at leading order. The resulting samples are then passed through the ALEPH detector simulation. We compare the Monte Carlo samples to each other, to samples generated using the KK2f generator interfaced with PYTHIA, and to the archived ALEPH data at both LEP1 and LEP2 energies. We focus on four-jet observables with particular attention given to dijet masses. The LO and NLO SHERPA samples show significant improvement over the KK2f generation for observables directly related to clustering events into four jets, while maintaining similar performance to KK2f for event-shape variables. We additionally reweight the dijet masses using LEP1 data and find that this greatly improves the agreement between the three Monte Carlo samples at LEP2 energies for these observables.
We compare the expected effects of so-called gravitationally enhanced depolarization of ultracold neutrons to measurements carried out in a spin-precession chamber exposed to a variety of vertical magnetic-field gradients. In particular, we have investigated the dependence upon these field gradients of spin depolarization rates and also of shifts in the measured neutron Larmor precession frequency. We find excellent qualitative agreement, with gravitationally enhanced depolarization accounting for several previously unexplained features in the data.
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