118459803
Sharp knee phenomenon of primary cosmic ray energy spectrum
Primary energy spectral models are tested in the energy range of 1-200 PeV using standardized extensive air shower responses from BASJE-MAS, Tibet, GAMMA and KASCADE scintillation shower arrays. Results point towards the two-component origin of observed cosmic ray energy spectra in the knee region (GAPS spectral model) consisting of a pulsar component superimposed upon rigidity-dependent power law diffuse galactic flux. The two-component energy spectral model accounts for both the sharp knee shower spectral phenomenon and observed irregularity of all-particle energy spectrum in the region of 50-100 PeV. Alternatively, tested multi-population primary energy spectra predicted by non-linear diffusive shock acceleration (DSA) models describe observed shower spectra in the knee region provided that the cutoff magnetic rigidities of accelerating particles are 6.0+/-0.3 PV and 45+/-2 PV for the first two populations respectively. Both tested spectral models confirm the predominant H-He primary nuclei origin of observed shower spectral knee. The parameters of tested energy spectra are evaluated using solutions of inverse problem on the basis of the corresponding parameterizations of energy spectra for primary H, He, O-like and Fe-like nuclei, standardized shower size spectral responses in the 550-1085 g/cm^2 atmospheric slant depth range and near vertical muon truncated size spectra detected by the GAMMA array.
17568500
An all-particle primary energy spectrum in the 3–200 PeV energy range
We present an all-particle primary cosmic-ray energy spectrum in the 3 × 10 6 – 2 × 10 8 GeV energy range obtained by a multi-parametric event-by-event evaluation of the primary energy. The results are obtained on the basis of an expanded EAS data set detected at mountain level (700 g cm −2 )b y the GAMMA experiment. The energy evaluation method has been developed using the EAS simulation with the SIBYLL interaction model taking into account the response of GAMMA detectors and reconstruction uncertainties of EAS parameters. Nearly unbiased (<5%) energy estimations regardless of a primary nuclear mass with an accuracy of about 15–10% in the 3 × 10 6 –2 × 10 8 GeV energy range respectively are attained. An irregularity (‘bump’) in the spectrum is observed at primary energies of ∼7.4 × 10 7 GeV. This bump exceeds a smooth power-law fit to the data by about 4 standard deviations. By not rejecting the stochastic nature of the bump completely, we examined the systematic uncertainties of our methods and conclude that they cannot be responsible for the observed feature.
15515326
Galactic diffuse gamma-ray flux at the energy about 175 TeV
We present an upper limit of galactic diffuse gamma-ray flux, measured with the GAMMA experiment at energy about 175 TeV. The results were obtained using selection of muon poor extensive air showers at mountain level (700 g/cm 2 , Mt. Ara- gats, Armenia) for 5 GeV muon energy threshold. An upper limit for the differential flux at energy E ≃ 175 +25 20 TeV is equal to (5.8 − 7.0) � 10 12 (ergm 2 � ssr) 1 for 95% confidence level 1 .
15964309
Mutually compensative pseudo solutions of primary energy spectra in the knee region
Abstract The problem of the uniqueness of solutions during the evaluation of primary energy spectra in the knee region using an extensive air shower (EAS) data set and the EAS inverse approach is investigated. It is shown that the unfolding of primary energy spectra in the knee region leads to mutually compensative pseudo solutions. These solutions may be the reason for the observed disagreements in the elementary energy spectra of cosmic rays in the 1–100 PeV energy range obtained from different experiments.
118825755
Alternative description of particle shower longitudinal profile
An alternative parametrization of the particle shower longitudinal profile is presented. The accuracy of the obtained shower profile description is about 2-3% for the 0-1500 g/cm^2 atmosphere slant depths and primary H, He,... Fe nuclei in the 1 PeV-10 EeV energy range. It is shown that the shape of shower profile depends only on the nucleon energy, whereas the maximum shower size also depends on the energy of the parental nucleus. Results are based on the CORSIKA simulated shower profiles and are presented in comparison with the Gaisser-Hillas parametrization.
118956991
Primary Energy Spectra and Elemental Composition. GAMMA Experiment
On the basis of the Extensive Air Shower data observed by the GAMMA experiment the energy spectra and elemental composition of the primary cosmic rays have been derived in the 1-100 PeV energy range. Reconstruction of the primary energy spectra is carried out in the framework of the SIBYLL and QGSJET interaction models and the hypothesis of the power-law steepening primary energy spectra. All presented results are derived taking into account the detector response, reconstruction uncertainties of EAS parameters and fluctuation of EAS development.
182593757
Numerical Methods of Calculation of Experimental Installation Gathering Power
121577231
Energy spectra and elemental composition of primary nuclei in the knee region: Recent results from the GAMMA experiment
On the basis of the extensive air shower (EAS) data obtained by the GAMMA experiment, the energy spectra and elemental composition of the primary cosmic rays are derived in the 1 – 100  PeV energy range. The reconstruction of the primary energy spectra is carried out using an EAS inverse approach with the hypothesis of power-law primary energy spectra with rigidity-dependent knees. The rigidity-dependent knee feature of the primary energy spectra is displayed at the rigidities E R ≃ 2.5 ± 0.2  PeV/Z and E R ≃ 3.1 – 4.2  PeV/Z for the SIBYLL and QGSJET interaction models respectively. Using the event-by-event method of the primary energy evaluation from the measured N c h , N μ and shower age (s) parameters, the all-particle energy spectrum is also obtained.
117993503
Search Capability for eta ---> nu(e, tau) anti-nu(e, tau) Decays in Cubic Kilometer Neutrino Detectors
We investigate the discovery potential of cubic-kilometer neutrino observatories such as IceCube to set stringent limits on the forbidden decays η → v e v e and η → v τ v τ . The signatures for these decays are cascade events resulting from the charged-current reactions of v e , v τ , v e , and v τ on nuclei in such detectors. Background cascade events are mainly due to v e 's from atmospheric μ, K + , and K 0 S decays and to a lesser extent from atmospheric v μ neutral-current interactions with nuclei. A direct upper limit for the branching ratio η → v e,τ v e,τ of 6.1 × 10 -4 at 90% CL can be achieved.
6435303
Rigidity-dependent cosmic ray energy spectra in the knee region obtained with the GAMMA experiment
On the basis of the extensive air shower (EAS) data obtained by the GAMMA experiment, the energy spectra and elemental composition of the primary cosmic rays are derived in the 10 3 –10 5 TeV energy range. The reconstruction of the primary energy spectra is carried out using an EAS inverse approach in the framework of the SIBYLL2.1 and QGSJET01 interaction models and the hypothesis of power-law primary energy spectra with rigidity-dependent knees. The energy spectra of primary H, He, O-like and Fe-like nuclei obtained with the SIBYLL interaction model agree with corresponding extrapolations of the balloon and satellite data to � 10 3 TeV energies. The energy spectra obtained from the QGSJET model show a predominantly proton composition in the knee region. The rigiditydependent knee feature of the primary energy spectra for each interaction model is displayed at the following rigidities: ER ’ 2500 � 200 TV (SIBYLL) and ER ’ 3100–4200 TV (QGSJET). All the results presented are derived taking into account the detector response, the reconstruction uncertainties of the EAS parameters, and fluctuations in the EAS development. � 2007 Elsevier B.V. All rights reserved. PACS: 96.40.Pq; 96.40.De; 96.40.� z; 98.70.Sa
123287657
Energy spectra and elemental composition determination on mountain altitudes and sea level
The accurate measurement of the elemental composition and energy spectra of primary cosmic rays in the energy range 10 14 – 10 17 eV is vitally important. The information carried by Extensive Air showers (EAS) in this energy range is limited by significant fluctuations of the shower development, insufficient experimental sampling and uncertainties of the detector response. Additional uncertainties arise from different simulation procedures and statistical methods used for inferring results from the measurements. We propose to combine an advanced EAS simulation program like CORSIKA with the ANI multivariate statistical analysis package for an event-by-event analysis and for a standardization of the inference from EAS data. As an example, the possibilities of modern EAS installations at mountain altitudes and sea level are explored. The accuracies of the elemental composition determination based on measured components of EAS are presented. The Neural Networks classification and Bayesian Decision Making approaches are used and compared. The new nonparametric methods of primary energy estimations are discussed.