130 Annual Report 2007

7.1 News from The KASCADE-Grande Experiment by J.Zabierowski and P.à uczak [I.11]

The KASCADE-Grande experiment [1], located at distribution of pseudorapidity of their parent mesons. the site of Forschungszentrum Karlsruhe in , This gives an insight into the hadronic interactions is a multi-detector extensive (EAS) array. It taking place during the development of EAS in the combines the and detectors of the atmosphere. In KASCADE-Grande it is possible to KASCADE array [2], calorimeter, Muon investigate up to 700 m from the shower Tracking Detector [3] and an array of 37 scintillators center. As shown in [9] this allows testing the high- (10 m2 each) spread over 0.5 km2. Its purpose is to and low-energy hadronic interaction models study cosmic rays in the energy range from just below separately. The preliminary results of the lateral the knee in the spectrum (1014.5 eV) to the pseudorapidity distributions in EAS measured by energy of the conjectured transition between galactic KASCADE-Grande and their comparison with and extra-galactic cosmic rays. simulation results are shown in Fig. 2. The analysis procedures for the KASCADE- <η> 5 PRELIMINARY Fe Grande data have been further developed and tuned. 4.5 H The Grande array data are analyzed with respect to of DATA shower core position, arrival directions and number of 4 charged particles (Nch). The number of muons in the 3.5 shower is retrieved from the KASCADE array muon 3 detectors. 2.5 Based on the data set from about 3 years of 2 operation, first shower size spectra were derived [4] 100 200 300 400 500 600 and limits on the anisotropy of the cosmic ray flux Rµ[m] were presented [5] at the international conferences. Fig. 2 Lateral distribution of EAS muon pseudorapidity distribution for showers with primary energy > 1016 eV and zenith First two-dimensional Ne-Nµ distributions for Grande o o 18 angle range 0 – 18 . Experimental data are compared with showers up to the energy 10 eV were obtained CORSIKA simulations using QGSJetII and FLUKA2002 models (Fig.1). for high and low hadronic interaction energies respectively, for proton and iron primaries [10]. Beyond 300 m distance more than 70% of muons stem from the interactions below 200 GeV, modelled with FLUKA code. Closer to the shower core the influence of higher energy interactions increases. This may be the reason for relatively better agreement with simulations at the remote distances. The investigations of interaction models with EAS muons pseudorapidities over the last few years have contributed significantly to the improvement of the QGSJet model. In version II, being currently in use, several changes were introduced, for which hints were Fig. 1 Reconstructed electron and muon number distribution of obtained in those investigations. air showers measured by KASCADE-Grande in the zenith range 18o o –25 . The dashed lines indicate average lines of constant energy [1] G.Navarra et al., NIM A518 (2004) 207 derived from CORSICA simulations [6]. [2] T.Antoni et al., NIM A513 (2003) 490 These distributions are the starting point for the [3] P.Doll et al., NIM A488 (2002) 517 unfolding analysis in order to obtain individual [4] F.Di Piero et al., Proc. 30th ICRC, 2007, Merida, spectrum of heavy primary component. Mexico, FZKA 7340B, 5 An important activity of the Collaboration consists [5] S.Over et al., Proc. 30th ICRC, 2007, Merida, in testing the hadronic interaction models. In 2007 the Mexico, FZKA 7340F, 21 results of such tests up to 40 PeV by studying [6] F.Cossavella et al., Proc. 30th ICRC, 2007, hadronic cores of EAS were published [7]. This paper Merida, Mexico, FZKA 7340C, 9 has been nominated by the Editorial Board of Journal [7] W.D.Apel et al, J.Phys.G34 (2007) 2581 of Physics G for inclusion in the 'Research Highlights' [8] J.Zabierowski et al., Nucl.Phys B (Proc. Suppl.) of 2007. 151 (2006) 291 th Investigation of the pseudorapidity of muons in [9] J.Zabierowski et al., Proc. 29 ICRC, 2005, Pune, EAS is an important tool for testing hadronic India, Vol.6.,357 th interaction models [8]. Pseudorapidity distribution of [10]J.Zabierowski et al., Proc. 30 ICRC, 2007, shower muons is a nearly exact picture of the Merida, Mexico, FZKA 7340J, 37