124 Annual Report 2004

PL0501183 7.1 Łódź Extensive Air Shower Array by K.Jędrzejczak, J.Karczmarczyk, S.Petrochenkov!), A.Polanski, J.Swarzyński, J.Szabelski and T.Wibig

Registrations of extensive air showers (EAS) of well with those registered in the boron counter. The cosmic rays at energies above 1015 eV are continued. only problem is the requirement of a great number of Studies of delayed signals correlated with showers are neutrons produced at the time of shower passage. We in progress. We assume the hypothesis that the EAS have obtained a one year financial support for these hadron interactions in the lead block produce MeV studies (Polish Science Committee grant 1 P031B 014 neutrons, which then undergo thermalization and are 26) detected as delayed signals in Geiger-MUller counters, We have collected 26 helium counters with boron counter and other detectors registering time polyethylene blocks and cadmium sheets for neutron structure of signals (10 MHz FADC, 8-bit converters, registrations. We plan to study in more details the 32 kB memory). The hypothesis that these spatial distribution of neutrons in EAS. From our registrations are due to a great number of neutrons computer simulations it comes that the effective range produced in the lead block by the EAS hadrons seems of neutrons is equal to 1.5 — 2.5 meters. very probable. We construct electronics for helium counters Together with our collaborators from J1NR in (FADC - 24 channels) and systems for individual Dubna we performed simulations of neutron diffusion registrations of signals from G-M counters together in the detector surroundings. We used the MCNP with the time structure of signals. These works will be code, which we introduced into a very detailed completed soon. geometry of the apparatus and its nearest vicinity

(including hydrogen abundance in the soil). Simulated !) neutrons started their diffusion from the lead block or Joint Institute for Nuclear Research, Dubna, from the surrounding ground. Time distributions of Russia slow neutrons obtained from simulations agree quite PL0501184

7.2 KASCADE: Astrophysical Results and Tests of Hadronic Interaction models by A.Risse and J.Zabierowski

KASCADE [1] is a multi-detector setup, operating Investigation of the energy spectra of individual at the site of Forschungszentrum Karlsruhe, Germany, mass groups of primaries by means of unfolding to get redundant information on single air shower procedure applied to KASCADE data [5] provided basis. conclusive evidence that the knee in the spectrum is The information obtained by KASCADE is used to caused by a decrease of the flux of light primaries, perform multiparameter analyses to solve the threefold where positions show a dependence on the primary problem of the reconstruction of (i) the unknown mass group. Systematic uncertainties for an estimate primary energy, (ii) the primary mass, and (iii) to of the elemental composition are dominated by the quantify the characteristics of the hadronic inadequacy of the hadronic interaction models interactions in the air-shower development. During the underlying the reconstruction of energy spectra of single mass groups. Hence, there are still only weak last year some results have been obtained. constraints for detailed astrophysical models to Investigation of anisotropies in the arrival explain the knee in the primary cosmic ray energy directions of the cosmic rays give additional spectrum. information on their origin and propagation. No large scale anisotropy has been found in KASCADE data Test of hadronic interaction models has been one set [2]. The limits on anisotropy obtained out of our of the key activity in KASCADE. Redundant data already exclude some model predictions. information on all shower components is used for these purposes. We have looked for the evidence of an existence of near-by point sources of cosmic rays in KASCADE Using data supplied by the hadron calorimeter the data. No such evidence has been found [3]. investigation of geometric structures of hadronic cores of EAS in the hadron calorimeter [6] continued Using the world-best data on cosmic ray hadrons - throughout the whole 2004. We found that the widely in this case single hadrons - obtained with KASCADE used alignment parameter A, , contrary to the existing hadron calorimeter the primary proton spectrum 4 claims, shows no sensitivity to the features of between E = 300 GeV and 1 PeV has been o hadronic interaction, such as primary type and determined [4]. It corroborates former results and in transverse momentum transfer. It was shown, that the lower energy end the proton flux compares well another geometric parameter, dependent on the with the results of recent direct measurements. DEPARTMENT OF COSMIC RAY PHYSICS 125 relative distance of hadrons in the core, shows such Tracking Detector and of the parent hadrons. sensitivity and can be used for tests of the models. Comparisons of the measured muon pseudorapidies Results will be published in 2005 [7]. and predictions given by different models have shown dN/dn inadequacy of their description of hadronic 30000r interactions in the atmosphere. Similar conclusions, that none of the present 25000 I I hadronic interaction models is able to describe all the 20000 it KASCADE data consistently (on a level a a few 15000 percent) are made based on the investigation of other _ muons on ground 10000 parameters of hadronic and muonic EAS component. ... parent hadrons However, the more recent models or improved L 5000 versions of the previous ones reproduce the data better | \ I than a few years ago. 10 12 Fig. 1 Pscudorapidity of muons registered on ground compared with the pscudorapidity of their mother hadrons. [1] T.Antoni et al.JNucl. Instr. Meth A513 (2003) 429 [2] T.Antoni et al., Astrophys. J. 604 (2004) 687 Hadronic interactions have been investigated also [3] T.Antoni et al., Astrophys. J. 608 (2004) 865 using data on the muonic EAS component. In [4] T.Antoni et a!., Astrophys. J. 612 (2004) 914 particular, the method [8], utilizing the excellent [5] H.Ulrich et al., Eur. Phys. J. C33 (2004) s944 angular resolution of the KASCADE Muon Tracking [6] A.Iwan et al., Proc. 28 1CRC, Tsukuba 2003, Detector, allows to investigate momenta and 1595 pseudorapidities of hadrons generated in high-energy [7] T.Antoni et al. submitted to Phys. Rev.D , 2005 hadronic interactions [9]. This is still an open question [8] J.Zabierowski et al., Nuci. Phys. B122 (2003) 275 and an important parameter for the model building. As [9] J.Zabierowski et al., Proc XIII ISVHECRI, Pylos, it is seen in Fig.l there is a strong correlation between Greece, 2004; to appear in Nuci. Phys. B, 2005 the pseudorapidity of muons measurable in the Muon

7.3 KASCADE-Grande EAS Experiment and LOPES Collaboration lil.il by A.Risse and J.Zabierowski PL0501185

The KASCADE-Grande extensive air shower Due to the short-falls of analog electronics in those experiment (EAS) [1], located in Germany at the site days, the measurements were very cumbersome and of Forschungszentrum Karlsruhe, has been taking data did not lead to useful relations between radio emission since the middle of 2003. It comprises the KASCADE and air shower parameters. As a consequence, the multi-detector facilities and the two new detectors: method was not pursued for a long time and the Grande and Piccolo, with the respective aims of historic results came into question. 2 providing a large acceptance area (0.5 km ). However, inspired by the new developments in The major goal of KASCADE-Grande is the radio astronomy, it was recently suggested that the observation of the 'iron knee' in the cosmic-ray new generation of digital radio arrays, such as Low- energy spectrum at around 100 PeV, which is Frequency Array (LOFAR), could be ideal for expected due to the recent KASCADE and EAS-TOP detecting radio emission from EAS induced by cosmic observations where the positions of the knees of rays (including neutrinos) [5]. Radio dipoles can be individual mass groups suggest a rigidity dependence cheaply produced in large numbers creating thus a [2,3]. The main observable characteristics of hadron cheap alternative to the traditional detectors in interactions to be compared with the expectations building arrays for detection of the highest energy from the simulations used will be investigated as well. cosmic rays (~1020eV), like Auger. In 2004, an effort was put into development of In order to explore this technique a LOPES data analysis software and the calibration of the whole (LOFAR PrototypE Station) [6] experiment has been experiment. The new, digital front-end electronics to built in conjunction with KASCADE-Grande in be used in parallel to the analogue one has been Forschungszentrum Karlsruhe in Germany. On the lsl designed and introduced [4]. of January 2004 The LOPES Collaboration was Recently, with the tremendous progress in digital established by all member institutes of KASCADE- electronics, an increased interest in the investigation Grande (so, SINS, as well), four radio-astronomy of radio signals generated by EAS has been observed. institutes from Germany and Netherlands and Radio pulses emitted in the atmosphere during the ASTRON - Netherlands Foundation for Research in EAS development were measured during the late Astronomy. 1960ies in the frequency range from 2 to 520 MHz.