Comparison Of High Energy Hadronic Interaction Models G. Battistoni(1), R. Ganugapati(2), A.Karle(2), J. L. Kelley(2), T. Montaruli(2,3) Univeristy of Milano & INFN, 20133, Milano, Italy University of Wisconsin, 53706, Madison, WI, USA on leave from University of Bari, 70126, Bari, Italy Muon Intensity vs. Zenith Angle Hadronic Interaction Models for Shower Development The hadronic interaction models used in cosmic ray air shower Monte Carlo codes are built based on various theoretical scenarios. These can be checked by accelerator experiments up to energies achievable by colliders but must be extrapolated to higher energies. The L3+C data (Ralph Engel, private communication) at lower energies show that the the muon flux predicted using different interaction models can differ by up to 30%. Differences of the model predictions when compared with measurements are observed. This could be due to differences in the physics of interaction models and how the data are extrapolated to cosmic ray energies. Therefore, more benchmarks with data and improvements of the hadronic interaction models are necessary. During the development of air showers, in the most forward region a large fraction of the collision energy is taken by the secondary particles. Here we show the energy fraction distributions of various secondaries of proton-Nitrogen collisions (charged pions, kaons, and charmed particles when possible) after the first interaction. Detecting Extra-Terrestrial Neutrinos and understanding Atmospheric Neutrino/Muon Fluxes Air Shower Development The main backgrounds for the detection of extraterrestrial neutrino fluxes are the atmospheric muons and neutrinos produced from the interaction of cosmic rays with the atmosphere. The predicted atmospheric neutrino and muon fluxes depend on the models used to describe these interactions, and discrepancies become very large at high energies (> 1 TeV). We have produced a detailed analysis of the interaction models. Intensity vs. Zenith Angle of down-going muons From ICRC 2003 (Paolo Desiati et al.). The simulated data using the QGSJET-01 interaction model is multiplied by 1.3 in this plot. A larger excess of experimental data with respect to MC is observed in the horizontal region were possibly muons from prompt charm hadron decays can contribute (not accounted for in MC). Hence AMANDA observes more muons than predicted by QGSJET-01! Transverse Momentum Plot 10 TeV Fixed Primary Energy 100 TeV Fixed Primary Energy 1 PeV Fixed Primary Energy Ch. Pions Kaons Kaons Ch. Pions Ch. Pions Kaons Transverse Momentum (GeV) Mean pT (MeV) RMS pT(MeV) Pions 446.50 287.43 Kaons 458.04 288.04 Charm Meson 467.33 289.01 Charm Baryon 467.624 289.02 Charm (Meson+Baryon) Charm (Meson+Baryon) Charm (Meson+Baryon) Esecondary/Eprimary>0.05 (region relevant for atmospheric showers) Conclusions From the plots on secondary energy fractions we see that SIBYLL and FLUKA+DPMJET-III are in very good agreement and in reasonable agreement with DPMJET-II for conventional mesons (charged pions and kaons). However, QGSJET-01 and -II predict a lower energy fraction in the region where secondaries take a very large fraction of the primary energy. This could explain the disagreement in the AMANDA-II muon intensity distribution, since the depth of the detector selects higher energy secondaries. For charmed hadrons, it seems that the implementation of DPMJET-II in CORSIKA underestimates diffractive processes, especially for charmed baryons. The first plot on the left of this panel shows the pT distribution of secondaries for p-Nitrogen interactions at 1 PeV. As indicated by the mean values, the pT is on average larger for charmed secondaries. This does not necessarily mean that the lateral distribution of muons at the surface will be larger for muons from prompt hadrons than conventional ones. This is demonstrated by the plots on the right. The plots on the right show the energy (almost equal to pL at these energies) and lateral separation (from the primary direction) of secondary muons produced in events with no charmed hadron (CONV - dashed lines) and in events with charmed hadron production (PROMPT) before (1st interaction only - pink lines) and after shower development (blue lines). The plots select those muons that would reach the AMANDA detector depth but quantities are given at the surface of the Earth. These plots are obtained with CORSIKA using the DPMJET interaction model for a fixed 1 PeV energy primary proton and 65 degree zenith angle. Average Multiplicity Z-Moment ch. pions ch. pions Account for spectral dependence of CRs interacting with atmospheric nuclei Acknowledgments We would like to acknowledge Athina Meli for providing a version of CORSIKA using DPMJET-II enabling charmed meson and baryon decays. kaons kaons