Cosmic ray astrophysics and hadronic interactions

Abstract

Research in cosmic rays is now nearly a century old, but most of the fundamental questions in this field remain unanswered, on the other hand the perspectives of future studies in the next decade are very bright. New detectors will provide higher quality data in the entire energy range from 10 8 to 10 20 eV (or more if particles of higher energy have non negligible fluxes), moreover cosmic ray astrophysics must now be considered, together with gamma, neutrino and gravitational wave astronomy, as one of the subfields of high energy astrophysics, and using information from these four "messengers" there is the potential of a detailed understanding of the origin of the high energy radiation in the universe. High energy cosmic rays are measured indirectly observing the showers they generate in the atmosphere, and a correct and detailed interpretation of these measurements will require an improved understanding of the properties of hadronic interactions. The new collider experiments, and in particular the LHC project at CERN offer the unique possibility to perform measurements of great value for cosmic ray astrophysics. It is of great importance for cosmic research that this possibility is fully exploited with the appropriate instrumentation and analysis.

The AGASA and SUGAR Anisotropies and TeV Gamma Rays from the Galactic Center: A Possible Signature of Extremely High Energy Neutrons

“…are independent of √ s (Lipari 2003). The ISR data are, in fact, well described by such scaling: the cross-section for leading neutron production was found to fall off exponentially in p ⊥ for fixed Feynman x F and could be parameterized by equation ( 48) with b parameter of (4.8 ± 0.3) (GeV/c) −1 , independent of s and x F in the range 0.2 ≥ x F ≥ 0.7 (Engler et al 1975).…”

“…Clearly if Feynman scaling always held exactly one could easily extrapolate low energy results to predict the properties of hadronic interactions at an arbitrarily high energy. Data obtained on pp interactions in general (conducted since the ISR experiments) at SppS, Tevatron and RHIC, however, have shown that Feynman scaling is violated with, in particular, both the afore-mentioned, slow cross-section growth and some evolution of secondary, charged particle multiplicity evident in the data (Lipari 2003). This can be naturally interpretted as symptomatic of the fact that at increasingly high 'probe' momenta, the detailed QCD structure of the hadron is progressively revealed (i.e., the description of the proton as a bag of three valence quarks breaks down).…”

“…These are based on Gribov's Reggeon Field Theory or the QCD eikonal approach (Ostapchenko 2003). In both these, a single hadronic interaction can be broken down into a set of pomeron exchanges between participating partons (Gribov 1968;Engel 2001;Lipari 2003) 14 . As explained above, the increasing number of parton-parton interactions that open up with increasing √ s explain the weak energy dependence (and, therefore Feynman-scaling violation) seen in the cross-section, multiplicity, etc., data.…”

“…Again, if scaling were exactly obeyed this ratio would show no dependence on √ s. More complicated models predict a small energy dependence in this ratio 15 (this is also the case for diffractive production). Such energy dependence as does arise is due to the increase in the number of sub-interactions between partons that occurs for increasing √ s (Lipari 2003). In a simple diquark-quark proton fragmentation scheme, the incident proton can fragment into either a uu or a ud diquark.…”

High energy physics in the atmosphere: phenomenology of cosmic ray air showers

“…where L is the integrated luminosity. Now, following [124,125], we can obtain the total cross section independently from L, by using σ tot = (σ el + σ inel ) = (N el + N inel )/L,…”