Abstract
The ARGO-YBJ detector layout, features and location offer a unique possibility for a detailed study of several characteristics of the hadronic component of the cosmic ray flux in an energy range hardly accessed by direct measurements. The proton-air cross section has already been measured by ARGO-YBJ in an energy region up to ~ 100 TeV where the primary cosmic ray composition is sufficiently well known for that measure to be unbiased. The analog readout of the RPC signals now provides new tools to measure the lateral distribution of particle density (LDF) as close as a few meters from the core and to investigate with unprecedented resolution the shower time structure. This allows to extend the hadronic interaction and mass composition studies up to ~PeV energies in the laboratory rest frame. Moreover, it is shown that the LDF of detected showers can be properly described, even very close to the shower axis, by a NKG-like function, whose shape parameter is clearly related to the shower age and can be used for studying the mass composition of cosmic rays.
Highlights
As known, cosmic rays (CR) can be measured only indirectly above E ∼1014eV, through the cascades of secondary particles (EAS) produced by their interactions in the atmosphere and detected by surface apparatuses, at sea level or at mountain altitudes
It is shown that the lateral distribution of particle density (LDF) of detected showers can be properly described, even very close to the shower axis, by a NKG-like function, whose shape parameter is clearly related to the shower age and can be used for studying the mass composition of cosmic rays
The Large Hadron Collider (LHC) at CERN allows for the first time to access the energy region above the knee of the primary CR stectrum (∼3 PeV), so the analysis of LHC inclusive particle data is interesting for constraining existing hadronic interaction models and for testing possible new mechanisms of hadron production
Summary
Cosmic rays (CR) can be measured only indirectly above E ∼1014eV, through the cascades of secondary particles (EAS) produced by their interactions in the atmosphere and detected by surface apparatuses, at sea level or at mountain altitudes. The primary particle parameters are inferred by simulating the generation of EAS through Monte Carlo (MC) and comparing predictions with measurements, so the modeling of hadronic multiparticle production in air-shower simulations becomes crucial. The interpretation of experimental air shower data is highly affected by the uncertainty of the hadronic interaction generators in MC simulations. The Large Hadron Collider (LHC) at CERN allows for the first time to access the energy region above the knee of the primary CR stectrum (∼3 PeV), so the analysis of LHC inclusive particle data is interesting for constraining existing hadronic interaction models and for testing possible new mechanisms of hadron production. The ARGO-YBJ result is consistent with the general trend of experimental data, favouring an asymptotic ln2(s) rise of the cross section. A preliminary analysis using a sub-set of these data has been presented in [2]
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