TY - JOUR
T1 - The cosmic ray primary composition in the "knee" region through the EAS electromagnetic and muon measurements at EAS-TOP
AU - Aglietta, M.
AU - Alessandro, B.
AU - Antonioli, P.
AU - Arneodo, F.
AU - Bergamasco, L.
AU - Bertaina, M.
AU - Castagnoli, C.
AU - Castellina, A.
AU - Chiavassa, A.
AU - Cini Castagnoli, G.
AU - D'Ettorre Piazzoli, B.
AU - Di Sciascio, G.
AU - Fulgione, W.
AU - Galeotti, P.
AU - Ghia, P. L.
AU - Iacovacci, M.
AU - Mannocchi, G.
AU - Morello, C.
AU - Navarra, G.
AU - Saavedra, O.
AU - Trinchero, G. C.
AU - Valchierotti, S.
AU - Vallania, P.
AU - Vernetto, S.
AU - Vigorito, C.
PY - 2004/9
Y1 - 2004/9
N2 - The evolution of the cosmic ray primary composition in the energy range 106-107 GeV (i.e. the "knee" region) is studied by means of the e.m. and muon data of the Extensive Air Shower EAS-TOP array (Campo Imperatore, National Gran Sasso Laboratories). The measurement is performed through: (a) the correlated muon number (Nμ) and shower size (Ne) spectra, and (b) the evolution of the average muon numbers and their distributions as a function of the shower size. From analysis (a) the dominance of helium primaries at the knee, and therefore the possibility that the knee itself is due to a break in their energy spectrum (at EkHe =(3.5±0.3)×106 GeV) are deduced. Concerning analysis (b), the measurement accuracies allow the classification in terms of three mass groups: light (p,He), intermediate (CNO), and heavy (Fe). At primary energies E0≈106 GeV the results are consistent with the extrapolations of the data from direct experiments. In the knee region the obtained evolution of the energy spectra leads to: (i) an average steep spectrum of the light mass group (γp,He>3.1), (ii) a spectrum of the intermediate mass group harder than the one of the light component (γCNO≃2.75, possibly bending at EkCNO≈(6-7)×106 GeV), (iii) a constant slope for the spectrum of the heavy primaries (γFe≃2.3-2.7) consistent with the direct measurements. In the investigated energy range, the average primary mass increases from 〈lnA〉=1.6-1.9 at E0≃1.5×106 GeV to 〈lnA〉=2.8-3.1 at E0≃1.5×107 GeV. The result supports the standard acceleration and propagation models of galactic cosmic rays that predict rigidity dependent cut-offs for the primary spectra of the different nuclei. The uncertainties connected to the hadronic interaction model (QGSJET in CORSIKA) used for the interpretation are discussed.
AB - The evolution of the cosmic ray primary composition in the energy range 106-107 GeV (i.e. the "knee" region) is studied by means of the e.m. and muon data of the Extensive Air Shower EAS-TOP array (Campo Imperatore, National Gran Sasso Laboratories). The measurement is performed through: (a) the correlated muon number (Nμ) and shower size (Ne) spectra, and (b) the evolution of the average muon numbers and their distributions as a function of the shower size. From analysis (a) the dominance of helium primaries at the knee, and therefore the possibility that the knee itself is due to a break in their energy spectrum (at EkHe =(3.5±0.3)×106 GeV) are deduced. Concerning analysis (b), the measurement accuracies allow the classification in terms of three mass groups: light (p,He), intermediate (CNO), and heavy (Fe). At primary energies E0≈106 GeV the results are consistent with the extrapolations of the data from direct experiments. In the knee region the obtained evolution of the energy spectra leads to: (i) an average steep spectrum of the light mass group (γp,He>3.1), (ii) a spectrum of the intermediate mass group harder than the one of the light component (γCNO≃2.75, possibly bending at EkCNO≈(6-7)×106 GeV), (iii) a constant slope for the spectrum of the heavy primaries (γFe≃2.3-2.7) consistent with the direct measurements. In the investigated energy range, the average primary mass increases from 〈lnA〉=1.6-1.9 at E0≃1.5×106 GeV to 〈lnA〉=2.8-3.1 at E0≃1.5×107 GeV. The result supports the standard acceleration and propagation models of galactic cosmic rays that predict rigidity dependent cut-offs for the primary spectra of the different nuclei. The uncertainties connected to the hadronic interaction model (QGSJET in CORSIKA) used for the interpretation are discussed.
KW - Cosmic rays composition
KW - Extensive Air Showers
KW - High energies
KW - Knee
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U2 - 10.1016/j.astropartphys.2004.04.005
DO - 10.1016/j.astropartphys.2004.04.005
M3 - Article
AN - SCOPUS:4544382419
SN - 0927-6505
VL - 21
SP - 583
EP - 596
JO - Astroparticle Physics
JF - Astroparticle Physics
IS - 6
ER -