Physics
Scientific paper
Jul 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003icrc....1..267s&link_type=abstract
Proceedings of the 28th International Cosmic Ray Conference. July 31-August 7, 2003. Trukuba, Japan. Under the auspices of the I
Physics
Scientific paper
An approach is proposed to solve the "knee" problem from the experimental point of view, whereas the primary spectrum would follow a pure power law. The EAS technique: proet contra 1. In 1958 there was published a paper[1] claiming the existence of the "knee" in primary cosmic ray spectrum and its possible explanation. Other experiments later confirmed the "knee" existence in various EAS components. Direct measurements of primary cosmic ray nuclei spectra at satellites[2] and balloons[3, 4] made up to energy ˜1 PeV do not confirm deviation from a pure power law at energies above 10 TeV. All the experimental data confirming the "knee" existence are originated from indirect measurements using the EAS technique. Some physicists tried to explain the visible knee by a dramatic change in parameters of particle interactions[5 - 7]. The details of current approach can found elsewhere[8]. An advantage of the EAS method is a possibility to work up to the highest energy. But, the indirect measurements have to be recalculated to primary spectrum. This is a complicated and model dependent problem. If the primary spectrum follows a power law function of a type: I˜E0 - γ and a secondary component Nx also follows a power law: Nx ˜ E0 α , then I˜Nx - β , where β =γ /α. If a break in a power law of experimental data distribution exists , then a change in any of the two indices (γ or α) may be responsible for this. suppose the primary spectrum index γ changes at a point E0 =Eknee from γ to γ +γ . Then, one can expect a predictable break in the index β for each component: β =γ /α. Typical values for α are the following: αe ≈1.1-1.25 for electron component and αh ≈0.8 0.9 for hadronic and muonic components. If γ =0.5, then expected values are: β e ≈0.44 for electrons and β h ≈0.6 for hadrons and muons. But this contradicts observations[9 - 11] where the knee in muonic and in hadronic components is equal toonly β h ≈0.1-0.2. The problem of primary spectrum recovering from observable EAS parameters is additionally complicated due to uncertainties in primaries mass composition. But, there exists a clear experimental evidence[12] against a significant change in mass composition: position of EAS maximum in the atmosphere (xmax ) can be described by a pure logarithmic law in a very wide primary energy (E0 ) range from 1010 eV to 1020 eV. The latter can be drawn[12] as:
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