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FIZIKA B 9 (2000) 4, 169-180
ALTITUDE DEPENDENCE OF THE ELECTROMAGNETIC SPECTRA INITIATED BY PRIMARY NUCLEON AIR COLLISIONSD. P. BHATACHARYYA, R. K. SAHA, RENA MAJUMDAR and MALA MITRA Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700 032, India Received 31 May 2000; Accepted 12 February 2001A study has been made of the altitude dependence of high-energy spectra of
electromagnetic components initiated by primary cosmic nucleon - air collisions. The
primary cosmic nucleon spectrum has been estimated from the directly measured elemental
fluxes at high energies obtained from the recent absolute measurements by different
groups. Considering the superposition model, the estimated all-particle primary nucleon
spectrum follows approximately the form 2.56 E-2.73
in the energy range 0.1 - 100 TeV. Taking this as the source of parent neutral mesons and
the spectrum-weighted moments for neutral pion production after Aguilar Benitez et al.,
the neutral pion production spectrum in the atmosphere has been calculated. The generated
neutral pions decay before reacting in the atmosphere. Therefore, the electromagnetic
cascades are generated through p0 ®2g decays. The unidirectional intensity
of g-rays at atmospheric depths of 540 and 735 g cm-2 air have been calculated by adopting the conventional
cascade theory, discussed earlier by Bhattacharyya and Roychoudhury. The results are found
comparable to the emulsion chamber data obtained at locations Mt. Chacaltaya and Mt.
Norikura. We also estimated the spectra of gamma rays and electrons at Mt. Kanbala and Mt.
Fuji at atmospheric depths 520 and 650 g cm-2,
with the adopted value of mean free path of electromagnetic component in air as Lem @ 120 g cm-2 from Daniel and Stephens. It is found that our result is in
accord with the experimental data obtained by Ren et al. at Mt. Kanbala while it is in
approximate agreement with the observed data of Shibata et al. at Mt. Fuji. PACS numbers: 13.85.Tp, 98.70.Sa
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Copyright by The Croatian Physical Society
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