An emulsion chamber was used to study the characteristics of high energy nuclear interactions from the production spectra ofγ-rays. The emulsion chamber, which comprised of two parts, namely the detector and the graphite producer unit, was exposed to cosmic rays for about 7 hr at an atmospheric depth of 10 g cm⁻² at Hyderabad (geomagnetic latitude 7·6°N). 720 electromagnetic cascades due toγ-rays were recorded in the detector. These cascades were classified into three groups; (a)γ-rays from nuclear interactions in the detector (b)γ-rays from nuclear interactions in the producer unit and (c)γ-rays of atmospheric origin. The energies of the cascades were determined using photometric method. The spectra ofγ-rays from groups (a) and (c) were determined and compared with similar spectra obtained at greater atmospheric depths. The spectra were found to obey a power law. The spectrum ofγ-rays of atmospheric origin was found to steepen at high energies,E_r>2200 GeV.

Twenty high energy nuclear interactions produced in the graphite units of an emulsion chamber were recorded. The emulsion chamber was exposed to cosmic rays at an atmospheric depth of 10 g cm⁻² for about 7 hr over Hyderabad, India. Fourteen interactions which radiated energyΣ E_r⩾1000 GeV in the form ofγ-rays were analysed in detail. The median energy 〈Σ E_r〉 of the interactions was 1600 GeV. Results concerning the multiplicity, the transverse and longitudinal momentum distributions, and the fractional energy distribution ofγ-rays in these interactions are presented. The average transverse momentum ofπ⁰—mesons <pt_π⁰> is found to increase very slowly with the primary energyE₀ and it can be approximated by the function <pt_π⁰>=0·238E₀^0.06.

Fifty two high energy cosmic ray interactions in graphite have been analysed. The analysis strongly suggests that some of the characteristics of high energy interactions are dependent on the total transverse momentum,Σp_t, of allγ-rays in an interaction. Out of the 52 events analysed, 29 haveΣp_t⩽2.5 GeV/c and the rest haveΣp_t>2.5 GeV/c; the former are called smallp_t events while the latter are designated as largep_t events. For these two types of events, the characteristics investigated are: (a) fractional energy distribution ofγ-rays, (b) the invariant mass ofγ-rays and (c) the energy distribution ofγ-rays in the emission system.

The integral energy spectrum of primary cosmic rays has been obtained. In the energy range (2.4×10³−1.1×10⁵ GeV), the spectrum of all nuclei is consistent with a power law of indexγ=1.55±0.06 and the flux of all nuclei is:N(⩾E₀)⋍(5.1±1.8)×10⁻¹×E₀^−1.55 particles/cm² sterad. sec., whereE₀ is in GeV. The spectrum of primaryα-particles in the energy range (4.4×10³−4.8×10⁴) GeV is also consistent with a power law of indexγ=1.71±0.12 and the flux is:N(⩾E₀)=(4.2±1.4)×10⁻¹×E₀^−1.71, particles per cm² sterad. sec, whereE₀ is in GeV.