Nuclear Interactions and Mean Free Paths of Protons, Neutrons, and Alpha Particles at Energies Around 250 Bev/Nucleon

Abstract

Nuclear interactions of protons, neutrons, a particles, and heavier nuclei of average energy 250 Bev/nuc were studied in nuclear emulsion. The source of these particles were fragmentations of heavy primary nuclei of the cosmic radiation. Their energy was determined from multiple scattering measurements. The interaction mean free path for protons is 41 ±10 cm, for a particles 27±7 cm. The mean free path shows no significant change compared with measurements at lower energies. The mean number of shower particles {n s ) depends appreciably on the mass of the target nucleus. Our best estimate for nucleon-nucleon collisions at 250 Bev is (»,) = 8.8=1= 1.9. A detailed comparison of the estimate of the primary energy obtained from the angular distribution of shower particles with the true primary energy is carried out. The angular distribution of the shower particles will, in an individual case, give a quite unreliable value for the primary energy. In the average, the angular distribution method will overestimate the true primary energy by a factor of 1.3 for interactions with a number of heavy prongs iVfc<5. If Nh>S, the angular distribution will underestimate the true energy in the average by a factor of 1.8. The angular distributions can be transformed into a system in which they are symmetric. This is even true for collisions with heavy target nuclei (Nh>S). The results for alpha particle and heavy nucleus collisions are quite similar.The inelasticity for the proton and neutron interactions shows large fluctuations for individual events. It depends weakly on the number of shower particles and on the mass of the target nucleus. Its mean value is 50%. The mean value for the alphaparticle collisions is 22%.

Multiple Meson Production by Heavy Primary Nuclei of Cosmic Origin and their Fragmentation Products at Energies above1012eV

“…1115-6, of the type (0+51+a, Li)Na seems to be another example of this kind of collision (in which the Castagnoli relation would give an overestimate of the primary energy.) Since there are many indications that in nucleon-nucleus collisions (the mirror case) the Castagnoli method underestimates the true energy, [7][8][9] and since the corresponding angular distributions are strongly asymmetric, these observations are not inconsistent with the above energy estimate obtained from symmetric collisions.…”

Anomalous interactions of secondary particles emitted from relativistic heavy primary interactions

“…The anomalous behavior of the secondary Li nuclei and some "anomalous events:', of course, have been observed, but the numbers obtained in any particular investigation were not sufficient to establish definitely the statistical significance of the effect. Some work on interactions --of secondary ci particles at higher energies has also been done (Jain et al 1959;Lohrmann et al 1961). However, according to the present evidence the anomalous effect for the He secondarv nuclei seems to b e confined almost exclusively to the particles emitted from interactions of the L and M primary nuclei with n,., > 7.…”

Systematic Investigation of Ultrahigh-Energy Interactions. I

“…8 If 30% of the 9 interactions are due to deuterons, the mean K C h reduces to 0.24. If the composition of the secondary particles, i.e., 70% pions and 30% kaons, is taken into account and charge-independent production of these particles is assumed, the total inelasticity K is obtained from Z=1.6Zch.…”

“…As for the nucleon-nucleus interactions, an additional correction factor proposed by Lohrmann et al 8 has been applied to the Castagnoli method. We modified their procedure slightly for our sample, and took the corrected incident-nucleon energy E to be related to the quantity Ei, derived from Eq.…”

“…First, the mean transverse momentum of the shower particles produced, mostly mesons, is about (0.3-0.4) GeV/c and depends on neither the primary energy nor the emission angle, except presumbaly in the extreme forward and/or backward directions. [1][2][3][4][5][6][7][8][9] This is verified also in the machineenergy range where the transverse momenta of the various kinds of particles were accurately measured individually. [10][11][12][13][14][15][16] Second, the inelasticity, i.e., the fraction of incident energy carried away by secondary particles, was estimated in the energy region up to 10 TeV, while in the still higher-energy region, estimation from air-shower experiments is less direct.…”