3 and 4 α-particles production channels in the 16Op-collisions at 3.25 A GeV/c and the isotropic phase space model

The study of the angular distribution of the light slow (T<10 MeV per nucleon) fragments - 2H1, 3H1 and 3He2 produced in the 16Op-collisions at 3.25 A GeV/c in the rest frame of the oxygen nuclei discovered the increase of the inclusive cross section at the values of |cosθ|→1 . This effect can be explained under the following suggestion. It is possible that the fragmenting nucleus acquires the angular momentum during the interaction with target. Early was established, that the azimuthal asymmetries and colinearities in the 12CEm-interactions at 4.5 A GeV/c in the channels of two and three α-particles production were discovered. These facts and disagreement between the transverse momentum experimental spectrum of the α-particles and the predictions of the fragmentation statistical model were qualitatively interpreted within the phenomenological model of cylinder phase volume with the transverse momentum, as well as the possible angular momentum being acquired by the 'remnant nucleus' during the interaction with the target. Therefore, to check the alternative physical picture allowing one to obtain the quantitative explanation we have conducted the similar experimental studied for the 3 and 4 α-particles production channels in the 16Op-collisions at 3.25 A GeV/c. The experimental results were compared with the corresponding original Monte-Carlo calculations differing from the calculation of the work. The main differences are: consideration of the energy-momentum conservation law in each event with the precision of 10-6, generation of the events with the experimental probabilities of every exclusive (excluding the pions) initial nucleus break p channel, generation of the components of the momentum being transferred to the fragmenting nucleus from the proton of the target as a gaussian distribution, and finally, consideration of the similarity effects of the 8Be nuclei decays and the interactions of the α--particles in the final state leading to the narrow angular correlations using the free parameter of the model - the probability to generate the α-particles pair momenta vectors colinearities. We have studied the azimuthal asymmetry and colinearity coefficients of the inclusive distribution over the pair azimuthal angle between the transverse momenta vectors of. the i-th j-th α-particles from the single acts of fragmentation (0≤εij≤π) and the average values of the azimuthal asymmetry and colinearity coefficients. The main results of our phenomenological analysis of the 3 and 4 α-particles production channels in the 16Op-collisions at 3.25 A GeV/c can be formulated shortly in the following way. It was shown that the azimuthal asymmetries appeared due to the transverse motion of the fragmenting nucleus, whereas the col linearity is related to the similarity effects, 8Be nuclei decays as well as interaction of pair of α-particles in the final state. The practical independence of the α-particles transverse momentum average values and the colinearities of their emission in the reaction plane on the transverse momentum acquired by the initial 16O nucleus were found