Coherent multifragmentation of relativistic nuclei

We have performed a search for the coherent break-up of carbon into three α-particles and oxygen into four α-particles. As a target we have used the propane (C3H8), nuclear emulsion (Em) and enriched by lead (Em+Pl) for the first reaction and Em for the second one. The primary momentum was (4,2 - 4,5) GeV/c per nucleon. We have estimated the cross-sections of coherent dissociation 12C → 3α and 16O → 4α on above mentioned target nuclei. The A-dependence of these cross-sections is consistent with the assumption on diffraction mechanism of coherent reactions at light targets. However, the Coulomb mechanism seems to be play the dominant role at heavy targets (Pb). We have investigate also the transverse momentum distributions and azimuthal correlation characteristics of relativistic α-particles in the laboratory and center-mass system. It was shown that the simple statistical model of prompt fragmentation do not describe the momentum and correlation characteristics of alphas in the rest system of fragmenting carbon and oxygen nuclei. The four-momentum transfer at Coulomb coherent dissociation is smaller than at the diffractive one. The decay 'temperatures' of fragmenting nuclei were estimated; they exhibit a weak dependence on target atomic number. It was shown also that the fragmenting projectile nuclei acquire the angular momenta after collision. (A.A.D.)