A Low energy pi/mu identifier

NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS RESEARC

A signal of spinodal decomposition around Fermi energy.

none25Using thermal photons to tag the reaction time a prompt IMF emission component has been identified in central Ni-58 + (197)An collisions at 45 MeV/amu. The comparison with theoretical calculations supports the hypothesis of dynamical emission in the spinodal regionnoneR. Alba;C. Agodi;C. Maiolino;A. Del Zoppo;M. Colonna;G. Bellia;R. Coniglione;P. Finocchiaro;K. Loukachine;E. Migneco;P. Piattelli;D. Santonocito;P. Sapienza;M. Bruno;M. D'Agostino;M.L. Fiandri;G. Vannini;N. Colonna;F. Gramegna;P.F. Mastinu;I. Iori;A. Moroni;G.V. Margagliotti;P.M. Milazzo;R. RuiR. Alba;C. Agodi;C. Maiolino;A. Del Zoppo;M. Colonna;G. Bellia;R. Coniglione;P. Finocchiaro;K. Loukachine;E. Migneco;P. Piattelli;D. Santonocito;P. Sapienza;M. Bruno;M. D'Agostino;M.L. Fiandri;G. Vannini;N. Colonna;F. Gramegna;P.F. Mastinu;I. Iori;A. Moroni;G.V. Margagliotti;P.M. Milazzo;R. Ru

The reaction entrance channel and isotopic composition of fragments in a dynamical and statistical multifragmentation regime.

From the study of the Ni+Ni,Ag 30 MeV/nucleon dissipative midperipheral collisions, it has been possible to detect events in which Intermediate Mass Fragments (IMF) are emitted by two different sources with different mechanisms. The sources are: a) a quasi-projectile (QP) (and a quasi-target (QT)), with an excitation energy that leads to multifragmentation totally described in terms of a statistical disassembly of a thermalized system (T <IMG SRC="/img/revistas/bjp/v34n3a/a59img01.gif">4. MeV, E*<IMG SRC="/img/revistas/bjp/v34n3a/a59img01.gif"> 4 MeV/nucleon); b) an intermediate source, emitting both light particles and IMF. In this second case, fragments are more neutron rich than the average matter of the overall system, and have a very different charge distribution, with respect to those statistically emitted from the QP. The above features can be considered as a signature of the dynamical origin of the midvelocity emission. The results of this analysis show that IMF can be produced via different mechanisms simultaneously present within the same collision. They also show that the probability of IMF production via dynamical reaction increase with the size of the target nucleus