Speaker
Description
Heavy ion nuclear reaction studies are an important tool to observe and disentangle different and competing mechanisms, which may arise in the different energy regimes. In particular, at relatively low bombarding energy the comparison between pre-equilibrium and thermal emission of light charged particles from hot nuclei is interesting. Indeed, nuclear structure of the interacting partners and reaction dynamics may be strongly correlated, especially at energies close to the Coulomb barrier, and it emerges when some nucleons or clusters of nucleons are emitted or captured [1].
In particular, a major attention has been devoted, in the last years, to the possible observation of cluster structure effects in the competing nuclear reaction mechanisms [2], especially when fast processes are involved.
At this purpose, the four reactions $^{16}$O+$^{30}$Si at 111 MeV, $^{16}$O+$^{30}$Si at 128 MeV, $^{18}$O+$^{28}$Si at 126 MeV and $^{19}$F+$^{27}$Al at 133 MeV have been measured, to study the onset of pre-equilibrium in an energy range where, for central collisions, complete fusion is expected to be the favorite mode. Experimental data were collected, using the GARFIELD+RCo array, fully equipped with digital electronics [3], at Legnaro National Laboratories.
Following the identification of particles and the energy calibration procedures, the complete analysis has been performed on an event-by-event basis. Experimental data are compared to some theoretical predictions: in particular, both dynamical models based on either Stochastic Mean Field (Twingo [5]) or Anti-symmetrized Molecular Dynamics (AMD [4]) and/or fully statistical model (Gemini++ [6]) have been considered. Events generated through these codes are filtered through a software replica of the setup, in order to take into consideration any possible distortions of the distributions due to the finite size of the apparatus.
Differences between the experimental data and the predicted data, which are based on very different physical assumptions, can evidence possible entrance channel effects, which may be due to the cluster nature of the colliding partners.
After a general introduction on the experimental campaign, this contribution will focus on the preliminary results obtained so far.
- P.E. Hodgson, E. Btk, Phys. Rep. 374, 1-89 (2003).
- L. Morelli et al., Journ. of Phys. G 41, 075107 (2014); L. Morelli et al., Journ. of Phys. G 41, 075108 (2014); D. Fabris et al., in PoS (X LASNPA), 2013, p. 061.D; V.L. Kravchuk et al., EPJ WoCs 2, 10006 (2010); O. V. Fotina et al., Int. Journ. Mod. Phys. E 19, 1134 (2010).
- F. Gramegna et al., Proceedings of IEEE Nucl. Symposium, 2004, Roma, Italy, p.0-7803-8701-5/04/; M. Bruno et al., Eur. Phys. Jour. A 49, 128 (2013).
- A. Ono, Phys. Rev. C59, 853 (1999).
- M. Colonna et al., Nucl. Phys. A 642, 449 (1998).
- R. J. Charity, Phys. Rev. C82 014610 (2010).
