A. Cunsolo

Heavy-ion double charge exchange reactions: A tool toward

Abstract.The knowledge of the nuclear matrix elements for the neutrinoless double beta decay is fundamental for neutrino physics. In this paper, an innovative technique to extract information on the nuclear matrix elements by measuring the cross section of a double charge exchange nuclear reaction is proposed. The basic point is that the initial- and final-state wave functions in the two processes are the same and the transition operators are similar. The double charge exchange cross sections can be factorized in a nuclear structure term containing the matrix elements and a nuclear reaction factor. First pioneering experimental results for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV incident energy show that such cross section factorization reasonably holds for the crucial 0+

0 \nu\beta\beta

\rightarrow

nuclear matrix elements

0+ transition to 40Args, at least at very forward angles.

Core excited Fano-resonances in exotic nuclei

Abstract Fano-resonances are investigated as a new continuum excitation mode in exotic nuclei. By theoretical model calculations we show that the coupling of a single particle elastic channel to closed core-excited channels leads to sharp resonances in the low-energy continuum. A signature for such bound states embedded in the continuum (BSEC) are characteristic interference effects leading to asymmetric line shapes. Following the quasiparticle-core coupling model we consider the coupling of 1-QP (one-quasiparticle) and 3-QP components and find a number of long-living resonance structures close to the particle threshold. Results for 15 C are compared with experimental data, showing that the experimentally observed spectral distribution and the interference pattern are in qualitative agreement with a BSEC interpretation.

Light charged particle and neutron velocity spectra in coincidence with projectile fragments in the reaction 40Ar(44A MeV)+27Al

Abstract We present a three source analysis of velocity spectra of light charged particles (LCP) and neutrons emitted in the reaction 40 Ar+ 27 Al at 44 A MeV . The light particle (LP) velocity spectra are studied as a function of the detection angle (1.5° θ 3 He, 4 He, d , t ratios and the PLF proton temperature parameter. The characteristics of the PLF sources are derived. Present results are discussed with regards to the degree of thermalization which could be achieved in the PLF and TLF sources.

Complex fragment production in Kr-induced reactions at intermediate energies

Abstract Several features of complex fragment production at intermediate energies can be understood from the coupling of a dynamical description, which takes into account entrance-channel properties, and a statistical decay of equilibrated primary sources. We discuss this point using two different models for the dynamics, both based on the idea of the competition between mean field and two-body effects in this intermediate-energy range. The importance of a slow emission of large clusters in the de-excitation state is stressed, with the possibility of using a suitably extended evaporation code. Fragment yields and spectra are analysed for Kr-induced reactions on C, Al, Ti at 34.4 MeV/ A and on Au at 43 MeV/ A . The effects of a different equation of state (e.o.s.) used in microscopic calculations is analysed. A stiffer e.o.s. implies more stopping of the fragments. Finally, projectile-like fragments produced in the Kr+Au reaction at 200 MeV/ A are analysed. The predictions of the participant-spectator model are confirmed in this energy range.

The40Ar(d, p)41Ar reaction at deuteron energies below the Coulomb barrier

SummarySpectroscopic factors are obtained from stripping reactions at energies below the Coulomb barrier. Compound-nucleus effects are taken into account. The dependence of spectroscopic factors on the energy of the incident particle, on the nuclear optical parameters and on the geometrical parameters of the captured-neutron potential well is investigated in detail.RiassuntoSi sono misurate le sezioni d’urto differenziali delle reazioni40Ar(d, d)40Ar e40Ar(d, p)41Ar nell’intervallo energetico ΔEd=(1.5÷2.5) MeV. In queste condizioni si sono ottenuti i fattori spettroscopici per energie dei deutoni inferiori alle barriere coulombiane, tenendo conto anche degli effetti di nucleo composto. Si è studiata dettagliatamente la dipendenza dei fattori spettroscopici sia dall’energia delle particelle incidenti che dai parametri ottici dei canali di ingresso e d’uscita e dai parametri geometrici della buca di potenziale del neutrone catturato.РеэюмеОпределяются спектроскопические факторы иэ реакций стриппинга при знергиях ниже кулоновского барьера. Учитываются зффекты компаунд-ядер. Подробно исследуется эависимость спектроскопических факторов от знергии падаюшей частицы, от ядерных оптических параметов и от геометруческих параметров потенциальной ямы эахваченного нейтрона.

New lines of research with the MAGNEX large‐acceptance spectrometer

A new design of magnetic spectrometer, MAGNEX, is under construction for the INFN‐LNS, Catania. It is primarily intended for use with the Tandem‐accelerated radioactive beams from the EXCYT facility. Both projects are expected to be completed by early 2004. Considering the broad choice of both stable and radioactive beams that will be available at the LNS, the spectrometer provides new opportunities for, e.g., spectroscopy of weakly bound nuclei by direct reactions, reaction mechanisms with large isospin and nuclear astrophysics.

The MAGNEX large acceptance spectrometer

The main features of the MAGNEX large acceptance magnetic spectrometer are described. It has a quadrupole + dipole layout and a hybrid detector located at the focal plane. The aberrations due to the large angular (50 msr) and momentum (± 13%) acceptance are reduced by an accurate hardware design and then compensated by an innovative software ray‐reconstruction technique. The obtained resolution in energy, angle and mass are presented in the paper. MAGNEX has been used up to now for different experiments in nuclear physics and astrophysics confirming to be a multipurpose device.

Study of the [sup 19]O states via the ([sup 7]Li,[sup 7]Be) reaction at 52 MeV

The 19F(7Li,7Be)19O reaction at 52 MeV incident energy has been performed at INFN‐LNS in Catania using the MAGNEX large acceptance spectrometer. The use of an algebraic ray‐reconstruction technique has allowed to extract the 19O excitation energy spectrum and the experimental angular distributions. A theoretical analysis based on the Quasi‐particle Random Phase Approximation has described the transitions to the 1p‐1h states of the 19O, in close agreement with the experimental cross sections without using any scaling factor.