A. Foti

Technique for 1st order design of a large-acceptance magnetic spectrometer

A general scheme of the layout of a large acceptance magnetic spectrometer based on a wide aperture quadrupole and a multipurpose bending magnet is described. Physical quantities such as momentum resolution, focal plane size and inclination are explicitly represented as functions of transport matrix elements. In this way such quantities are directly related to the parameters defining the configuration of the spectrometer. Realistic assumptions on the shapes, the distances and the fields of the magnetic elements are taken into account in order to limit the parameter space to be spanned. A self-consistent technique simplifies the search for the best configuration and avoids the problem of ending in local minima. This technique is applied to the MAGNEX spectrometer, for which two competitive configurations, characterised by different bending angle, are found and discussed.

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.

Study of the rainbow-like pattern in the elastic scattering of 16O on 27Al at Elab. = 100 MeV

Recently, a rainbow pattern in the elastic scattering of 16O + 27Al at Elab. = 100 MeV was reported. In the present paper, we show that the predicted change of slope of the cross section, as a function of angle, is mostly due to the far-side component of the scattering, which is affected by the inelastic couplings. The experimental data is consistent with the calculations up to the inflection point, where the effect of the couplings is significant. New experimental data, in very good agreement with the theoretical expectations around the Coulomb rainbow angle, are also presented.

A low-pressure gas detector for heavy-ion tracking and particle identification

A low-pressure gas tracker for heavy ions is described. It is based on a drift chamber with four series of multiplying wires for energy loss measurement and underlying strips for position and angle determination. Results of tests with an α-source and with low-energy heavy-ion beams are presented. They indicate the suitability of such a detector in a wide range of experiments with heavy ions where a low energy threshold, a large solid angle, together with a precise measurement of ion trajectories and identification is needed. In particular, the application as a prototype of the focal plane detector for the large-acceptance spectrometer MAGNEX is discussed.

On the 18O positive-parity rotational band

Deuteron-alpha angular correlations have been measured for the reaction 14C(6Li,d)18O∗→α0+14C at E(6Li)=34 MeV and θdlab=10°. Transitions involving the 11.69 MeV (6+) and the 17.6±0.2 MeV 18O states have been analyzed. Spin and parity are confirmed for the known 11.69 MeV (6+) state and assigned to be 8+ for the 17.6 MeV level. This last is suggested to be the fifth member of the positive-parity 18O rotational band built on the 3.63 MeV (0+) level.

(18O,18Ne) double charge-exchange with MAGNEX

An experimental study concerning Double Gamow-Teller (DGT) modes in (18O,18Ne) Double Charge-Exchange reactions has been very recently performed at INFN-LNS laboratory in Catania. The experiment was performed using a 40Ca solid target and a 18O Cyclotron beam at 270 MeV incident energy. Charged ejectiles produced in the reaction were momentum analyzed and identified by MAGNEX spectrometer at very forward angles. Preliminary results are presented in the present paper.

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.