Giant Pairing Vibrations in light nuclei Cavallaro, M.; Cappuzzello, F.; Carbone, D. ...
The European physical journal. A, Hadrons and nuclei,
12/2019, Letnik:
55, Številka:
12
Journal Article
Recenzirano
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Signatures of the population of the Giant Pairing Vibration (GPV), a correlated two-nucleon excitation across major shell expected to be populated in two-nucleon transfer reactions, have been ...observed for the first time in carbon isotopes. In the present paper, a review of the experimental methods and of the analysis leading to that observation is reported. A new case, with new experimental data, regarding the possible population of the GPV in another light nucleus,
11
Be , by the same reaction, is introduced and discussed.
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The article describes the main achievements of the NUMEN project together with an updated and detailed overview of the related R&D activities and theoretical developments. NUMEN proposes an ...innovative technique to access the nuclear matrix elements entering the expression of the lifetime of the double beta decay by cross section measurements of heavy-ion induced Double Charge Exchange (DCE) reactions. Despite the fact that the two processes, namely neutrinoless double beta decay and DCE reactions, are triggered by the weak and strong interaction respectively, important analogies are suggested. The basic point is the coincidence of the initial and final state many-body wave functions in the two types of processes and the formal similarity of the transition operators. First experimental results obtained at the INFN-LNS laboratory for the
40
Ca(
18
O,
18
Ne)
40
Ar reaction at 270MeV give an encouraging indication on the capability of the proposed technique to access relevant quantitative information. The main experimental tools for this project are the K800 Superconducting Cyclotron and MAGNEX spectrometer. The former is used for the acceleration of the required high resolution and low emittance heavy-ion beams and the latter is the large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the experimental resolution and sensitivity required for the accurate measurement of the DCE cross sections at forward angles. However, the tiny values of such cross sections and the resolution requirements demand beam intensities much larger than those manageable with the present facility. The on-going upgrade of the INFN-LNS facilities in this perspective is part of the NUMEN project and will be discussed in the article.
An innovative technique to access the nuclear matrix elements entering the expression of the life time of the double beta decay by relevant cross sections of double charge exchange reactions is ...proposed. The basic point is the coincidence of the initial and final state wave-functions in the two classes of processes and the similarity of the transition operators, which in both cases present a superposition of Fermi, Gamow-Teller and rank-two tensor components with a relevant implicit momentum transfer. First pioneering experimental results obtained at the INFN-LNS laboratory for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV, give encouraging indication on the capability of the proposed technique to access relevant quantitative information. A key aspect of the project is the use of the K800 Superconducting Cyclotron (CS) for the acceleration of the required high resolution and low emittance heavy- ion beams and of the MAGNEX large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the high mass, angular and energy resolution required even at very low cross section. The LNS set-up is today an ideal one for this research even in a worldwide perspective. However a main limitation on the beam current delivered by the accelerator and the maximum rate accepted by the MAGNEX focal plane detector must be sensibly overcome in order to systematically provide accurate numbers to the neutrino physics community in all the studied cases. The upgrade of the LNS facilities in this view is part of this project.
Nuclear fragmentation measurements are necessary when using heavy-ion beams in hadrontherapy to predict the effects of the ion nuclear interactions within the human body. Moreover, they are also ...fundamental to validate and improve the Monte Carlo codes for their use in planning tumor treatments. Nowadays, a very limited set of carbon fragmentation cross sections are being measured, and in particular, to our knowledge, no double-differential fragmentation cross sections at intermediate energies are available in the literature. In this work, we have measured the double-differential cross sections and the angular distributions of the secondary fragments produced in the (12)C fragmentation at 62 A MeV on a thin carbon target. The experimental data have been used to benchmark the prediction capability of the Geant4 Monte Carlo code at intermediate energies, where it was never tested before. In particular, we have compared the experimental data with the predictions of two Geant4 nuclear reaction models: the Binary Light Ions Cascade and the Quantum Molecular Dynamic. From the comparison, it has been observed that the Binary Light Ions Cascade approximates the angular distributions of the fragment production cross sections better than the Quantum Molecular Dynamic model. However, the discrepancies observed between the experimental data and the Monte Carlo simulations lead to the conclusion that the prediction capability of both models needs to be improved at intermediate energies.
The Giant Pairing Vibration (GPV) is a correlated two-nucleon excitation mode in atomic nuclei predicted long time ago. It is expected to be excited in two-nucleon transfer reactions, similarly to ...the pairing vibrations feeding the ground states of even-even nuclei near shell-closure. Recent experiments have provided evidence for this mode in
14
C and
15
C nuclei populated via
12
C,
13
C(
18
O,
16
O)
14
C,
15
C two-neutron transfer reactions at 84 MeV beam energy. In the present paper, new data show the persistence of the same structures in the energy spectra of
14
C and
15
C populated by the same reactions at a higher bombarding energy of 275 MeV. The extracted centroid, width, spin-parity and transition probability fully agree with the previous observation thus giving a robust confirmation that the GPV mode is populated in such transfer reactions.
Pulse-shape discrimination in NE213 liquid scintillator detectors Cavallaro, M.; Tropea, S.; Agodi, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2013, Letnik:
700
Journal Article
Recenzirano
The 16-channel fast stretcher BaFPro module, originally developed for processing signals of Barium Fluoride scintillators, has been modified to make a high performing analog pulse-shape analysis of ...signals from the NE213 liquid scintillators of the EDEN neutron detector array. The module produces two Gaussian signals, whose amplitudes are proportional to the height of the fast component of the output light and to the total energy deposited into the scintillator, respectively. An in-beam test has been performed at INFN-LNS (Italy) demonstrating a low detection threshold, a good pulse-shape discrimination even at low energies and a wide dynamic range for the measurement of the neutrons energy.
The most promising probe to establish the Majorana or Dirac nature of the neutrino is the neutrinoless double beta decay and the effective neutrino mass would be evaluated by the knowledge of the ...corresponding nuclear matrix elements. Also measurements of the Double Charge Exchange (DCE) interactions of heavy ion beams can get information on them. The NUMEN experiment based on the pre-existing large acceptance MAGNEX spectrometer and integrated with new challenging components aims at measuring DCE cross sections using ion beams of unprecedented intensity (10
13
pps) on specific isotopes at INFN-LNS in Catania. Expected rate on the sensitive area of about 0.15 m
2
reaches up to about 5 Mpps, demanding for adequate detectors in measuring position, direction, energy, mass and charge of the ions produced by interactions. Gamma detectors surround a scattering chamber containing the target.
In this contribution, we present first experimental results for the deuteron pickup transfer in the 16O+28Si system at Elab. = 240 MeV. This reaction populates states in the 26Al target-like nucleus. ...In the same experimental campaign we have also measured the one-proton transfer 28Si(16O,17F)27Al and one-neutron transfer 27Al(16O,17O)26Al at the same beam energy. Comparison between the energy spectrum of these transfer reactions indicate that: i) the one-proton and one-neutron transfers favor the population of the low-lying states; ii) deuteron transfer to the ground state in 26Al is highly suppressed; iii) the cross-sections for deuteron transfer that populates low-lying states in 26Al are roughly 3 times less than the one-neutron transfer.
An intense activity in the field of experimental, as well as theoretical, nuclear structure is ongoing at the INFN-LNS laboratory in Catania. A short overview of the main recent results is reported.
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