Study of proton-unbound states in 24Al^{24}{\rm Al} relevant for the 23Mg(p,γ)^{23}{\rm Mg}(p,\gamma) reaction in novae

Background: The nucleosynthesis of several proton-rich nuclei is determined by radiative proton-capture reactions on unstable nuclei in nova explosions. One such reaction is $^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}$, which links the NeNa and MgAl cycles in oxygen-neon (ONe) novae. Purpose: To extract $^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}$ resonance strengths from a study of proton-unbound states in $^{24}{\rm Al}$, produced via the $^{24}$Mg($^{3}$He,$t$) reaction. Methods: A beam of $^3 {\rm He}^{2+}$ ions at 50.7 MeV was used to produce the states of interest in $^{24}$Al. Proton-triton angular correlations were measured with a $K=600$ QDD magnetic spectrometer and a silicon detector array, located at iThemba LABS, South Africa. Results: We measured the excitation energies of the four lowest proton-unbound states in $^{24}$Al and place lower-limits on $\Gamma_p/\Gamma$ values for these four states. Together with USD-C shell-model calculations of partial gamma widths, the experimental data are also used to determine resonance strengths for the three lowest $^{23}{\rm Mg}(p,\gamma)^{24}{\rm Al}$ resonances. Conclusions: The energy of the dominant first $^{23}{\rm Mg}(p,\gamma)$ resonance is determined to be $E_{r} = 481.4 \pm 1.1$ keV, with a resonance strength $\omega \gamma = 18 \pm 6$ meV

From the stable to the exotic: clustering in light nuclei

A great deal of research work has been undertaken in alpha-clustering study since the pioneering discovery of 12C+12C molecular resonances half a century ago. Our knowledge on physics of nuclear molecules has increased considerably and nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. The occurrence of "exotic" shapes in light N=Z alpha-like nuclei is investigated. Various approaches of the superdeformed and hyperdeformed bands associated with quasimolecular resonant structures are presented. Evolution of clustering from stability to the drip-lines is examined: clustering aspects are, in particular, discussed for light exotic nuclei with large neutron excess such as neutron-rich Oxygen isotopes with their complete spectroscopy.Comment: 15 pages, 5 figures, Presented at the International Symposium on "New Horizons in Fundamental Physics - From Neutrons Nuclei via Superheavy Elements and Supercritical Fields to Neutron Stars and Cosmic Rays" held at Makutsi Safari Farm, South Africa, December 23-29, 2015. arXiv admin note: substantial text overlap with arXiv:1402.6590, arXiv:1303.0960, arXiv:1408.0684, arXiv:1011.342

Recent results on Heavy-Ion induced reactions of interest for 0νββ decay

An updated overview of recent results on Heavy-Ion induced reactions of interest for neutrinoless double beta decay is reported in the framework of the NUMEN project. The NUMEN idea is to study heavy-ion induced Double Charge Exchange (DCE) reactions with the aim to get information on the nuclear matrix elements for neutrinoless double beta (0νββ) decay. Moreover, to infer the neutrino average masses from the possible measurement of the half- life of 0νββ decay, the knowledge of the nuclear matrix elements is a crucial aspec

Recent results on heavy-ion direct reactions of interest for 0νββ decay at INFN LNS

Neutrinoless double beta decay of nuclei, if observed, would have important implications on fundamental physics. In particular it would give access to the effective neutrino mass. In order to extract such information from 0νββ decay half-life measurements, the knowledge of the Nuclear Matrix Elements (NME) is of utmost importance. In this context the NUMEN and the NURE projects aim to extract information on the NME by measuring cross sections of Double Charge Exchange reactions in selected systems which are expected to spontaneously decay via 0νββ. In this work an overview of the experimental challenges that NUMEN is facing in order to perform the experiments with accelerated beams and the research and development activity for the planned upgrade of the INFN-LNS facilities is reported

Gamma ray detection with CHIMERA at LNS: Results and perspectives

We describe the use of the 4tt CHIMERA charged particle detector as a large efficiency y-ray detector. The CsI(Tl) stage of the CHIMERA telescope is used to detect and identify y-rays. The high detection efficiency and the sufficient energy resolution guaranteed by CsI(Tl) allows us to use the detector for the study of rare decays. Two examples are reported: the low probability gamma decay (<10%) of the Pygmy resonance of a radioactive nucleus as the 68Ni; the measurement of the gamma decay probability of excited levels of 12C as the Hoyle state at 7.65 (∼10-4) MeV and the 3- level at 9.64 MeV (∼107), both important for the Carbon production in stars. Future experiments made possible at INFN-LNS by the availability of the new fragment separator FRAISE are also outlined

Investigating γ -ray decay of excited C 12 levels with a multifold coincidence analysis

Background: The γ decay of C12 levels above the particle emission threshold plays a crucial role in the production of C12 in astrophysical environments. The Hoyle state is fundamental in the helium-burning phase of red giant stars, while the 9.64-MeV level can be involved in higher temperature explosive environments. Purpose: The aim of this work was to explore the feasibility of measuring the γ-decay widths of the 9.64-MeV state. The experiments were performed at Laboratori Nazionali del Sud of INFN (INFN-LNS), in Catania, using α and proton beams impinging on a carbon target. Methods: The method used consists in the detection of all charged products and γ rays emitted in the reaction, in order to strongly reduce the background. Results: Few events of γ decay of the 9.64-MeV level were observed in the reaction α+C12. Also the decay yield of the Hoyle state was measured in both the measured reactions α+C12 and p+C12. Conclusions: The γ decay of the 9.64-MeV level is, inside error bars, in reasonable agreement with the yield recently reported in literature by measuring the C12 residue. The observed yield is larger than previously accepted lower limit. Also, the decay yield of the Hoyle state seems larger than the one reported in literature, even if the limited statistics do not allow a definite conclusion

Challenges in double charge exchange measurements for neutrino physics

International audienceThe neutrinoless double beta (0νββ) decay, if observed, has important implications on particle physics, cosmology and fundamental physics. In particular it can give access to the effective neutrino mass. In order to extract such information from the 0νββ-decay half-life measurement, the knowledge of the Nuclear Matrix Elements (NME) is of utmost importance. In this context the NUMEN and the NURE projects aim to extract information on the NME by measuring the Double Charge Exchange (DCE) reaction cross section in selected systems of interest for the 0νββ-decay. The experimental difficulties that have to be faced are the measurements at very forward-angle, the very low cross section of the process to be measured, the requirement of a high energy resolution and, eventually, the unambiguous identification of the DCE reaction from other competing processes. The large-acceptance spectrometer MAGNEX, present at INFN-LNS, Catania fulfills all the requirement above mentioned

The NUMEN project @ LNS: Status and perspectives

The NUMEN project aims at accessing experimentally driven information on Nuclear Matrix Elements (NME) involved in the half-life of the neutrinoless double beta decay (0υββ), by high-accuracy measurements of the cross sections of Heavy Ion (HI) induced Double Charge Exchange (DCE) reactions. Particular interest is given to the (18O,18Ne) and (20Ne,20O) reactions as tools for β+ β+ and β-β- decays, respectively. First evidence about the possibility to get quantitative information about NME from experiments is found for both kind of reactions. In the experiments, performed at INFN - Laboratory Nazionali del Sud (LNS) in Catania, the beams are accelerated by the Superconducting Cyclotron (CS) and the reaction products are detected by the MAGNEX magnetic spectrometer. The measured cross sections are challengingly low, limiting the present exploration to few selected isotopes of interest in the context of typically low-yield experimental runs. A major upgrade of the LNS facility is foreseen in order to significantly increase the experimental yield, thus making feasible a systematic study of all the cases of interest. Frontiers technologies are going to be developed, to this purpose, for the accelerator and the detection systems. In parallel, advanced theoretical models are developed aiming at extracting the nuclear structure information from the measured cross sections