Reaction studies with low-energy weakly-bound beams at INFN-LNS

The reaction dynamics of collisions involving halo or weakly bound nuclei, at energies around the Coulomb barrier, can be strongly affected by the structure of such nuclei. Very strong entrance channel effects have been observed on various reaction pocess such as, elastic scattering, fusion and direct reactions when comparing collision induced by the 6He and 11Be halo nuclei with the ones induced by their cores 4He and 10Be. Collisions induced by the stable weakly bound nuclei 6Li, 7Li show also some peculiarities in comparison to the ones induced by well bound nuclei; coupling with the break-up channel is in fact very important in reproducing low energy data. In this contribution an overview of our present understanding of the discussed topic will be given along with the discussion of some new preliminary results

15O+α resonant elastic scattering to study cluster states in19Ne

Clustering phenomena are well known in nuclear physics for stable nuclei, both α-conjugate (N=Z, A=2N), like8Be,16O,20Ne, and non-α-conjugate, like6Li and7Li. In general, it is expected that light exotic nuclei may also exhibit cluster behavior. Moving out of the valley of stability configurations can be found where at least one of the clusters is unbound or weakly bound, thus not satisfying the strong internal correlation requirement of classical clusters. This is so-called exotic clustering. The study of such systems presents many difficulties, due, mainly, to the low intensities typical of radioactive ion beams. Therefore, few significant experimental studies have been performed so far. In this work we searched for α-cluster states in19Ne above its α-decay threshold measuring, for the first time, the15O(4He,4He) elastic scattering excitation function. Moreover, this study classified low-energy states in Ne in the astrophysically important region in this HCNO-break-out nucleus.European Unions Horizon 2020 65974

Global study of 9 Be + p at 2.72 A MeV

Background: In our recent experiment, 9 Be + p at 5.67 A MeV, the breakup decay rates to the three configurations, α + α + n , 8 Be ∗ + n and 5 He + 4 He of 9 Be , were observed and quantified in the proton recoil spectra, in a full kinematics approach. Unfolding step by step the accessibility to the above configurations, it will require similar experiments at lower or/and higher energies. It will also require the interpretation of the data in a theoretical framework. Three-body models for the structure of 9 Be have been developed and applied to reactions with heavy targets. Further research on lighter targets is required for the best establishment of the model. Such models are relevant for the calculation of the corresponding radiative capture reaction rate, α ( α , γ ) 9 Be followed by 9 Be ( α , n ) 12 C . The last is essential for the r -process abundance predictions. Purpose: Investigate the breakup decay rate of 9 Be + p at 2.72 A MeV, where the direct configuration α + α + n is mainly accessible. Compare and interpret data at this low energy and at the higher energy of 5.67 A MeV into a four-body continuum discretized coupled-channel formalism. Point out and discuss couplings to continuum. Methods: Our experimental method includes an exclusive breakup measurement in a full kinematic approach of 9 Be incident on a proton target at 24.5 MeV ( 2.72 A MeV). Complementary the elastic scattering is measured and other reaction channels are evaluated from previous measurements under the same experimental conditions. The interpretation of present data at 2.72 A MeV and previous data at 5.67 A MeV, are considered in a four-body continuum discretized coupled channel (CDCC) approach, using the transformed harmonic oscillator method for the three-body projectile. Results: An elastic scattering angular distribution at 2.72 A MeV is measured, which compares very well with CDCC calculations, indicating a strong coupling to continuum. At the same energy, the breakup and total reaction cross sections are measured as σ break = 2.5 ± 1 mb and σ tot = 510 ± L 90 mb , in good agreement with the calculated values of 3.7 and 433 mb, respectively. Further on, into the same theoretical framework, the elastic scattering and breakup cross section data at 5.67 A MeV are found in very good agreement with the CDCC calculations. Conclusions: It was confirmed in a global experimental framework that four-body CDCC calculations can describe very well the data even at low energies. Coupling to continuum is very strong despite the small measured breakup cross section. Moreover, the present results support further our three-body model for the structure of 9 Be , validating relevant radiative reaction rates obtained previously.Programa de investigación e innovación de la Unión Europea HORIZON2020 No. 654002-ENSAR2European Research Council (ERC) 714625Ministerio de Ciencia, Innovación y Universidades de España. PGC2018-095640-B-I00Ministerio de España de Economía y Competitividad y Fondo de Desarrollo de la Unión Europea (FEDER) FIS2017- 88410-PFondos SID 2019 (Università degli Studi di Padua, Italia) CASA_SID19_0

A new analysis procedure to extract fusion excitation function with large beam energy dispersions: Application to the 6Li+120Sn and 7Li+119Sn

In the present paper it is described an analysis procedure suited for experiments where cross-sections strongly varying with energy are measured using beams having large energy dispersion. These cross-sections are typically the sub-barrier fusion excitation function of reactions induced by radioactive beams. The large beam energy dispersion, typical of these experiments, can lead to ambiguities in the association of the effective beam energy to the reaction product yields and consequently to an error in the determination of the excitation function. As a test case, the approach is applied to the experiments 6Li+120Sn and 7Li+119Sn measured in the energy range 14 MeV ≤ Ecm. ≤28 MeV. The complete fusion cross sections are deduced from activation measurements using the stacked target technique. The results of these experiments, that employ the two weakly-bound stable Li isotopes, show that the complete fusion cross sections above the barrier are suppressed of about 70% and 85% with respect to the Universal Fusion Function, used as a standard reference, in the 6Li and 7Li induced reactions respectively. Moreover, the excitation functions of the two systems at energies below the barrier, do not show significant differences, despite the two systems have different n-transfer Qvalue

Interesting states in A = 10 mass region, populated in 10B + 10B nuclear reactions

The 10B+10B reactions are measured at beam energies of 50 and 72.2 MeV. The large spin of 10B nucleus (J= 3+) makes this reaction particularly suitable to populate high spin states in the exit channels. Population and decay of different states in A≈10 mass region is studied, and the results are discussed from the structure point of view. In particular, a new state in 12C at Ex= 24.4 MeV is observed to be strongly populated in the triple α-particle coincidences

Thick-target inverse kinematic method in order to investigate alpha-clustering in212Po

The inverse-kinematic thick-target method has been used in order to investigate 212Po alpha-structure by the elastic scattering of 208Pb on 4He target. A 208Pb beam, accelerated by the Superconducting Cyclotron (CS) of Laboratori Nazionali del Sud - INFN, at the incident energy of 10.1 A MeV was impinging onto a specifically designed 4He gas cell, two meter long. The gas cell wasacting both as target and as beam degrader, stopping the beam before reaching the alpha-particle detection system placed at 0° with respect to the beam axis. In order to disentangle the elastic contribution from other reaction channels (e.g. inelastic scattering) a microchannel plate was used to measure the Time of Flight(ToF) of both the 208Pb beam particles and the ejectiles along the gas cell. The 208Pbstopping power in the 4He gas target was also measured, as a key ingredient in order to establish theinteraction point inside the gas cell, in turn determining the solid angle covered by the detector. In the following, the experimental technique will be described, and the results of a preliminary data analysis will be shown

A new analysis procedure to extract fusion excitation function with large beam energy dispersions: application to the 6Li+120Sn and 7Li+119Sn

In the present paper it is described an analysis procedure suited for experiments where cross-sections strongly varying with energy are measured using beams having large energy dispersion. These cross-sections are typically the sub-barrier fusion excitation function of reactions induced by radioactive beams. The large beam energy dispersion, typical of these experiments, can lead to ambiguities in the association of the effective beam energy to the reaction product yields and consequently to an error in the determination of the excitation function. As a test case, the approach is applied to the experiments 6 Li+ 120 Sn and 7 Li+ 119 Sn measured in the energy range 14 MeV ≤ E c.m. ≤28 MeV. The complete fusion cross sections are deduced from activation measurements using the stacked target technique. The results of these experiments, that employ the two weakly-bound stable Li isotopes, show that the complete fusion cross sections above the barrier are suppressed of about 70% and 85% with respect to the Universal Fusion Function, used as a standard reference, in the 6 Li and 7 Li induced reactions respectively. Moreover, the excitation functions of the two systems at energies below the barrier, do not show significant differences, despite the two systems have different n -transfer Q value

A prototype for the real-time analysis of the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) observatory will be one of the biggest ground-based very-high-energy (VHE) γ- ray observatory. CTA will achieve a factor of 10 improvement in sensitivity from some tens of GeV to beyond 100 TeV with respect to existing telescopes. The CTA observatory will be capable of issuing alerts on variable and transient sources to maximize the scientific return. To capture these phenomena during their evolution and for effective communication to the astrophysical community, speed is crucial. This requires a system with a reliable automated trigger that can issue alerts immediately upon detection of γ-ray flares. This will be accomplished by means of a Real-Time Analysis (RTA) pipeline, a key system of the CTA observatory. The latency and sensitivity requirements of the alarm system impose a challenge because of the anticipated large data rate, between 0.5 and 8 GB/s. As a consequence, substantial efforts toward the optimization of highthroughput computing service are envisioned. For these reasons our working group has started the development of a prototype of the Real-Time Analysis pipeline. The main goals of this prototype are to test: (i) a set of frameworks and design patterns useful for the inter-process communication between software processes running on memory; (ii) the sustainability of the foreseen CTA data rate in terms of data throughput with different hardware (e.g. accelerators) and software configurations, (iii) the reuse of nonreal- time algorithms or how much we need to simplify algorithms to be compliant with CTA requirements, (iv) interface issues between the different CTA systems. In this work we focus on goals (i) and (ii)

NURE: An ERC project to study nuclear reactions for neutrinoless double beta decay

Neutrinoless double beta decay (0νββ) is considered the best potential resource to access the absolute neutrino mass scale. Moreover, if observed, it will signal that neutrinos are their own anti-particles (Majorana particles). Presently, this physics case is one of the most important research “beyond Standard Model” and might guide the way towards a Grand Unified Theory of fundamental interactions. Since the 0νββ decay process involves nuclei, its analysis necessarily implies nuclear structure issues. In the NURE project, supported by a Starting Grant of the European Research Council (ERC), nuclear reactions of double charge-exchange (DCE) are used as a tool to extract information on the 0νββ Nuclear Matrix Elements. In DCE reactions and ββ decay indeed the initial and final nuclear states are the same and the transition operators have similar structure. Thus the measurement of the DCE absolute cross-sections can give crucial information on ββ matrix elements. In a wider view, the NUMEN international collaboration plans a major upgrade of the INFN-LNS facilities in the next years in order to increase the experimental production of nuclei of at least two orders of magnitude, thus making feasible a systematic study of all the cases of interest as candidates for 0νββ