Determining the 13C(α, n)16O absolute cross section through the concurrent application of ANC and THM and astrophysical consequences for the s-process in AGB-LMSs.

The 13 C( α , n) 16 O reaction is considered to be the most important neutron source for the s -process main component in low-mass asymptotic giant branch stars. No direct experimental data exist at very low energies and measurements performed through direct techniques show inconsistent results, mostly in their absolute values. In this context, we reversed the usual normalization procedure combining two indirect approaches, the asymptotic normalization coefficient and the Trojan Horse Method, to unambiguously determine the absolute value of the 13 C( α , n) 16 O astrophysical S ( E )-factor in the most relevant energy-region for astrophysics. Adopting the new reaction rate for the n-source in the NEWTON s -process nucleosynthesis code, astrophysical calculations show only limited variations, less than 1%, for those nuclei whose production is considered to be totally due to slow neutron captures

THE 8 Li(α, n) 11 B REACTION RATE AT ASTROPHYSICAL TEMPERATURES

At temperatures (0.5-1.2) × 109 K, the 8Li + 4He → 11B+n reaction can allow for 12C and heavier element production in the framework of the inhomogeneous big bang nucleosynthesis. At temperatures (2.5-5) × 109 K, it can influence the production of seed nuclei, later burnt to heavier elements by means of rapid neutron capture reactions, during Type II supernova explosions. Previous determinations of the reaction rate show an untenable disagreement. In this work, a new reaction rate calculation is proposed for the intervals of astrophysical interest. This new recommendation turns out to be up to a factor of five larger than the most recent rate in the literature, thus enforcing the role of 8Li + 4He → 11B+n as a candidate for key astrophysical reactions. The analytical expression of the recommended reaction rate is given

few body reactions investigated with the trojan horse method

The Trojan Horse Method is an indirect method to measure reaction cross sections at energies of interest for nuclear astrophysics, exploiting the nuclei clustering properties. Here it is presented with its general features and detailed for the case of the ^22H(d,p)^33H and ^22H(d,n)^33He measurements, where interesting results for astrophysics and energy fusion power plants have been obtained

Determination of alpha spectroscopic factors for unbound 17O states

It has been recently suggested that hydrogen ingestion into the helium shell of massive stars could lead to high 13C and 15N excesses when the blast of a core collapse supernova (ccSN) passes through its helium shell. This prediction questions the origin of extremely high 13C and 15N abundances observed in rare presolar SiC grains which is usually attributed to classical novae. In this context the 13N(α,p)16O reaction plays an important role since it is in competition with 13N β+-decay to 13C. As a first step to the determination of the 13N(α,p)16O reaction rate, we present a study aiming at the determination of alpha spectroscopic factors of 17O states which are the analog ones to those in 17F, the compound nucleus of the 13N(α,p)16O reaction

Advanced age, time to treatment and long-term mortality: single centre data from the FAST-STEMI network

Background. Optimization of the techniques and larger accessibility to mechanical reperfusion have significantly improved the outcomes of patients with ST-segment elevation myocardial infarction (STEMI). However, suboptimal results have been observed in certain higher-risk subsets of patients, as in advanced age, where the benefits of primary PCI are more debated. We evaluated the impact of systematic primary percutaneous coronary intervention (PCI) and an optimized STEMI network on the long-term prognosis from a single centre experience.Methods. We included STEMI patients included in the FAST-STEMI network between 2016 and 2019. Ischemia duration was defined as the time from symptoms onset to coronary reopening (pain-to-balloon, PTB). The primary study endpoint (PE) was a composite of mortality and recurrent MI at long-term follow-up. Indywidual outcome endpoints were also assessed.Results. We included 253 patients undergoing primary PCI and discharged alive. Mean age was 67.2 ± 12.5 years, 75.1% males and 19.8% diabetics. At a median follow-up of 581 [307–922] days, the primary endpoint occurred in 24 patients (7.9%), of whom 5.5% died. The occurrence of a cardiovascular event was significantly associated with advanced age (p < 0.001), renal failure (p = 0.03), lower ejection fraction at discharge (p = 0.04) and longer in-hospital stay (p = 0.01). The median PTB was 198 minutes [IQR: 125–340 min], that was significantly longer among patients experiencing the PE (p = 0.01). A linear relationship was observed between age and PTB (r = 0.13, p = 0.009). However, both age ≥ 75 years and PTB above the median emerged as independent predictors of the primary endpoint (age: HR [95%CI] = 5.56 [2.26–13.7], p < 0.001, PTB: HR [95%CI] = 3.59 [1.39–9.3], p = 0.01). Similar results were observed for overall mortality.Conclusion. The present study shows that among STEMI patients undergoing primary PCI in a single centre, the duration of ischemia and advance age are independently associated to long-term mortality and recurrent myocardial infarction. However, longer time to reperfusion was observed among elderly patients

New direct measurement of the 10 B(p,α) 7 Be reaction with the activation technique

Boron plays an important role in astrophysics and, together with lithium and beryllium, is a probe of stellar structure during the pre-main sequence and main-sequence phases. In this context, the 10 B(p, α ) 7 Be reaction is of particular interest.The literature data show discrepancies in the energy range between 100 keV and 2 MeV. This also poses a normalization problem for indirect data obtained with the Trojan Horse Method.A new measurement of the 10 B(p, α ) 7 Be reaction cross section was performed at Legnaro National Laboratories (LNL). At LNL, the cross section was determined with the activation technique by measuring the activated samples at a low-background counting facility. The analysis of that experiment is now complete and the results are here presented

Trojan Horse Investigation for AGB Stellar Nucleosynthesis

Asymptotic Giant Branch (AGB) stars are among the most important astrophysical sites influencing the nucleosynthesis and the chemical abundances in the Universe. From a pure nuclear point of view, several processes take part during this peculiar stage of stellar evolution thus requiring detailed experimental cross section measurements. Here, we report on the most recent results achieved via the application of the Trojan Horse Method (THM) and Asymptotic Normalization Coefficient (ANC) indirect techniques, discussing the details of the experimental procedure and the deduced reaction rates. In addition, we report also on the on going studies of interest for AGB nucleosynthesis

Trojan Horse Method experiments with radioactive ion beams

The Trojan Horse Method (THM) is an indirect method that allows to get information about a two body reaction cross-section even at very low energy, avoiding the suppression effects due to the presence of the Coulomb barrier. The method requires a very accurate measurement of a three body reaction in order to reconstruct the whole kinematics and discriminate among different reaction mechanisms that can populate the same final state. These requirements hardly match with the typical low intensity and large divergence of radioactive ion beams (RIBs), and experimental improvements are mandatory for the applicability of the method. The first reaction induced by a radio activeion beam studied by applying the THM was the 18F(p,α)15O. Two experiments were performed in two different laboratories and using different experimental set-ups. The two experiments will be discussed and some results will be presented