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An experiment was performed by means of Trojan Horse Method (THM) at the LNS Tandem in Catania. The investigation of the relevant 19F(p,α)16O two-body reaction was performed by selecting the quasi free (QF) contribution of the 19F(²H,α16O)n three-body reaction, using the deuteron target as TH nucleus. The aim of this measurement is to obtain the 19F(p,α)16O cross section. The experimental set-up and the calibration of the detectors will be presented. [ABSTRACT FROM AUTHOR]

Owing the presence of the Coulomb barrier at astrophysically relevant kinetic energies, it is very difficult, or sometimes impossible to measure astrophysical reaction rates in laboratory. To overcome the problems related to the use of extrapolation procedure, the Trojan Horse Method (THM) has been applied extensively for the last 25 years to measure nuclear reaction cross sections of astrophysical interest. Although it has been mainly applied for charged particle-induced reactions, recently the THM has been found to have also a relevant role for neutron-induced ones. Here, the basic principle and a review of the main application of the Trojan Horse Method are presented, following a step-by-step description of the results concerning the study of the 17O(n,α)14C reaction. [ABSTRACT FROM AUTHOR]

The 12C(12C,α0,1)20Ne and 12C(12C,p0,1)23Na reactions have been measured from Ec.m.=2.7 MeV down to 0.8 MeV via the Trojan Horse Method o the deuteron in 14N. This range of energies is relevant in astrophysical scenarios, from superburst ignition to explosive stellar carbon burning. The deduced astrophysical S(E) factors exhibit several resonances that are responsible for a very large increase of the reaction rate at the relevant temperatures. [ABSTRACT FROM AUTHOR]

The experimental study of the 17O(n,α)14C reaction has been performed in the energy range 0-350 keV. This reaction could play an important role in explaining heavy elements (s-process) nucleosynthesis in various astrophysical scenario. To overcome the practical problems arising from the neutrons production, a new application of the Trojan Horse Method has been recently suggested. In more details, the 17O(n,α)14C reaction has been studied using the quasi-free ²H(17O,α14C)¹H reaction, induced at an energy of 43.5 MeV. The measurement allows one to investigate the ℓ=3, 75 keV resonance (E*=8.125 MeV, Jπ=5-), absent in the available direct measurements because of centrifugal suppression effects. Moreover, the results show that the contribution of the 166 keV and 236 keV resonances is in energy agreement with the available direct data. A clear contribution of the -7 keV subthreshold level is also present. [ABSTRACT FROM AUTHOR]

The 12C(14N,α20Ne)²H and 12C(14N,p23Na)²H reactions have been measured at a 14N beam energy of 30.0 MeV. The experiment aims to explore 24Mg excited states that can be populated in the quasi-free reaction off the deuteron in 14N. In particular, the 24Mg excitation region explored in the measurement plays a key role in stellar carbon burning whose cross section is obtained by extrapolating high-energy fusion data. From preliminary results, α and proton channels are clearly identified. In particular, ground and first excited states of 20Ne and 23Na play a major role. [ABSTRACT FROM AUTHOR]

In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of protoninduced reactions on 17O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17O(p,α)14N reaction via the THM by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. Two measurements will be described and the experimental THM cross sections will be shown for both experiments. [ABSTRACT FROM AUTHOR]

The 17O(p,α)14N reaction is of paramount importance for the nucleosynthesis in a number of stellar sites, including red giants (RG), asymptotic giant branch (AGB) stars, massive stars and classical novae. We report on the indirect study of the 17O(p,α)14N reaction via the Trojan Horse Method by applying the approach recently developed for extracting the resonance strength of the narrow resonance at Ec.m.R = 65 keV (EX =5.673 MeV). The strength of the 65 keV resonance in the 17O(p,α)14N reaction, measured by means of the THM, has been used to renormalize the corresponding resonance strength in the 17O + p radiative capture channel. [ABSTRACT FROM AUTHOR]

Boron abundances in stellar atmospheres, as well as berillium and lithium ones, can give useful hints for non-standard transport processes discrimination in stars. They can also be relevant for understanding several astrophysical processes (e.g. primordial nucleosynthesis and spallation reactions in ISM). A comprehensive study of Li Be B abundances can therefore confirm or not the presence of non-standard mixing processes in stellar envelopes. For this reason nuclear processes producing or depleting boron isotope abundance need to be studied at astrophysical energies. The 10B(p,α)7Be reaction has been studied by means of the Trojan Horse Method. The Trojan Horse Method was thus applied to the 10B(d,α 7Be)n reaction, studied at 24 MeV. The obtained results will be discussed. [ABSTRACT FROM AUTHOR]

Novae are astrophysical events (violent explosion) occurring in close binary systems consisting of a white dwarf and a main-sequence star or a star in a more advanced stage of evolution. They are called "narrow systems" because the two components interact with each other: there is a process of mass exchange with resulting in the transfer of matter from the companion star to the white dwarf, leading to the formation of this last of the so-called accretion disk, rich mainly of hydrogen. Over time, more and more material accumulates until the pressure and the temperature reached are sufficient to trigger nuclear fusion reactions, rapidly converting a large part of the hydrogen into heavier elements. The products of "hot hydrogen burning" are then placed in the interstellar medium as a result of violent explosions. Studies on the element abundances observed in these events can provide important information about the stages of evolution stellar. During the outbursts of novae some radioactive isotopes are synthesized: in particular, the decay of short-lived nuclei such as 13N and 18F with subsequent emission of gamma radiation energy below 511 keV. The gamma rays from products electronpositron annihilation of positrons emitted in the decay of 18F are the most abundant and the first observable as soon as the atmosphere of the nova starts to become transparent to gamma radiation. Hence the importance of the study of nuclear reactions that lead both to the formation and to the destruction of 18F. Among these, the 18F(p, α)15O reaction is one of the main channels of destruction. This reaction was then studied at energies of astrophysical interest. The experiment done at Riken, Japan, has as its objective the study of the 18F(p, α)15O reaction, using a beam of 18F produced at CRIB, to derive important information about the phenomenon of novae. In tis paper we present the experimental technique and the Monte Carlo code developed to be used in the data analysis process. [ABSTRACT FROM AUTHOR]

The Trojan Horse method is a powerful indirect technique to determine the astrophysical factor for binary rearrangement processes A+x → b+B at astrophysical energies by measuring the cross section for the Trojan Horse (TH) reaction A+a→B+b+s in quasi free kinematics. The Trojan Horse Method has been successfully applied to many reactions of astrophysical interest, both direct and resonant. In this paper, we will focus on direct sub-processes. The theory of the THM for direct binary reactions will be shortly presented based on a few-body approach that takes into account the off-energy-shell effects and initial and final state interactions. Examples of recent results will be presented to demonstrate how THM works experimentally. [ABSTRACT FROM AUTHOR]

The neutron capture rate 18O(n,? )19O is important for analysis of nucleosynthesis in inhomogeneous Big Bang models and also for models of processes in massive red giant stars and AGB stars. Angular distributions of the 18O(d,p)19O reaction were measured at a deuteron energy of 16.3 MeV in NPI in Řež, Czech Republic, with the aim to determine Asymptotic Normalization Coefficients which can then be used for indirect determination of the direct contribution to the 18O(n,? )19O process. In the experiment, the gas target with 18O isotope of high purity 99.9 % was used thus eliminating any contaminating reactions. Reaction products were measured by the set of 8 ?E -E telescopes consisting of thin and thick silicon surface-barrier detectors. Angular distributions of proton transfers corresponding to 6 levels of 19O up to the 4.1093 MeV excitation energy were determined. The analysis of angular distributions in the angular range from 6 to 64 degree including also the angular distribution of elastically scattered deuterons was carried out by means of ECIS and DWUCK codes. From the determined ANCs the direct contribution to the radiative capture 18O(n,? )19O was deduced and compared with existing direct measurements. [ABSTRACT FROM AUTHOR]

The role of oxygen in astrophysics is related to different problems as novae nucleosynthesis and gamma-ray astronomy. In particular, owing to the still present uncertainties on its rate, the 17O(p,α)14N is one of the most important reaction to be studied in order to get more information about the fate of oxygen in different astrophysical scenarios. [ABSTRACT FROM AUTHOR]

The abundance of 18F in Nova explosions is considered to be an important piece of information for the understanding of this astrophysical phenomenon. It is then necessary to study the nuclear processess that both produce and destroy this isotope in Novae. Among these latter reactions, the 18F(p,á)15O is one of the most important 18F destruction channels. Here we report on an experiment performed using the CRIB apparatus of the Center for Nuclear Study of the University of Tokyo. This was the first experiment that used the Trojan Horse method applied to a Radioactive Ion Beam induced reaction. [ABSTRACT FROM AUTHOR]

The 2H(3He,p3H)1H and 2H(3He,n3He)1H processes have been measured in quasi free kinematics to investigate for the first time the 2H(d,p)3H and 2H(d,n)3He reactions by means of the Trojan Horse Method. The 3He+d experiment was performed at 18 MeV, corresponding the a d-d energy range from 1.5 MeV down to 2 keV. This range overlaps with the relevant region for Standard Big Bang Nucleosynthesis as well as with the thermal energies of future fusion reactors and deuterium burning in the Pre Main Sequence phase of stellar evolution. This is the first pioneering experiment in quasi free regime where the charged spectator is detected. Both the energy dependence and the absolute value of the bare nucleus S(E) factors have been extracted for the first time. They deviate by more than 15% from available direct data with new S(0) values of 57.4±1.8 MeVb for 3H+p and 60.1±1.9 MeVb for 3He+n. None of the existing fitting curves is able to provide the correct slope of the new data in the full range, thus calling for a revision of the theoretical description. This has consequences in the calculation of the reaction rates with more than a 25% increase at the temperatures of future fusion reactors. [ABSTRACT FROM AUTHOR]

The abundance of 18F in Nova explosions is an important issue for the understanding of this astrophysical phenomenon. For this reason it is necessary to study the nuclear reactions that produce or destroy this isotope in novae. Among these latter processes, the 18F(p,α)15O is one of the main 18F destruction channels. We report here on the preliminary results of the first experiment that applies the Trojan Horse Method to a Radioactive Ion Beam induced reaction. The experiment was performed using the CRIB apparatus of the Center for Nuclear Study of The Tokyo University. [ABSTRACT FROM AUTHOR]

Nuclear clusters play a key role in the Trojan Horse Method for Nuclear Astrophysics studies. The Trojan Horse Method is an indirect technique to determine the astrophysical S(E) factor at ultra-low energies, free of Coulomb suppression and electron screening effect. Clustering makes it possible to use a few-body approach to derive a simple relationship between the measured 2 → 3 cross section and that of the 2 → 2 cross section of interest for astrophysics. The basic features of the Trojan Horse Method will be discussed and some recent results will be presented. [ABSTRACT FROM AUTHOR]

The 18O(p,α)15N reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as 19F, 18O and 15N. In this work, a high accuracy 18O(p,α)15N reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. In particular, we have focused on the study of the broad 660 keV 1/2+ resonance. Since Γ∼100-300 keV, it strongly influences the nearly-zero-energy region of the cross section by means of the low-energy tail of the resonant contribution and dominates the cross section at higher energies. Here we provide a factor of 2 larger reaction rate above T∼0.5 109 K based over our new improved determination of its resonance parameters. [ABSTRACT FROM AUTHOR]

The Trojan Horse Method (THM) was applied to the 3He+6Li interaction in order to investigate the quasi-free 6Li(d,α)4He reaction. The experiment was performed at 17 MeV at the Cyclotron Institute of the Czech Academy of Science. The extracted 6Li(d,α)4He quasi-free cross-section was compared with the behavior of direct data. A good agreement between data sets shows up throughout the energy range investigated, providing a very important validity test of the pole approximation for the THM above the Coulomb barrier. [ABSTRACT FROM AUTHOR]

We present here an important test of the main feature of the Trojan Horse Method (THM), namely the suppression of Coulomb effects in the entrance channel due to off-energy-shell effects. This is done by measuring the THM p-p elastic scattering via the p+d→p+p+n reaction at 4.7 and 5 MeV, corresponding to a p-p relative energy ranging from 80 to 670 keV. In contrast to the on-energy-shell (OES) case, the extracted p-p cross section does not exhibit the Coulomb-nuclear interference minimum due to the suppression of the Coulomb amplitude. This is confirmed by the half-off-energy shell (HOES) calculations and strengthened by the agreement with the calculated OES nuclear cross sections. [ABSTRACT FROM AUTHOR]

In order to understand primordial and stellar nucleosynthesis, we have studied 2H(d,p)3H reaction at 0.4 MeV down to astrophysical energies. Knowledge of its S-factor is interesting also to plan reactions for fusion reactors to produce energy. The 2H(d,p)H reaction has been studied through the Trojan Horse Method applied to the three-body reaction 2H(He,pt)H, at beam energy of 17 MeV. Once selection of protons and tritons detected in coincidence and the selection of quasi-free events, the obtained S-factor is compared with direct measurements. Such data are in agreement with the direct ones and a pole invariance test has been obtained comparing the present results with another 2H(d,p)3H THM measurements, where a different spectator particle was employed. [ABSTRACT FROM AUTHOR]

In order to understand primordial and stellar nucleosynthesis, we have studied 2H(d,p)3H reaction at 0, 4 MeV down to astrophysical energies. Knowledge of this S-factor is interesting also to plan reactions for fusion reactors to produce energy. 2H(d,p)3H has been studied through the Trojan Horse Method applied to the three-body reaction 2H(3He,pt)H, at a beam energy of 17 MeV. Once protons and tritons are detected in coincidence and the quasi-free events are selected, the obtained S-factor has been compared with direct reactions results. Such data are in agreement with the direct ones, and a pole invariance test has been obtained comparing the present result with another 2H(d,p)3H THM one, performed with a different spectator particle (see fig. 1). [ABSTRACT FROM AUTHOR]

We present here an important test of the main feature of the Trojan Horse Method (THM), namely the suppression of Coulomb effects in the entrance channel due to off-energy-shell effects. This is done by measuring the THM p—p elastic scattering via the p+d→p+p+n reaction at 4.7 and 5 MeV, corresponding to a p—p relative energy ranging from 80 to 670 keV. In contrast to the on-energy-shell (OES) case, the extracted p-p cross section does not exhibit the Coulomb-nuclear interference minimum due to the suppression of the Coulomb amplitude. This is confirmed by the half-off-energy shell (HOES) calculations and strengthened by the agreement with the calculated OES nuclear cross sections. [ABSTRACT FROM AUTHOR]

The Trojan Horse Method (THM) is an unique indirect technique allowing to measure astrophysical rearrangement reactions down to astrophysical relevant energies. The basic principle and a review of the recent applications of the Trojan Horse Method are presented. The applications aiming to the extraction of the bare astrophysical Sb(E) for some two-body processes are discussed. [ABSTRACT FROM AUTHOR]

The low-energy bare-nucleus cross section for 15N(p,α)12C is extracted by means of the Trojan-horse Method applied to the 2H(15N,α)12C)n reaction at Ebeam = 60 MeV. The astrophysical S-factor is deduced and compared to the direct data in the same energy region. A fair agreement with direct data down to 80 keV is found if energy resolution effects are taken into account. [ABSTRACT FROM AUTHOR]

The Trojan Horse Method has been recently applied to the study of reactions involved in fluorine nucleosynthesis inside AGB stars. Fluorine abundance is important since it allows to constrain mixing models from the comparison of the observed fluorine abundances with the ones predicted by models. Anyway direct measurements of the cross section do not extend down to the Gamow peak, which is the astrophysically relevant energy region. In particular the study focuses on the 15N(p,α)12C and the 18O(p,α)15N reactions which can influence fluorine yield as they are part of 19F production/destruction network. [ABSTRACT FROM AUTHOR]

The THM has been applied to the study of reactions involved in the fluorine production in AGB stars with the aim of extending these measurements down to the Gamow peak. Fluorine abundance is important since it allows to constrain mixing models from the comparison of the observed fluorine abundances with the ones predicted by models. In particular the study focuses on the 15N(p,α)12C and the 18O(p,α)15N reactions which can influence fluorine yield as they are part of 19F production (and destruction) network. [ABSTRACT FROM AUTHOR]

The 17O(p,a)14N reaction is of paramount importance for the nucleosynthesis in a number of stellar sites, including red giants (RG), asymptotic giant branch (AGB) stars, massive stars and classical novae. We report on the indirect study of the 17O(p,a)14N reaction via the Trojan Horse Method by applying the approach recently developed for extracting the resonance strength of narrow resonance in the ultra-low energy region. [ABSTRACT FROM AUTHOR]

The 19F(p,α)16O reaction is an important fluorine destruction channel in the proton-rich outer layers of asymptotic giant branch (AGB) stars and it might also play a role in hydrogendeficient post-AGB star nucleosynthesis. So far, available direct measurements do not reach the energy region of astrophysical interest (Ecm ∼ 300 keV), because of the hindrance effect of the Coulomb barrier. The Trojan Horse (TH) method was thus used to access this energy region, by extracting the quasi-free contribution to the 2H(19F,α16O)n reaction. The TH measurement of the α0 channel, which is the dominant one at such energies, shows the presence of resonant structures not observed before that cause an increase of the reaction rate at astrophysical temperatures up to a factor of 1.7, with potential important consequences for stellar nucleosynthesis. [ABSTRACT FROM AUTHOR]

In this work the analysis of the 10B(23p, α)7Be and 11B(p, α)8Be reactions, studied via the indirect Trojan Horse Method (THM), is discussed. In the astrophysical context of light nuclei LiBeB depletion, the above mentioned reactions are the main responsible for the destruction of boron in the stellar interior. The THM application allows their investigation in the astrophysically relevant energy region, around the Gamow Peak (≈10 keV), overcoming the problems due to the presence of the Coulomb barrier and electron screening effect. The experimental procedure and the preliminary results are shown. [ABSTRACT FROM AUTHOR]

The 10B(p,α)7Be reaction is the main responsible for 10B destruction in stellar interior. In such environments the process takes places mainly through a resonant state of the compound 11C nucleus. The 10B(p,α)7Be reaction has been studied by means of the Trojan Horse Method using the 2H(10B,α7Be)n three-body reaction. The experiment was performed at the Laboratori Nazionali del Sud in Catania. The 10B(p,α)7Be reaction cross section has been extracted at low neutron momentum. [ABSTRACT FROM AUTHOR]

Because of the still present uncertainties on its rate, the 17O(p,α)14N is one of the most important reaction to be studied in order to get more information about the fate of 17O in different astrophysical scenarios. The preliminary study of the three-body reaction 2H(17O,α14N)n is presented here as a first stage of the indirect study of this important 17O(p,α)14N reaction through the Trojan Horse Method (THM) [ABSTRACT FROM AUTHOR]