Trojan Horse Method Research Articles

Nuclear Physics in Stellar Lifestyles with the Trojan Horse Method

The Trojan Horse Method is an indirect technique to measure nuclear reactions of astrophysical relevance at the energies of interest, free of Coulomb suppression and electron screening effects. Its basic features in the framework of the theory of direct reactions will be discussed and the physics case of the 12C+12C fusion will be addressed.

On the fluorine nucleosynthesis in AGB stars in the light of the 19F(p,α)16O and 19F(α,p)22Ne reaction rate measured via THM

In the last years the [Formula: see text]O and the [Formula: see text]F([Formula: see text],p)[Formula: see text]Ne reactions have been studied via the Trojan Horse Method in the energy range of interest for astrophysics. These are the first experimental data available for the main channels of [Formula: see text]F destruction that entirely cover the energy regions typical of the stellar H- and He- burning. In both cases the reaction rates are significantly larger than the previous estimations available in the literature. We present here a re-analysis of the fluorine nucleosynthesis in Asymptotic Giant Branch stars by employing in state-of-the-art models of stellar nucleosynthesis the THM reaction rates for [Formula: see text]F destruction.

Nuclear physics and its role for describing the early universe

Big Bang Nucleosynthesis (BBN) requires several nuclear physics inputs and nuclear reaction rates. An up-to-date compilation of direct cross sections of [Formula: see text], [Formula: see text]He and [Formula: see text]He reactions is given, being these ones among the most uncertain bare-nucleus cross sections. An intense experimental effort has been carried on in the last decade to apply the Trojan Horse Method (THM) to study reactions of relevance for the BBN and measure their astrophysical S(E)-factor. The reaction rates and the relative error for the four reactions of interest are then numerically calculated in the temperature ranges of relevance for BBN [Formula: see text]. These value were then used as input physics for primordial nucleosynthesis calculations in order to evaluate their impact on the calculated primordial abundances and isotopical composition for H, He and Li. New results on the [Formula: see text]He reaction rate were also taken into account.These were compared with the observational primordial abundance estimates in different astrophysical sites. Reactions to be studied in perspective will also be discussed.

Application of the THM to the investigation of reactions induced by unstable nuclei: the 18F(p,α)15O case

The Trojan Horse Method is applied to the investigation of the 18F(p,α)15O reaction, by extracting the quasi free contribution to the 2H(18F,α15O)n process. For the first time the method is applied to a reaction of astrophysical importance involving a radioactive nucleus. After investigating the reaction mechanism populating the a + 15O + n exit channel, we could extract the 18F(p,α)15O cross section and calculate the astrophysical factor over the 0 – 1 MeV energy interval. The possibility of exploring the cross section with no need of extrapolation allowed us to to point out the possible occurrence of a 7/2+ state at 126 keV, which would strongly influence the trend of the astrophysical factor at the energies of astrophysical interest. However, the low energy resolution prevents us to draw definite conclusions. Possible astrophysical consequences are also discussed, motivating further work on this reaction.

Application of the pathogen Trojan horse approach in maize (Zea mays)

ABSTRACTMaize, Zea mays, the second-most-widely-grown crop, yields 20 % of all consumed calories worldwide.1 Despite its agronomic importance, research progress is limited by costly transformation. We recently described the Trojan horse method as a useful tool to study maize proteins in situ that circumvents time- and space-consuming whole plant transformation. The Trojan horse approach uses the protein-folding and secretory properties of the corn smut fungus Ustilago maydis to secrete maize proteins from fungal cells into the maize apoplast. Here, we discuss the timing and location of U. maydis during infection and the protein secretion site in relation to anther anatomy. This spatiotemporal analysis enables the study of apoplastic anther proteins in various premeiotic anther developmental stages, and could be adapted for larger screens.

Study of the 10B(p,$\alpha_{1}$α1)7Be reaction by means of the Trojan Horse Method

Study of the 10B(p,$\alpha_{1}$α1)7Be reaction by means of the Trojan Horse Method

Impacts of the new carbon fusion cross-sections on type Ia supernovae

ABSTRACT Type Ia supernovae (SNe Ia) are thought to be thermonuclear explosion of white dwarfs (WDs). Their progenitors are not well understood. One popular scenario is the double-degenerate (DD) scenario, which attributes SNe Ia to WD–WD binary mergers. The fates of the WD mergers depend on the rate of 12C + 12C reaction. Recently, the 12C + 12C cross-sections have been measured and the analysis of the data using the Trojan Horse Method suggested that the astrophysical reaction rate is larger than conventional rates at astrophysical temperatures due to possible resonances. The resonance contribution results in a decrease of the carbon burning ignition temperature. Therefore, accretion-induced collapse occurs more easily and increases the birth rate of Galactic neutron stars with the contribution of the DD scenario to the SNe Ia rate becoming even smaller.

Direct measurement of astrophysical factor S(E) and screening potential for [formula omitted] reaction at low energy

As Beryllium is an important element in primary nucleosynthesis, its nuclear reaction cross-sections induced by charged projectiles need to be measured precisely. The astrophysical S(Ei) factors were measured in the ultra-low energy range from Elab=18 to 100 keV in 2-keV increments (42 points). Both the astrophysical S(E) curve (Sbare(0)=16.2±1.8MeVb) and the screening energy (Us=545±98eV) were deduced. In regard to astrophysical applications of the Sbare(E) curve, the present results are consistent with Zahnow's direct measurement. For the long-standing problem of ‘abnormal’ screening effect, our screening energy result also agrees with that obtained using the Trojan-horse method (Us=676±86eV) but smaller than Zahnow's value (900±50eV), although all results are much larger than that obtained in the adiabatic limit (∼264 eV).

Probing the Early Universe through nuclear physics

Big Bang Nucleosynthesis (BBN) requires several nuclear physics inputs and nuclear reaction rates. An up-to-date compilation of direct cross sections of d(d,p)t, d(d,n)3 He and 3He(d,p)4He reactions is given, being these ones among the most uncertain bare-nucleus cross sections. An intense experimental effort has been carried on in the last decade to apply the Trojan Horse Method (THM) to study reactions of relevance for the BBN and measure their astrophysical S(E)-factor. The reaction rates and the relative error for the four reactions of interest are then numerically calculated in the temperature ranges of relevance for BBN (0.01 < T9 < 10). These value were then used as input physics for primordial nucleosynthesis calculations in order to evaluate their impact on the calculated primordial abundances and isotopical composition for H, He and Li. New results on the 7Be(n, α)4 He reaction rate were also taken into account. These were compared with the observational primordial abundance estimates in different astrophysical sites. Reactions to be studied in perspective will also be discussed

The 19F(α, p)22Ne Reaction at Energies of Astrophysical Relevance by Means of the Trojan Horse Method and Its Implications in AGB Stars

Abstract The main source of 19F in the universe has not yet been clearly identified and this issue represents one of the unanswered questions of stellar modeling. This lack of knowledge can be due to the 19F(α, p)22Ne reaction cross-section that has proven to be difficult at low energies: direct measurements stop only at about ∼660 keV, leaving roughly half of the astrophysical relevant energy region (from 200 keV to 1.1 MeV) explored only by R-matrix calculations. In this work, we applied the Trojan Horse Method to the quasi-free three-body 6Li(19F, p22Ne)d reaction performed at E beam = 6 MeV in order to indirectly study the 19F(α, p)22Ne reaction in the sub-Coulomb energy region. In this way, we obtained the cross-section and the reaction rate in the temperature region of interest for astrophysics and free from electron screening effects. A brief analysis of the impact of the new measured reaction rate in AGB star nucleosynthesis is also presented.

Trojan horse measurement of the B10(p,α0)Be7 cross section in the energy range from 3 keV to 2.2 MeV

The $^{10}\mathrm{B}(p,{\ensuremath{\alpha}}_{0})^{7}\mathrm{Be}$ excitation function has been studied in a wide energy range, from 2.2 MeV down to astrophysical energies, reproducing the cross section above and below the Coulomb barrier in a single experiment. An optimized experimental setup ensured good energy resolution and for the first time a clear separation of ${\ensuremath{\alpha}}_{0}$ and ${\ensuremath{\alpha}}_{1}$ channels of the $^{10}\mathrm{B}+^{2}\mathrm{H}$ interaction has been achieved by applying the Trojan Horse method. An improved normalization of the Trojan Horse bare-nucleus astrophysical $S$($E$)-factor to direct data was performed and a value of ${U}_{e}=391\ifmmode\pm\else\textpm\fi{}74\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ was obtained for the electron screening potential.

Effectiveness of using a magnetic spectrograph with the Trojan Horse method

The Trojan Horse method relies on performing reactions in a specific kinematic phase space that maximizes contributions of a quasi-free reaction mechanism. The hallmark of this method is that the incident particle can be accelerated to high enough energies to overcome the Coulomb barrier of the target, but once inside the target nucleus the relative motion of the clustered nuclei allows the reaction of interest to proceed at energies below this Coulomb Barrier. This method allows the experimentalist to probe reactions that have significance in astrophysics at low reaction energies that would otherwise be impossible due to the vanishing cross section. Traditionally the Trojan Horse method has been applied with the use of silicon detectors to observe the reaction products. In this study we apply the Trojan Horse method to a well studied reaction to examine the potential benefits of using a splitpole magnetic spectrograph to detect one of the reaction products. We have measure the three body 7Li(d,αn)α reaction to constrain the energy 7Li(d,α)α cross section. Measurements were first made using two silicon detectors, and then by replacing one detector with the magnetic spectrograph. The experimental design, limitations, and early results are discussed.

The Trojan Horse Method in Nuclear Astrophysics

The Trojan Horse Method (THM) represents the indirect way to measure reactions between charged particles at astrophysical energies. This is done by measuring the quasi free cross section of a suitable three body process. The basic features of the THM will be presented together with some applications to demonstrate its practical use.

The Treiman-Yang Criterion: validating the Trojan Horse Method by experimentally probing the reaction mechanism

Proper selection of the quasi-free (QF) break-up channel in a three-body reaction is a key aspect for the applicability of the Trojan Horse Method (THM). The Treiman-Yang (TY) Criterion is a model-independent experimental test for the dominance of the QF mechanism, and hence constitutes one of the strongest validity tests of the THM. An experiment was performed at LNS to apply the test to the d(10B, 7Be α)n reaction. Here, the criterion is described and some preliminary data from the experiment are shown.

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.

The 19F(α, p)22Ne and 23Na(p,α)20Ne reaction in AGB nucleosynthesis via THM

In AGB environment, fluorine and sodium abundances are still matter of debate. About 19F (only stable isotope of fluorine), its abundance in the universe is strictly related to standard and extra-mixing processes taking place inside AGB-stars, that are considered to be the most important sites for its production. Nevertheless the way in which it is destroyed is far from being well understood. On the other hand, 23Na presence in Globular Clusters, along with is well-known anticorrelation with oxygen has made clear that this element must be produced in previous generations stars, and intermediatemass AGB stars are one of the possible candidates for its production. For this reason we studied the 19F(α,p)22Ne and 23Na(p,α)20Ne reactions in the energy range of relevance for astrophysics via the Trojan Horse Method (THM), using the three-body reactions 6Li(19F, p22Ne)d and 23Na(d, pn)20Ne.

Trojan Horse cross section measurements and their impact on primordial nucleosynthesis

Big Bang Nucleosynthesis (BBN) nucleosynthesis requires several nuclear physics inputs and, among them, an important role is played by nuclear reaction rates. They are among the most important input for a quantitative description of the early Universe. An up-to-date compilation of direct cross sections of d(d,p)t, d(d,n)3He and 3He(d,p)4He reactions is given, being these ones among the most uncertain bare-nucleus cross sections.An intense experimental effort has been carried on in the last decade to apply the Trojan Horse Method (THM) to study reactions of relevance for the BBN and measure their astrophysical S(E)-factor. The result of these recent measurements is reviewed and compared with the available direct data. The reaction rates and the relative error for the four reactions of interest are then numerically calculated in the temperature ranges of relevance for BBN (0.01<T9 <10) and compared with up-to-date reaction rate compilations. Their value were therefore used as input physics for primordial nucleosynthesis calculations in order to evaluate their impact on the calculated primordial abundances of D, 3,4He and 7Li. These ones were then compared with the observational primordial abundance estimates in different astrophysical sites. A comparison was also performed with calculations using other reaction rates compilations available in literature.

Experimental Studies of Nuclear Reactions of Astrophysical Relevance by Means of the Trojan Horse Method Applied to Resonant Reactions

Experimental Studies of Nuclear Reactions of Astrophysical Relevance by Means of the Trojan Horse Method Applied to Resonant Reactions

Improved information on astrophysical S-factor for the 10B(p,α0)7Be reaction using the Trojan Horse method

The 10B(p,α0)7Be reaction has been studied by applying the Trojan Horse method to the 2H(10B,α0 7Be)n reaction. The bare-nucleus astrophysical S(E)-factor in absolute units was extracted in a wide energy range, from 2.2 MeV to 3 keV and normalized to the direct experimental data, thus allowing determination of the electron screening potential for which a value of Ue=391±74 eV was obtained.

Assessing the foundation of the Trojan Horse Method

We discuss the foundation of the Trojan Horse Method (THM) within the Inclusive Non-Elastic Breakup (INEB) theory. We demonstrate that the direct part of the INEB cross section, which is of two-step character, becomes, in the DWBA limit of the three-body theory with appropriate approximations and redefinitions, similar in structure to the one-step THM cross section. We also discuss the connection of the THM to the Surrogate Method (SM), which is a genuine two-step process.