The $$^{27}\hbox {Al}(\hbox {p},\alpha )^{24}\hbox {Mg}$$ reaction at astrophysical energies studied by means of the Trojan Horse Method applied to the $$^2\hbox {H}(^{27}\hbox {Al},\alpha ^{24}\hbox {Mg})\hbox {n}$$ reaction

Abstract

The $$^{27}\hbox {Al}(\hbox {p},\alpha )^{24}\hbox {Mg}$$ 27 Al ( p , α ) 24 Mg reaction, which drives the destruction of $$^{27}$$ 27 Al and the production of $$^{24}\hbox {Mg}$$ 24 Mg in stellar hydrogen burning, has been investigated via the Trojan Horse Method (THM), by measuring the $$^2\hbox {H}(^{27}\hbox {Al},\alpha ^{24}\hbox {Mg})\hbox {n}$$ 2 H ( 27 Al , α 24 Mg ) n three-body reaction. The experiment covered a broad energy range ($$E_\mathrm{c.m.}\le \,1.5\,\hbox {MeV}$$ E c . m . ≤ 1.5 MeV ), aiming to investigate those of interest for astrophysics. The results confirm the THM as a valuable technique for the experimental study of fusion reactions at very low energies and suggest the presence of a rich pattern of resonances in the energy region close to the Gamow window of stellar hydrogen burning (70–120 keV), with potential impact on astrophysics. To estimate such an impact a second run of the experiment is needed, since the background due the three-body reaction hampered to collect enough data to resolve the resonant structures and extract the reaction rate.

A New Reaction Rate of the 27Al(p/α)24Mg Reaction Based on Indirect Measurements at Astrophysical Energies and Implications for 27Al Yields of Intermediate-mass Stars

“…As discussed above, the results from Palmerini et al (2021) showed us that no particle identification was necessary using the ΔE-E technique. Instead, we carried out channel identification using the kinematic techniques discussed in, e.g., La Cognata et al (2010).…”

“…The beam energy was chosen to span the 27 Al−p energy range between the threshold and ∼1.5 MeV for normalization to measured resonance strengths. In this work, a higher beam energy than in the previous run (see Palmerini et al 2021 for details) was considered to explore a phase-space region where the contribution of the 25 Mg compound-nucleus decay to the reaction yield is negligible.…”

“…5 on opposite sides of the beam axis. The use of DSSSDs in the place of PSDs as in Palmerini et al (2021) made it possible to increase statistics, each DSSSD covering a solid angle 5 times larger than a PSD. Also, the symmetric setup made it possible to double statistics.…”

“…Also, the symmetric setup made it possible to double statistics. Thanks to a reanalysis of the data in Palmerini et al (2021), it turned out that no ΔE-E technique was necessary to perform particle selection, as will be clear later in this paper. The nonuse of an ionization chamber as a ΔE detector, as in Palmerini et al (2021), made it possible to improve the energy resolution in the particle detection and to improve the accuracy of measurement by reducing the systematic errors due, for instance, to the measurement of the pressure in the ionization chambers.…”

“…Thanks to a reanalysis of the data in Palmerini et al (2021), it turned out that no ΔE-E technique was necessary to perform particle selection, as will be clear later in this paper. The nonuse of an ionization chamber as a ΔE detector, as in Palmerini et al (2021), made it possible to improve the energy resolution in the particle detection and to improve the accuracy of measurement by reducing the systematic errors due, for instance, to the measurement of the pressure in the ionization chambers. Given the reaction kinematics, the forward detectors were used to detect the heavy fragment emitted in the reaction, while the other two detectors, placed closer to the target, were used to measure the light fragment.…”