المؤلفون: Masha, E., Barbieri, L., Skowronski, J., Aliotta, M., Ananna, C., Barile, F., Bemmerer, D., Best, A., Boeltzig, A., Broggini, C., Bruno, C. G., Caciolli, A., Campostrini, M., Casaburo, F., Cavanna, F., Ciani, G. F., Ciapponi, A., Colombetti, P., Compagnucci, A., Corvisiero, P., Csedreki, L., Davinson, T., Depalo, R., Di Leva, A., Elekes, Z., Ferraro, F., Fiore, E. M., Formicola, A., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Imbriani, G., José, J., Junker, M., Lugaro, M., Manoj, P., Marigo, P., Menegazzo, R., Paticchio, V., Piatti, D., Prati, P., Rapagnani, D., Rigato, V., Robb, D., Schiavulli, L., Sidhu, R. S., Straniero, O., Szücs, T., Zavatarelli, S.

مصطلحات موضوعية: Nuclear Experiment, Astrophysics - Solar and Stellar Astrophysics

الوصف: The $\mathrm{^{20}Ne(p, \gamma)^{21}Na}$ reaction is the slowest in the NeNa cycle and directly affects the abundances of the Ne and Na isotopes in a variety of astrophysical sites. Here we report the measurement of its direct capture contribution, for the first time below $E\rm_{cm} = 352$~keV, and of the contribution from the $E^{\rm }_{cm} = 368$~keV resonance, which dominates the reaction rate at $T=0.03-1.00$~GK. The experiment was performed deep underground at the Laboratory for Underground Nuclear Astrophysics, using a high-intensity proton beam and a windowless neon gas target. Prompt $\gamma$ rays from the reaction were detected with two high-purity germanium detectors. We obtain a resonance strength $\omega \gamma~=~(0.112 \pm 0.002_{\rm stat}~\pm~0.005_{\rm sys})$~meV, with an uncertainty a factor of $3$ smaller than previous values. Our revised reaction rate is 20\% lower than previously adopted at $T < 0.1$~GK and agrees with previous estimates at temperatures $T \geq 0.1$~GK. Initial astrophysical implications are presented.
Comment: 8 pages, 4 figures, accepted to PRC (letter)

الوصول الحر: http://arxiv.org/abs/2311.04089Test

المؤلفون: Skowronski, J., Boeltzig, A., Ciani, G. F., Csedreki, L., Piatti, D., Aliotta, M., Ananna, C., Barile, F., Bemmerer, D., Best, A., Broggini, C., Bruno, C. G., Caciolli, A., Campostrini, M., Cavanna, F., Colombetti, P., Compagnucci, A., Corvisiero, P., Davinson, T., Depalo, R., Di Leva, A., Elekes, Z., Ferraro, F., Formicola, A., Fülöp, Zs., Gervino, G., Gesuè, R. M., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Imbriani, G., Junker, M., Lugaro, M., Marigo, P., Masha, E., Menegazzo, R., Paticchio, V., Perrino, R., Prati, P., Rapagnani, D., Rigato, V., Schiavulli, L., Sidhu, R. S., Straniero, O., Szücs, T., Zavatarelli, S.

المصدر: Phys. Rev. Lett. 131, 162701 (2023)

مصطلحات موضوعية: Nuclear Experiment

الوصف: The ${}^{12}\mathrm{C}/{}^{13}\mathrm{C}$ ratio is a significant indicator of nucleosynthesis and mixing processes during hydrogen burning in stars. Its value mainly depends on the relative rates of the ${}^{12}\mathrm{C}(p,\gamma){}^{13}\mathrm{N}$ and ${}^{13}\mathrm{C}(p,\gamma){}^{14}\mathrm{N}$ reactions. Both reactions have been studied at the Laboratory for Underground Nuclear Astrophysics (LUNA) in Italy down to the lowest energies to date ($E_\mathrm{c.m.} = 60\,\mathrm{keV}$) reaching for the first time the high energy tail of hydrogen burning in the shell of giant stars. Our cross sections, obtained with both prompt $\gamma$-ray detection and activation measurements, are the most precise to date with overall systematic uncertainties of $7-8\%$. Compared with most of the literature, our results are systematically lower, by $25\%$ for the ${}^{12}\mathrm{C}(p,\gamma){}^{13}\mathrm{N}$ reaction and by $30\%$ for ${}^{13}\mathrm{C}(p,\gamma){}^{14}\mathrm{N}$. We provide the most precise value up to now of $(3.6 \pm 0.4)$ in the $20-140\,\mathrm{MK}$ range for the lowest possible ${}^{12}\mathrm{C}/{}^{13}\mathrm{C}$ ratio that can be produced during H burning in giant stars.
Comment: Submitted to Phys. Rev. Lett

الوصول الحر: http://arxiv.org/abs/2308.16098Test

المؤلفون: Piatti, D., Masha, E., Aliotta, M., Balibrea-Correa, J., Barile, F., Bemmerer, D., Best, A., Boeltzig, A., Broggini, C., Bruno, C. G., Caciolli, A., Cavanna, F., Chillery, T., Ciani, G. F., Compagnucci, A., Corvisiero, P., Csedreki, L., Davinson, T., Depalo, R., di Leva, A., Elekes, Z., Ferraro, F., Fiore, E. M., Formicola, A., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Imbriani, G., Junker, M., Lugaro, M., Marigo, P., Menegazzo, R., Mossa, V., Pantaleo, F. R., Paticchio, V., Perrino, R., Prati, P., Rapagnani, D., Schiavulli, L., Skowronski, J., Stöckel, K., Straniero, O., Szücs, T., Takács, M. P., Zavatarelli, S.

المصدر: Eur. Phys. J. A 58, 194 (2022)

مصطلحات موضوعية: Nuclear Experiment

الوصف: In stars, the fusion of $^{22}$Ne and $^4$He may produce either $^{25}$Mg, with the emission of a neutron, or $^{26}$Mg and a $\gamma$ ray. At high temperature, the ($\alpha,n$) channel dominates, while at low temperature, it is energetically hampered. The rate of its competitor, the $^{22}$Ne($\alpha$,$\gamma$)$^{26}$Mg reaction, and, hence, the minimum temperature for the ($\alpha,n$) dominance, are controlled by many nuclear resonances. The strengths of these resonances have hitherto been studied only indirectly. The present work aims to directly measure the total strength of the resonance at $E$_{r}$\,=\,$334$\,$keV (corresponding to $E$_{x}$\,=\,$10949$\,$keV in $^{26}$Mg). The data reported here have been obtained using high intensity $^4$He$^+$ beam from the INFN LUNA 400 kV underground accelerator, a windowless, recirculating, 99.9% isotopically enriched $^{22}$Ne gas target, and a 4$\pi$ bismuth germanate summing $\gamma$-ray detector. The ultra-low background rate of less than 0.5 counts/day was determined using 67 days of no-beam data and 7 days of $^4$He$^+$ beam on an inert argon target. The new high-sensitivity setup allowed to determine the first direct upper limit of 4.0$\,\times\,$10$^{-11}$ eV (at 90% confidence level) for the resonance strength. Finally, the sensitivity of this setup paves the way to study further $^{22}$Ne($\alpha$,$\gamma$)$^{26}$Mg resonances at higher energy.
Comment: Submitted to Eur. Phys. J. A

الوصول الحر: http://arxiv.org/abs/2209.03051Test

المؤلفون: Ferraro, F., Ciani, G. F., Boeltzig, A., Cavanna, F., Zavatarelli, S.

المصدر: Front. Astron. Space Sci. 7:617946 (2021)

مصطلحات موضوعية: Nuclear Experiment

الوصف: The chemical evolution of the Universe and several phases of the stellar life are regulated by minute nuclear reactions. The key point for each of these reactions is the value of cross sections at the energies at which they take place in stellar environments. Direct cross-section measurements are mainly hampered by the very low counting rate and by cosmic background, nevertheless they have become possible by combining the best experimental techniques with the cosmic silence of an underground laboratory. In the nineties the LUNA (Laboratory for Underground Nuclear Astrophysics) collaboration opened the era of underground nuclear astrophysics installing first a home-made 50 kV and later on, a second 400 kV accelerator under the Gran Sasso mountain in Italy: in 25 years of experimental activity, important reactions responsible for hydrogen burning could have been studied down to the relevant energies thanks to the high current proton and helium beams provided by the machines. The interest to the next and warmer stages of star evolution (i.e. post main sequence, helium and carbon burning) drove a new project based on an ion accelerator in the MV range called LUNA-MV, able to deliver proton, helium and carbon beams. The present contribution is aimed to discuss the state-of-the-art for some selected key processes of post main sequence stellar phases: the 12Cag and the 12C+12C fundamental for helium and carbon burning phases, and 13Can and 22Neag that are relevant to the synthesis of heavy elements in AGB stars. The perspectives opened by an underground MV-facility will be highlighted.
Comment: 18 pages, 13 figures

الوصول الحر: http://arxiv.org/abs/2208.09283Test

المؤلفون: Ciani, G. F., Csedreki, L., Rapagnani, D., Aliotta, M., Balibrea-Correa, J., Barile, F., Bemmerer, D., Best, A., Boeltzig, A., Broggini, C., Bruno, C. G., Caciolli, A., Cavanna, F., Chillery, T., Corvisiero, P., Cristallo, S., Davinson, T., Depalo, R., DiLeva, A., Elekes, Z., Ferraro, F., Fiore, E., Formicola, A., Fulop, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyurky, Gy., Imbriani, G., Junker, M., Lugaro, M., Marigo, P., Masha, E., Menegazzo, R., Mossa, V., Pantaleo, F. R., Paticchio, V., Perrino, R., Piatti, D., Prati, P., Schiavulli, L., Stockel, K., Straniero, O., Szucs, T., Takacs, M. P., Terrasi, F., Vescovi, D., Zavatarelli, S .

مصطلحات موضوعية: Nuclear Experiment

الوصف: One of the main neutron sources for the astrophysical s-process is the reaction 13C({\alpha},n)16O, taking place in thermally pulsing Asymptotic Giant Branch stars at temperatures around 90 MK. To model the nucleosynthesis during this process the reaction cross section needs to be known in the 150-230keV energy window (Gamow peak). At these sub-Coulomb energies cross section direct measurements are severely affected by the low event rate, making us rely on input from indirect methods and extrapolations from higher-energy direct data. This leads to an uncertainty in the cross section at the relevant energies too high to reliably constrain the nuclear physics input to s-process calculations. We present the results from a new deep-underground measurement of 13C({\alpha},n)16O, covering the energy range 230-300keV, with drastically reduced uncertainties over previous measurements and for the first time providing data directly inside the s-process Gamow peak. Selected stellar models have been computed to estimate the impact of our revised reaction rate. For stars of nearly solar composition, we find sizeable variations of some isotopes, whose production is influenced by the activation of close-by branching points that are sensitive to the neutron density, in particular the two radioactive nuclei 60Fe and 205Pb, as well as 152Gd
Comment: 7 pages, 4 figures, accepted on PRL on 17th August 2021

الوصول الحر: http://arxiv.org/abs/2110.00303Test

المؤلفون: Mossa, V., Stöckel, K., Cavanna, F., Ferraro, F., Aliotta, M., Barile, F., Bemmerer, D., Best, A., Boeltzig, A., Broggini, C., Bruno, C. G., Caciolli, A., Csedreki, L., Chillery, T., Ciani, G. F., Corvisiero, P., Davinson, T., Depalo, R., Di Leva, A., Elekes, Z., Fiore, E. M., Formicola, A., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, G., Imbriani, G., Junker, M., Kochanek, I., Lugaro, M., Marcucci, L. E., Marigo, P., Masha, E., Menegazzo, R., Pantaleo, F. R., Paticchio, V., Perrino, R., Piatti, D., Prati, P., Schiavulli, L., Straniero, O., Szücs, T., Takács, M. P., Trezzi, D., Zavatarelli, S., Zorzi, G.

مصطلحات موضوعية: Physics - Instrumentation and Detectors, Astrophysics - Cosmology and Nongalactic Astrophysics, Nuclear Experiment

الوصف: Among the reactions involved in the production and destruction of deuterium during Big Bang Nucleosynthesis, the deuterium-burning D(p,gamma)3He reaction has the largest uncertainty and limits the precision of theoretical estimates of primordial deuterium abundance. Here we report the results of a careful commissioning of the experimental setup used to measure the cross-section of the D(p,gamma)3He reaction at the Laboratory for Underground Nuclear Astrophysics of the Gran Sasso Laboratory (Italy). The commissioning was aimed at minimising all sources of systematic uncertainty in the measured cross sections. The overall systematic error achieved (< 3 %) will enable improved predictions of BBN deuterium abundance.
Comment: 11 pages, 11 figures

الوصول الحر: http://arxiv.org/abs/2005.00002Test

المؤلفون: Ciani, G. F., Csedreki, L., Balibrea-Correa, J., Best, A., Aliotta, M., Barile, F., Bemmerer, D., Boeltzig, A., Broggini, C., Bruno, C. G., Caciolli, A., Cavanna, F., Chillery, T., Colombetti, P., Corvisiero, P., Davinson, T., Depalo, R., Di Leva, A., Di Paolo, L., Elekes, Z., Ferraro, F., Fiore, E. M., Formicola, A., Fulop, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyurky, Gy., Imbriani, G., Junker, M., Kochanek, I., Lugaro, M., Marigo, P., Masha, E., Menegazzo, R., Mossa, V., Pantaleo, F. R., Paticchio, V., Perrino, R., Piatti, D., Prati, P., Schiavulli, L., Stockel, K., Straniero, O., Szucs, T., Takacs, M. P., Terrasi, F., Trezzi, D., Zavatarelli, S.

المصدر: The European Physical Journal A volume 56, Article number: 75 (2020)

مصطلحات موضوعية: Physics - Instrumentation and Detectors, Nuclear Experiment

الوصف: Direct measurements of reaction cross-sections at astrophysical energies often require the use of solid targets able to withstand high ion beam currents for extended periods of time. Thus, monitoring target thickness, isotopic composition, and target stoichiometry during data taking is critical to account for possible target modifications and to reduce uncertainties in the final cross-section results. A common technique used for these purposes is the Nuclear Resonant Reaction Analysis (NRRA), which however requires that a narrow resonance be available inside the dynamic range of the accelerator used. In cases when this is not possible, as for example the 13C(alpha,n)16O reaction recently studied at low energies at the Laboratory for Underground Nuclear Astrophysics (LUNA) in Italy, alternative approaches must be found. Here, we present a new application of the shape analysis of primary gamma rays emitted by the 13C(p,g)14N radiative capture reaction. This approach was used to monitor 13C target degradation {\em in situ} during the 13C(alpha,n)16O data taking campaign. The results obtained are in agreement with evaluations subsequently performed at Atomki (Hungary) using the NRRA method. A preliminary application for the extraction of the 13C(alpha,n)16O reaction cross-section at one beam energy is also reported.
Comment: 10 pages, 6 figures, to be published in EPJ A

الوصول الحر: http://arxiv.org/abs/2001.08744Test

المؤلفون: Ferraro, F., Takács, M. P., Piatti, D., Cavanna, F., Depalo, R., Aliotta, M., Bemmerer, D., Best, A., Boeltzig, A., Broggini, C., Bruno, C. G., Caciolli, A., Chillery, T., Ciani, G. F., Corvisiero, P., Davinson, T., D'Erasmo, G., DiLeva, A., Elekes, Z., Fiore, E. M., Formicola, A., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Imbriani, G., Junker, M., Karakas, A., Kochanek, I., Lugaro, M., Marigo, P., Menegazzo, R., Mossa, V., Pantaleo, F. R., Paticchio, V., Perrino, R., Prati, P., Schiavulli, L., Stöckel, K., Straniero, O., Szücs, T., Trezzi, D., Zavatarelli, S.

المصدر: Phys. Rev. Lett. 121, 172701 (2018)

مصطلحات موضوعية: Nuclear Experiment

الوصف: The $^{22}$Ne($p,\gamma$)$^{23}$Na reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying non-resonant component. Three new resonances at $E_p$ = 156.2, 189.5, and 259.7 keV have recently been observed and confirmed. However, significant uncertainty on the reaction rate remains due to the non-resonant process and to two suggested resonances at $E_p$ = 71 and 105 keV. Here, new $^{22}$Ne($p,\gamma$)$^{23}$Na data with high statistics and low background are reported. Stringent upper limits of 6$\times$10$^{-11}$ and 7$\times$10$^{-11}$\,eV (90\% confidence level), respectively, are placed on the two suggested resonances. In addition, the off-resonant S-factor has been measured at unprecedented low energy, constraining the contributions from a subthreshold resonance and the direct capture process. As a result, at a temperature of 0.1 GK the error bar of the $^{22}$Ne($p,\gamma$)$^{23}$Na rate is now reduced by three orders of magnitude.
Comment: Submitted to Phys. Rev. Lett

الوصول الحر: http://arxiv.org/abs/1810.01628Test

المؤلفون: Cristallo, S., La Cognata, M., Massimi, C., Best, A., Palmerini, S., Straniero, O., Trippella, O., Busso, M., Ciani, G. F., Mingrone, F., Piersanti, L., Vescovi, D.

مصطلحات موضوعية: Astrophysics - Solar and Stellar Astrophysics

الوصف: Low mass Asymptotic Giant Branch stars are among the most important polluters of the interstellar medium. In their interiors, the main component (A>90) of the slow neutron capture process (the s-process) is synthesized, the most important neutron source being the 13C(alpha,n)16O reaction. In this paper we review its current experimental status discussing possible future synergies between some experiments currently focused on the determination of its rate. Moreover, in order to determine the level of precision needed to fully characterize this reaction, we present a theoretical sensitivity study, carried out with the FUNS evolutionary stellar code and the NEWTON post-process code. We modify the rate up to a factor of two with respect to a reference case. We find that variations of the 13C(alpha,n)16O rate do not appreciably affect s-process distributions for masses above 3 Msun at any metallicity. Apart from a few isotopes, in fact, the differences are always below 5%. The situation is completely different if some 13C burns in a convective environment: this occurs in FUNS models with M<3 Msun at solar-like metallicities. In this case, a change of the 13C(alpha,n)16O reaction rate leads to non-negligible variations of the elements Surface distribution (10% on average), with larger peaks for some elements (as rubidium) and for neutron-rich isotopes (as 86Kr and 96Zr). Larger variations are found in low-mass low-metallicity models, if protons are mixed and burnt at very high temperatures. In this case, the surface abundances of the heavier elements may vary by more than a factor 50.
Comment: Accepted for publication on ApJ

الوصول الحر: http://arxiv.org/abs/1804.10751Test

المؤلفون: Ferraro, F., Takács, M. P., Piatti, D., Mossa, V., Aliotta, M., Bemmerer, D., Best, A., Boeltzig, A., Broggini, C., Bruno, C. G., Caciolli, A., Cavanna, F., Chillery, T., Ciani, G. F., Corvisiero, P., Csedreki, L., Davinson, T., Depalo, R., D'Erasmo, G., Di Leva, A., Elekes, Z., Fiore, E. M., Formicola, A., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Imbriani, G., Junker, M., Kochanek, I., Lugaro, M., Marcucci, L. E., Marigo, P., Menegazzo, R., Pantaleo, F. R., Paticchio, V., Perrino, R., Prati, P., Schiavulli, L., Stöckel, K., Straniero, O., Szücs, T., Trezzi, D., Zavatarelli, S.

المصدر: Eur. Phys. J. A (2018) 54: 44

مصطلحات موضوعية: Nuclear Experiment, Astrophysics - Instrumentation and Methods for Astrophysics

الوصف: The experimental study of nuclear reactions of astrophysical interest is greatly facilitated by a low-background, high-luminosity setup. The Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator offers ultra-low cosmic-ray induced background due to its location deep underground in the Gran Sasso National Laboratory (INFN-LNGS), Italy, and high intensity, 250-500 $\mu$A, proton and $\alpha$ ion beams. In order to fully exploit these features, a high-purity, recirculating gas target system for isotopically enriched gases is coupled to a high-efficiency, six-fold optically segmented bismuth germanate (BGO) $\gamma$-ray detector. The beam intensity is measured with a beam calorimeter with constant temperature gradient. Pressure and temperature measurements have been carried out at several positions along the beam path, and the resultant gas density profile has been determined. Calibrated $\gamma$-intensity standards and the well-known $E_p$ = 278 keV $\mathrm{^{14}N(p,\gamma)^{15}O}$ resonance were used to determine the $\gamma$-ray detection efficiency and to validate the simulation of the target and detector setup. As an example, the recently measured resonance at $E_p$ = 189.5 keV in the $^{22}$Ne(p,$\gamma$)$^{23}$Na reaction has been investigated with high statistics, and the $\gamma$-decay branching ratios of the resonance have been determined.
Comment: 11 pages, 11 figures, accepted in Eur. Phys. Journal A

الوصول الحر: http://arxiv.org/abs/1802.04164Test