227 results on '"Davids, B."'
Search Results
2. Use of Bayesian Optimization to understand the structure of nuclei
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Hooker, J., Kovoor, J., Jones, K.L., Kanungo, R., Alcorta, M., Allen, J., Andreoiu, C., Atar, L., Bardayan, D.W., Bhattacharjee, S.S., Blankstein, D., Burbadge, C., Burcher, S., Catford, W.N., Cha, S., Chae, K., Connolly, D., Davids, B., Esker, N., Garcia, F.H., Gillespie, S., Ghimire, R., Gula, A., Hackman, G., Hallam, S., Hellmich, M., Henderson, J., Holl, M., Jassal, P., King, S., Knight, T., Kruecken, R., Lepailleur, A., Liang, J., Morrison, L., O’Malley, P.D., Pain, S.D., Pereira-Lopez, X., Psaltis, A., Radich, A., Shotter, A.C., Vostinar, M., Williams, M., and Workman, O.
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- 2022
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3. Beyond the acceptance limit of DRAGON: The case of the [formula omitted]Li([formula omitted])[formula omitted]B reaction
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Psaltis, A., Chen, A.A., Connolly, D.S., Davids, B., Gilardy, G., Giri, R., Greife, U., Huang, W., Hutcheon, D.A., Karpesky, J., Lennarz, A., Liang, J., Lovely, M., Paneru, S.N., Ruiz, C., Tenkila, G., and Williams, M.
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- 2021
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4. The GRIFFIN facility for Decay-Spectroscopy studies at TRIUMF-ISAC
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Garnsworthy, A.B., Svensson, C.E., Bowry, M., Dunlop, R., MacLean, A.D., Olaizola, B., Smith, J.K., Ali, F.A., Andreoiu, C., Ash, J.E., Ashfield, W.H., Ball, G.C., Ballast, T., Bartlett, C., Beadle, Z., Bender, P.C., Bernier, N., Bhattacharjee, S.S., Bidaman, H., Bildstein, V., Bishop, D., Boubel, P., Braid, R., Brennan, D., Bruhn, T., Burbadge, C., Cheeseman, A., Chester, A., Churchman, R., Ciccone, S., Caballero-Folch, R., Cross, D.S., Cruz, S., Davids, B., Varela, A. Diaz, Dillmann, I., Dunlop, M.R., Evitts, L.J., Garcia, F.H., Garrett, P.E., Georges, S., Gillespie, S., Gudapati, R., Hackman, G., Hadinia, B., Hallam, S., Henderson, J., Ilyushkin, S.V., Jigmeddorj, B., Kilic, A.I., Kisliuk, D., Kokke, R., Kuhn, K., Krücken, R., Kuwabara, M., Laffoley, A.T., Lafleur, R., Leach, K.G., Leslie, J.R., Linn, Y., Lim, C., MacConnachie, E., Mathews, A.R., McGee, E., Measures, J., Miller, D., Mills, W.J., Moore, W., Morris, D., Morrison, L.N., Moukaddam, M., Natzke, C.R., Ortner, K., Padilla-Rodal, E., Paetkau, O., Park, J., Patel, H.P., Pearson, C.J., Peters, E., Peters, E.E., Pore, J.L., Radich, A.J., Rajabali, M.M., Rand, E.T., Raymond, K., Rizwan, U., Ruotsalainen, P., Saito, Y., Sarazin, F., Shaw, B., Smallcombe, J., Southall, D., Starosta, K., Ticu, M., Timakova, E., Turko, J., Umashankar, R., Unsworth, C., Wang, Z.M., Whitmore, K., Wong, S., Yates, S.W., Zganjar, E.F., and Zidar, T.
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- 2019
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5. Measuring the 15O(α,γ)19Ne Reaction in Type I X-ray Bursts using the GADGET II TPC: Software
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Mahajan Ruchi, Adams A., Allmond J., Alvarez Pol H., Argo E., Ayyad Y., Bardayan D., Bazin D., Budner T., Chen A., Chipps K., Davids B., Dopfer J., Friedman M., Fynbo H., Grzywacz R., Jose J., Liang J., Pain S., Perez-Loureiro D., Pollacco E., Psaltis A., Ravishankar S., Rogers A., Schaedig L., Sun L. J., Surbrook J., Wheeler T., Weghorn L., and Wrede C.
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Physics ,QC1-999 - Abstract
15O(α,γ)19Ne is regarded as one of the most important thermonuclear reactions in type I X-ray bursts. For studying the properties of the key resonance in this reaction using β decay, the existing Proton Detector component of the Gaseous Detector with Germanium Tagging (GADGET) assembly is being upgraded to operate as a time projection chamber (TPC) at FRIB. This upgrade includes the associated hardware as well as software and this paper mainly focusses on the software upgrade. The full detector set up is simulated using the ATTPCROOTv 2 data analysis framework for 20Mg and 241Am.
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- 2022
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6. Measuring the 15O(α, γ)19Ne reaction in Type I X-ray bursts using the GADGET II TPC: Hardware
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Wheeler Tyler, Adams A., Allmond J., Alvarez Pol H., Argo E., Ayyad Y., Bardayan D., Bazin D., Budner T., Chen A., Chipps K., Davids B., Dopfer J., Friedman M., Fynbo H., Grzywacz R., Jose J., Liang J., Mahajan R., Pain S., Pérez-Loureiro D., Pollacco E., Psaltis A., Ravishankar S., Rogers A., Schaedig L., Sun L. J., Surbrook J., Weghorn L., and Wrede C.
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Physics ,QC1-999 - Abstract
Sensitivity studies have shown that the 15O(α, γ)19Ne reaction is the most important reaction rate uncertainty affecting the shape of light curves from Type I X-ray bursts. This reaction is dominated by the 4.03 MeV resonance in 19Ne. Previous measurements by our group have shown that this state is populated in the decay sequence of 20Mg. A single 20Mg(βp α)15O event through the key 15O(α, γ)19Ne resonance yields a characteristic signature: the emission of a proton and alpha particle. To achieve the granularity necessary for the identification of this signature, we have upgraded the Proton Detector of the Gaseous Detector with Germanium Tagging (GADGET) into a time projection chamber to form the GADGET II detection system. GADGET II has been fully constructed, and is entering the testing phase.
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- 2022
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7. High-resolution radioactive beam study of the 26Al(d,p) reaction and measurements of single-particle spectroscopic factors
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Lotay, G., Woods, P. J., Moukaddam, M., Aliotta, M., Christian, G., Davids, B., Davinson, T., Doherty, D. T., Howell, D., Margerin, V., and Ruiz, C.
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- 2020
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8. Cross Sections of the $^{83}$Rb(p,$\gamma)^{84}$Sr and $^{84}$Kr(p,$\gamma)^{85}$Rb Reactions at Energies Characteristic of the Astrophysical $\gamma$ Process
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Williams, M., Davids, B., Lotay, G., Nishimura, N., Rauscher, T., Gillespie, S. A., Alcorta, M., Amthor, A. M., Ball, G. C., Bhattacharjee, S. S., Bildstein, V., Catford, W. N., Doherty, D. T., Esker, N. E., Garnsworthy, A. B., Hackman, G., Hudson, K., Lennarz, A., Natzke, C., Olaizola, B., Psaltis, A., Svensson, C. E., Williams, J., Walter, D., and Yates, D.
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Astrophysics - Solar and Stellar Astrophysics ,Nuclear Experiment - Abstract
We have measured the cross section of the $^{83}$Rb(p,$\gamma)^{84}$Sr radiative capture reaction in inverse kinematics using a radioactive beam of $^{83}$Rb at incident energies of 2.4 and $2.7 A$ MeV. Prior to the radioactive beam measurement, the $^{84}$Kr(p,$\gamma)^{85}$Rb radiative capture reaction was measured in inverse kinematics using a stable beam of $^{84}$Kr at an incident energy of $2.7 A$ MeV. The effective relative kinetic energies of these measurements lie within the relevant energy window for the $\gamma$ process in supernovae. The central values of the measured partial cross sections of both reactions were found to be $0.17-0.42$ times the predictions of statistical model calculations. Assuming the predicted cross section at other energies is reduced by the same factor leads to a slightly higher calculated abundance of the $p$ nucleus $^{84}$Sr, caused by the reduced rate of the $^{84}$Sr($\gamma$,p)$^{83}$Rb reaction derived from the present measurement., Comment: 11 pages, 11 figures. arXiv admin note: text overlap with arXiv:2109.06775
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- 2023
9. New Opportunities in Decay Spectroscopy with the GRIFFIN and DESCANT Arrays
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Bildstein, V., Andreoiu, C., Ball, G.C., Ballast, T., Bartlett, C., Bender, P.C., Bernier, N., Bianco, L., Bishop, D., Brennan, D., Bruhn, T., Cheeseman, A., Churchman, R., Ciccone, S., Davids, B., Demand, G., Dillmann, I., Garnsworthy, A.B., Garrett, P.E., Georges, S., Hackman, G., Hadinia, B., Kokke, R., Krücken, R., Linn, Y., Lim, C., Martin, J.-P., Miller, D., Mills, W.J., Morrison, L.N., Ohlmann, C.A., Park, J., Pearson, C.J., Pore, J.L., Rajabali, M.M., Rand, E.T., Rizwan, U., Sarazin, F., Shaw, B., Starosta, K., Svensson, C.E., Sumithrarachchi, C., Unsworth, C., Voss, P., Wang, Z.M., Williams, J., Wong, J., and Wong, S.
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- 2015
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10. First application of Markov chain Monte Carlo-based Bayesian data analysis to the Doppler-shift attenuation method
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Sun, L.J., Fry, C., Davids, B., Esker, N., Wrede, C., Alcorta, M., Bhattacharjee, S., Bowry, M., Brown, B.A., Budner, T., Caballero-Folch, R., Evitts, L., Friedman, M., Garnsworthy, A.B., Glassman, B.E., Hackman, G., Henderson, J., Kirsebom, O.S., Lighthall, J., Machule, P., Measures, J., Moukaddam, M., Park, J., Pearson, C., Pérez-Loureiro, D., Ruiz, C., Ruotsalainen, P., Smallcombe, J., Smith, J.K., Southall, D., Surbrook, J., Weghorn, L.E., and Williams, M.
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- 2023
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11. Elastic scattering of 3He+4He with SONIK
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Paneru, S. N., Brune, C. R., Connolly, D., Odell, D., Poudel, M., Phillips, D. R., Karpesky, J., Davids, B., Ruiz, C., Lennarz, A., Greife, U., Alcorta, M., Giri, R., Lovely, M., Bowry, M., Delgado, M., Esker, N. E., Garnsworthy, A., Seeman, C., Machule, P., Fallis, J., Chen, A. A., Laddaran, F., Firmino, A., and Weinerman, C.
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Nuclear Theory (nucl-th) ,Nuclear Theory ,FOS: Physical sciences ,Nuclear Experiment (nucl-ex) ,Nuclear Experiment - Abstract
Measurements of the elastic scattering cross section of 3He and 4He are important in order to improve constraints on theoretical models of 4He(3He,g)7Be, a key reaction in Big Bang nucleosynthesis and solar neutrino production. The astrophysical S-factor for this reaction is a significant source of uncertainty in the standard solar-model prediction of the 7Be and 8B solar neutrino fluxes. The elastic scattering measurements reported in the literature do not extend to low energies and lack proper uncertainty quantification. A new measurement of the 4He(3He,3He)4He reaction has been made at center-of-mass energies Ec.m. = 0.38-3.13 MeV using the Scattering of Nuclei in Inverse Kinematics (SONIK) scattering chamber: a windowless, extended gas target surrounded by an array of 30 collimated silicon charged particle detectors situated at TRIUMF. This is the first elastic scattering measurement of 3He+4He made below 500 keV and it has greater angular range and better precision than previous measurements. The elastic scattering data were analyzed using both R-matrix and Halo Effective Field Theory (Halo EFT) frameworks, and values of the s-wave scattering length and effective range were extracted. The resulting improvement in knowledge of the s-wave effective-range function at low energies will reduce the overall uncertainty in S34 at solar energies., 21 pages, 16 figures
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- 2022
12. Direct measurement of resonances in $^7$Be($\alpha,\gamma$)$^{11}$C relevant to $\nu p$-process nucleosynthesis
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Psaltis, A., Chen, A. A., Longland, R., Connolly, D. S., Brune, C. R., Davids, B., Fallis, J., Giri, R., Greife, U, Hutcheon, D. A., Kroll, L., Lennarz, A., Liang, J., Lovely, M., Luo, M., Marshall, C., Paneru, S. N., Parikh, A., Ruiz, C., Shotter, A. C., and Williams, M.
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Astrophysics - High Energy Astrophysical Phenomena ,Nuclear Experiment - Abstract
We have performed the first direct measurement of two resonances of the $^7$Be($\alpha,\gamma$)$^{11}$C reaction with unknown strengths using an intense radioactive $^7$Be beam and the DRAGON recoil separator. We report on the first measurement of the 1155 and 1110 keV resonance strengths of $1.73 \pm 0.25(stat.) \pm 0.40(syst.)$ eV and $125 ^{+27}_{-25}(stat.) \pm 15(syst.)$ meV, respectively. The present results have reduced the uncertainty in the $^7$Be($\alpha,\gamma$)$^{11}$C reaction rate to $\sim$ 9.4-10.7% over T = 1.5-3 GK, which is relevant for nucleosynthesis in the neutrino-driven outflows of core-collapse supernovae ($\nu p$-process). We find no effect of the new, constrained reaction rate on $\nu p$-process nucleosynthesis., Comment: 5 pages, 3 figures. Accepted for publication in Phys. Rev. Lett
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- 2022
13. First inverse kinematics measurement of resonances in $^7$Be($\alpha,\gamma$)$^{11}$C relevant to neutrino-driven wind nucleosynthesis using DRAGON
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Psaltis, A., Chen, A. A., Longland, R., Connolly, D. S., Brune, C. R., Davids, B., Fallis, J., Giri, R., Greife, U, Hutcheon, D. A., Kroll, L., Lennarz, A., Liang, J., Lovely, M., Luo, M., Marshall, C., Paneru, S. N., Parikh, A., Ruiz, C., Shotter, A. C., and Williams, M.
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Astrophysics - High Energy Astrophysical Phenomena ,Nuclear Experiment - Abstract
A possible mechanism to explain the origin of the light $p$-nuclei in the Galaxy is the nucleosynthesis in the proton-rich neutrino-driven wind ejecta of core-collapse supernovae via the $\nu p$-process. However this production scenario is very sensitive to the underlying supernova dynamics and the nuclear physics input. As far as the nuclear uncertainties are concerned, the breakout from the $pp$-chains via the $^7$Be($\alpha,\gamma$)$^{11}$C reaction has been identified as an important link which can influence the nuclear flow and therefore the efficiency of the $\nu p$-process. However its reaction rate is poorly known over the relevant temperature range, T = 1.5-3 GK. We report on the first direct measurement of two resonances of the $^7$Be($\alpha,\gamma$)$^{11}$C reaction with previously unknown strengths using an intense radioactive $^7$Be beam from the ISAC facility and the DRAGON recoil separator in inverse kinematics. We have decreased the $^7$Be($\alpha,\gamma$)$^{11}$C reaction rate uncertainty to $\sim$ 9.4-10.7% over the relevant temperature region., Comment: 15 pages, 12 figures. Accepted for publication in Phys. Rev. C
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- 2022
14. Single neutron transfer on Ne and its relevance for the pathway of nucleosynthesis in astrophysical X-ray bursts
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Lotay, G., Henderson, J., Catford, W.N., Ali, F.A., Berean, J., Bernier, N., Bhattacharjee, S.S., Bowry, M., Caballero-Folch, R., Davids, B., Drake, T.E., Garnsworthy, A.B., Ghazi Moradi, F., Gillespie, S.A., Greaves, B., Hackman, G., Hallam, S., Hymers, D., Kasanda, E., Levy, D., Luna, B.K., Mathews, A., Meisel, Z., Moukaddam, M., Muecher, D., Olaizola, B., Orr, N.A., Patel, H.P., Rajabali, M.M., Saito, Y., Smallcombe, J., Spencer, M., Svensson, C.E., Whitmore, K., and Williams, M.
- Abstract
We present new experimental measurements of resonance strengths in the astrophysical $^{23}$Al(p,γ)$^{24}$Si reaction, constraining the pathway of nucleosynthesis beyond $^{22}$Mg in X-ray burster scenarios. Specifically, we have performed the first measurement of the (d,p) reaction using a radioactive beam of $^{23}$Ne to explore levels in $^{24}$Ne, the mirror analog of $^{24}$Si. Four strong single-particle states were observed and corresponding neutron spectroscopic factors were extracted with a precision of ∼20%. Using these spectroscopic factors, together with mirror state identifications, we have reduced uncertainties in the strength of the key ℓ = 0 resonance at Er = 157 keV, in the astrophysical $^{23}$Al(p,γ) reaction, by a factor of 4. Our results show that the $^{22}$Mg(p,γ)$^{23}$Al(p,γ) pathway dominates over the competing $^{22}$Mg(α,p) reaction in all but the most energetic X-ray burster events (T>0.85 GK), significantly affecting energy production and the preservation of hydrogen fuel.
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- 2022
15. Single neutron transfer on 23Ne and its relevance for the pathway of nucleosynthesis in astrophysical X-ray bursts
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Lotay, G., Henderson, J., Catford, W.N., Ali, F.A., Berean, J., Bernier, N., Bhattacharjee, S.S., Bowry, M., Caballero-Folch, R., Davids, B., Drake, T.E., Garnsworthy, A.B., Ghazi Moradi, F., Gillespie, S.A., Greaves, B., Hackman, G., Hallam, S., Hymers, D., Kasanda, E., Levy, D., Luna, B.K., Mathews, A., Meisel, Z., Moukaddam, M., Muecher, D., Olaizola, B., Orr, N.A., Patel, H.P., Rajabali, M.M., Saito, Y., Smallcombe, J., Spencer, M., Svensson, C.E., Whitmore, K., and Williams, M.
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- 2022
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16. Constraints on key $^{17}$O($\alpha,\gamma$)$^{21}$Ne resonances and impact on the weak s-process
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Williams, M., Laird, A. M., Choplin, A., Adsley, P., Davids, B., Greife, U., Hudson, K., Hutcheon, D., Lennarz, A., and Ruiz, C.
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Astrophysics - Solar and Stellar Astrophysics ,Nuclear Theory ,Astrophysics::High Energy Astrophysical Phenomena ,Nuclear Experiment - Abstract
The efficiency of the slow neutron-capture process in massive stars is strongly influenced by neutron-capture reactions on light elements. At low metallicity, $^{16}$O is an important neutron absorber, but the effectiveness of $^{16}$O as a light-element neutron poison is modified by competition between subsequent $^{17}$O$(\alpha,n)^{20}$Ne and $^{17}$O$(\alpha,\gamma)^{21}$Ne reactions. The strengths of key $^{17}$O$(\alpha,\gamma)^{21}$Ne resonances within the Gamow window for core helium burning in massive stars are not well constrained by experiment. This work presents more precise measurements of resonances in the energy range $E_{c.m.} = 612 - 1319$ keV. We extract resonance strengths of $\omega\gamma_{638} = 4.85\pm0.79$ $\mu$eV, $\omega\gamma_{721} = 13.0^{+3.3}_{-2.4}$ $\mu$eV, $\omega\gamma_{814} = 7.72\pm0.55$ meV and $\omega\gamma_{1318} = 136\pm 13$ meV, for resonances at $E_{c.m.} =$ 638, 721, 814 and 1318 keV, respectively. We also report an upper limit for the 612 keV resonance of $\omega\gamma, Comment: Accepted in Physical Review C
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- 2022
17. New measurement of the $E_{\mathrm{c.m.}}=323$ keV resonance in the $^{19}$F$($p,\gamma$)$^{20}$Ne reaction
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Williams, M., Adsley, P., Davids, B., Greife, U., Hutcheon, D., Karpesky, J., Lennarz, A., Lovely, M., and Ruiz, C.
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Astrophysics - Solar and Stellar Astrophysics ,Nuclear Experiment - Abstract
At temperatures below 0.1 GK the $^{19}$F$(p,\gamma)^{20}$Ne reaction is the only breakout path out of the CNO cycle. Experimental studies of this reaction are challenging from a technical perspective due to copious $\gamma$-ray background from the far stronger $^{19}$F$(p,\alpha)^{16}$O reaction channel. Here we present the first inverse kinematics study of the $^{19}$F$(p,\gamma)^{20}$Ne reaction, in which we measure the strength of the 323-keV resonance. We find a strength value of $\omega\gamma = 3.3^{+1.1}_{-0.9}$ meV, which is a factor of two larger than the most recent previous study. The discrepancy is likely the result of a direct to ground state transition which previous studies were not sensitive to. We also observe the transition to the first $2^{-}$ state, which has not been observed for this resonance in previous studies. A new thermonuclear reaction rate is calculated and compared with the literature., Comment: arXiv admin note: text overlap with arXiv:1910.01698
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- 2022
18. First application of Markov Chain Monte Carlo-based Bayesian data analysis to the Doppler-Shift Attenuation Method
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Sun, L. J., Fry, C., Davids, B., Esker, N., Wrede, C., Alcorta, M., Bhattacharjee, S., Bowry, M., Brown, B. A., Budner, T., Caballero-Folch, R., Evitts, L., Friedman, M., Garnsworthy, A. B., Glassman, B. E., Hackman, G., Henderson, J., Kirsebom, O. S., Kurkjian, A., Lighthall, J., Machule, P., Measures, J., Moukaddam, M., Park, J., Pearson, C., Pérez-Loureiro, D., Ruiz, C., Ruotsalainen, P., Smallcombe, J., Smith, J. K., Southall, D., Surbrook, J., Williams, M., and Weghorn, L. E.
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Nuclear and High Energy Physics ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Nuclear Experiment (nucl-ex) ,Nuclear Experiment - Abstract
Motivated primarily by the large uncertainties in the thermonuclear rate of the $^{30}$P(p,γ)31S reaction that limit our understanding of classical novae, we carried out lifetime measurements of $^{31}$S excited states using the Doppler Shift Lifetimes (DSL2) facility at the TRIUMF Isotope Separator and Accelerator (ISAC-II) facility. The $^{31}$S excited states were populated by the $^{3}$He(32S,α)31S reaction. The deexcitation γ rays were detected by a clover-type high-purity germanium detector in coincidence with the α particles detected by a silicon detector telescope. We have applied modern Markov chain Monte Carlo-based Bayesian statistical techniques to perform lineshape analyses of Doppler-shift attenuation method γ-ray data for the first time. We have determined the lifetimes of the two lowest-lying $^{31}$S excited states. First experimental upper limits on the lifetimes of four higher-lying states have been obtained. The experimental results were compared to shell-model calculations using five universal sd-shell Hamiltonians. Evidence for γ rays originating from the astrophysically important Jπ=3/2+, 260-keV $^{30}$P(p,γ)31S resonance with an excitation energy of Ex=6390.2(7) keV in $^{31}$S has also been observed, although strong constraints on the lifetime will require better statistics.
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- 2022
19. Proton inelastic scattering reveals deformation in He
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Holl, M., Kanungo, R., Sun, Z.H., Hagen, G., Lay, J.A., Moro, A.M., Navrátil, P., Papenbrock, T., Alcorta, M., Connolly, D., Davids, B., Diaz Varela, A., Gennari, M., Hackman, G., Henderson, J., Ishimoto, S., Kilic, A.I., Krücken, R., Lennarz, A., Liang, J., Measures, J., Mittig, W., Paetkau, O., Psaltis, A., Quaglioni, S., Randhawa, J.S., Smallcombe, J., Thompson, I.J., Vorabbi, M., and Williams, M.
- Abstract
A measurement of proton inelastic scattering of $^{8}$He at 8.25A MeV at TRIUMF shows a resonance at 3.54(6) MeV with a width of 0.89(11) MeV. The energy of the state is in good agreement with coupled cluster and no-core shell model with continuum calculations, with the latter successfully describing the measured resonance width as well. Its differential cross section analyzed with phenomenological collective excitation form factor and microscopic coupled reaction channels framework consistently reveals a large deformation parameter β2 = 0.40(3), consistent with no-core shell model predictions of a large neutron deformation. This deformed double-closed shell at the neutron drip-line opens a new paradigm.
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- 2021
20. Proton inelastic scattering reveals deformation in 8He
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Holl, M., Kanungo, R., Sun, Z.H., Hagen, G., Lay, J.A., Moro, A.M., Navrátil, P., Papenbrock, T., Alcorta, M., Connolly, D., Davids, B., Diaz Varela, A., Gennari, M., Hackman, G., Henderson, J., Ishimoto, S., Kilic, A.I., Krücken, R., Lennarz, A., Liang, J., Measures, J., Mittig, W., Paetkau, O., Psaltis, A., Quaglioni, S., Randhawa, J.S., Smallcombe, J., Thompson, I.J., Vorabbi, M., and Williams, M.
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- 2021
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21. First direct measurement of $^{59}$Cu(p,$\alpha$)$^{56}$Ni: A step towards constraining the Ni-Cu cycle in the Cosmos
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Randhawa, J. S., Kanungo, R., Refsgaard, J., Mohr, P., Ahn, T., Alcorta, M., Andreoiu, C., Bhattacharjee, S. S., Davids, B., Christian, G., Chen, A. A., Coleman, R., Garrett, P., Grinyer, G. F., Fuakye, E. Gyabeng, Hackman, G., Jain, R., Kapoor, K., Krücken, R., Laffoley, A., Lennarz, A., Liang, J., Meisel, Z., Nikhil, N., Psaltis, A., Radich, A., Rocchini, M., Saei, N., Saxena, M., Singh, M., Svensson, C., Subramaniam, P., Talebitaher, A., Upadhyayula, S., Waterfield, C., Williams, J., and Williams, M.
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Nuclear Experiment - Abstract
Reactions on the proton-rich nuclides drive the nucleosynthesis in Core-Collapse Supernovae (CCSNe) and in X-ray bursts (XRBs). CCSNe eject the nucleosynthesis products to the interstellar medium and hence are a potential inventory of p-nuclei, whereas in XRBs nucleosynthesis powers the light curves. In both astrophysical sites the Ni-Cu cycle, which features a competition between $^{59}$Cu(p,$\alpha$)$^{56}$Ni and $^{59}$Cu(p,$\gamma$)$^{60}$Zn, could potentially halt the production of heavier elements. Here, we report the first direct measurement of $^{59}$Cu(p,$\alpha$)$^{56}$Ni using a re-accelerated $^{59}$Cu beam and cryogenic solid hydrogen target. Our results show that the reaction proceeds predominantly to the ground state of $^{56}$Ni and the experimental rate has been found to be lower than Hauser-Feshbach-based statistical predictions. New results hint that the $\nu p$-process could operate at higher temperatures than previously inferred and therefore remains a viable site for synthesizing the heavier elements.
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- 2021
22. The electromagnetic mass analyser EMMA
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Davids, B.
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- 2014
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23. The doppler shift lifetimes facility
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Davids, B.
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- 2014
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24. Constraining the 19Ne(p,γ)20Na Reaction Rate Using a Direct Measurement at DRAGON
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Wilkinson R., Lotay G., Lennarz A., Ruiz C., Christian G., Akers C., Catford W. N., Chen A. A., Connolly D., Davids B., Hutcheon D. A., Jedrejcic D., Laird A. M., Martin L., McNeice E., Riley J., and Williams M.
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Physics ,QC1-999 - Abstract
A direct measurement of the 19Ne(p, γ)20 Na reaction has been performed in inverse kinematics at the DRAGON recoil separator, at an energy ∼ 10 keV higher than previous measurements. The key resonance in the 19 Ne + p system relevant for ONe novae and Type-I X-ray burst temperatures have been successfully measured for the first time. Preliminary estimates of the resonance energy and strength are reported as Ec.m. ≈ 458 keV and ωγ ≈ 18 meV. These results are consistent with previous direct measurements, but disagree with the most recent study of the 19Ne(p, γ)20 Na reaction rate. These preliminary results will be finalised after a forthcoming negative log-likelihood analysis.
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- 2017
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25. Beyond the acceptance limit of DRAGON: The case of the $^6Li(\alpha,\gamma )^{10}B$ reaction
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Psaltis, A., Chen, A.A., Connolly, D.S., Davids, B., Gilardy, G., Giri, R., Greife, U., Huang, W., Hutcheon, D.A., Karpesky, J., Lennarz, A., Liang, J., Lovely, M., Paneru, S.N., Ruiz, C., Tenkila, G., Williams, M., Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), and Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Recoil separators ,Physics - Instrumentation and Detectors ,Inverse kinematics ,Resonance strength ,Radiative capture ,[PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det] ,[PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex] ,Nuclear Experiment - Abstract
Radiative capture reactions play a pivotal role for our understanding of the origin of the elements in the cosmos. Recoil separators provide an effective way to study these reactions, in inverse kinematics, and take advantage of the use of radioactive ion beams. However, a limiting factor in the study of radiative capture reactions in inverse kinematics is the momentum spread of the product nuclei, which can result in an angular spread larger than the geometric acceptance of the separator. The DRAGON facility at TRIUMF is a versatile recoil separator, designed to study radiative capture reactions relevant to astrophysics in the $\mathrm{A \sim 10-30}$ region. In this work we present the first attempt to study with DRAGON a reaction, $\mathrm{^6Li(\alpha,\gamma)^{10}B}$ , for which the recoil angular spread exceeds DRAGON's acceptance. Our result is in good agreement with the literature value, showing that DRAGON can measure resonance strengths of astrophysically important reactions even when not all the recoils enter the separator., Comment: 11 pages, 8 figures, Accepted for publication in Nucl. Instrum. Methods. Phys. Res. A
- Published
- 2021
26. First inverse kinematics measurement of key resonances in the Ne( , ) Na reaction at stellar temperatures
- Author
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Lennarz, A., Williams, M., Laird, A.M., Battino, U., Chen, A.A., Connolly, D., Davids, B., Esker, N., Garg, R., Gay, M., Greife, U., Hager, U., Hutcheon, D., José, J., Lovely, M., Lyons, S., Psaltis, A., Riley, J.E., Tattersall, A., and Ruiz, C.
- Abstract
In this Letter we report on the first inverse kinematics measurement of key resonances in the Ne22(p,γ)23Na reaction which forms part of the NeNa cycle, and is relevant for $^{23}$Na synthesis in asymptotic giant branch (AGB) stars. An anti-correlation in O and Na abundances is seen across all well-studied globular clusters (GC), however, reaction-rate uncertainties limit the precision as to which stellar evolution models can reproduce the observed isotopic abundance patterns. Given the importance of GC observations in testing stellar evolution models and their dependence on NeNa reaction rates, it is critical that the nuclear physics uncertainties on the origin of $^{23}$Na be addressed. We present results of direct strengths measurements of four key resonances in Ne22(p,γ)23Na at Ec.m. = 149 keV, 181 keV, 248 keV and 458 keV. The strength of the important Ec.m. = 458 keV reference resonance has been determined independently of other resonance strengths for the first time with an associated strength of ωγ = 0.439(22) eV and with higher precision than previously reported. Our result deviates from the two most recently published results obtained from normal kinematics measurements performed by the LENA and LUNA collaborations but is in agreement with earlier measurements. The impact of our rate on the Na-pocket formation in AGB stars and its relation to the O-Na anti-correlation was assessed via network calculations. Further, the effect on isotopic abundances in CO and ONe novae ejecta with respect to pre-solar grains was investigated.
- Published
- 2020
27. First inverse kinematics measurement of key resonances in the 22Ne(p,γ)23Na reaction at stellar temperatures
- Author
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Lennarz, A., Williams, M., Laird, A.M., Battino, U., Chen, A.A., Connolly, D., Davids, B., Esker, N., Garg, R., Gay, M., Greife, U., Hager, U., Hutcheon, D., José, J., Lovely, M., Lyons, S., Psaltis, A., Riley, J.E., Tattersall, A., and Ruiz, C.
- Published
- 2020
- Full Text
- View/download PDF
28. Direct neutron decay of the isoscalar giant dipole resonance
- Author
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Hunyadi, M., van den Berg, A. M., Davids, B., Harakeh, M. N., de Huu, M. A., Wörtche, H. J., Csatlós, M., Gulyás, J., Krasznahorkay, A., Sohler, D., Garg, U., Fujiwara, M., and Blasi, N.
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- 2007
- Full Text
- View/download PDF
29. Preliminary study of the 10Li nucleus via one-neutron transfer
- Author
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Cavallaro M., De Napoli M., Cappuzzello F., Agodi C., Bondí M., Carbone D., Cunsolo A., Davids B., Davinson T., Foti A., Galinski N., Kanungo R., Lenske H., Orrigo S.E.A., Ruiz C., and Sanetullaev A.
- Subjects
Physics ,QC1-999 - Abstract
The structure of the 10Li unbound nucleus is a subject of large interest and its description is nowadays a matter of debate. We have investigated this system using the d(9Li,p)10 Li one-neutron transfer reaction at 100 MeV in inverse kinematics. The experiment was performed at the ISACII facility at TRIUMF laboratory. The excitation energy spectrum has been reconstructed by measuring the emitted protons at backward angles and the 9Li at forward angles.
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- 2016
- Full Text
- View/download PDF
30. First inverse kinematics study of the Ne 22 (p,γ) Na 23 reaction and its role in AGB star and classical nova nucleosynthesis
- Author
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Williams, M., Lennarz, A., Laird, A. M., Battino, U., José, J., Connolly, D., Ruiz, C., Chen, A., Davids, B., Esker, N., Fulton, B. R., Garg, R., Gay, M., Greife, U., Hager, U., Hutcheon, D., Lovely, M., Lyons, S., Psaltis, A., Riley, J. E., and Tattersall, A.
- Abstract
Background: Globular clusters are known to exhibit anomalous abundance trends such as the sodium-oxygen anticorrelation. This trend is thought to arise via pollution of the cluster interstellar medium from a previous generation of stars. Intermediate-mass asymptotic giant branch stars undergoing hot bottom burning (HBB) are a prime candidate for producing sodium-rich oxygen-poor material, and then expelling this material via strong stellar winds. The amount of Na23 produced in this environment has been shown to be sensitive to uncertainties in the Ne22(p,γ)Na23 reaction rate. The Ne22(p,γ)Na23 reaction is also activated in classical nova nucleosynthesis, strongly influencing predicted isotopic abundance ratios in the Na-Al region. Therefore, improved nuclear physics uncertainties for this reaction rate are of critical importance for the identification and classification of pre-solar grains produced by classical novae. Purpose: At temperatures relevant for both HBB in AGB stars and classical nova nucleosynthesis, the Ne22(p,γ)Na23 reaction rate is dominated by narrow resonances, with additional contribution from direct capture. This study presents new strength values for seven resonances, as well as a study of direct capture. Method: The experiment was performed in inverse kinematics by impinging an intense isotopically pure beam of Ne22 onto a windowless H2 gas target. The Na23 recoils and prompt γ rays were detected in coincidence using a recoil mass separator coupled to a 4π bismuth-germanate scintillator array surrounding the target. Results: For the low-energy resonances, located at center of mass energies of 149, 181, and 248 keV, we recover stength values of ωγ149=0.17-0.04+0.05, ωγ181=2.2±0.4, and ωγ248=8.2±0.7 μeV, respectively. These results are in broad agreement with recent studies performed by the LUNA and TUNL groups. However, for the important reference resonance at 458 keV we obtain a strength value of ωγ458=0.44±0.02 eV, which is significantly lower than recently reported values. This is the first time that this resonance has been studied completely independently from other resonance strengths. For the 632-keV resonance we recover a strength value of ωγ632=0.48±0.02 eV, which is an order of magnitude higher than a recent study. For reference resonances at 610- A nd 1222-keV, our strength values are in agreement with the literature. In the case of direct capture, we recover an S factor of 60 keV b, consistent with prior forward kinematics experiments. Conclusions: In summary, we have performed the first direct measurement of Ne22(p,γ)Na23 in inverse kinematics. Our results are in broad agreement with the literature, with the notable exception of the 458-keV resonance, for which we obtain a lower strength value. We assessed the impact of the present reaction rate in reference to a variety of astrophysical environments, including AGB stars and classical novae. Production of Na23 in AGB stars is minimally influenced by the factor of 4 increase in the present rate compared to the STARLIB-2013 compilation. The present rate does however impact upon the production of nuclei in the Ne-Al region for classical novae, with dramatically improved uncertainties in the predicted isotopic abundances present in the novae ejecta.
- Published
- 2020
31. First inverse kinematics measurement of key resonances in the 22Ne(p, γ)23Na reaction at stellar temperatures
- Author
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Lennarz, A., Williams, M., Laird, A. M., Battino, U., Chen, A. A., Davids, B., Esker, N., Garg, R., Gay, M., Greife, U., Hager, U., Hutcheon, D., José, J., Lovely, M., Lyons, S., Psaltis, A., Riley, J. E., Tattersall, A., and Ruiz, C.
- Subjects
Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
In this Letter we report on the first inverse kinematics measurement of key resonances in the ${}^{22}\text{Ne}(p,\gamma)^{23}\text{Na}$ reaction which forms part of the NeNa cycle, and is relevant for ${}^{23}$Na synthesis in asymptotic giant branch (AGB) stars. An anti-correlation in O and Na abundances is seen across all well-studied globular clusters (GC), however, reaction-rate uncertainties limit the precision as to which stellar evolution models can reproduce the observed isotopic abundance patterns. Given the importance of GC observations in testing stellar evolution models and their dependence on NeNa reaction rates, it is critical that the nuclear physics uncertainties on the origin of ${}^{23}$Na be addressed. We present results of direct strengths measurements of four key resonances in ${}^{22}\text{Ne}(p,\gamma)^{23}\text{Na}$ at E$_{{\text c.m.}}$ = 149 keV, 181 keV, 248 keV and 458 keV. The strength of the important E$_{{\text c.m.}}$ = 458 keV reference resonance has been determined independently of other resonance strengths for the first time with an associated strength of $\omega\gamma$ = 0.439(22) eV and with higher precision than previously reported. Our result deviates from the two most recently published results obtained from normal kinematics measurements performed by the LENA and LUNA collaborations but is in agreement with earlier measurements. The impact of our rate on the Na-pocket formation in AGB stars and its relation to the O-Na anti-correlation was assessed via network calculations. Further, the effect on isotopic abundances in CO and ONe novae ejecta with respect to pre-solar grains was investigated.
- Published
- 2020
32. First inverse kinematics study of the 22Ne(p, γ) 23Na reaction and its role in AGB star and classical nova nucleosynthesis
- Author
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Williams, M., Lennarz, A., Laird, A.M., Battino, U., José, Jordi, Connolly, D., Ruiz, C., Chen, A., Davids, B., Esker, N., Fulton, B. R., Garg, R., Gay, M., Greife, U., Hager, U., Hutcheon, D., Lovely, M., Lyons, S., Psaltis, A., Riley, J. E., Tattersall, A., European Commission, European Research Council, Natural Sciences and Engineering Research Council of Canada, Ministerio de Ciencia, Innovación y Universidades (España), Science and Technology Facilities Council (UK), Agencia Estatal de Investigación (España), Generalitat de Catalunya, and Department of Energy (US)
- Abstract
[Background]: Globular clusters are known to exhibit anomalous abundance trends such as the sodium-oxygen anticorrelation. This trend is thought to arise via pollution of the cluster interstellar medium from a previous generation of stars. Intermediate-mass asymptotic giant branch stars undergoing hot bottom burning (HBB) are a prime candidate for producing sodium-rich oxygen-poor material, and then expelling this material via strong stellar winds. The amount of 23Na produced in this environment has been shown to be sensitive to uncertainties in the 22Ne(p,γ)23Na reaction rate. The 22Ne(p,γ)23Na reaction is also activated in classical nova nucleosynthesis, strongly influencing predicted isotopic abundance ratios in the Na-Al region. Therefore, improved nuclear physics uncertainties for this reaction rate are of critical importance for the identification and classification of pre-solar grains produced by classical novae., [Purpose]: At temperatures relevant for both HBB in AGB stars and classical nova nucleosynthesis, the 22Ne(p,γ)23Na reaction rate is dominated by narrow resonances, with additional contribution from direct capture. This study presents new strength values for seven resonances, as well as a study of direct capture., [Method]: The experiment was performed in inverse kinematics by impinging an intense isotopically pure beam of 22Ne onto a windowless H2 gas target. The 23Na recoils and prompt γ rays were detected in coincidence using a recoil mass separator coupled to a 4π bismuth-germanate scintillator array surrounding the target., [Results]: For the low-energy resonances, located at center of mass energies of 149, 181, and 248 keV, we recover stength values of ωγ149=0.17+0.05−0.04, ωγ181=2.2±0.4, and ωγ248=8.2±0.7 μeV, respectively. These results are in broad agreement with recent studies performed by the LUNA and TUNL groups. However, for the important reference resonance at 458 keV we obtain a strength value of ωγ458=0.44±0.02 eV, which is significantly lower than recently reported values. This is the first time that this resonance has been studied completely independently from other resonance strengths. For the 632-keV resonance we recover a strength value of ωγ632=0.48±0.02 eV, which is an order of magnitude higher than a recent study. For reference resonances at 610- and 1222-keV, our strength values are in agreement with the literature. In the case of direct capture, we recover an S factor of 60 keV b, consistent with prior forward kinematics experiments., [Conclusions]: In summary, we have performed the first direct measurement of 22Ne(p,γ)23Na in inverse kinematics. Our results are in broad agreement with the literature, with the notable exception of the 458-keV resonance, for which we obtain a lower strength value. We assessed the impact of the present reaction rate in reference to a variety of astrophysical environments, including AGB stars and classical novae. Production of 23Na in AGB stars is minimally influenced by the factor of 4 increase in the present rate compared to the STARLIB-2013 compilation. The present rate does however impact upon the production of nuclei in the Ne-Al region for classical novae, with dramatically improved uncertainties in the predicted isotopic abundances present in the novae ejecta., The authors thank the ISAC operations and technical staff at TRIUMF. TRIUMFs core operations are supported via a contribution from the federal government through the National Research Council Canada, and the Government of British Columbia provides building capital funds. DRAGON is supported by funds from the National Sciences and Engineering Research Council of Canada. UK authors gratefully acknowledge support from the Science and Technology Facilities Council (STFC). J.J. acknowledges support from the Spanish MINECO Grant No. AYA2017-86274-P, the EU FEDER funds and the AGAUR/ Generalitat de Catalunya Grant No. SGR-661/2017. Authors from the Colorado School of Mines acknowledge funding via U.S. Department of Energy Grant No. DE-FG02-93ER40789. U.B. acknowledges support from the European Research Council (Grant No. ERC-2015-STG Nr. 677497). This article also benefited from discussions within the ChETEC COST Action (Grant No. CA16117).
- Published
- 2020
33. A direct measurement of the 17O(α,γ)21Ne reaction in inverse kinematics and its impact on heavy element production
- Author
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Taggart, Matthew Paul, Akers, C., Laird, Alison Monica, Hager, U, Ruiz, C, Hutcheon, D, Bentley, Michael Anthony, Brown, James Robert, Buchmann, L, Chen, Jie, Chipps, Kelly Anne, Choplin, A., D'Auria, J.M., Davids, B, Davis, C, Diget, Christian Aaen, Erikson, L., Fallis, J., Fox, Simon Paul, Frischknecht, U., Fulton, Brian Robert, Galinski, N., Greife, U, Hirschi, R., Howell, D., Martin, L., Mountford, D. J., Murphy, A, Ottewell, D., Pignatari, M., Reeve, Scott, Ruprecht, G, Sjue, S. K. L., Veloce, L., and Williams, M.
- Published
- 2019
34. First inverse kinematics study of the $^{22}$Ne$(p,\gamma)^{23}$Na reaction and its role in AGB star and classical nova nucleosynthesis
- Author
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Williams, M., Lennarz, A., Laird, A. M., Battino, U., Connolly, J. José D., Ruiz, C., Chen, A., Davids, B., Esker, N., Fulton, B. R., Garg, R., Gay, x M., Greife, U., Hager, U., Hutcheon, D., Lovely, M., Lyons, S., Psaltis, A., Riley, J. E., and Tattersall, A.
- Subjects
Nuclear Experiment - Abstract
The abundances of sodium and oxygen are observed to be anti-correlated in all well-studied globular clusters. Asymptotic giant branch (AGB) stars undergoing hot bottom burning (HBB) are thought to be prime candidates for producing sodium-rich oxygen-poor material and expelling it into the cluster ISM. The 22Ne(p,gamma)23Na reaction has been shown to strongly influence the amount of 23Na produced during HBB. This reaction is also important for classical novae nucleosynthesis, with sensitivity studies showing that the abundances of several isotopes in the Ne-Al region are significantly altered when varying the reaction rate between available compilations. Here we present the first inverse kinematics measurements of key resonances strengths as well as the direct capture S-factor. Together, this study represents the largest centre of mass energy range (149-1222 keV) over which this reaction has been measured in a single experiment. Our results for low-energy resonances at Ecm=149, 181 and 248 keV are in good agreement with recent forward kinematics results; we also find a direct capture S-factor consistent with the literature value of 62 keV.b. However, in the case of the important reference resonance at Ecm = 458 keV we find a strength value of wg=0.44 +/- 0.02 eV, which is significantly lower than recent results. Using our new recommended rate we explore the impact of these results on both AGB star and classical novae nucleosynthesis. In the case of AGB stars we see very little abundance changes with respect to the rate included in the STARLIB-2013. However, we observe changes of up to a factor of 2 in isotopes produced in both the carbon-oxygen (CO) and oxygen-neon (ONe) classical novae models considered here. The 22Ne(p,gamma)23Na reaction rate is now sufficiently well constrained to not significantly contribute toward abundance uncertainties from classical novae nucleosynthesis models., Comment: 19 pages, 19 figures, 8 tables
- Published
- 2019
35. First inverse kinematics measurement of key resonances in the ${}^{22}\text{Ne}(p,\gamma)^{23}\text{Na}$ reaction at stellar temperatures
- Author
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Lennarz, A., Williams, M., Laird, A. M., Battino, U., Chen, A. A., Connolly, D., Davids, B., Esker, N., Garg, R., Gay, M., Greife, U., Hager, U., Hutcheon, D., José, J., Lovely, M., Lyons, S., Psaltis, A., Riley, J. E., Tattersall, A., and Ruiz, C.
- Subjects
Astrophysics::Solar and Stellar Astrophysics ,Nuclear Experiment ,Astrophysics::Galaxy Astrophysics - Abstract
In this Letter we report on the first inverse kinematics measurement of key resonances in the ${}^{22}\text{Ne}(p,\gamma)^{23}\text{Na}$ reaction which forms part of the NeNa cycle, and is relevant for ${}^{23}$Na synthesis in asymptotic giant branch (AGB) stars. An anti-correlation in O and Na abundances is seen across all well-studied globular clusters (GC), however, reaction-rate uncertainties limit the precision as to which stellar evolution models can reproduce the observed isotopic abundance patterns. Given the importance of GC observations in testing stellar evolution models and their dependence on NeNa reaction rates, it is critical that the nuclear physics uncertainties on the origin of ${}^{23}$Na be addressed. We present results of direct strengths measurements of four key resonances in ${}^{22}\text{Ne}(p,\gamma)^{23}\text{Na}$ at E$_{{\text c.m.}}$ = 149 keV, 181 keV, 248 keV and 458 keV. The strength of the important E$_{{\text c.m.}}$ = 458 keV reference resonance has been determined independently of other resonance strengths for the first time with an associated strength of $\omega\gamma$ = 0.439(22) eV and with higher precision than previously reported. Our result deviates from the two most recently published results obtained from normal kinematics measurements performed by the LENA and LUNA collaborations but is in agreement with earlier measurements. The impact of our rate on the Na-pocket formation in AGB stars and its relation to the O-Na anti-correlation was assessed via network calculations. Further, the effect on isotopic abundances in CO and ONe novae ejecta with respect to pre-solar grains was investigated., Comment: 6 pages, 5 figures, preprint for PRL submission
- Published
- 2019
36. Coulomb breakup of 8B and the flux of 8B neutrinos from the Sun
- Author
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Davids, B., Austin, S.M., Bazin, D., Esbensen, H., Sherrill, B.M., Thompson, I.J., and Tostevin, J.A.
- Published
- 2002
- Full Text
- View/download PDF
37. The 7Be(p, γ) 8B Reaction and its Future
- Author
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Cyburt, R.H., Davids, B., and Jennings, B.K.
- Published
- 2005
- Full Text
- View/download PDF
38. Investigation of Isovector Excitations via the (t, 3He) reaction at [formula omitted] on 58Ni and 48Ca targets: microscopic interpretation
- Author
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Guillot, J., Bäumer, C., Beaumel, D., van den Berg, A.M., Brandenburg, S., Colò, G., Davids, B., Fortier, S., Frekers, D., Grewe, E.-W., Fujiwara, M., Galès, S., Haefner, P., Harakeh, M.N., Hunyadi, M., de Huu, M., Junk, B.C., Rich, E., Van Giai, N., van der Werf, S.Y., and Wörtche, H.J.
- Published
- 2005
- Full Text
- View/download PDF
39. A direct measurement of the O( , ) Ne reaction in inverse kinematics and its impact on heavy element production
- Author
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Taggart, M.P., Akers, C., Laird, A.M., Hager, U., Ruiz, C., Hutcheon, D.A., Bentley, M.A., Brown, J.R., Buchmann, L., Chen, A.A., Chen, J., Chipps, K.A., Choplin, A., D'Auria, J.M., Davids, B., Davis, C., Diget, C.Aa., Erikson, L., Fallis, J., Fox, S.P., Frischknecht, U., Fulton, B.R., Galinski, N., Greife, U., Hirschi, R., Howell, D., Martin, L., Mountford, D., Murphy, A.St.J., Ottewell, D., Pignatari, M., Reeve, S., Ruprecht, G., Sjue, S., Veloce, L., and Williams, M.
- Subjects
Nuclear Experiment ,Computer Science::Digital Libraries - Abstract
During the slow neutron capture process in massive stars, reactions on light elements can both produce and absorb neutrons thereby influencing the final heavy element abundances. At low metallicities, the high neutron capture rate of $^{16}$O can inhibit s-process nucleosynthesis unless the neutrons are recycled via the $^{17}$O(α,n)$^{20}$Ne reaction. The efficiency of this neutron recycling is determined by competition between the $^{17}$O(α,n)$^{20}$Ne and $^{17}$O(α,γ)$^{21}$Ne reactions. While some experimental data are available on the former reaction, no data exist for the radiative capture channel at the relevant astrophysical energies.The $^{17}$O(α,γ)$^{21}$Ne reaction has been studied directly using the DRAGON recoil separator at the TRIUMF Laboratory. The reaction cross section has been determined at energies between 0.6 and 1.6 MeV Ecm, reaching into the Gamow window for core helium burning for the first time. Resonance strengths for resonances at 0.63, 0.721, 0.81 and 1.122 MeV Ecm have been extracted. The experimentally based reaction rate calculated represents a lower limit, but suggests that significant s-process nucleosynthesis occurs in low metallicity massive stars.
- Published
- 2019
40. A direct measurement of the ¹⁷O(α,γ)²¹Ne reaction in inverse kinematics and its impact on heavy element production
- Author
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Taggart, M.P., Akers, C., Laird, A.M., Hager, U., Ruiz, C., Hutcheon, D.A., Bentley, M.A., Brown, J.R., Buchmann, L., Chen, A.A., Chen, J., Chipps, K.A., Choplin, A., D'Auria, J.M., Davids, B., Davis, C., Diget, C.Aa., Erikson, L., Fallis, J., Fox, S.P., Frischknecht, U., Fulton, B.R., Galinski, N., Greife, U., Hirschi, R., Howell, D., Martin, L., Mountford, D., Murphy, A.St.J., Ottewell, D., Pignatari, M., Reeve, S., Ruprecht, G., Sjue, S., Veloce, L., and Williams, M.
- Abstract
During the slow neutron capture process in massive stars, reactions on light elements can both produce and absorb neutrons thereby influencing the final heavy element abundances. At low metallicities, the high neutron capture rate of 16O can inhibit s-process nucleosynthesis unless the neutrons are recycled via the ¹⁷O(α,n)²⁰Ne reaction. The efficiency of this neutron recycling is determined by competition between the ¹⁷O(α,n)²⁰Ne and ¹⁷O(α,γ)²¹Ne reactions. While some experimental data are available on the former reaction, no data exist for the radiative capture channel at the relevant astrophysical energies. The ¹⁷O(α,n)²⁰Ne reaction has been studied directly using the DRAGON recoil separator at the TRIUMF Laboratory. The reaction cross section has been determined at energies between 0.6 and 1.6 MeV , reaching into the Gamow window for core helium burning for the first time. Resonance strengths for resonances at 0.63, 0.721, 0.81 and 1.122 MeV have been extracted. The experimentally based reaction rate calculated represents a lower limit, but suggests that significant s-process nucleosynthesis occurs in low metallicity massive stars.
- Published
- 2019
41. Observation of excited states in $^{20}$Mg sheds light on nuclear forces and shell evolution
- Author
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Randhawa, J. S., Kanungo, R., Holl, M., Holt, J. D., Navratil, P., Stroberg, S. R., Hagen, G., Jansen, G. R., Alcorta, M., Andreoiu, C., Barnes, C., Burbadge, C., Burke, D., Chen, A. A., Chester, A., Christian, G., Cruz, S., Davids, B., Even, J., Hackman, G., Henderson, J., Ishimoto, S., Jassal, P., Kaur, S., Keefe, M., Kisliuk, D., Krucken, R., Liang, J., Lighthall, J., McGee, E., Measures, J., Moukaddam, M., Padilla-Rodal, E., Shotter, A., Thompson, I. J., Turko, J., Williams, M., and Workman, O.
- Subjects
Nuclear Theory (nucl-th) ,Nuclear Theory ,FOS: Physical sciences ,Nuclear Experiment (nucl-ex) ,Nuclear Experiment - Abstract
The exotic Borromean nucleus $^{20}$Mg with $N$ = 8, located at the proton drip-line provides a unique testing ground for nuclear forces and the evolution of shell structure in the neutron-deficient region. We report on the first observation of proton unbound resonances together with bound states in $^{20}$Mg from the $^{20}$Mg($d$,$d'$) reaction performed at TRIUMF. Phenomenological shell-model calculations offer a reasonable description. However, our experimental results present a challenge for current first-principles nuclear structure approaches and point to the need for improved chiral forces and {\it ab initio} calculations. Furthermore, the differential cross section of the first excited state is compared with distorted-wave Born approximation calculations to deduce a neutron quadrupole deformation parameter of $\beta_n$=0.46$\pm$0.21. This provides the first indication of a possible weakening of the $N$ = 8 shell closure at the proton drip-line., Comment: 6 pages, 4 figures
- Published
- 2019
42. S-wave scattering lengths for the Be 7 +p system from an R-matrix analysis
- Author
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Johnson, M.S., Visser, D.W., Stracener, D.W., Shriner, J.F., Jr., Livesay, R.J., Paneru, S.N., Thomas, J.S., Jones, K.L., Deibel, C., Connolly, D.S., Bardayan, D.W., Blackmon, J.C., Giri, R., Brune, C.R., Nesaraja, C.D., Kozub, R.L., Wrede, C., Champagne, A.E., Chipps, K.A., Chae, K.Y., Davids, B., Greife, U., Sarazin, F., Ma, Z., Smith, M.S., and Pain, S.D.
- Abstract
The astrophysical S factor for the radiative proton capture reaction on Be7 (S17) at low energies is affected by the s-wave scattering lengths. We report the measurement of elastic and inelastic scattering cross sections for the Be7+p system in the center-of-mass energy range 0.474-2.740 MeV and center-of-mass angular range 70-150. A radioactive Be7 beam produced at Oak Ridge National Laboratory's (ORNL) Holifield Radioactive Ion Beam Facility was accelerated and bombarded a thin polypropylene (CH2)n target. Scattered ions were detected in the segmented Silicon Detector Array. Using an R-matrix analysis of ORNL and Louvain-la-Neuve cross-section data, the s-wave scattering lengths for channel spins 1 and 2 were determined to be 17.34-1.33+1.11 and -3.18-0.50+0.55 fm, respectively. The uncertainty in the s-wave scattering lengths reported in this work is smaller by a factor of 5-8 compared to the previous measurement, which may reduce the overall uncertainty in S17 at zero energy. The level structure of B8 is discussed based upon the results from this work. Evidence for the existence of 0+ and 2+ levels in B8 at 1.9 and 2.21 MeV, respectively, is observed.
- Published
- 2019
- Full Text
- View/download PDF
43. 3He(α,γ)7Be cross section measured using complementary techniques
- Author
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Carmona-Gallardo M., Rojas A., Borge M.J.G., Davids B., Fulton B.R., Hass M., Nara Singh B.S., Ruiz C., and Tengblad O.
- Subjects
Physics ,QC1-999 - Abstract
The astrophysical S-factor for the 3He(α,γ)7Be reaction plays an important role in the Solar Standard Model and in the Big Bang Nucleosynthesis scenario. The advances from two recent experiments performed using complementary techniques at center of mass (C.M.) energies between 1 and 3 MeV are discussed.
- Published
- 2014
- Full Text
- View/download PDF
44. Investigation of IVGRs via the 58Ni(t, 3He) 58Co reaction
- Author
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Guillot, J., Beaumel, D., van den Berg, A.M., Brandenburg, S., Davids, B., Fortier, S., Fujiwara, M., Gale`s, S., Harakeh, M.N., Hunyadi, M., de Huu, M., and Wo¨rtche, H.J.
- Published
- 2004
- Full Text
- View/download PDF
45. Particle decay of the isoscalar giant dipole resonance in 208Pb
- Author
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Hunyadi, M., Ba¨umer, C., van den Berg, A.M., Blasi, N., Csatlo´s, M., Csige, L., Davids, B., Garg, U., Gulya´s, J., Harakeh, M.N., de Huu, M., Junk, B.C., Krasznahorkay, A., Rakers, S., Sohler, D., and Wo¨rthce, H.J.
- Published
- 2004
- Full Text
- View/download PDF
46. Measuring the 15O(α,γ)19Ne Reaction in Type I X-ray Bursts using the GADGET II TPC: Software.
- Author
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Mahajan, Ruchi, Adams, A., Allmond, J., Alvarez Pol, H., Argo, E., Ayyad, Y., Bardayan, D., Bazin, D., Budner, T., Chen, A., Chipps, K., Davids, B., Dopfer, J., Friedman, M., Fynbo, H., Grzywacz, R., Jose, J., Liang, J., Pain, S., and Perez-Loureiro, D.
- Subjects
FUSION reactor reaction chamber ,PROTONS ,GERMANIUM ,DATA analysis ,HARDWARE - Abstract
15 O(α,γ)19 Ne is regarded as one of the most important thermonuclear reactions in type I X-ray bursts. For studying the properties of the key resonance in this reaction using β decay, the existing Proton Detector component of the Gaseous Detector with Germanium Tagging (GADGET) assembly is being upgraded to operate as a time projection chamber (TPC) at FRIB. This upgrade includes the associated hardware as well as software and this paper mainly focusses on the software upgrade. The full detector set up is simulated using the ATTPCROOTv 2 data analysis framework for20 Mg and241 Am. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
47. Halo-induced large enhancement of soft dipole excitation of 11Li observed via proton inelastic scattering
- Author
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Tanaka, J., Kanungo, R., Alcorta, M., Aoi, N., Bidaman, H., Burbadge, C., Christian, G., Cruz, S., Davids, B., Diaz Varela, A., Even, J., Hackman, G., Harakeh, M.N., Henderson, J., Ishimoto, S., Kaur, S., Keefe, M., Krücken, R., Leach, K.G., Lighthall, J., Padilla Rodal, E., Randhawa, J.S., Ruotsalainen, P., Sanetullaev, A., Smith, J.K., Workman, O., and Tanihata, I.
- Published
- 2017
- Full Text
- View/download PDF
48. Radiative Alpha Capture on $^{7}$Be with DRAGON at Energies Relevant to the $\nu$p-Process
- Author
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Psaltis, A., Chen, A.A., Connolly, D.S., Davids, B., Esker, N., Gilardy, G., Greife, Uwe, Huang, W., Hutcheon, D.A., Karpesky, J., Lennarz, A., Liang, J., Lovely, M., Paneru, S.N., Giri, R., Ruiz, C., Tenkila, G., Wen, A., Williams, M., Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), and Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
[PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex] - Abstract
International audience; The origin of the p-nuclei, has been a long-standing puzzle in nuclear astrophysics. The $\nu $ p-process is a candidate for the production of the light p-nuclei, but it presents high sensitivity to both supernova dynamics and nuclear physics. It has been recently shown that the breakout from pp-chains through the$^{7}$Be $(\alpha ,\gamma )^{11}$C reaction, which occurs prior to $\nu $ p-process, can significantly influence the reaction flow, and subsequently the production of p-nuclei in the $90
- Published
- 2018
49. Direct measurement of resonance strengths in S 34 (α,γ) Ar 38 at astrophysically relevant energies using the DRAGON recoil separator
- Author
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Connolly, D., O'Malley, P. D., Akers, C., Chen, A A, Christian, G., Davids, B, Erikson, L, Fallis, J., Fulton, B. R., Greife, U, Hager, U, Hutcheon, A D, Ilyushkin, S., Laird, A. M., Mahl, A., and Ruiz, C
- Abstract
Background: Nucleosynthesis of mid-mass elements is thought to occur under hot and explosive astrophysical conditions. Radiative α capture on S34 has been shown to impact nucleosynthesis in several such conditions, including core and shell oxygen burning, explosive oxygen burning, and type Ia supernovae. Purpose: Broad uncertainties exist in the literature for the strengths of three resonances within the astrophysically relevant energy range (ECM=1.94-3.42MeV at T=2.2GK). Further, there are several states in Ar38 within this energy range which have not been previously measured. This work aimed to remeasure the resonance strengths of states for which broad uncertainty existed as well as to measure the resonance strengths and energies of previously unmeasured states. Methods: Resonance strengths and energies of eight narrow resonances (five of which had not been previously studied) were measured in inverse kinematics with the DRAGON facility at TRIUMF by impinging an isotopically pure beam of S34 ions on a windowless He4 gas target. Prompt γ emissions of de-exciting Ar38 recoils were detected in an array of bismuth germanate scintillators in coincidence with recoil nuclei, which were separated from unreacted beam ions by an electromagnetic mass separator and detected by a time-of-flight system and a multianode ionization chamber. Results: The present measurements agree with previous results. Broad uncertainty in the resonance strength of the ECM=2709keV resonance persists. Resonance strengths and energies were determined for five low-energy resonances which had not been studied previously, and their strengths were determined to be significantly weaker than those of previously measured resonances. Conclusions: The five previously unmeasured resonances were found not to contribute significantly to the total thermonuclear reaction rate. A median total thermonuclear reaction rate calculated using data from the present work along with existing literature values using the STARLIB rate calculator agrees with the NON-SMOKER statistical model calculation as well as the REACLIB and STARLIB library rates at explosive and nonexplosive oxygen-burning temperatures (T=3-4GK and T=1.5-2.7GK, respectively).
- Published
- 2018
50. Direct measurement of astrophysically important resonances in ^(38)K(p,γ)^(39)Ca
- Author
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Christian, G, Lotay, Gavin, Ruiz, C, Akers, C, Burke, D, Catford, Wilton, Chen, A, Connolly, D, Davids, B, Fallis, J, Hager, U, Hutcheon, D, Mahl, A, Rojas, A, and Sun, X
- Subjects
Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Solar and Stellar Astrophysics ,Nuclear Experiment - Abstract
Background: Classical novae are cataclysmic nuclear explosions occurring when a white dwarf in a binary system accretes hydrogen-rich material from its companion star. Novae are partially responsible for the galactic synthesis of a variety of nuclides up to the calcium ( A ∼ 40 ) region of the nuclear chart. Although the structure and dynamics of novae are thought to be relatively well understood, the predicted abundances of elements near the nucleosynthesis endpoint, in particular Ar and Ca, appear to sometimes be in disagreement with astronomical observations of the spectra of nova ejecta. Purpose: One possible source of the discrepancies between model predictions and astronomical observations is nuclear reaction data. Most reaction rates near the nova endpoint are estimated only from statistical model calculations, which carry large uncertainties. For certain key reactions, these rate uncertainties translate into large uncertainties in nucleosynthesis predictions. In particular, the 38 K ( p , γ ) 39 Ca reaction has been identified as having a significant influence on Ar, K, and Ca production. In order to constrain the rate of this reaction, we have performed a direct measurement of the strengths of three candidate ℓ = 0 resonances within the Gamow window for nova burning, at 386 ± 10 keV, 515 ± 10 keV, and 689 ± 10 keV. Method: The experiment was performed in inverse kinematics using a beam of unstable 38 K impinged on a windowless hydrogen gas target. The 39 Ca recoils and prompt γ rays from 38 K ( p , γ ) 39 Ca reactions were detected in coincidence using a recoil mass separator and a bismuth-germanate scintillator array, respectively. Results: For the 689 keV resonance, we observed a clear recoil- γ coincidence signal and extracted resonance strength and energy values of 120 + 50 − 30 ( stat . ) + 20 − 60 ( sys . ) meV and 679 + 2 − 1 ( stat . ) ± 1 ( sys . ) keV , respectively. We also performed a singles analysis of the recoil data alone, extracting a resonance strength of 120 ± 20 ( stat . ) ± 15 ( sys . ) meV, consistent with the coincidence result. For the 386 keV and 515 keV resonances, we extract 90 % confidence level upper limits of 2.54 meV and 18.4 meV, respectively. Conclusions: We have established a new recommended 38 K ( p , γ ) 39 Ca rate based on experimental information, which reduces overall uncertainties near the peak temperatures of nova burning by a factor of ∼ 250 . Using the rate obtained in this work in model calculations of the hottest oxygen-neon novae reduces overall uncertainties on Ar, K, and Ca synthesis to factors of 15 or less in all cases.
- Published
- 2018
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