Production of Heavy Elements in Inhomogeneous Cosmologies

Rauscher, T.; Applegate, James H.; Cowan, J. J.; Thielemann, Friedrich‐Karl; Wiescher, M.

doi:10.1007/978-3-642-48840-5_8

Cited by 109 publications

(6 citation statements)

References 52 publications

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“…It was also claimed that it could be usefully incorporated in explaining the abundances of boron isotopes including the present theory of spallative generation of l elements [4,5]. Furthermore, in theoretical investigations of primordial abundances of elements, its rate has to be incorporated in the reaction networks employed in nucleosynthesis calculations for inhomogeneous big bang scenarios [6,7].…”

Section: Introductionmentioning

confidence: 99%

Astrophysical reaction rates forB10(p,α)7
Rauscher
¹
,
Raimann
²

1996
Phys. Rev. C
32
1
25
0
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The reactions 10 B(p,α) 7 Be and 11 B(p,α) 8 Be are studied at thermonuclear energies using DWBA calculations. For both reactions, transitions to the ground states and first excited states are investigated. In the case of 10 B(p,α) 7 Be, a resonance at E Res = 10 keV can be consistently described in the potential model, thereby allowing the extension of the astrophysical S-factor data to very low energies. Strong interference with a resonance at about E Res = 550 keV require a Breit-Wigner description of that resonance and the introduction of an interference term for the reaction 10 B(p,α 1 ) 7 Be * . Two isospin T = 1 resonances (at E Res1 = 149 keV and E Res2 = 619 keV) observed in the 11 B+p reactions necessitate Breit-Wigner resonance and interference terms to fit the data of the 11 B(p,α) 8 Be reaction. S-factors and thermonuclear reaction rates are given for each reaction. The present calculation is the first consistent parametrization for the transition to the ground states and first excited states * current address 1 at low energies.

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Section: Introductionmentioning

confidence: 99%

Astrophysical reaction rates forB10(p,α)7
Rauscher
¹
,
Raimann
²

1996
Phys. Rev. C
32
1
25
0
View full text Add to dashboard Cite

show abstract

“…Beryllium SBBN predicts no significant primordial abundances for any element heavier than 7Li, but some versions of inhomogeneous models have predicted significant amounts of heavier elements, especially for large values Of fb (28), although this is not confirmed in later versions (29). Even for low fb, it has been suggested that for certain combinations of parameters there might be significant production of primordial Be (30) although this again is not confirmed by more detailed calculations (31).…”

Section: Lithium-7mentioning

confidence: 96%

Abundances of light elements.

Pagel¹

1993

Proc. Natl. Acad. Sci. U.S.A.

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Recent developments in the study of abundances of light elements and their relevance to cosmological nucleosynthesis are briefly reviewed. The simplest model, based on standard cosmology and particle physics and assuming homogeneous baryon density at the relevant times, continues to stand up well.The "standard" Big Bang nucleosynthesis (SBBN) model (1-6), which assumes a homogeneous baryon density at the relevant times, standard cosmology, and particle physics, makes definite predictions of primordial abundances as a function of a single free parameter: the ratio of baryons to photons, which has remained unchanged since the epoch of positron-electron annihilation a few seconds after the Big Bang and is related through the known temperature of the microwave background to the mean density of baryons in the universe today. Previous discussions (4-10) have shown that the best fit to what has been deduced about primordial abundances from extrapolations of cosmochemical and astrophysical data concerning 2H, 3He, 4He, and 7Li occurs within a quite narrow range of this density parameter corresponding to flboh2oo in the range 0.010-0.015, where ilbo is the present-day contribution of baryons to the cosmological density in units of the Einstein-de Sitter closure density and h1oo is the Hubble expansion parameter in units of 100 km s-l Mpc-1 or (1010 years)-1 [1 parsec (pc) = 3.09 x 1016 m], which has a value somewhere between about 0.5 and 1. These results have been very successfully used, furthermore, to predict upper bounds on the mean life offree neutrons and on the number of light neutrino families (6, 11). Some reservations about SBBN, however, have motivated investigations of more complicated models involving either nonstandard particle physics or baryon density inhomogeneities following the quark-hadron phase transition (12). These reservations include the idea that perhaps Qb = 1 [which is actually excluded even in inhomogeneous models (13)], the possibility (discussed below) that the primordial helium mass fraction Yp might be significantly less than the minimum of 0.235 or 0.236 (6, 14) required for compatibility within SBBN theory with the upper limit on primordial (2H + 3He)/H, and the possibility that there might be a primordial "floor" (analogous to those displayed by 4He and 7Li) to the abundance of heavier elements (e.g., Be) that are not predicted to have detectable primordial values within SBBN theory. In what follows I report and comment on some of the most recent developments in studies of the distribution of elements that are relevant to these questions.Deuterium and Helium-3

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“…. 2.46 Densidades de nêutrons em uma zona rica em nêutrons e de baixa densidade em um big bang inomogêneo, com Ω b = 1, (Thielemann, Applegate et al, 1991). .…”

Section: Lista De Figurasunclassified

“…O resultado obtido apresenta um fator 10 3 vezes menor que a abundância do Sistema Solar e 10 vezes menor que a menor abundância devido ao processo r encontrada em estrelas de baixa metalicidade. Os picos são deslocados para próximos das posições do processo s, (Thielemann, Applegate et al, 1991). .…”

Section: 47unclassified

“…Figura 2.46: Densidades de nêutrons em uma zona rica em nêutrons e de baixa densidade em um big bang inomogêneo, com Ω b = 1, (Thielemann, Applegate et al, 1991). Figura 2.47: Cálculo de abundâncias para o processo r primordial(pontos ×), considerando o ciclo da fissão, que contribui para uma fração de massa final de 1.5×10 −11 .…”

Section: • Produção Primordialunclassified

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Estudo das reações >sup<nat>/sup<Pb(p,xn)>sup<201-207>/sup<Bi e discussão de possíveis contribuições astrofísicas para o processo r

Guillaumon¹

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We analyzed the possible neutron sources for r-process production in stars of first, second and third generation. We propose a new mechanism of dynamic production for r-elements based on (p, xn) and (n, ) reactions on heavy nuclides. We called this r 2 p mechanism. We investigated proton and neutron energies that make that mechanism possible. Our model was able to reproduce r-elements like thorium and uranium with neutron flux of 10 20 neutrons ⋅ s −1 cm −3 . Critical conditions for neutrons flux of > 10 30 neutrons ⋅ s −1 cm −3 or slow r-process neutron flux (∼ 10 10 neutrons ⋅ s −1 cm −3 ) can be reproduced by our model, depending on the initial conditions. We discussed possible astrophysical sites for that mechanism and possible consequences for 232 Th, 235,238 U, and 244 Pu nucleochronometers.The study of nat Pb(p, xn) 201−207 Bi reactions have been made using 18−30 MeV proton beam energies from IPEN/CNEN's cyclotrons. We measured the cross-sections for these reactions and compared with theoretical simulations made with TALYS code. The nuclear reaction threshold of 204 Pb(p, 3n) 202 Bi, and 204 Pb(p, 4n) 201 Bi are determined. We discuss possible consequences of that results for the r-process. Also, we discuss possible discrepancies among our results and theoretical simulations for the neutron bind energy and Coulomb barrier of bismuth.The spectroscopy study with HPGe detectors has been made in association with the half-live measurement in order to fully identify the isotopes' formation. We noted some discrepancies in the energy levels of the IT isotope 204 Pb that comes from 204,206 Pb(p, xn) 204 Bi reactions. This may be related to a new possible state for this reaction at low energies above the Coulomb barrier. Finally, we have for the first time measured the cross reactions for these reactions at that proton energies.A new non-linear energy calibration method is developed, based in Principal Components Analysis (PCA). Our method is called Weighted Principal Polynomial Analysis (WPPA). We discuss possible uses of that method in nuclear physics and astronomy measurements. Machine learning for physics analysis could also use that algorithm.

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Production of Heavy Elements in Inhomogeneous Cosmologies

Cited by 109 publications

References 52 publications

Astrophysical reaction rates forB10(p,α)7
Rauscher
¹
,
Raimann
²

1996
Phys. Rev. C
32
1
25
0
View full text Add to dashboard Cite

Astrophysical reaction rates forB10(p,α)7
Rauscher
¹
,
Raimann
²

1996
Phys. Rev. C
32
1
25
0
View full text Add to dashboard Cite

Abundances of light elements.

Estudo das reações >sup<nat>/sup<Pb(p,xn)>sup<201-207>/sup<Bi e discussão de possíveis contribuições astrofísicas para o processo r

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Production of Heavy Elements in Inhomogeneous Cosmologies

Cited by 109 publications

References 52 publications

Astrophysical reaction rates forB10(p,α)7Rauscher1, Raimann2 1996Phys. Rev. C321250View full textAdd to dashboardCite

Astrophysical reaction rates forB10(p,α)7Rauscher1, Raimann2 1996Phys. Rev. C321250View full textAdd to dashboardCite

Abundances of light elements.

Estudo das reações >sup<nat>/sup<Pb(p,xn)>sup<201-207>/sup<Bi e discussão de possíveis contribuições astrofísicas para o processo r

Contact Info

Product

Resources

About

Astrophysical reaction rates forB10(p,α)7
Rauscher
¹
,
Raimann
²

1996
Phys. Rev. C
32
1
25
0
View full text Add to dashboard Cite

Astrophysical reaction rates forB10(p,α)7
Rauscher
¹
,
Raimann
²

1996
Phys. Rev. C
32
1
25
0
View full text Add to dashboard Cite