Proton-Induced Reactions of Astrophysical Interest

A discrepancy exists between the 6Li abundances predicted from big bang nucleosynthesis models and those measured in pre-main sequence stars. To further constrain the predicted abundances of 6Li in these stars, high accuracy measurements are required of reactions destroying 6Li. Namely 6Li(p,γ)7Be and 6Li(p,α) 3He. These have recently been studied at the Laboratory for Underground Nuclear Astrophysics (LUNA) to measure their low energy cross sections. I present both the campaign’s experimental setup and current status of the data analysis.

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Underground Measurement of 6Li(p,γ)7Be and 6Li(p,3He)4He Performed at LUNA

Journal of Physics Conference Series ◽

10.1088/1742-6596/1643/1/012046 ◽

2020 ◽

Vol 1643 (1) ◽

pp. 012046

Author(s):

T Chillery

Keyword(s):

Composition Studies ◽

Nuclear Astrophysics ◽

Big Bang ◽

Abundance Ratio ◽

Low Energy ◽

Big Bang Nucleosynthesis ◽

Target Composition ◽

S Factor ◽

Background Measurement ◽

Proton Induced Reactions

Abstract Proton-induced reactions on 6Li play an important role in nuclear astrophysics studies in relation to primordial lithium abundances. Whilst big bang nucleosynthesis theory excludes the existence of primordial 6Li, the 6Li/7Li abundance ratio observed in pre-main sequence stars is ≃ 0.5. The 6Li(p,3He)4He and 6Li(p,γ)7Be reactions are the main processes that contribute to 6Li destruction in stars. Both reactions were recently studied at LUNA via proton bombardment of 6Li-enriched targets, with complementary target composition studies performed at HZDR. Improvements on the precision of the low-energy S-factor values are expected from this study. Notably, the low-background measurement at LUNA will assist the search for a recently claimed 6Li(p,γ)7Be low energy resonance at E r ≃ 195 keV. I present the LUNA experimental setup and preliminary results of the ongoing analysis.

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Nuclear Astrophysics Deep Underground

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194518600030 ◽

2018 ◽

Vol 46 ◽

pp. 1860003 ◽

Cited By ~ 1

Author(s):

Rosanna Depalo

Keyword(s):

Cross Sections ◽

Nuclear Reactions ◽

Nuclear Astrophysics ◽

Cosmic Ray ◽

Big Bang ◽

Big Bang Nucleosynthesis ◽

Present Contribution ◽

Hydrogen Burning ◽

The Earth ◽

Deep Underground

Cross sections of nuclear reactions relevant for astrophysics are crucial ingredients to understand the energy generation inside stars and the synthesis of the elements. At astrophysical energies, nuclear cross sections are often too small to be measured in laboratories on the Earth surface, where the signal would be overwhelmed by the cosmic-ray induced background. LUNA is a unique Nuclear Astrophysics experiment located at Gran Sasso National Laboratories. The extremely low background achieved at LUNA allows to measure nuclear cross sections directly at the energies of astrophysical interest. Over the years, many crucial reactions involved in stellar hydrogen burning as well as Big Bang nucleosynthesis have been measured at LUNA. The present contribution provides an overview on underground Nuclear Astrophysics as well as the latest results and future perspectives of the LUNA experiment.

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Lithium evolution from Pre-Main Sequence to the Spite plateau: an environmental solution to the cosmological lithium problem

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315007073 ◽

2015 ◽

Vol 11 (S317) ◽

pp. 300-301

Author(s):

Xiaoting Fu ◽

Alessandro Bressan ◽

Paolo Molaro ◽

Paola Marigo

Keyword(s):

Main Sequence ◽

Big Bang ◽

Stellar Atmosphere ◽

Main Sequence Stars ◽

Lower Mass ◽

Big Bang Nucleosynthesis ◽

Lithium Abundance ◽

Wide Range ◽

Nuclear Burning ◽

And Diffusion

AbstractLithium abundance derived in metal-poor main sequence stars is about three times lower than the primordial value of the standard Big Bang nucleosynthesis prediction. This disagreement is referred to as the lithium problem. We reconsider the stellar Li evolution from the pre-main sequence to the end of main sequence phase by introducing the effects of overshooting and residual mass accretion. We show that 7Li could be significantly depleted by convective overshooting in the pre-main sequence phase and then partially restored in the stellar atmosphere by residual accretion which follows the Li depletion phase and could be regulated by EUV photo-evaporation. By considering the conventional nuclear burning and diffusion along the main sequence we can reproduce the Spite plateau for stars with initial mass m0=0.62–0.80 M⊙, and the Li declining branch for lower mass dwarfs, e.g, m0=0.57–0.60 M⊙, for a wide range of metallicities (Z=0.00001 to Z=0.0005), starting from an initial Li abundance A(Li) = 2.72.

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The Lithium Isotope Ratio In Old Stars

Highlights of Astronomy ◽

10.1017/s1539299600011667 ◽

1995 ◽

Vol 10 ◽

pp. 443-444

Author(s):

P.E. Nissen

Keyword(s):

Isotope Ratio ◽

Main Sequence ◽

Cosmic Ray ◽

Big Bang ◽

Stellar Atmosphere ◽

Lithium Isotope ◽

Stellar Rotation ◽

Main Sequence Stars ◽

Big Bang Nucleosynthesis ◽

Upper Limits

The lithium isotope ratio in stars can be determined from high resolution observations of the profile of the Li I 6707 Å absorption line. Earlier studies of old F and G stars (Andersen et al. 1984, Maurice et al. 1984, Pilachowski et al. 1989) have led to upper limits of 6Li/7Li ranging from 0.05 to 0.10. Recently, Smith, Lambert & Nissen (1993) seem to have detected 6Li in HD 84937 - a metal-poor turnoff star with Teff ⋍ 6200 K and [Fe/H] ⋍ —2.4. An isotope ratio 6Li/7Li = 0.05 ± 0.02 was determined (see Fig. 1) The detection has been confirmed by Hobbs & Thorburn (1994), who derived 6Li/7Li = 0.07 ± 0.03. The main contribution to the quoted (1σ) errors comes from the noise in the spectrum (S/N = 400) and possible errors in the Doppler broadening of the Li line (Nissen 1994). This broadening is due to stellar rotation and macro-turbulent motions in the stellar atmosphere and can be determined from the profiles of unblended metallic absorption lines.As discussed in detail by Steigman et al. (1993) the presence of 6Li in the atmosphere of HD 84937 is consistent with the measured Be abundance (Boesgaard & King 1993) within the context of i) Standard Big Bang nucleosynthesis, ii) Pop. II cosmic ray nucleosynthesis and iii) standard (non-rotating) models for Li depletion. In particular, Steigman et al. derive D6 > 0.2, where D6 is the depletion factor for 6Li. As shown by Chaboyer (1994) standard stellar evolution models with new opacities predict D6≃ 0.4 for turnoff stars and subgiants with Teff > 5900 K. The same models predict D7 ≃ 1.0, i.e. no 7Li depletion for main sequence stars as well as subgiants with Teff ≥ 5800 K.

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Erratum: Measurement of d+Be7 Cross Sections for Big-Bang Nucleosynthesis [Phys. Rev. Lett. 122 , 182701 (2019)]

Physical Review Letters ◽

10.1103/physrevlett.123.239902 ◽

2019 ◽

Vol 123 (23) ◽

Cited By ~ 3

Author(s):

N. Rijal ◽

I. Wiedenhöver ◽

J. C. Blackmon ◽

M. Anastasiou ◽

L. T. Baby ◽

...

Keyword(s):

Cross Sections ◽

Big Bang ◽

Big Bang Nucleosynthesis

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The Galactic Evolution of Boron

Symposium - International Astronomical Union ◽

10.1017/s0074180900166987 ◽

2000 ◽

Vol 198 ◽

pp. 405-414 ◽

Cited By ~ 1

Author(s):

Francesca Primas

Keyword(s):

Hubble Space Telescope ◽

Cosmic Ray ◽

Big Bang ◽

Stellar Structure ◽

Current Status ◽

Big Bang Nucleosynthesis ◽

Medium Resolution ◽

The Galaxy ◽

Stellar Interiors ◽

Astrophysical Research

Boron, together with lithium and beryllium, belongs to the group of the so-called light elements, the importance of which ranges from providing important tests to Big Bang nucleosynthesis scenarios to being useful probes of stellar interiors and useful tools to further constrain the chemical evolution of the Galaxy.Since it became operative in the late eighties, the Hubble Space Telescope (HST) and its high- and medium-resolution spectrographs have played a key role in analyzing boron. Boron has now been observed in several stars and in the interstellar medium (ISM), providing important information in different fields of astrophysical research (nucleosynthesis, cosmic-ray spallation, stellar structure). In particular, determinations of boron in unevolved stars of different metallicity have allowed to study how boron evolves with iron.After a general review of the current status of boron observations and of the major uncertainties affecting the measurements of its abundance, I will mainly concentrate on unevolved stars and discuss the ‘evolutionary’ picture emerging from the most recent analyses and how its interpretation compares with theoretical expectations. A brief discussion on future prospects will conclude this contribution, showing how the field may evolve and improve.

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STAU-CATALYZED BIG-BANG NUCLEOSYNTHESIS AND NUCLEAR CLUSTER MODEL

International Journal of Modern Physics A ◽

10.1142/s0217751x09045649 ◽

2009 ◽

Vol 24 (11) ◽

pp. 2076-2083 ◽

Cited By ~ 1

Author(s):

M. KAMIMURA ◽

Y. KINO ◽

E. HIYAMA

Keyword(s):

Cross Sections ◽

Cluster Model ◽

Nuclear Reactions ◽

Light Element ◽

Bound State ◽

Big Bang ◽

Reaction Cross ◽

Big Bang Nucleosynthesis ◽

Model Calculations ◽

Three Body

Three-body cluster-model calculations are performed for the new types of big-bang nucleosynthesis (BBN) reactions that are calalyzed by a supersymmetric (SUSY) particle stau, a scalar partner of the tau lepton. If a stau has a lifetime ≳ 103s, it would capture a light element previously synthesized in standard BBN and form a Coulombic bound state. The bound state, an exotic atom, is expected to induce various reactions, such as (αX-) + d → 6 Li + X-, in which a negatively charged stau (denoted as X-) works as a catalyzer. Recent literature papers have claimed that some of these stau-catalyzed reactions have significantly large cross sections so that inclusion of the reactions into the BBN network calculation can change drastically abundances of some elements, giving not only a solution to the 6 Li -7 Li problem (calculated underproduction of 6 Li by ~ 1000 times and overproduction of 7 Li +7 Be by ~ 3 times) but also a constraint on the lifetime and the primordial abundance of the elementary particle stau. However, most of these literature calculations of the reaction cross sections were made assuming too naive models or approximations that are unsuitable for those complicated low-energy nuclear reactions. We use a few-body calculational method developed by the authors, and provides precise cross sections and rates of the stau-catalyzed BBN reactions for the use in the BBN network calculation.

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THE 2H(α, γ)6LI REACTION AT LUNA AND BIG BANG NUCLEOSYNTHETIS

Acta Polytechnica ◽

10.14311/ap.2013.53.0534 ◽

2013 ◽

Vol 53 (A) ◽

pp. 534-537 ◽

Cited By ~ 1

Author(s):

Carlo Gustavino

Keyword(s):

Cross Section ◽

Preliminary Data ◽

Big Bang ◽

Low Energy ◽

Big Bang Nucleosynthesis ◽

Lithium Abundance ◽

Halo Stars ◽

First Time ◽

Standard Production ◽

Production Channel

The 2H(α, γ)6Li reaction is the leading process for the production of 6Li in standard Big Bang Nucleosynthesis. Recent observations of lithium abundance in metal-poor halo stars suggest that there might be a 6Li plateau, similar to the well-known Spite plateau of 7Li. This calls for a re-investigation of the standard production channel for 6Li. As the 2H(α, γ)6Li cross section drops steeply at low energy, it has never before been studied directly at Big Bang energies. For the first time the reaction has been studied directly at Big Bang energies at the LUNA accelerator. The preliminary data and their implications for Big Bang nucleosynthesis and the purported 6Li problem will be shown.

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The Point on the Theoretical Changes of Surface Chemistry During Massive Star Evolution

International Astronomical Union Colloquium ◽

10.1017/s0252921100093489 ◽

1988 ◽

Vol 108 ◽

pp. 79-85

Author(s):

André Maeder

Keyword(s):

Surface Chemistry ◽

Cross Sections ◽

Massive Star ◽

Main Sequence ◽

Tidal Mixing ◽

Main Sequence Stars ◽

Star Evolution ◽

Cno Abundances ◽

Massive Star Evolution ◽

Nuclear Processing

For main sequence stars, the central nuclear processing generally has no effect on surface abundances. Later in the evolution, the newly synthetized elements may be revealed at the stellar surface by processes such as mass loss, convective dredge-up, overshooting, diffusion, rotational and tidal mixing, etc. The changes of CNO abundances are the most conspicuous and the easiest to observe spectroscopically; some abundance ratios like C/N, O/N may undergo changes by more than 102. On the whole, surface chemistry is a most powerful diagnostics of stellar evolution, model assumptions and nuclear cross sections.

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