Big-bang nucleosynthesis and the relic abundance of dark matter in a stau-neutralino coannihilation scenario

Jittoh, Toshifumi; Kohri, Kazunori; Koike, Masafumi; Sato, Joe; Shimomura, Takashi; Yamanaka, Masato

doi:10.1103/physrevd.78.055007

Cited by 46 publications

(40 citation statements)

References 19 publications

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“…Many solutions for this discrepancy have been proposed, including new physics at the time of the big bang (Jedamzik 2004(Jedamzik , 2006Jittoh et al 2008;Hisano et al 2009), astration in the pristine Galaxy (Piau et al 2006, hereafter P06), and turbulent diffusion to deplete lithium in the stellar atmospheres (Richard et al 2005).…”

Section: Introductionmentioning

confidence: 99%

The lithium content ofω Centauri

Monaco

Bonifacio

Sbordone

et al. 2010

A&A

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Context.A discrepancy has emerged between the cosmic lithium abundance inferred by the WMAP satellite measurement coupled with the prediction of the standard big-bang nucleosynthesis theory, and the constant Li abundance measured in metal-poor halo dwarf stars (the so-called Spite plateau). Several models are being proposed to explain this discrepancy, involving either new physics, in situ depletion, or the efficient depletion of Li in the pristine Galaxy by a generation of massive first stars. The realm of possibilities may be narrowed considerably by observing stellar populations in different galaxies, which have experienced different evolutionary histories. Aims. The ω Centauri stellar system is commonly considered as the remnant of a dwarf galaxy accreted by the Milky Way. We investigate the lithium content of a conspicuous sample of unevolved stars in this object. Methods. We obtained moderate resolution (R = 17 000) spectra for 91 main-sequence/early sub-giant branch (MS/SGB) ω Cen stars using the FLAMES-GIRAFFE/VLT spectrograph. Lithium abundances were derived by matching the equivalent width of the Li i resonance doublet at 6708 Å to the prediction of synthetic spectra computed with different Li abundances. Synthetic spectra were computed using the SYNTHE code along with ATLAS-9 model atmospheres. The stars effective temperatures are derived by fitting the wings of the H α line with synthetic profiles. Results. We obtain a mean content of A(Li) = 2.19 ± 0.14 dex for ω Centauri MS/SGB stars. This is comparable to what is observed in Galactic halo field stars of similar metallicities and temperatures. Conclusions. The Spite plateau seems to be an ubiquitous feature of old, warm metal-poor stars. It exists also in external galaxies, if we accept the current view about the origin of ω Cen. This implies that the mechanism(s) that causes the "cosmological lithium problem" may be the same in the Milky Way and other galaxies.

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Section: Introductionmentioning

confidence: 99%

The lithium content ofω Centauri

Monaco

Bonifacio

Sbordone

et al. 2010

A&A

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“…The white region is the parameter space, which is consistent with all the observational abundance including that of 7 Li/H. The region enclosed by dashed lines is excluded by the observational abundance of 6 Li/ 7 Li, and the one enclosed by solid lines are allowed by those of 7 The qualitative feature of the allowed region is explained from the following physical consideration. First, we note that Yτ ,FO (10 −13 -10 −12 ) is required so that a sufficient number of bound state (τ 7 Be) is formed to destruct 7 Be by the internal conversion into 7 Li.…”

Section: Numerical Resultsmentioning

confidence: 94%

“…The stau-nucleus bound state decays through the following processes: where the parentheses denote the bound states. The 6 He nucleus can also decay into 6 Li via β decay with the lifetime 817 msec. We do not take this process into account since this process is much slower than the scattering process (2.4).…”

Section: Solving the LI Problem By Long Lived Staumentioning

confidence: 99%

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Solving the Li problem by long lived stau in a stau-neutralino coannihilation scenario

Yamanaka¹

2010

Proceedings of European Physical Society Europhysics Conference on High Energy Physics — PoS(EPS-HEP 2009)

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We study the Big-Bang Nucleosynthesis (BBN) within the minimal supersymmetric standard model. We find that we can account for the possible discrepancy of the abundance of 7 Li between the observation and the prediction of the big-bang nucleosynthesis by taking the mass of the neutralino as 300 GeV and the mass difference between the stau and the neutralino as (100 -120) MeV. We can therefore simultaneously explain the abundance of the dark matter and that of 7 Li by these values of parameters. The lifetime of staus in this scenario is predicted to be O(100 -1000) sec.

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“…); (c) the standard Big Bang nucleosynthesis (SBBN) calculations should be revised, possibly with the introduction of new physics (see e.g. Jedamzik 2004Jedamzik , 2006Jittoh et al 2008;Hisano et al 2009). The observed Li abundances, A(Li), in metal-poor stars appear to show a very well defined plateau with very little dispersion at relatively high metallicities, whereas at low metallicities there seems to be an increased scatter, or perhaps even a sharp down turn in the Li abundances (Bonifacio et al 2007a;González Hernández et al 2008;Sbordone et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Lithium in the globular cluster NGC 6397

Hernández¹,

Bonifacio

Caffau³

et al. 2009

A&A

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Context. Most globular clusters are believed to host a single stellar population. They can thus be considered a good place to study the Spite plateau and to search for possible evolutionary modifications of the Li content. Aims. We want to determine the Li content of subgiant (SG) and main sequence (MS) stars of the old, metal-poor globular cluster NGC 6397. This work was aimed not only at studying possible Li abundance variations but also to investigate the cosmological Li discrepancy. Methods. Here, we present FLAMES/GIRAFFE observations of a sample of 84 SG and 79 MS stars in NGC 6397 selected in a narrow range of B − V colour and, therefore, effective temperatures. We determine both effective temperatures and Li abundances using three-dimensional hydrodynamical model atmospheres for all the MS and SG stars of the sample. Results. We find a significant difference in the Li abundance between SG stars and MS stars, the SG stars having an abundance higher by almost 0.1 dex on average. We also find a decrease in the lithium abundance with decreasing effective temperature, both in MS and SG stars, albeit with a significantly different slope for the two classes of stars. This suggests that the lithium abundance in these stars is, indeed, altered by some process, which is temperature-dependent. Conclusions. The lithium abundance pattern observed in NGC 6397 is different from what is found among field stars, casting some doubt on the use of globular cluster stars as representative of Population II with respect to the lithium abundance. None of the available theories of Li depletion appears to satisfactorily describe our observations.

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Big-bang nucleosynthesis and the relic abundance of dark matter in a stau-neutralino coannihilation scenario

Cited by 46 publications

References 19 publications

The lithium content ofω Centauri

The lithium content ofω Centauri

Solving the Li problem by long lived stau in a stau-neutralino coannihilation scenario

Lithium in the globular cluster NGC 6397

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