High Baryon Density Region Research Articles

Molecular fluorine chemistry in the early Universe

Some models of Big Bang nucleosynthesis suggest that very high baryon density regions were formed in the early Universe, and generated the production of heavy elements other than lithium such as fluorine F. We present a comprehensive chemistry of fluorine in the post-recombination epoch. Calculation of F, F- and HF abundances, as a function of redshift z, are carried out. The main result is that the chemical conditions in the early Universe can lead to the formation of HF. The final abundance of the diatomic molecule HF is predicted to be close to 3.75 10(-17) when the initial abundance of neutral fluorine F is 10(-15). These results indicate that molecules of fluorine HF were already present during the dark age. This could have implications on the evolution of proto-objects and on the anisotropies of cosmic microwave background radiation. Hydride of fluorine HF may affect enhancement of the emission line intensity from the proto-objects and could produce spectral-spatial fluctuations.

Reply to “Comment on ‘Heavy element production in inhomogeneous big bang nucleosynthesis’”

This is a reply to Rauscher [Phys. Rev. D 75, 068301 (2007)]. We studied heavy element production in the high baryon density region in the early universe [Phys. Rev. D 72, 123505 (2005)]. However, it is claimed by Rauscher [Phys. Rev. D 75, 068301 (2007)] that a small scale but high baryon density region contradicts observations for the light element abundance or, in order not to contradict the observations, the high density region must be so small that it cannot affect the present heavy element abundance. In this paper, we study big bang nucleosynthesis in the high baryon density region and show that in certain parameter spaces it is possible to produce enough of the heavy element without contradiction to cosmic microwave background and light element observations.

Comment on “Heavy element production in inhomogeneous big bang nucleosynthesis”

The work of Matsuura et al. [Phys. Rev. D 72, 123505 (2005)] claims that heavy nuclei could have been produced in a combined p- and r-process in very high baryon density regions of an inhomogeneous big bang. However, they do not account for observational constraints and previous studies which show that such high baryon density regions did not significantly contribute to big bang abundances.

The Compressed Baryonic Matter Experiment at FAIR

The study of high-energy nucleus-nucleus collisions will be one of the major activities at the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt. The goal of the research program is to explore the QCD phase diagram in the region of high baryon densities. The relevant observables and the lavout of the proposed Compressed Baryonic Matter (CBM) experiment will be discussed.

Strangeness and charm in the CBM experiment

The heavy-ion experiment CBM, considered as one of the core projects of the future accelerator facility FAIR in Darmstadt, will investigate nucleus–nucleus collisions from 10 to 45 A GeV, thus exploring the QCD phase diagram in the region of highest baryon densities. High machine availability and interaction rates will give access to rare observables like charm near threshold. We discuss the physics motivation, the proposed detector system and results of feasibility studies.

The CBM experiment at FAIR

The study of high-energy nucleus-nucleus collisions will be one of the major activities at the future accelerator complex FAIR in Darmstadt. The goal of the research program is the exploration of the QCD phase diagram in the region of high baryon densities.

The CBM experiment at GSI/FAIR

The heavy-ion experiment CBM, considered as one of the core projects of the future accelerator facility FAIR in Darmstadt, will investigate nucleus-nucleus collisions from 10 to 45 AGeV, thus exploring the QCD phase diagram in the region of highest baryon densities. High machine availability and interaction rates will give access to rare observables like charm near threshold. We discuss the physics motivation, the proposed detector system and results of feasibility studies.

Heavy element production in inhomogeneous big bang nucleosynthesis

We present a new astrophysical site of the big bang nucleosynthesis (BBN) that are very peculiar compared with the standard BBN. Some models of the baryogenesis suggest that very high baryon density regions were formed in the early universe. On the other hand, recent observations suggest that heavy elements already exist in high red-shifts and the origin of these elements become a big puzzle. Motivated by these, we investigate BBN in very high baryon density regions. BBN proceeds in proton-rich environment, which is known to be like the p-process. However, by taking very heavy nuclei into account, we find that BBN proceeds through both the p-process and the r-process simultaneously. P-nuclei such as {sup 92}Mo, {sup 94}Mo, {sup 96}Ru, {sup 98}Ru whose origin is not well known are also synthesized.

Neutron diffusion and nucleosynthesis in an inhomogeneous big bang model

This article presents an original code for big bang nucleosynthesis in a baryon inhomogeneous model of the Universe. In this code neutron diffusion between high and low baryon density regions is calculated simultaneously with the nuclear reactions and weak decays that compose the nucleosynthesis process. The size of the model determines the time when neutron diffusion becomes significant. This article describes in detail how the time of neutron diffusion relative to the time of nucleosynthesis affects the final abundances of $^{4}\mathrm{He}$, deuterium and $^{7}\mathrm{Li}$. These results will be compared with the most recent observational constraints of $^{4}\mathrm{He}$, deuterium and $^{7}\mathrm{Li}$. This inhomogeneous model has $^{4}\mathrm{He}$ and deuterium constraints in concordance for baryon-to-photon ratio $\ensuremath{\eta}=(4.3\ensuremath{-}12.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ $^{7}\mathrm{Li}$ constraints are brought into concordance with the other isotope constraints by including a depletion factor as high as 5.9. These ranges for the baryon-to-photon ratio and for the depletion factor are larger than the ranges from a standard big bang nucleosynthesis model.

Strangeness and charm of compressed baryonic matter—the CBM experiment at FAIR

A major field of research at the future accelerator facility at GSI will be the exploration of the QCD phase diagram in the region of high baryon densities. Experimental observables and the proposed detector system will be discussed.

The compressed baryonic matter experiment at FAIR in Darmstadt

The study of high-energy nucleus–nucleus collisions will be one of the major activities at the future facility for antiproton and ion research (FAIR) in Darmstadt. The goal of the research programme is the exploration of the QCD phase diagram in the region of high baryon densities. First results of feasibility studies will be discussed.

The strangeness and charm of dense nuclear matter

The creation of strangeness and charm in nucleus-nucleus collisions at threshold beam energies is discussed as a probe for compressed baryonic matter. Experimental data on strangeness production at SIS energies indicate that the properties of kaons and antikaons are modified in dense nuclear matter. The yield of K+ mesons emitted in heavy-ion collisions at beam energies below 1.5 AGeV is found to be sensitive to the nuclear equation-of-state. An experiment is proposed at the future GSI facility to explore the QCD phase diagram in the region of highest baryon densities. This approach is complementary to the studies of matter at high temperatures performed at the CERN-SPS, RHIC and the future LHC. Experimental observables and the proposed detector system will be discussed.

The compressed baryonic matter experiment

A major field of research at the future accelerator facility at GSI will be the exploration of the QCD phase diagram in the region of high baryon densities. This approach is complementary to the studies of matter at high temperatures performed at the CERN-SPS, RHIC and the future LHC. Experimental observables and the proposed detector system will be discussed.

Modeling relativistic heavy ion collisions: From AGS to SPS

The importance of hadronic resonances in relativistic heavy ion collisions, from AGS to SPS energies, is now widely recognized. The systematics from Si beams to Au beams, provide overwhelming evidence that the hadronic resonance description of the heavy ion collisions is quite accurate at AGS energies with the possible exception when the highest baryon densities are reached. The authors have seen the importance of resonance rescattering in nucleus-nucleus collisions. However, they have very little direct knowledge on the cross-sections and the rescattering mechanisms of these resonances. They also have the formation of high baryon density regions, but they have no direct knowledge on the medium dependence of the hadronic cross sections involved. In the hadronic cascade model, ARC, they have assumed that baryon resonances rescatter as nucleons and the meson resonances as pions, and the free space cross-sections for nucleons and pions are used through out the collisions. It would be much better if these assumptions could be verified independently through experiments. For details of resonance rescattering, they obtain some information by reconstructing the resonances from the observed hadrons. Determining the hadronic cross sections in a dense medium is a hard problem. The authors describe tests on the sensitivities ofmore » medium dependence to the observed spectra. These tests make very drastic and unrealistic assumptions on the density dependence of the hadronic cross sections, but as sensitivity tests they are nevertheless quite revealing.« less