The open question of where, when, and how the heavy elements beyond iron enrich our Universe has triggered a new era in nuclear physics studies. Of all the relevant nuclear physics inputs, the mass of very neutron-ric...The open question of where, when, and how the heavy elements beyond iron enrich our Universe has triggered a new era in nuclear physics studies. Of all the relevant nuclear physics inputs, the mass of very neutron-rich nuclides is a key quantity for revealing the origin of heavy elements beyond iron. Although the precise determination of this property is a great challenge, enormous progress has been made in recent decades, and it has contributed significantly to both nuclear structure and astrophysical nucleosynthesis studies. In this review, we first survey our present knowledge of the nuclear mass surface, emphasizing the importance of nuclear mass precision in r-process calculations. We then discuss recent progress in various methods of nuclear mass measurement with a few selected examples. For each method, we focus on recent breakthroughs and discuss possible ways of improving the weighing of r-process nuclides.展开更多
In a recent series of papers, we introduced a new model of nucleosynthesis in which the matter content of the universe came into existence at a time of about 4 × 10<sup>-5</sup> s. At that time, a sma...In a recent series of papers, we introduced a new model of nucleosynthesis in which the matter content of the universe came into existence at a time of about 4 × 10<sup>-5</sup> s. At that time, a small percentage of the vacuum energy was converted into neutron/antineutron pairs with a very small excess of neutrons. This process was regulated by an imprint that was established in the vacuum during an initial Plank-era inflation. Immediately after their inception, annihilation and charge exchange reactions proceeded at a very high rate and ran to completion after an interval of about 10<sup>-11</sup> s. By then, all the antibaryons had disappeared thereby establishing the matter/antimatter asymmetry of the universe. What remained were very high densities of mesons and leptons, somewhat lower densities of protons and neutrons, and finally, the very high density of photons that eventually became the CMB. The density of matter so created varied from one location to another in such a manner as to account for all cosmic structures and because the energy density of the photons varied in proportion to that of the matter, the CMB-to-be came into existence with an anisotropic spectrum already in place. For structures, the size of galaxy clusters, the initial anisotropy magnitudes were on the order of 25%. In this paper, we will follow the subsequent evolution of the photons and show that this model predicts with accuracy the temperature of the warmest anisotropies in the observed CMB spectrum. .展开更多
In this paper, we present a new cosmology based on the idea of a universe dominated by vacuum energy with time-varying curvature. In this model, the universe began with an exponential Plank era inflation before transi...In this paper, we present a new cosmology based on the idea of a universe dominated by vacuum energy with time-varying curvature. In this model, the universe began with an exponential Plank era inflation before transitioning to a spacetime described by Einstein’s equations. While no explicit model of the Plank era is yet known, we do establish a number of properties that the vacuum of that time must have exhibited. In particular, we show that structures came into existence during that inflation that were later responsible for all cosmic structures. A new solution of Einstein’s equations incorporating time-varying curvature is presented which predicts that the scaling was initially power law with a parameter of <em>y</em>=1/2 before transitioning to an exponential acceleration of the present-day scaling. A formula relating the curvature to the vacuum energy density is also a part of the solution. A non-conventional model of nucleosynthesis provides a solution for the matter/antimatter asymmetry problem and a non-standard origin of the CMB. The CMB power spectrum is shown to be a consequence of uncertainties embedded during the initial inflation and the existence of superclusters. Using Einstein’s equations, we show that so-called dark matter is, in fact, vacuum energy. A number of other issues are discussed.展开更多
Motivated by the fact that calibrated light curves of Type Ia supernovae （SNe Ia） have become a major tool to determine the expansion history of the Universe, considerable attention has been given to, both, observat...Motivated by the fact that calibrated light curves of Type Ia supernovae （SNe Ia） have become a major tool to determine the expansion history of the Universe, considerable attention has been given to, both, observations and models of these events over the past 15 years. Here, we summarize new observational constraints, address recent progress in modeling Type Ia supernovae by means of three-dimensional hydrodynamic simulations, and discuss several of the still open questions. It will be be shown that the new models have considerable predictive power which allows us to study observable properties such as light curves and spectra without adjustable non-physical parameters. This is a necessary requisite to improve our understanding of the explosion mechanism and to settle the question of the applicability of SNe Ia as distance indicators for cosmology. We explore the capabilities of the models by comparing them be applied to study the origin of the diversity with observations and we show how such models can of SNe Ia.展开更多
Big Bang nucleosynthesis(BBN)theory predicts the primordial abundances of the light elements^(2) H(referred to as deuterium,or D for short),^(3)He,^(4)He,and^(7) Li produced in the early universe.Among these,deuterium...Big Bang nucleosynthesis(BBN)theory predicts the primordial abundances of the light elements^(2) H(referred to as deuterium,or D for short),^(3)He,^(4)He,and^(7) Li produced in the early universe.Among these,deuterium,the first nuclide produced by BBN,is a key primordial material for subsequent reactions.To date,the uncertainty in predicted deuterium abundance(D/H)remains larger than the observational precision.In this study,the Monte Carlo simulation code PRIMAT was used to investigate the sensitivity of 11 important BBN reactions to deuterium abundance.We found that the reaction rate uncertainties of the four reactions d(d,n)^(3)He,d(d,p)t,d(p,γ)^(3)He,and p(n,γ)d had the largest influence on the calculated D/H uncertainty.Currently,the calculated D/H uncertainty cannot reach observational precision even with the recent LUNA precise d(p,γ)^(3) He rate.From the nuclear physics aspect,there is still room to largely reduce the reaction-rate uncertainties;hence,further measurements of the important reactions involved in BBN are still necessary.A photodisintegration experiment will be conducted at the Shanghai Laser Electron Gamma Source Facility to precisely study the deuterium production reaction of p(n,γ)d.展开更多
We investigate the impact of inelastic collisions between dark matter(DM)and heavy cosmic ray(CR)nuclei on CR propagation.We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured pr...We investigate the impact of inelastic collisions between dark matter(DM)and heavy cosmic ray(CR)nuclei on CR propagation.We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured proton-nuclei scattering cross-sections,allowing us to assess how these collisions affect the spectra of CR boron and carbon.We derive new CR spectra from DM-CR collisions by incorporating their cross-sections into the source terms and solving the diffusion equation for the complete network of reactions involved in generating secondary species.In a specific example with a coupling strength of b_(χ)=0.1 and a DM mass of m_(χ)=0.1 GeV,considering a simplified scenario where DM interacts exclusively with oxygen,a notable modification in the boron-to-carbon spectrum due to the DM-CR interaction is observed.Particularly,the peak within the spectrum,spanning from 0.1 to 10 GeV,experiences an enhancement of approximately 1.5 times.However,in a more realistic scenario where DM particles interact with all CRs,this peak can be amplified to twice its original value.Utilizing the latest data from AMS-02 and DAMPE on the boron-to-carbon ratio,we estimate a 95%upper limit for the effective inelastic cross-section of DM-proton as a function of DM mass.Our findings reveal that at m_(χ)?2 MeV,the effective inelastic cross-section between DM and protons must be less than O(10^(-32))cm^(2).展开更多
The influence of electron screening on electron capture rate in strong screening is investigated, in which the Gamow-Teller resonance transition is considered and the matrix elements for the resonance transition are c...The influence of electron screening on electron capture rate in strong screening is investigated, in which the Gamow-Teller resonance transition is considered and the matrix elements for the resonance transition are calculated on the basis of a shell model. The effect of electron screening on electron capture by 56Co is discussed. It is shown that the screening decreases evidently the capture rates in lower temperature and higher density. The effect of electron screening on other nuclear capture rates is estimated. The conclusion derived may influence the research for late stellar evolution and supernova explosion.展开更多
A more compact representation of the Segré chart of nuclides can be obtained replacing the isotopic neutron with the corresponding neutron excess number;a first sight inspection of all the natural isotopes is pro...A more compact representation of the Segré chart of nuclides can be obtained replacing the isotopic neutron with the corresponding neutron excess number;a first sight inspection of all the natural isotopes is produced. The resulting representation shows a built-inorder in the organization of the nuclear components into the nuclei of the natural isotopes, sustained by the relevant role of the magic numbers. The interpretation, on the identical foot, of the nuclear instability of Tc, Pm and of the elements following Bi is suggested. The present representation reminds the spheron model of the nuclear structure suggested by L. Pauling. The alpha decay paths of radioactive isotopes are shown, side by side to the low energy nuclear transmutations (LENR). Representations of the artificial isotopes of the chemical elements and of the stellar nucleosynthesis processes are also proposed.展开更多
Lithium isotopes have attracted an intense interest because the abundance of both 6Li and 6Li from big bang nucleosynthesis (BBN) is one of the puzzles in nuclear astrophysics. Many investigations of both astrophysic...Lithium isotopes have attracted an intense interest because the abundance of both 6Li and 6Li from big bang nucleosynthesis (BBN) is one of the puzzles in nuclear astrophysics. Many investigations of both astrophysical observation and nucleosynthesis calculation have been carried out to solve the puzzle, but it is not solved yet. Several nuclear reactions involving lithium have been indirectly measured at China Institute of Atomic Energy, Beijing. The Standard BBN (SBBN) network calculations are then performed to investigate the primordial Lithium abundance. The result shows that these nuclear reactions have minimal effect on the SBBN abundances of 6Li and 7Li.展开更多
The ＇lithium problem, in Big Bang nucleosynthesis（BBN） has recently focused on reactions involving ^7 Be.The ^6 Li（p,γ）^7 Be reaction can provide us not only with information about ^6 Li destruction but also wit...The ＇lithium problem, in Big Bang nucleosynthesis（BBN） has recently focused on reactions involving ^7 Be.The ^6 Li（p,γ）^7 Be reaction can provide us not only with information about ^6 Li destruction but also with information about ^7 Be production. In the present work, the proton spectroscopic factor in ^7 Be is extracted to be 0.70 ± 0.17 from the angular distribution of ^7 Be（d, ^3 He）^6 Li at Ec.m. = 6.7 MeV. This value is then used to compute the direct component of the astrophysical ^6 Li（p,γ）^7 Beg.s. S（E） factors and determine the resonance parameters from the total S（E） factors.展开更多
In the standard Big Bang nucleosynthesis （SBBN） model, the lithium puzzle has attracted intense interest over the past few decades, but still has not been solved. Conventionally, the approach is to include more reac...In the standard Big Bang nucleosynthesis （SBBN） model, the lithium puzzle has attracted intense interest over the past few decades, but still has not been solved. Conventionally, the approach is to include more reactions flowing into or out of lithium, and study the potential effects of those reactions which were not previously considered. 7Be（d, 3He）6Li is a reaction that not only produces 6Li but also destroys 7Be, which decays to 7Li, thereby affecting 7Li indirectly. Therefore, this reaction could alleviate the lithium discrepancy if its reaction rate is sufficiently high. However, there is not much information available about the 7Be（d, 3He）6Li reaction rate. In this work, the angular distributions of the 7Be（d, 3He）6Li reaction are measured at the center of mass energies Ecm=4.0 MeV and 6.7 MeV with secondary 7Be beams for the first time. The excitation function of the 7Be（d, 3He）6Li reaction is first calculated with the computer code TALYS and then normalized to the experimental data, then its reaction rate is deduced. A SBBN network calculation is performed to investigate its influence on the 6Li and 7Li abundances. The results show that the 7Be（d, 3He）6Li reaction has a minimal effect on 6Li and 7Li because of its small reaction rate. Therefore, the 7Be（d, 3He）6Li reaction is ruled out by this experiment as a means of alleviating the lithium discrepancy.展开更多
The thermonuclear^19F（p,α0）16O reaction rate in the temperature region 0.007–10 GK has been derived by re-evaluating the available experimental data, together with the low-energy theoretical R-matrix extrapolation...The thermonuclear^19F（p,α0）16O reaction rate in the temperature region 0.007–10 GK has been derived by re-evaluating the available experimental data, together with the low-energy theoretical R-matrix extrapolations.Our new rate deviates by up to about 30% compared to the previous results, although all rates are consistent within the uncertainties. At very low temperature（e.g. 0.01 GK） our reaction rate is about 20% lower than the most recently published rate, because of a difference in the low energy extrapolated S-factor and a more accurate estimate of the reduced mass used in the calculation of the reaction rate. At temperatures above ^1 GK, our rate is lower, for instance, by about 20% around 1.75 GK, because we have re-evaluated the previous data（Isoya et al., Nucl. Phys.7, 116（1958）） in a meticulous way. The present interpretation is supported by the direct experimental data. The uncertainties of the present evaluated rate are estimated to be about 20% in the temperature region below 0.2 GK,and are mainly caused by the lack of low-energy experimental data and the large uncertainties in the existing data.Asymptotic giant branch（AGB） stars evolve at temperatures below 0.2 GK, where the^19F（p,α）16O reaction may play a very important role. However, the current accuracy of the reaction rate is insufficient to help to describe, in a careful way, the fluorine over-abundances observed in AGB stars. Precise cross section（or S factor） data in the low energy region are therefore needed for astrophysical nucleosynthesis studies.展开更多
We report the discovery of an extremely metal-poor（EMP） giant,LAMOST J110901.22＋075441.8, which exhibits a large excess of r-process elements with [Eu/Fe] ～ ＋1.16. The star is one of the newly discovered EMP star...We report the discovery of an extremely metal-poor（EMP） giant,LAMOST J110901.22＋075441.8, which exhibits a large excess of r-process elements with [Eu/Fe] ～ ＋1.16. The star is one of the newly discovered EMP stars identified from the LAMOST low-resolution spectroscopic survey and a highresolution follow-up observation with the Subaru Telescope. Stellar parameters and elemental abundances have been determined from the Subaru spectrum. Accurate abundances for a total of 23 elements including 11 neutron-capture elements from Sr through Dy have been derived for LAMOST J110901.22＋075441.8. The abundance pattern of LAMOST J110901.22＋075441.8 in the range of C through Zn is in line with the ＂normal＂ population of EMP halo stars, except that it shows a notable underabundance in carbon. The heavy element abundance pattern of LAMOST J110901.22＋075441.8 is in agreement with other well studied cool r-II metal-poor giants such as CS 22892-052 and CS 31082-001. The abundances of elements in the range from Ba through Dy match the scaled solar r-process pattern well.LAMOST J110901.22＋075441.8 provides the first detailed measurements of neutroncapture elements among r-II stars at such low metallicity with [Fe/H]-3.4, and exhibits similar behavior as other r-II stars in the abundance ratio of Zr/Eu as well as Sr/Eu and Ba/Eu.展开更多
In Part 1 of this work, we showed that our new model of cosmology can account for the origin of all cosmic structures ranging in size from stars up to superclusters. In this model, at the time of nucleosynthesis, an i...In Part 1 of this work, we showed that our new model of cosmology can account for the origin of all cosmic structures ranging in size from stars up to superclusters. In this model, at the time of nucleosynthesis, an imprint embedded in the vacuum regulated the creation of the protons (and electrons) that later made up the structures. Immediately after nucleosynthesis and for a considerable period afterward, the evolution was completely determined by the expansion of the universe. Gradually, however, gravitational influences became more important until finally, the expansion of the structures-to-be ceased at their zero velocity points. Stars, galaxies, and galaxy clusters all reached their zero velocity points more or less simultaneously at the usually accepted time of the beginning of galaxy formation. From that point onward, the evolution gravitation came to dominate the evolution although the expansion still exerted its influence. In this paper, we examine the subsequent cluster evolution in some detail. We establish the conditions required to prevent a free-fall collapse of the clusters and then show that galaxies with quasar-like active nuclei located within the cluster were the sources of the necessary radiation. We also show that the required galactic supermassive black holes were a consequence of the initial free-fall collapse of all galaxies.展开更多
In our original paper, we outlined a new model of nucleosynthesis which began when a small percentage of the vacuum energy was converted primarily into neutron-antineutron pairs but with a very small excess of neutron...In our original paper, we outlined a new model of nucleosynthesis which began when a small percentage of the vacuum energy was converted primarily into neutron-antineutron pairs but with a very small excess of neutrons. In this paper, we present a detailed study of that original idea. We show that immediately after their inception, annihilation and charge exchange reactions proceeded at a very high rate and after an interval of no more than 10<sup>-12</sup> s, the matter/antimatter asymmetry of the universe and the present-day abundance of baryons had been established. The annihilations produced the high density of leptons critical for the weak interactions and the photons that make up the CMB. The model predicts a photon temperature in agreement with the present-day CMB value and also explains the origin of the CMB anisotropy spectrum. We also show how the nucleosynthesis density variations needed to explain all cosmic structures can resolve the difficulties that arise when trying to explain observed primordial element abundances in terms of a single-density universal model of nucleosynthesis.展开更多
文摘The open question of where, when, and how the heavy elements beyond iron enrich our Universe has triggered a new era in nuclear physics studies. Of all the relevant nuclear physics inputs, the mass of very neutron-rich nuclides is a key quantity for revealing the origin of heavy elements beyond iron. Although the precise determination of this property is a great challenge, enormous progress has been made in recent decades, and it has contributed significantly to both nuclear structure and astrophysical nucleosynthesis studies. In this review, we first survey our present knowledge of the nuclear mass surface, emphasizing the importance of nuclear mass precision in r-process calculations. We then discuss recent progress in various methods of nuclear mass measurement with a few selected examples. For each method, we focus on recent breakthroughs and discuss possible ways of improving the weighing of r-process nuclides.
文摘In a recent series of papers, we introduced a new model of nucleosynthesis in which the matter content of the universe came into existence at a time of about 4 × 10<sup>-5</sup> s. At that time, a small percentage of the vacuum energy was converted into neutron/antineutron pairs with a very small excess of neutrons. This process was regulated by an imprint that was established in the vacuum during an initial Plank-era inflation. Immediately after their inception, annihilation and charge exchange reactions proceeded at a very high rate and ran to completion after an interval of about 10<sup>-11</sup> s. By then, all the antibaryons had disappeared thereby establishing the matter/antimatter asymmetry of the universe. What remained were very high densities of mesons and leptons, somewhat lower densities of protons and neutrons, and finally, the very high density of photons that eventually became the CMB. The density of matter so created varied from one location to another in such a manner as to account for all cosmic structures and because the energy density of the photons varied in proportion to that of the matter, the CMB-to-be came into existence with an anisotropic spectrum already in place. For structures, the size of galaxy clusters, the initial anisotropy magnitudes were on the order of 25%. In this paper, we will follow the subsequent evolution of the photons and show that this model predicts with accuracy the temperature of the warmest anisotropies in the observed CMB spectrum. .
文摘In this paper, we present a new cosmology based on the idea of a universe dominated by vacuum energy with time-varying curvature. In this model, the universe began with an exponential Plank era inflation before transitioning to a spacetime described by Einstein’s equations. While no explicit model of the Plank era is yet known, we do establish a number of properties that the vacuum of that time must have exhibited. In particular, we show that structures came into existence during that inflation that were later responsible for all cosmic structures. A new solution of Einstein’s equations incorporating time-varying curvature is presented which predicts that the scaling was initially power law with a parameter of <em>y</em>=1/2 before transitioning to an exponential acceleration of the present-day scaling. A formula relating the curvature to the vacuum energy density is also a part of the solution. A non-conventional model of nucleosynthesis provides a solution for the matter/antimatter asymmetry problem and a non-standard origin of the CMB. The CMB power spectrum is shown to be a consequence of uncertainties embedded during the initial inflation and the existence of superclusters. Using Einstein’s equations, we show that so-called dark matter is, in fact, vacuum energy. A number of other issues are discussed.
文摘Motivated by the fact that calibrated light curves of Type Ia supernovae （SNe Ia） have become a major tool to determine the expansion history of the Universe, considerable attention has been given to, both, observations and models of these events over the past 15 years. Here, we summarize new observational constraints, address recent progress in modeling Type Ia supernovae by means of three-dimensional hydrodynamic simulations, and discuss several of the still open questions. It will be be shown that the new models have considerable predictive power which allows us to study observable properties such as light curves and spectra without adjustable non-physical parameters. This is a necessary requisite to improve our understanding of the explosion mechanism and to settle the question of the applicability of SNe Ia as distance indicators for cosmology. We explore the capabilities of the models by comparing them be applied to study the origin of the diversity with observations and we show how such models can of SNe Ia.
基金supported by the National Key R&D Program of China(No.2022YFA1602401)by the National Natural Science Foundation of China(No.11825504)。
文摘Big Bang nucleosynthesis(BBN)theory predicts the primordial abundances of the light elements^(2) H(referred to as deuterium,or D for short),^(3)He,^(4)He,and^(7) Li produced in the early universe.Among these,deuterium,the first nuclide produced by BBN,is a key primordial material for subsequent reactions.To date,the uncertainty in predicted deuterium abundance(D/H)remains larger than the observational precision.In this study,the Monte Carlo simulation code PRIMAT was used to investigate the sensitivity of 11 important BBN reactions to deuterium abundance.We found that the reaction rate uncertainties of the four reactions d(d,n)^(3)He,d(d,p)t,d(p,γ)^(3)He,and p(n,γ)d had the largest influence on the calculated D/H uncertainty.Currently,the calculated D/H uncertainty cannot reach observational precision even with the recent LUNA precise d(p,γ)^(3) He rate.From the nuclear physics aspect,there is still room to largely reduce the reaction-rate uncertainties;hence,further measurements of the important reactions involved in BBN are still necessary.A photodisintegration experiment will be conducted at the Shanghai Laser Electron Gamma Source Facility to precisely study the deuterium production reaction of p(n,γ)d.
基金supported by the National Key Research and Development Program of China(2022YFF0503304,2020YFC2201600,2018YFA0404504 and 2018YFA0404601)the Ministry of Science and Technology of China(2020SKA0110402,2020SKA0110401 and 2020SKA0110100)+4 种基金the National Natural Science Foundation of China(11890691,12205388 and 12220101003)the CAS Project for Young Scientists in Basic Research(YSBR-061,YSBR-092)the China Manned Space Project with No.CMS-CSST-2021(A02,A03 and B01)the Major Key Project of PCLthe 111 project(B20019)。
文摘We investigate the impact of inelastic collisions between dark matter(DM)and heavy cosmic ray(CR)nuclei on CR propagation.We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured proton-nuclei scattering cross-sections,allowing us to assess how these collisions affect the spectra of CR boron and carbon.We derive new CR spectra from DM-CR collisions by incorporating their cross-sections into the source terms and solving the diffusion equation for the complete network of reactions involved in generating secondary species.In a specific example with a coupling strength of b_(χ)=0.1 and a DM mass of m_(χ)=0.1 GeV,considering a simplified scenario where DM interacts exclusively with oxygen,a notable modification in the boron-to-carbon spectrum due to the DM-CR interaction is observed.Particularly,the peak within the spectrum,spanning from 0.1 to 10 GeV,experiences an enhancement of approximately 1.5 times.However,in a more realistic scenario where DM particles interact with all CRs,this peak can be amplified to twice its original value.Utilizing the latest data from AMS-02 and DAMPE on the boron-to-carbon ratio,we estimate a 95%upper limit for the effective inelastic cross-section of DM-proton as a function of DM mass.Our findings reveal that at m_(χ)?2 MeV,the effective inelastic cross-section between DM and protons must be less than O(10^(-32))cm^(2).
基金Climbing Program from the State and Technology CommissionNational Natural Science Foundation of China.
文摘The influence of electron screening on electron capture rate in strong screening is investigated, in which the Gamow-Teller resonance transition is considered and the matrix elements for the resonance transition are calculated on the basis of a shell model. The effect of electron screening on electron capture by 56Co is discussed. It is shown that the screening decreases evidently the capture rates in lower temperature and higher density. The effect of electron screening on other nuclear capture rates is estimated. The conclusion derived may influence the research for late stellar evolution and supernova explosion.
文摘A more compact representation of the Segré chart of nuclides can be obtained replacing the isotopic neutron with the corresponding neutron excess number;a first sight inspection of all the natural isotopes is produced. The resulting representation shows a built-inorder in the organization of the nuclear components into the nuclei of the natural isotopes, sustained by the relevant role of the magic numbers. The interpretation, on the identical foot, of the nuclear instability of Tc, Pm and of the elements following Bi is suggested. The present representation reminds the spheron model of the nuclear structure suggested by L. Pauling. The alpha decay paths of radioactive isotopes are shown, side by side to the low energy nuclear transmutations (LENR). Representations of the artificial isotopes of the chemical elements and of the stellar nucleosynthesis processes are also proposed.
基金supported by the National Basic Research Programme of China (Grant No. 2007CB815003)the National Natural Science Foundation of China (Grant Nos. 10675173, 10705053, 10735100,11021504)
文摘Lithium isotopes have attracted an intense interest because the abundance of both 6Li and 6Li from big bang nucleosynthesis (BBN) is one of the puzzles in nuclear astrophysics. Many investigations of both astrophysical observation and nucleosynthesis calculation have been carried out to solve the puzzle, but it is not solved yet. Several nuclear reactions involving lithium have been indirectly measured at China Institute of Atomic Energy, Beijing. The Standard BBN (SBBN) network calculations are then performed to investigate the primordial Lithium abundance. The result shows that these nuclear reactions have minimal effect on the SBBN abundances of 6Li and 7Li.
基金Supported by National Natural Science Foundation of China(11375269,11490563,11505117)Natural Science Foundation of Guangdong Province(2015A030310012)+1 种基金National Basic Research Program of China(2013CB834406)National Key Research and Development Program of China(2016YFA0400502)
文摘The ＇lithium problem, in Big Bang nucleosynthesis（BBN） has recently focused on reactions involving ^7 Be.The ^6 Li（p,γ）^7 Be reaction can provide us not only with information about ^6 Li destruction but also with information about ^7 Be production. In the present work, the proton spectroscopic factor in ^7 Be is extracted to be 0.70 ± 0.17 from the angular distribution of ^7 Be（d, ^3 He）^6 Li at Ec.m. = 6.7 MeV. This value is then used to compute the direct component of the astrophysical ^6 Li（p,γ）^7 Beg.s. S（E） factors and determine the resonance parameters from the total S（E） factors.
基金Supported by National Natural Science Foundation of China(11375269,11505117,11490560,11475264,11321064)Natural Science Foundation of Guangdong Province(2015A030310012)+1 种基金973 program of China(2013CB834406)National key Research and Development Province(2016YFA0400502)
文摘In the standard Big Bang nucleosynthesis （SBBN） model, the lithium puzzle has attracted intense interest over the past few decades, but still has not been solved. Conventionally, the approach is to include more reactions flowing into or out of lithium, and study the potential effects of those reactions which were not previously considered. 7Be（d, 3He）6Li is a reaction that not only produces 6Li but also destroys 7Be, which decays to 7Li, thereby affecting 7Li indirectly. Therefore, this reaction could alleviate the lithium discrepancy if its reaction rate is sufficiently high. However, there is not much information available about the 7Be（d, 3He）6Li reaction rate. In this work, the angular distributions of the 7Be（d, 3He）6Li reaction are measured at the center of mass energies Ecm=4.0 MeV and 6.7 MeV with secondary 7Be beams for the first time. The excitation function of the 7Be（d, 3He）6Li reaction is first calculated with the computer code TALYS and then normalized to the experimental data, then its reaction rate is deduced. A SBBN network calculation is performed to investigate its influence on the 6Li and 7Li abundances. The results show that the 7Be（d, 3He）6Li reaction has a minimal effect on 6Li and 7Li because of its small reaction rate. Therefore, the 7Be（d, 3He）6Li reaction is ruled out by this experiment as a means of alleviating the lithium discrepancy.
基金Supported by National Natural Science Foundation of China(11490562,11490560,11675229)National Key Research and Development Program of China(2016YFA0400503)
文摘The thermonuclear^19F（p,α0）16O reaction rate in the temperature region 0.007–10 GK has been derived by re-evaluating the available experimental data, together with the low-energy theoretical R-matrix extrapolations.Our new rate deviates by up to about 30% compared to the previous results, although all rates are consistent within the uncertainties. At very low temperature（e.g. 0.01 GK） our reaction rate is about 20% lower than the most recently published rate, because of a difference in the low energy extrapolated S-factor and a more accurate estimate of the reduced mass used in the calculation of the reaction rate. At temperatures above ^1 GK, our rate is lower, for instance, by about 20% around 1.75 GK, because we have re-evaluated the previous data（Isoya et al., Nucl. Phys.7, 116（1958）） in a meticulous way. The present interpretation is supported by the direct experimental data. The uncertainties of the present evaluated rate are estimated to be about 20% in the temperature region below 0.2 GK,and are mainly caused by the lack of low-energy experimental data and the large uncertainties in the existing data.Asymptotic giant branch（AGB） stars evolve at temperatures below 0.2 GK, where the^19F（p,α）16O reaction may play a very important role. However, the current accuracy of the reaction rate is insufficient to help to describe, in a careful way, the fluorine over-abundances observed in AGB stars. Precise cross section（or S factor） data in the low energy region are therefore needed for astrophysical nucleosynthesis studies.
基金the paper.H.N.L.and G.Z.acknowledge supports by the National Natural Science Foundation of China (Grant Nos.11103030, 11233004 and 11390371)W.A.and T.S.are supported by the JSPS Grant-in-Aid for Scientific Research (S: 23224004)+1 种基金S.H.is supported by the JSPS Grant-in-Aid for Scientific Research (c:26400231)N.C.acknowledges support from Sonderforschungsbereich 881 "The Milky Way System" (subproject A4) of the German Research Foundation (DFG)
文摘We report the discovery of an extremely metal-poor（EMP） giant,LAMOST J110901.22＋075441.8, which exhibits a large excess of r-process elements with [Eu/Fe] ～ ＋1.16. The star is one of the newly discovered EMP stars identified from the LAMOST low-resolution spectroscopic survey and a highresolution follow-up observation with the Subaru Telescope. Stellar parameters and elemental abundances have been determined from the Subaru spectrum. Accurate abundances for a total of 23 elements including 11 neutron-capture elements from Sr through Dy have been derived for LAMOST J110901.22＋075441.8. The abundance pattern of LAMOST J110901.22＋075441.8 in the range of C through Zn is in line with the ＂normal＂ population of EMP halo stars, except that it shows a notable underabundance in carbon. The heavy element abundance pattern of LAMOST J110901.22＋075441.8 is in agreement with other well studied cool r-II metal-poor giants such as CS 22892-052 and CS 31082-001. The abundances of elements in the range from Ba through Dy match the scaled solar r-process pattern well.LAMOST J110901.22＋075441.8 provides the first detailed measurements of neutroncapture elements among r-II stars at such low metallicity with [Fe/H]-3.4, and exhibits similar behavior as other r-II stars in the abundance ratio of Zr/Eu as well as Sr/Eu and Ba/Eu.
文摘In Part 1 of this work, we showed that our new model of cosmology can account for the origin of all cosmic structures ranging in size from stars up to superclusters. In this model, at the time of nucleosynthesis, an imprint embedded in the vacuum regulated the creation of the protons (and electrons) that later made up the structures. Immediately after nucleosynthesis and for a considerable period afterward, the evolution was completely determined by the expansion of the universe. Gradually, however, gravitational influences became more important until finally, the expansion of the structures-to-be ceased at their zero velocity points. Stars, galaxies, and galaxy clusters all reached their zero velocity points more or less simultaneously at the usually accepted time of the beginning of galaxy formation. From that point onward, the evolution gravitation came to dominate the evolution although the expansion still exerted its influence. In this paper, we examine the subsequent cluster evolution in some detail. We establish the conditions required to prevent a free-fall collapse of the clusters and then show that galaxies with quasar-like active nuclei located within the cluster were the sources of the necessary radiation. We also show that the required galactic supermassive black holes were a consequence of the initial free-fall collapse of all galaxies.
文摘In our original paper, we outlined a new model of nucleosynthesis which began when a small percentage of the vacuum energy was converted primarily into neutron-antineutron pairs but with a very small excess of neutrons. In this paper, we present a detailed study of that original idea. We show that immediately after their inception, annihilation and charge exchange reactions proceeded at a very high rate and after an interval of no more than 10<sup>-12</sup> s, the matter/antimatter asymmetry of the universe and the present-day abundance of baryons had been established. The annihilations produced the high density of leptons critical for the weak interactions and the photons that make up the CMB. The model predicts a photon temperature in agreement with the present-day CMB value and also explains the origin of the CMB anisotropy spectrum. We also show how the nucleosynthesis density variations needed to explain all cosmic structures can resolve the difficulties that arise when trying to explain observed primordial element abundances in terms of a single-density universal model of nucleosynthesis.
