TOURS SYMPOSIUM ON NUCLEAR PHYSICS AND ASTROPHYSICS—VII
1238(2010); http://dx.doi.org/10.1063/1.3455973View Description Hide Description
Charles Darwin’s calculation of a life of Earth had ignited Kelvin’s insight on a life of Sun, which had eventually inherited to the physical study of stellar structure and energy source. Nuclear energy had secured a longevity of the universe and the goal of the cosmic evolution has been secured by the entropy of black holes.
1238(2010); http://dx.doi.org/10.1063/1.3455981View Description Hide Description
We review the properties of supernovae (SNe) as a function of the progenitor’s mass M. (1) stars are super‐AGB stars and resultant electron capture SNe may be Faint supernovae like Type IIn SN 2008S. (2) stars undergo Fe‐core collapse to form neutron stars (NSs) and Faint supernovae. (3) stars undergo Fe‐core collapse to form NSs and normal core‐collapse supernovae. (4) stars undergo Fe‐core collapse to form Black Holes. Resultant supernovae are bifurcate into Hypernovae and Faint supernovae. (5) stars produce Luminous SNe, like SNe 2007 bi and 2006 gy (6) stars become pair‐instability supernovae which could be Luminous supernovae (SNe 2007 bi and 2006 gy). (7) Very massive stars with undergo core‐collapse to form intermediate mass black holes. Some SNe could be more Luminous supernovae (like SN 2006 gy).
1238(2010); http://dx.doi.org/10.1063/1.3455926View Description Hide Description
Stellar nucleosynthesis is a vastly interdisciplinary field. There is a large number of different problems invoked calling for a variety of different and complementary research fields. Impressive progress has been made for the last decades in the various fields related to nucleosynthesis, especially in experimental and theoretical nuclear physics, as well as in ground‐based or space astronomical observations and astrophysical modellings. In spite of that success, major problems and puzzles remain. The three major nucleosynthesis processes called for to explain the origin of the elements heavier than iron are described and the major pending questions discussed. As far as nuclear physics is concerned, good quality nuclear data is known to be a necessary condition for a reliable modelling of stellar nucleosynthesis. Through some specific examples, the need for further theoretical or experimental developments is also critically discussed in view of their impact on nucleosynthesis predictions.
1238(2010); http://dx.doi.org/10.1063/1.3455948View Description Hide Description
GANIL presently offers unique opportunities in nuclear physics and many other fields that arise from not only the provision of low‐energy stable beams, fragmentation beams and re‐accelerated radioactive species, but also from the availability of a wide range of state‐of‐the‐art spectrometers and instrumentation. A few examples of recent highlights are presented.
With the construction of SPIRAL2 over the next few years, GANIL is in a good position to retain its world‐leading capability. As selected by the ESFRI committee, the next generation of ISOL facility in Europe is represented by the SPIRAL2 project to be built at GANIL (Caen, France). SPIRAL 2 is based on a high power, CW, superconducting LINAC, delivering 5 mA of deuteron beams at 40 MeV (200 KW) directed on a C converter+ Uranium target and producing therefore more The expected radioactive beams intensities in the mass range from to will surpass by two order of magnitude any existing facilities in the world. These unstable atoms will be available at energies between few KeV/n to 15 MeV/n. The same driver will accelerate high intensity (100*A to 1 mA), heavier ions (Ar up to Xe) at maximum energy of 14 MeV/n.
Under the 7FP program of European Union called*Preparatory phase*, the SPIRAL2 project has been granted a budget of about 4 M€ to build up an international consortium around this new venture. The status of the construction of SPIRAL2 accelerator and associated physics instruments in collaboration with EU and International partners will be presented.
1238(2010); http://dx.doi.org/10.1063/1.3455970View Description Hide Description
We review new developments regarding experimental thermonuclear reaction rates. First, it is pointed out that published experimental thermonuclear reaction rates have no rigorous statistical meaning. To overcome this problem, we have been working for the past 3 years on a new method of estimating experimental reaction rates by using a Monte Carlo method. Our new reaction rate evaluation for charged‐particle reactions on target nuclei, which is based on this method, has just been completed. With these new reaction rates, many interesting aspects of nucleosynthesis and energy generation can be addressed that were previously not accessible. Second, as an example for a direct measurement, we discuss the recent study of the direct capture component in the reaction at our LENA facility. The reactions in classical novae are particularly important for the production of radioactive nuclei (mainly for the Galactic origin of and for oxygen isotopic ratios in nova presolar grains. Third, as an example for an indirect measurement, we discuss the recent nuclear resonance fluorescence study at our HIγS facility. By measuring angular correlations using a linearly polarized γ‐ray beam, we determined the spins and parities of 5 levels near the α‐particle threshold in Thus we could substantially reduce the rate uncertainties for the neutron source. Our new reaction rates may have an important impact on the s‐process in both massive stars and in AGB stars.
1238(2010); http://dx.doi.org/10.1063/1.3455974View Description Hide Description
Novel simple properties of the monopole component of the effective nucleon‐nucleon interaction are presented in the first half of this talk, leading to the so‐called monopole‐based universal interaction. Shell structures are shown to change as functions of N and Z consistently with experiments. Some key cases of this shell evolution are discussed, clarifying the effects of central and tensor forces. The validity of the present tensor force is examined in terms of the low‐momentum interaction and the formalism. In the second half of this talk, I discuss effects of the three‐body force in exotic nuclei. The limit of neutron‐rich nuclei, the neutron drip‐line, evolves regularly from light to medium‐mass nuclei except for a striking anomaly in the oxygen isotopes. This anomaly is not reproduced in shell‐model calculations derived from microscopic two‐nucleon forces. Here, we present the first microscopic explanation of the oxygen anomaly based on three‐nucleon forces that have been established in few‐body systems. This leads to repulsive contributions to the interactions among excess neutrons that change the location of the neutron drip‐line from to the experimentally observed Since the mechanism is robust and general, our findings impact the prediction of the most neutron‐rich nuclei and the synthesis of heavy elements in neutron‐rich environments.
1238(2010); http://dx.doi.org/10.1063/1.3455975View Description Hide Description
Mass‐energy distributions, as well as capture cross‐section of fission‐like fragments for the reactions of and ions with actinides leading to the formation of superheavy compound system with at energies near the Coulomb barrier have been measured. Fusion‐fission cross sections were estimated from the analysis of mass and total kinetic energy distributions. It was found that the fusion probability is approximately the same for the reactions with ions and drops three orders of magnitude at the transition to ions.
1238(2010); http://dx.doi.org/10.1063/1.3455976View Description Hide Description
The nuclear shell model predicts that the next doubly magic shell‐closure beyond is at a proton number 120, or 126 and at a neutron number The outstanding aim of experimental investigations is the exploration of this region of spherical ‘SuperHeavy Elements’ (SHEs). Experimental methods are described, which allowed for the identification of elements produced on a cross‐section level of about 1 pb. Reactions used at SHIP are based on targets of lead and uranium. The decay data reveal that for the heaviest elements, the dominant decay mode is alpha emission, not fission. Decay properties as well as reaction cross‐sections are compared with results obtained at other laboratories and with results of theoretical investigations. Finally, plans are presented for the further development of the experimental set‐up and the application of new techniques, as for instance the precise mass measurement of the produced nuclei using ion traps. At increased sensitivity, detailed exploration of the region of spherical SHEs will start, after first steps on the island of SHEs were made in recent years.
1238(2010); http://dx.doi.org/10.1063/1.3455977View Description Hide Description
Our common knowledge that a proton is made of just three quarks is not true if one looks at the proton which undergoes high‐energy scattering with any kind of target. QCD rather predicts that the proton in high‐energy scattering looks like a bunch of huge numbers of ‘gluons’, which are gauge particles mediating interaction between quarks. Such dense gluonic states are called “Color Glass Condensates (CGC)”. I will explain how the CGC appears at high energies and show several experimental evidences for that. I will also discuss the importance of CGC in the physics of LHC and high‐energy cosmic rays.
1238(2010); http://dx.doi.org/10.1063/1.3455978View Description Hide Description
The field of high energy nuclear physics has recently reached epoch making discoveries at the Relativistic Heavy Ton Collider at Brookhaven National Laboratory, highlighted with that of new state of nuclear matter with partonic degrees of freedom. The ALICE experiment at the Large Hadron Collider at CERN aims at comprehensive investigation and understanding of properties of the hot and dense partonic matter, as the only experiment dedicated to nucleus‐nucleus collisions at the facility. Physics prospects at ALICE are reviewed including jet quenching as a probe of energy loss of quarks in the created medium, direct and thermal photons as vital probes of the thermal properties, and quarkonia as a beloved probe of color deconfinement, along with latest status of the detector systems including the high resolution electromagnetic calorimeter, PHOS, and a quick report from the first operation of LHC and ALICE in December, 2009.
1238(2010); http://dx.doi.org/10.1063/1.3455979View Description Hide Description
The present status of cosmic ray researches in the highest energy region is reviewed. The latest experimental results up to 2009 are presented, including cosmic ray energy spectra, mass compositions and anisotropies in the arrival direction distributions.
1238(2010); http://dx.doi.org/10.1063/1.3455980View Description Hide Description
The standard cosmological model predicts that the first cosmological objects are formed when the age of the universe is a few hundred million years. Recent theoretical studies and numerical simulations consistently suggest that the first objects are very massive primordial stars. We introduce the key physics and explain why the first stars are thought to be massive, rather than to be low‐mass stars. The state‐of‐the‐art simulations include all the relevant atomic and molecular physics to follow the thermal evolution of a prestellar gas cloud to very high “stellar” densities. We also show the evolutionary calculation of very massive stars.
1238(2010); http://dx.doi.org/10.1063/1.3455909View Description Hide Description
A hybrid simulator FIRST is built up to perform three‐dimensional high‐resolution simulations on the first objects in the universe. As a result of simulations with FIRST, we find that dark matter cusps can reduce the mass of first collapsed objects to a level of in baryon. It is by more than one order of magnitude smaller than previous simulations. Hence, much more Pop III stars are expected than the previous prediction.
1238(2010); http://dx.doi.org/10.1063/1.3455910View Description Hide Description
Using thee‐dimensional radiation hydrodynamics (RHD) simulations, we explore the radiative feedback process on the secondary Population III (Pop III) star formation. As recently shown by Umemura et al. (2010), a density peak can independently collapse in the distance of ∼60 pc from a precollapsed density peak. Since Pop III stars are expected to be very massive, strong UV radiation from a Pop III star born in a precollapsed density peak is likely to play a crucial role on the fate of an adjacent density peak. By RHD simulations, we find that the adjacent peak can survive although a shock associated with ionization front strips a large amount of gas. The surviving cloud is never ionized, but molecule fraction is higher than that in usual Pop III cloud. Based on the obtained physical quantities of the cloud, we also discuss the mass of the secondary Pop III star.
1238(2010); http://dx.doi.org/10.1063/1.3455911View Description Hide Description
We study the evolution of low‐metallicity star‐forming clouds up to the formation of protostars by way of radiation hydrodynamics with spherical symmetry. From obtained thermal evolution, we discuss their fragmentation mass scales. From the structure of the envelope at the time of protostar formation, we derive the protostellar accretion rate and calculate the evolution of protostars in the main accretion phase. Finally, we evaluate the upper limit on the stellar mass by the stellar feedback.
1238(2010); http://dx.doi.org/10.1063/1.3455912View Description Hide Description
The origin of the stellar Initial Mass Function (IMF) and its variation with cosmic time or with diverse environmental conditions still lack a complete physical interpretation. Observationally, the present‐day stellar IMF appears to have an almost universal profile, characterized by a power‐law at large masses and flattening below a characteristic mass of Among the many proposed explanations, the origin of the characteristic stellar mass and the broad peak of the IMF are best attributed to gravitational fragmentation, which sets the mean Jeans mass at cloud fragmentation. We present the results of a self‐consistent study of the response of the mean Jeans mass at cloud fragmentation to metal line‐cooling, dust‐cooling and the Cosmic Microwave Background (CMB) based on a semi‐analytic model of the thermal evolution of clouds with varying initial metal‐licities and dust contents at different redshifts. We then discuss the implications of our findings for observational samples of very metal poor stars observed in the halo of our Galaxy.
1238(2010); http://dx.doi.org/10.1063/1.3455913View Description Hide Description
We investigate the effect of the triple‐α reaction rates on the evolution of low‐mass stars and massive stars. The former is compared with the observations of metal‐poor stars known to date. For the latter, we discuss the impact of recent calculation of triple‐α reaction rate by Ogata et al. (2009, PTP, 122, 1055) on the evolution until carbon burning.
1238(2010); http://dx.doi.org/10.1063/1.3455914View Description Hide Description
Extremely metal‐poor (EMP) stars in the Galactic halo are the remaining survivors of the early generations of stars. Their surface element abundances are signature of the nucleosynthesis in the first and second generation of stars. From comparison between the observationsof EMP stars and calculations of stellar evolution, it is suggested that typical mass of EMP stars are much higher than more metal‐rich one and the majority of observed EMP stars are formed in binary systems. I review the effect of binarity and difference of initial mass function on the EMP stars and chemical evolution of galaxy. We calculate chemical enrichment history in the context of hierarchical Galaxy formation with high mass IMF and binary contribution. We compare resultant abundance distributions with observations. Additionally, I discuss the origin of the most metal‐deficient stars known to date.
1238(2010); http://dx.doi.org/10.1063/1.3455915View Description Hide Description
Recent discovery of galaxies emitting surprisingly strong Lyman continuum at redshift with Subaru telescope is discussed. These galaxies are brighter at 900 Å in their rest‐frame (i.e. hydrogen ionizing radiation) than at 1600 Å (non‐ionizing radiation). Such an extreme spectrum, which we call Lyman limit ‘bump’, has been never expected by any spectral models of galaxies so far. Here, we show that the observed strength of the Lyman bump can be explained by a model spectrum of a galaxy which has matter‐bounded nebulae photoionized by very massive and metal‐free (so‐called Population III) stars. This suggests that such a primordial stellar population still exists at rather late epoch of the cosmic evolution.