Hirschegg workshop: Jan. 15 - 21, 2006

So far the following abstracts have been handed in:

Clean Beams at ISOL Facilities
Arndt, O. (IKMz); Jost, C. (IKMz); Kratz,K.-L. (IKMz); Köster, U. (CERN); Franberg, H. (CERN)
Abstract: In order to obtain isotopicaly clean beams at ISOL facilities such as CERN/ISOLDE a number of seslectivity steps has to be combined. So far, a neutron converter, laser ion sources (RILIS), a high-resolution mass separator (HRS) together with multi-coincidence and beta-delayed neutron detection techniques have been used for spectroscopic studies of r-process isotopes. Most recently, as additional selectivity steps molecular sidebands and "chemistry" between target and ion source have been applied. Clean beams of neutron-rich Sn isotopes in the A=135 region were obtained by adding S to the target, and in this way shifting the SnS compounds to higher masses in the A=165 region. With respect to "chemistry", thermochromatography (TC) in a quartz transfere line has been tested offline and applied online at CERN/ISOLDE. In this way, pure beams of neutron-rich Zn isotopes of 80-Zn to 82-Zn have been obtained. The surface-ionized isobars Ga and Rb were highly suppressed in the TC column. Similarly, a laser-off gamma spectrum of A=131 was essentially free of 131-In and 131-Cs. This opens new perspectives for further detailed spectroscopic investigations of N=50 and N=82 r-process waiting-point nuclei.

Modeling of Supernova Dynamics via Kinetic Theory
Bauer, W (MSU), Strother, T (MSU)
Abstract: Kinetic theory has been very successful as a tool to construct transport theories for heavy ion collisions. We have taken the same approach to construct a theory for supernova explosion dynamics. The main advantage of this approach over conventional hydrodynamics simulations is that we can couple neutrino Boltzmann transport to the baryon dynamics within a consistent framework. First results of three-dimensional simulations including the effects of angular momentum will be presented.

Weak interaction rates for nuclei near the r-process paths
I.N.Borzov
Abstract: Large-scale calculations of the weak interaction rates are performed in a wide region of nuclei relevant to the r-process nucleosynthesis. The Gamow-Teller and first-forbidden $\beta$-strength functions are calculated within the continuum $QRPA$ approximation based on the density functional description of the nuclear ground state properties [1]. A simultaneous analysis of the total $\beta$-decay half-lives and $\beta$-delayed neutron branchings show an importance of the high-energy first-forbidden decay to the states outside the $Q_{\beta}-B_n$-window in the daughter nuclei. A possible role of the forbidden decays in the $\beta$-delayed and neutrino-induced fission is also discussed. [1]. I.N.Borzov., Phys.ReV.C71 (2005) 065801.

Performance and predictive power of self-consistent mean-field models
Thomas J. Buervenich, J. A. Maruhn, P.-G. Reinhard
Abstract: We discuss the perfomance and predictive power of modern self-consistent mean-field models with respect to nuclear ground-state observables. Model differences are analyzed, and consequences for the ability of these models to extrapolate to unknown regions of the nuclear chart are discussed. Applications to exotic nuclei are shown.

Neutrino nucleosynthesis of the exotic nuclei $^{138}$La and $^{180}$Ta by charged current reactions$^{*}$
Byelikov, A.; Adachi, T.; von Brentano, P.; Frekers, D.; De Frenne, D.; Fujita, H.; Fujita, Y.; Heger, A.; Jakobs, E.; Kalmykov, Y.; Langanke, K.; Kolbe, E.; Negret, A.; von Neumann-Cosel, P.; Popescu, L.; Rakers, S.; Richter, A.; Shevchenko, A.; Shimbara, Y.
Abstract: The origin of the exotic isotopes $^{138}$La and $^{180}$Ta is an open question so far. The latest calculations $[1]$ with detailed modelling of nucleosynthesis in massive stars $>10M_{\odot}$ predict a significant production through charged current reactions $(\nu_{e},e)$ on $^{138}$Ba and $^{180}$Hf, respectively. The cross sections at low energies in the daughter nuclei are dominated by GT transitions. The GT response could be measured in high resolution $^{138}$Ba,$^{180}$Hf$(^{3}$He,t) experiments under zero degree. The talk presents the final experimental results and discusses their astrophysical relevance. \newline [1]~A. Heger et al., Phys. Lett. B606 (2005) 258 \newline *Supported by the DFG through SFB 634 and 446 JAP-113/267/0-1.

Recent studies of Astrophysics Using DRAGON at ISAC
DRAGON Collaboration
Abstract: This talk will cover an summary discussion of both TRIUMF-ISAC Radioactive Beams Facility and DRAGON (Detector of Recoils And Gammas of Nuclear reactions) but will then focus on the recent studies in progress or performed. DRAGON was built to perform radiative proton and alpha capture reaction using both stable and radioactive heavy ion beams, using inverse kinematics. Recent studies will include direct measurements of the Al26g(p,g)Si27 study, the Ca40(a,g)Ti44 reactions which are important for production of the Al26 and Ti44 in the universe. In addition a progress report on the Na22(p,g) study will be presented along with plans for the near term future, and status of the new ISAC-2 facility.

Symmetric nuclear matter with hyperons
Djapo, H.(TUD); Schaefer,BJ.(Uni Graz); Wambach, J.(TUD & GSI)
Abstract: Based on the novel V_{lowk} RG approach a Hartree-Fock calculation for a hyperon-nucleon system is presented including three body nucleon forces. In this framework the influence of increasing hyperon content to the symmetric nuclear matter at finite temperatures is investigated.

Neutrino Nucleosynthesis in Core Collapse Supernovae (Type II)
Fröhlich, C (Basel); F.-K. Thielemann (Basel), Martinez Pinedo, G. (GSI), Liebendörfer, M. (Basel)
Abstract: A new nucleosynthesis process, the $\nu p$-process, will be presented. This process occurs in proton-rich ejecta which are subject to large neutrino fluxes (e.g. in core collapse supernovae and possibly in gamma-ray bursts). This process allows for the nucleosynthesis of nuclei with mass number $A>64$, making it a possible candidate to explain the origin of solar light p-nuclei and to explain to large Sr abundance observed in a hyper-metal-poor star.

Gamow-Teller Transitions of Astrophysics Interest
Y. Fujita, high resolution collaboration in Osaka
Abstract: Under supernova conditions electron capture and beta decay are dominated by Gamow-Teller (and also by Fermi) transitions. The most direct information on the GT transition strength B(GT) can be obtained from beta-decay studies, but the accessible excitation energies are limited by the decay Q values. On the other hand, a charge-exchange reaction, the (3He},t) reaction at 140 MeV/u and at 0-degrees, can access analogous GT states at higher energies. In addition, with a high resolution of 30 keV now available in Osaka, discrete states have been observed up the the giant resonce region of about 10 MeV. We discuss the GT transition strengths in fp-shell nuclei that are of astrophysics interest. In deriving absolute B(GT) values, we can use the isospin symmetry nature of isomers, the nuclei with the same mass number A.

Low-lying resonance states in $^{9}$Be
Borge, M.J.G. Prezado, Y. and Tengblad, O. (Instituto Estructura de la Materia, CSIC, Serrano 113bis, E-28006 Madrid, Spain)
Abstract: The interest in very light nuclei has renew recently due to the progress in ab initio calculations applied to the structure of light nuclei, now reaching the lowest energy states for several spin values in isobars with mass 9 and 10. This development presents a challenge for experimentalists to complete the knowledge on the excited states. This task gets increasingly harder when one moves to the unbound part of the spectrum. Even for a well studied stable nucleus such as 9Be there are large uncertainties at about 5 MeV excitation energy. Ab-initio calculations are not yet there and the different theoretical approaches: shell model, anti-symmetrised molecular dynamic model and the cluster model predict more states than seen experimentally. Besides, the properties of low-lying unbound states in $^{9}$Be are relevant in the calculation of $^{4}$He($\alpha$n,$\gamma$)$^{9}$Be reaction rate in the stellar scenario. In a neutron rich environment the formation of 9Be can proceed via the reaction $\alpha$($\alpha$n,$\gamma$)that followed by $^{9}$Be($\alpha$,n) $^{12}$C can compete with the triple alpha reaction. A ternary process hardly plays a role in the formation of $^{9}$Be. Instead the reaction reflects nuclear structure of $^{9}$Be with large neutron widths. It has been pointed out$^1$ that the reaction $\alpha$+n = $^{5}$He($\alpha$,$\gamma$)$^{9}$Be can have an additional contribution to the formation of $^{9}$Be. Lack from experimental information has prevented for incorporating this channel in photodisintegration calculations. In this contribution I will report on a method where the combined use of a selective and clean probe, the $\beta$-delayed particle emission of the short-lived nucleus $^{9}$Li, and a state of the art detection set-up with essentially full kinematical coverage allows for a complete characterization of the three-body final state. I will review the new physics that emerged from an extension of this work to the broader and overlapping lower-lying states in $^{9}$Be. A new 3/2$^-$ broad state at 5 MeV in $^{9}$Be is found to be fed in the $\beta$-decay of $^{9}$Li mainly decaying through the $^{5}$He+$\gamma$ channel$^2$. Comparison with the different models will be also presented in this contribution. 1. L. Buchmann et al., Phys. Rev. C63 (2001) 034303. 2. Y. Prezado et al., Phys. lett. B618 (2005) 43.

The s process in low metallicity stars
Gallino, R. (University of Torino), Bisterzo ,S. (University of Torino)
Abstract: The so-called s-process main and strong components in the solar system are the outcome of many generations of Asymptotic Giant Branch stars (AGB), polluting the interstellar medium before the solar system formed. The s-process in AGB stars depends on the efficiency of the so-called C13-pocket, with the C13 abundance in the pocket deriving from proton capture on newly synthesized C12, on the initial mass, and on the metallicity. The neutron exposure is mainly determined by the ratio C13/Fe. Consequently, for a given C13-pocket efficiency, decreasing the metallicity and starting from a solar composition, the s-process fluence progressively feeds the first s-peak (ls) then the second s-peak (hs) and eventually the third s-peak at the termination point of the s-process. On the other hand, for a fixed metallicity, very different s-process distributions may be obtained by varying the C13-pocket efficiency. AGB models offer the most likely interpretation for the recent spectroscopically discoveries of very metal-poor C-rich, s-process and lead-rich stars.

The r-process nucleosynthesis: nuclear physics and astrophysics challenges
Goriely, S.
Abstract: About half of the nuclei heavier than iron observed in nature are produced by the so-called rapid neutron capture process, or r-process, of nucleosynthesis. The identification of the astrophysics site and the specific conditions in which the r-process takes place remains, however, one of the still-unsolved mysteries of modern astrophysics. Another underlying difficulty associated with our understanding of the r-process concerns the uncertainties in the predictions of nuclear properties for the few thousands exotic neutron-rich nuclei involved in the r-process and for which essentially no experimental data exist. Both the astrophysics and the nuclear physics difficulties are critically reviewed.

Three-body radiative capture reactions in astrophysics
Grigorenko, L.V. (JINR,Dubna,Russia), Langanke, K. (GSI, Darmstadt, Germany), Zhukov, M.V. (Chalmers, Geteborg, Sweden)
Abstract: We develop the three-body formalism for treatment of the three-body radiative capture reactions in the astrophysics. The S matrix for 3 → 3 scattering is used to derive the direct three-body resonant radiative capture reaction rate. Within this formalism, the states that decay only/predominantly directly into the three-body continuum should also be included in the capture rate calculations (the feature missing in the previous studies). We have also found a high contribution of the nonresonant E1 radiative capture to the rate. The implementations for the 15O(2p,γ)17Ne, 18Ne(2p,γ)20Mg, 38Ca(2p,γ)40Ti, and 4He(nα,γ)9Be reactions are discussed.

Breakout from the CNO cycle
Görres, J. (University of Notre Dame)
Abstract: In many astrophysical scenarios energy production is limited by the CNO cycle. The cycle time is determined by the lifetimes of the involved beta-decays. Breakout from this cycle can increase the energy production and thus will have a significant influence on the dynamics of stellar explosions. Several of these breakout reactions have been studied at the Nuclear Structure Laboratory at Notre Dame and first results will be presented,

Nucleon entrainment in superfluid neutron-star core
Haensel P. (CAMK Warsaw, Poland) and Gusakov M.E. (Ioffe Institute, St. Petersburg, Russia)
Abstract: Phenomenon of entrainment in a mixture of superfluids is introduced. The entrainment matrix (also termed the Andreev-Bashkin matrix or the mass-density matrix) for a neutron-proton mixture in superfluid neutron-star cores is calculated in the frame of the Landau Fermi-liquid theory generalized to account for superfluidity of nucleons. The entrainment matrix is important for dynamics of neutron stars (in particular, in the studies of star pulsations and pulsar glitches).

The weak s process
Heil, M. (Forschungszentrum Karlsruhe, Postfach 3640, 76021 Karlsruhe, Germany)
Abstract: Considerable effort in experimental nuclear astrophysics, stellar modelling, and observations led to an improved understanding of various nucleosynthesis scenarios in the last decades. This is particularly true for the main s process in low-mass AGB stars, which is largely responsible for the production of about half of the elemental abundances in the mass range 90 ≤ A ≤ 209. The weak s process, which produces elements with A ≤ 90, however, is much less understood. Since this process operates in massive stars it is ultimately linked with the abundance contributions of explosive nucleosynthesis in supernovae (SN II). In this field more accurate neutron capture cross sections in the mass range 56 ≤ A ≤ 90 are indispensable for meaningful comparison of model predictions with observational data. The more abundant light elements with A < 56 play an important role, since they act as neutron poisons and affect the neutron balance in the star. In this context, new results for neutron capture cross sections on light and medium mass nuclei will be presented and new experimental developments in this field will be discussed.

The outer crust on non-accreting cold neutron stars
Hempel, M; Rüster, S.; Schaffner-Bielich, J
Abstract: The outer crust of non-accreting cold neutron stars is studied in the framework of modern nuclear mass models. A comparison to the classic work of Baym, Pethick, and Sutherland (BPS) and an update of the work by Haensel and Pichon is performed. The most recent experimental nuclear data from the atomic mass table of Audi, Wapstra, and Thibault from 2003 is taken. Extrapolation to the dripline is utilized by different theoretical nuclear models: relativistic mean-field models and non-relativistic Hartree-Fock-Bogoliubov (HFB) models based on Skyrme parametrization with and without effects from deformation. The different nuclear models are compared to check their differences with respect to the neutron dripline, magic numbers, equation of state and occurences of nuclei in the outer crust.

Accurate mass measurements of short-lives radionuclides for nuclear structure and astrophysics studies with ISOLTRAP
Herlert, Alexander (CERN) for the ISOLTRAP collaboration
Abstract: The triple-trap mass spectrometer ISOLTRAP is devoted to the accurate determination of atomic masses of short-lived nuclides. Located at the ISOLDE facility at CERN over 70 different elements and over 700 isotopes are accessible. Mass measurements at ion production rates of as low as 100 per second or at half-lives of less than 100 ms have been achieved, where the limit of the relative mass uncertainty is below 10$^{-8}$ [1]. These accurate mass measurements provide experimental data for tests of nuclear structure [2], e.g. halos or shell effects, and tests of astrophysical models [3,4] that describe the nucleosynthesis, e.g. in stellar explosions. Recent results will be presented as well as new technical developments to further improve the mass-measurement process. [1] K. Blaum et al., Nucl. Phys. A 752, 317c (2005) [2] J. Van Roosbroeck et al., Phys. Rev. Lett. 92, 112501 (2004) [3] D. Rodriguez et al., Phys. Rev. Lett. 93, 161104 (2004) [4] M. Mukherjee et al., Phys. Rev. Lett. 93, 150801 (2004)

Hydrodynamic and hydrostatic stellar burning
Herwig, Falk
Abstract: I will review several recent studies of how nuclear reaction rate uncertainties effect hydrostatic stellar burning yields, that are needed, for example, for interpretation of stellar observations or for galaxy chemical evolution models. Next, I will talk about recent progress in hydrodynamic simulations of hydrostatic stellar burning. These new models target directly mixing processes that have so far limited progress in predicitve stellar nucleosynthesis yields. Finally, I will speak about the astrophysics theory part of a new integrated nuclear astrophysics program at LANL, that aims to use s-process branchings as a diagnostic tool to constrain hydrodynamic mixing processes.

Models of Stellar Core-Collapse, Pulsar Kicks, and Nucleosynthesis
Janka, H.-Th. (for the Garching SNII group)
Abstract: The talk will review the current status of modeling supernova explosions of massive stars, focussing mostly on the activities of the group in Garching. It will be argued that neutrino-driven explosions are in the reach of current simulations for stars near the lower end of the mass spectrum of supernova progenitors, and it will be shown that neutrino-driven explosions offer promising perspectives for explaining the observed high pulsar velocities, the morphology and asymmetry of SN explosions, and the origin of important p-process nuclei.

A suggestion for matter phase transitions in galactic cores
Jooss, Ch., (Dep. of Physics, University of Göttingen, Germany), Lutz, J. (Dep. ET/IT, Chemnitz University of Technology, D-09107 Chemnitz, Germany)
Abstract: Big bang theory in different variations postulates that most of the galaxies have formed simultaneously in a time short after the big bang. However, observational facts tend to contradict more and more this assumption and support the picture that galaxy formation is happening also today and there is an evolution process of galaxies, which is governed by the massive object in the galaxy core. High spatial resolution images of the central area of different type of galaxies indicate that galaxy cores exist in different states. Relatively quite core-states can evolve into highly excited states present in differnt types of active galaxies. These states eject matter in from of jets (e.g. Cygnus A or M87) but propably also pieces of the core. The new step of this contribution is to relate different states of galaxy cores to phase transitions for baryonic matter and the related QCD background condensates. The QCD phase diagram predicts low temperature, dense phases at high pressures such as e.g. color superconductivity and quark crystals. They may be present in neutron stars. We suggest, by extending the QCD phase diagramm towards the high density and high temperature regime that a new ultradense phase is present in galactic cores. We derive properties of this new ultradense phase in a qualitative way by comparing the QCD background condensates with other well-known quantum liquids such as superfluid 3He. In our model, the phase transitions of this ultradense core phase governs the behaviour of the entire galaxy core, e.g. the emergence of instabilities at a critical density and ejection of matter, as observed. In this way, baryogenesis is related to processes and phase transitions in cores of active galaxies.

Fidelity of Type Ia Supernovae Nucleosynthesis with Tracer Particles
Jordan, G. University of Chicago, Plewa, T. Univeristy of Chicago
Abstract: Calculating the nucleosynthetic yields from large-scale hydrodynamical simulations of astrophysical phenomena (such as Type Ia supernovae) involves the post-processing of tracer particles that track the individual fluid elements in the object. The number of tracer particles in the simulation can be on the order of hundreds of thousands; however, the question of the number of tracer particles needed to accurately predict output of the nucleosynthesis has not been addressed. We present preliminary results of a systematic study aimed at resolving this issue, specifically in the context of turbulent combustion in Type Ia supernovae.

Explosive nucleosynthesis: classical novae vs. X-Ray Bursts
Jordi, Jose
Abstract: Thermonuclear runaways are at the origin of some of the most energetic and frequent stellar cataclysmic events. In this review talk, we outline our understanding of the mechanisms leading to classical nova explosions and x-ray bursts, together with their associated nucleosynthesis. In particular, we focus on the interplay between nova outbursts and the Galactic chemical abundances (mainly $^{13}$C, $^{15}$N, and $^{17}$O), the synthesis of radioactive nuclei of interest for gamma-ray astronomy ($^{7}$Be-$^{7}$Li, $^{22}$Na, or $^{26}$Al), the endpoint of nova nucleosynthesis, based both on theoretical and observational grounds, and the discovery of presolar meteoritic grains, both in the Murchison and Acfer 094 meteorites, likely condensed in nova shells. Recent progress in the modeling of x-ray bursts as well as an insight into the nuclear uncertainties affecting critical reactions, for both novae and x-ray bursts, will also be presented.

Photodissociation studies of p-process nuclei with bremsstrahlung at ELBE
Junghans, A.R., Erhard, M., Grosse, E., Kosev, K., Klug, J., Nair, C., Nankov, N., Rusev, G., Schilling, K.D., Schwengner, R., and Wagner, A.
Abstract: Photodissociation reactions of neutron-deficient nuclei between Se and Pb close to stability lead to the production of the p-process nuclides. A research program has been started to study experimentally the near-threshold photodissociation of nuclides in the chain of cosmic heavy element production with bremsstrahlung from the ELBE accelerator. Photodissociation cross sections and the electric dipole strength distribution near threshold are important parameters for nuclear astrophysics network calculations. These quantities can be tested with photodissociation and photon scattering experiments, to find out if the predicted consistent underproduction of Mo and Ru isotopes is depending on them. An important prerequisite for such studies is good knowledge of the bremsstrahlung distribution which was determined by measuring the photodissociation of the deuteron and by comparison with model calculations. First data on (gamma,p), (gamma,n) and (gamma,alpha) reactions were obtained for the astrophysically relevant target nucleus 92Mo by observing the radioactive decay of the nuclides produced by bremsstrahlung irradiation at end-point energies between 11.8 and 14.0 MeV. The results are compared to recent statistical model calculations.

Experimental Approach to Explosive Hydrogen Burning with Low-Energy RI Beams
S. Kubono, and CRIB collaboration at CNS
Abstract: Experimental efforts for investigating the nuclear reactions in explosive hydrogen burning will be discussed, including some experiments for important nuclear reactions and a development of an extensive in-flight RI beam method.

The role of fission in r-process nucleosynthesis
Kelic, A. (GSI), Schmidt, K.-H. (GSI)
Abstract: In the r-process fission has the decisive influence on the termination of the r-process as well as on the determination of the age of the Universe. Fission can also influence the abundances of nuclei in the region A~90 and 130 due to the fission cycling. First studies on the role of fission in the r-process have been started forty years ago. In the meanwhile, extensive investigations on the beta-delayed, neutron- and neutrino-induced fission have been made. One of the common conclusions from all this work is that the role of fission in the r-process is very sensitive to the fission-barrier heights of heavy nuclei with A>190 and Z>84. Unfortunately, experimental information on the height of the fission barrier is only available for nuclei in a limited region of the nuclide chart, and for heavy r-process nuclei one has to rely on theoretically calculated barriers. Due to the limited number of available experimental barriers, in any model the constraint on the parameters defining the dependence of the fission barrier on neutron excess is rather weak. This leads to large uncertainties in estimating the fission-barrier heights of heavy nuclei involved in the r-process. Using available experimental data on saddle-point and ground-state masses, a detailed study on the predictions of different models concerning the isospin dependence of saddle-point masses will be presented. It will be shown that several macroscopic models yield unrealistic barriers for very neutron-rich nuclei.

Nuclear Physics far from Stability and r-Process Nucleo Synthesis
Kratz, K.-L. (IKMz/VISTARS)
Abstract: In this talk, I will discuss the astrophysically relevant nuclear-physics input for the r-process. Astronomical and meteoritic observebals witness the interplay between nuclear-structure aspects far from stability and the appropiate astrophysical enviroments, and can give guidance to and constraints on stellar conditions.

Production and $\beta$ lifetimes of heavy neutron-rich nuclei approaching the r-process path
Kurtukian-Nieto, T., Benlliure, J. (Universidad de Santiago de Compostela), Schmidt, K.-H. (GSI), Casarejos, E., Cortina-Gil, D., Fernandez-Ordo\~nez, M., Pereira, J. (Universidad de Santiago de Compostela, Audouin, L. (Institute de Physique Nucl\'eaire, Orsay), Blank, B., Becker, F. (GSI), Giovinazzo, J. (CENBG, Gradignan), Henzlova, D. (GSI), Jurado, B. (GSI), Rejmund, F. (Institute de Physique Nucl\'eaire, Orsay), Yordanov, O. (GSI)
Abstract: One of the major challenges of nuclear physics is to enlarge the present limits of the chart of the nuclides and in particular, to reach the r-process path in the medium- and heavy-mass regions. Promising results have been obtained during the last years in experiments investigating the properties of medium-mass neutron-rich nuclei close to the waiting point around N=82 [1] while the waiting point around N=126 remains unexplored [2]. Fission has been used succesfully to produce medium-mass neutron-rich isotopes [3] while the present limits of the chart of the nuclides in the heavy neutron-rich region still lie close to the stability. However, few years ago, cold-fragmentation reactions induced by relativistic projectiles were proposed [4] as the optimum reaction mechanism to populate the heavy neutron-rich side of the chart of nuclides. In this paper we report on an experiment performed with the FRS at GSI to explore the production of heavy neutron-rich nuclei close to the neutron shell N=126 and to measure their $\beta$ half-lives. We used cold-fragmentation reactions induced by $^{208}Pb$ at 1 AGeV impinging a Be target. The isotopic identification was achieved by measuring both the atomic number and the mass-over-charge ratio of each nucleus by means of the measurements of the magnetic rigidities, time-of-flight and energy loss of each fragment passing through the FRS. The identified isotopes were implanted on an active catcher made of four 5 x 5 cm Double-Side Silicon Strip Detectors. The position and time correlation between the implanted isotopes and the subsequent $\beta$-decay allow to determine their half-lives. In this measurement we were able to identify for the first time 30 new neutron-rich isotopes approaching N=126. In adition, the half-life of some of them has been determined. These half-lives have been compared with model calculations [5,6] which seems to overestimate the measured data. [1] K.-L~Kratz {\it et al}., Z. Phys. A {\bf 325}, 489 (1986). \\ [2] B.~Pfeiffer {\it et al}., Nucl. Phys. A {\bf 693}, 282 (2001).\\ [3] M.~Bernas {\it et al}., Phys. LettB. {\bf 415}, 111 (1997). \\ [4] J.~Benlliure {\it et al}., Nucl. Phys. A {\bf 660}, 87 (1999). \\ [5] T.~Tachibana and M.~Yamada, Proc. Int. conf. on Exotic Nuclei and Masses, {\bf A 660}, Arles (1995) 763\\ [6] P. M\"oller et al. Atomic Data and Nuc. Data. Tables, {\bf 66}, 131 (1997)

The s-process: messages from stellar He burning
Käppeler, F. (Forschungszentrum Karlsruhe, Institut für Kernphysik, Postfach 3640, 76021 Karlsruhe
Abstract: Neutron reactions are responsible for the origin of the heavy elements from iron to uranium. The resulting abundances contain numerous clues for the astrophysical processes in the stellar burning zones, where they are synthesized. The slow neutron capture process is a particularly illustrative example, since the respective abundance patterns can be analyzed to constrain stellar evolution models and to yield surprisingly detailed information on the physics of the stellar interior. In this context, accurate reaction rates, which constitute the essential nuclear physics input for such studies, are of crucial importance. Since many of the available data require significant improvement, further challenges have to be met in order to establish a sound basis for defining the role of Red Giant stars in the chemical history of the Universe.

The Equation of State of High Density Matter through Neutron Star Observations
Lattimer, J.M. (Stony Brook University)
Abstract: Neutron stars are laboratories for dense matter physics. New observations of neutron stars from radio pulsars, X-ray binaries, quasi-periodic oscillators, X-ray bursters and thermally-emitting isolated neutron stars are setting bounds to masses, radii, rotation rates, radiation radii, redshifts, moments of inertia, temperatures and ages. Mass (M) measurements constrain the equation of state (EOS) at the highest densities and set bounds to the highest possible matter density. Radii (R) constrain the EOS in the vicinity of the nuclear saturation density and yield information about the density dependence of the nuclear symmetry energy. Laboratory measurements of the neutron skin thickness of Pb and other experiments can extend this knowledge to lower densities. Radiation radius estimates from observations of thermal emission from neutron stars are the most reliable, and if supplemented by redshift information from the same source, could yield precision radii. A moment of inertia measurement from a binary pulsar could ultimately yield precise radius estimates since their component masses are known. The largest pulsar rotation rates set upper bounds to the ratio R**3/M, and quasi-periodic oscillations, if associated with the innermost stable orbit, set upper limits to both M and R. Observations of cooling neutron stars up to a million years old shed light on the internal compositions, including their superfluid properties, by constraining the neutrino emission rates.

Nuclear Reactions as a tool for Structure Studies of exotic nuclei
Lenske, H.
Abstract: An essential part for extracting nuclear structure information from measured cross section data on a quantitative level is reaction theory. Modern applications of direct reaction theory in spectroscopic studies of exotic nuclei are discussed. Low-energy transfer reactions in inverse kinematics are a particular useful tool for investigations of ground states and excited states in neutron-rich nuclei. A distinct advantage of inverse kinematics is that even at the lowest energies compound contributions are strongly suppressed. By combining cross section measurements with gamma-ray detection, practically background free spectra can be obtained. Recent applications to REX-ISOLDE data are discussed. The high potential of charge exchange reaction for exotic structure studies and for the extraction of beta-decay rate is addressed. Exploratory theoretical results on antiproton absorption on exotic nuclei in colliding-beam experiments are presented. Such reactions are an interesting alternative to more conventional methods for investigations of neutron-skins. They are also ideal for gaining information on the poorly understood antiproton-neutron interactions.

Supernova core collapse
Liebendörfer, M. (University of Basel), Pen, U.-L. (CITA), Thompson, C. (CITA)
Abstract: The collapse phase at the end of stellar evolution is determined by electron capture rates on nuclei and the ability of neutrinos to thermalize and stream out of the stellar core. The corresponding deleptonization can be parameterized for efficient multi-dimensional simulations so that results obtained with general relativistic Boltzmann neutrino transport are reproduced in spherical symmetry. Based on this parameterization, stellar collapse and bounce is simulated in three dimensions for the investigation of the effects of rotation and magnetic fields.

Beta-decay of neutron-rich Ni and Cu isotopes in shell model approach
Lisetskiy, A.F. (GSI), Brown, B.A. (MSU) , Schatz, H. (MSU)
Abstract: The results of shell model calcuations for beta-decay of neutron-rich Ni and Cu isotopes with new effective interaction for the f5/2pg9/2 configurational space are presented.

Mass and lifetime studies with stored exotic nuclei
Litvinov, Yu.A. (GSI)
Abstract: Recent progress will be presented from experiments on masses and lifetimes of bare and few-electron exotic nuclei at GSI. Relativistic rare isotopes produced via projectile fragmentation or fission are separated in flight by the fragment separator FRS and injected into the storage ring ESR. This worldwide unique experimental technique gives access to all fragments with half-lives down to the microsecond range. New isotopes were discovered along with simultaneous measurements of mass and lifetime. Single-particle decay measurements and the continuous recording of both stored mother and daughter nuclei open up a new era for spectroscopy. The ILIMA project at the future FAIR facility aims to study the r- and rp-process nuclei.

Investigating the EOS of Asymmetric Matter
Lynch, W.G. (MSU)
Abstract: The asymmetry term of nuclear equation of state governs both many of the properties of neutron-rich nuclei and of neutron stars. Neutron star radii, moments of inertia, phase transitions in the stellar interior and the cooling of proto-neutron stars are among the stellar properties that are most strongly affected. Collisions induced by rare isotope beams provide opportunities to probe the density dependence of the asymmetry term under laboratory-controlled conditions. Experiments have been performed to investigate these issues. Results from these experiments will be presented and prospects for more stringent constraints on the asymmetry term will be discussed.

The Nuclear Cycle that Powers the Stars: Fusion, Gravitational Collapse, and Dissociation
Manuel, O. (University of Missouri), Mozina, M. (Emerging Technologies, Inc.), and Ratcliffe, H. (Astronomical Society of South Africa)
Abstract: The finding of an unexpectedly large source of energy from repulsive interactions between neutrons in the 2,850 known nuclides has challenged the assumption that H-fusion is the main source of energy that powers the Sun and other stars. We show here that neutron repulsion in compact objects produced by the collapse of stars and collisions between galaxies may power more energetic astrophysical events (quasars, gamma ray bursts, and active galactic centers) that had been attributed to black holes before neutron repulsion was recognized. The universe may cycle nuclear matter between fusion, gravitational collapse, and dissociation (including neutron-emission) rather than evolve in one direction by fusion.

Is there a weak r-process?
F. Montes, T. Beers, J. Cowan, T.K. Farouqi, R. Gallino, M. Heil, K.-L. Kratz and H. Schatz
Abstract: When modeling the r-process, the region Sr-Ag is not only of particular interest due the challenges in obtaining the observed solar r-process abundance pattern, but also because there are some discrepancies between elemental abundances from r-process rich metal-poor stars and solar system r-process abundances. Recent abundance studies in metal-poor stars reveal an underproduction of elements 42$\le Z \le$47 compared to the solar system r-process abundance. These observations suggest that an additional mechanism besides the $strong$ r-process is required to create the missing or residual abundances in this region. The astrophysical conditions ($n_{n},T,\tau$) in which a neutron capture process would produce the necessary residual abundance pattern were studied. Neutron density and temperature were varied from $10^{7}$ (s-process) to $10^{22}~cm^{-3}$ (r-process) and from $0.09$ to $1.5$ $GK$, respectively, in a network calculation. Neutron densities and temperatures resembling an r-process-like scenario were found to better fit the residual abundance pattern. A description of the method, results and discussion will be presented.

Coulomb dissociation studies on astrophysical processes using fast exotic beams
Motobayashi, T (RIKEN)
Abstract: Radiative capture reactions can be studied indirectrly with the Coulomb dissociation method. Especially for cases involving short-lived nuclei, experiments with fast radioactive ion beams have provided new information on the processes in exposive hydrogen burning. Recent results on several reactions in the hot pp chain and rp process are presented, and related questions on the reaction mechanism will be discussed. Perspective of studies with the RIKEN RI Beam Factory, which will come into operation in 2007, will also be discussed.

Microscopic calculation of nuclear reactions within the FMD approach
Neff, T. (MSU), Feldmeier, H. (GSI), Cribeiro, A. (GSI),
Abstract: The Fermionic Molecular Dynamics model uses Gaussian wave packets localized in phase space as a single particle basis for nuclear structure. The possibility to translate and boost the FMD wave functions allows us to construct wave functions in the sense of the microscopic cluster model for applications in low energy nuclear reactions. In addition the Unitary Correlation Operator Method povides us with an effective nucleon nucleon interaction based on the phase shifts that can be used for structure as well as reaction studies. We will present calculations for the fusion cross sections of neutron rich oxygen isotopes. The experimental $^{16}$O-$^{16}O$ fusion cross section is very well reproduced without adjusting a single parameter. The cross sections for the neutron rich $^{22}$O and $^{24}$O show a large enhancement compared to $^{16}$O. Preliminary results on phase shifts, widths of resonances and an outlook for the calculation of radiative capture cross sections within the microscopic FMD approach will be given.

Nuclear ground state and collective excitations
Paar, N. (TU-Darmstadt), Roth, R. (TU-Darmstadt), Papakonstantinou, P. (TU-Darmstadt), Hergert, H. (TU-Darmstadt)
Abstract: The correlated realistic nucleon-nucleon interactions are constructed within the Unitary Correlation Operator Method (UCOM), and employed in nuclear structure calculations. The interaction induced short-range central and tensor correlations are included via unitary transformation within the UCOM framework. By using the correlated Argonne V18 interaction, the ground state properties in closed-shell nuclei throughout the nuclear chart are studied within the Hartree-Fock scheme. The long-range correlations are accounted by using the many-body perturbation theory, random-phase approximation (RPA) correlations, and shell model diagonalization approach. In addition, the fully self-consistent RPA is formulated in the UCOM scheme and employed in studies of collective multipole modes of excitations.

Effects of $\delta$ meson and $\rho-\omega$ cross couplings in effective field theory motivated lagrangian approach
S.K. Patra and B.K. Sharma
Abstract: Recently it is realised that the importance of $\delta$ meson and the cross coupling of $\omega$ and $\rho$-mesons can not be neglected while studying the nuclear and neutron matter properties in the relativistic mean field models. It is also shown that the self and cross couplings of $\omega$ meson plays an important role to make the nuclear equation of state (EOS) softer. The parameter set G2, obtained from the effective field theory motivated lagrangian (E-RMF) approach, is very successful to reproduce the nuclear matter properties including the structure of neutron star as well as of finite nuclei. In the E-RMF formalism, the effect of $\delta$ meson and the influence of $g_{mx}\rho\omega$ is neglected. Here, the $\delta$ and $rho-\omega$ couplings are included on top of the E-RMF lagrangian. In the calculation, the G2 parameter set is used. The coupling constants $g_{\delta}$ and $g_{mx}$ for $\delta$ and $\rho-\omega$ is obtained in a least square fitting with the experimental EOS. We calculate the pressure and energy for symmetric and asymmetric nuclear matter. Also, computed the properties of neutron star structure. From our calculations, we find that a readjustment of G2 parameter set along with $g_{\delta}$ and $g_{mx}$ couplings is urgently needed to meet the versatility of G2 set both for finite nuclei and infinite nuclear matter including neutron star. Work in this direction is in progress.

Detonating Failed Deflagrations of Type Ia Supernovae
Plewa, T. (University of Chicago)
Abstract: Numerical models of thermonuclear supernovae must include realistic initial conditions, an element that appears exceedingly important and may prove crucial in our quest to explain the nature of those fascinating objects. Supported by recent analytic and numerical studies, we consider a simple model of Type Ia supernova in which a massive white dwarf is incinerated following the mild ignition of a thermonuclear flame at small number of isolated points located near the stellar center. In this scenario, the initial off-center deflagrations only consume a small amount of the stellar fuel and fail to unbind the star. The energy released during that early stage is, however, sufficient to expand the stellar material and accelerate the outer layers of the white dwarf. These flows interact and then trigger a detonation. The overall evolution resembles that of the previously discussed gravitationally confined detonation model and shares many of its properties. The present numerical model features a revised energy delivery scheme resulting in a weaker deflagration, longer evolutionary timescales, and stronger preexpansion of the stellar material. Several observable properties of the proposed model, including preliminary model spectra and light curves, are presented and compared against observations.

Underground nuclear astrophysics at LUNA
Paolo Prati for the LUNA Collaboration
Abstract: LUNA (Laboratory for Underground Nuclear Astrophysics) is an international Collaboration (Germany, Hungary, Italy, Portugal) aimed to the direct measurement of cross section of nuclear reactions of astrophysics interest. The Collaboration manages a 400 kV electrostatic accelerator installed in the underground laboratory of Gran Sasso, in Italy. Thanks to the extremely low cosmic rays background and to the high luminosity of the beam, several important reactions have been studied in the past at extremely low energies and, in some cases, even inside the energy window of the Gamow peak. The latest results have been obtained in the study of the 14N(p,gamma)15O reaction: the cross section has been measured down to 71 keV c.m.. The Collaboration is presently working on a new experiment i.e. the study of the 3He(4He,gamma)7Be by the counting of the prompt gamma emission and of the delayed 7Be activity. The very last results from the 14N(p,)15O data analysis as well the status of the new experiment will be presented

Reaction rate uncertainties in the p-process
Rauscher, T (Basel)
Abstract: The uncertainties in the reaction rates relevant for the location of and branchings in the (classic) p-process path are discussed. Suggestions for experimental measurements of relevant reactions are made.

A New Measurement of the E1 Component of the $^{12}$C($\alpha,\gamma$)$^{16}$O Reaction
K. E. Rehm, Physics Division, Argonne National Laboratory
Abstract: The radiative capture reaction $^{12}$C($\alpha,\gamma$)$^{16}$O is an important process in nuclear astrophysics. Since the cross sections at red-giant temperatures are extremely small (~10$^{-17}$ b), indirect techniques have to be used to determine its astrophysical reaction rate. One of the best methods to determine S(E1) is a measurement of the beta-delayed $\alpha$ decay of $^{16}$N. In these experiment S(E1) is extracted from the height of a satellite peak located at E=0.9 MeV in the $\alpha$ energy spectrum, which originates from the interference between the sub-threshold 1$^-$ state with the higher-lying 1$^-$ state in $^{16}$O at E$_x$=9.585 MeV. For a measurement of this decay we have built a system of high-acceptance gas ionization detectors, which are practically insensitive to beta particles that limited earlier measurements. Beam impurities that affected one of the earlier experiments were eliminated through the choice of the $^{16}$N production technique. Results from this experiment and comparisons with earlier data will be presented. This work was supported by the US Department of Energy, Nuclear Physics Divisions, under contract No. W-31-109-ENG and by the NSF Grant No. PHY-02-16783 (Joint Institute of Nuclear Astrophysics)

Experimental approaches to s-process branchings
Reifarth, Rene (Los Alamos)
Abstract: Almost all of the heavy elements are produced via neutron capture reactions in a multitude of stellar production sites. Stellar models yield the element production during the quiescent phase as well as the initial configuration for supernova simulations. Their predictive power is currently limited because they contain poorly constrained physics components such as convection, rotation or magnetic fields. Neutron captures on heavy radioactive isotopes provide a unique opportunity to largely improve these physics components. The analysis of branch-points of the s-process path in combination with isotopic abundance information from pre-solar meteoritic grains offer a very powerful tool to address important questions of nuclear astrophysics. Experimental approaches to the desired reaction rates will be discussed during the presentation.

Numerical Simulations of Type Ia Supernova Explosions
Röpke, F. K., Hillebrandt, W.
Abstract: The application of type Ia supernovae (SNe Ia) as distance indicators in observational cosmology indicated an accelerated expansion of the Universe. To correct for the intrinsic scatter in the luminosities of SNe Ia, these measurements need to be calibrated based on empirical correlations between observables. A theoretical reasoning of these correlations is still lacking and can only be achieved by a sound understanding of the mechanism of SNe Ia. Three-dimensional simulations of SN Ia explosions contribute here, since they facilitate the construction of self-consistent models. In these models a subsonic thermonuclear flame ignites near the center of a Chandrasekhar-mass carbon/oxygen white dwarf star and propagates outward strongly accelerated by the interaction with turbulence. In this way, large fractions of the material are burned to iron group and intermediate mass elements. The corresponding energy release unbinds the white dwarf and leads to a powerful explosion. We report on recent progress in numerical simulations based on this model and compare the results with observations of nearby SNe Ia. To tackle questions arising from SN Ia cosmology, a first step is to reproduce the observed diversity in the observations. We demonstrate how the variation of initial parameters of three-dimensional explosion models effects the results in a way that at least parts of the diversity can be accounted for.

Versatility of field theory motivated nuclear effective Lagrangian approach
B.K. Sharma, S.K. Patra
Abstract: We analyze the results for infinite nuclear and neutron matter using the standard relativistic mean field model and its recent effective field theory motivated generalization. For the first time, we show quantitatively that the inclusion in the effective theory of vector meson self-interaction and scalar-vector cross-interactions explains naturally the recent experimental observations of softness of the nuclear equation of state, without losing the advantages of the standard relativistic model for finite nuclei.

Exotic Nuclei in Compact Stars
Jürgen Schaffner-Bielich
Abstract: The composition of a neutron star, be it the crust or the core, depends crucially on the properties of nuclei as well as hypernuclei. We discuss the interdependence of nuclear and hypernuclear structure calculations with the physics of neutron star interiors which is of particular interest for the upcoming experiments on exotic nuclei as well as for hypernuclear experiments. The presence of hyperons is of importance not only for the equation of state and the mass-radius relation but also for neutron star cooling as well as for gravitational wave emission. We also comment shortly on other exotic phases (kaon condensation etc) which can appear in neutron stars.

Cross Sections for p- and s-Process: Experiments with Real Photons
Sonnabend, K., Hasper, J., M\"uller, S., Zarza, M., Zilges, A.
Abstract: Photons can be used to determine cross sections of reactions occuring during s-process nucleosynthesis. The cross sections of the so-called branching points of the s-process are needed very precisely to perform network calculations, e.g. in the AGB star model. Especially the short-living ones are interesting because their behaviour during the onset of the $^{22}$Ne($\alpha$,n) neutron source determines the final relative isotopic abundances. The half-lives of these branching points are in the order of a dozen of days. Thus, a direct measurement of the (n,$\gamma$) cross section is nearly impossible. However, theoretical predictions can be constrained if the cross section of the inverse ($\gamma$,n) reaction is measured and the principle of detailed balance is used. In some special cases, like e.g. $^{151}$Sm, low-lying excited states play a crucial role in the s-process scenario. It is not possible to measure the cross section of such an excited state in the laboratory. However, these states are populated in the inverse ($\gamma$,n) reaction, so that its measurement can be used again to constrain calculations of the (n,$\gamma$) cross section under stellar conditions. Several ($\gamma$,n) cross sections have been measured at the injector of the superconducting linear accelerator S--DALINAC at TU Darmstadt. Details of the above mentioned methods will be explained and recent results of the data analysis will be discussed. This work is supported by the Deutsche Forschungsgemeinschaft (SFB 634).

Explaining the large 48Ca/46Ca in the EK1-4-1 meteorite through neutron-capture process
Sorlin, O., (GANIL), L. Gaudefroy (GANIL), D. Beaumel (IPN Orsay), Y. Blumenfeld(IPNO), Z. Dombradi (Atomki), S. Fortier(IPNO), S. Franchoo (IPNO), M. Gélin (GANIL), J. Gibelin (IPNO), S. Grévy (GANIL), F. Hammache (IPNO), F. Ibrahim (IPNO), K.-L. Kratz (Kenrnchemie -Mainz), S.M. Lukyanov (FLNR Dubna), C. Monrozeau (IPNO), L. Nalpas( CEA Saclay), F. Nowacki (IReS Strasbourg), A.N. Ostrowski (Kernchemie Mainz), Yu-E. Penionzhkevich (FLNR Dubna), E. Pollaco (CEA Saclay),T. Rauscher (Univ. Basel) P. Roussel-Chomaz (GANIL), E. Rich (IPNO), J.A. Scarpaci (IPNO), M.G. St Laurent (GANIL), D. Sohler (Atomki), M. Stanoiu(GSI), D. Verney (IPNO)
Abstract: The large overabundances in the neutron-rich 48Ca, 50Ti, 54Cr, 58Fe and 64Ni observed in the EK-1-4-1 meteorite could be produced by a weak r process scenario in which neutron-captures and beta-decay compete. Beta-decay studies have been made at GANIL to measure the lifetimes of the neutron-rich S-Co progenitors of the Ca-Ti-Cr-Fe-Ni nuclei. Radiative neutron captures have been determined in the 44,46,48Ar nuclei using the measured Ar(d,p) transfer reaction information obtained at the SPIRAL1/GANIL facility. It is shown that the 48Ar could be the main progenitor of 48Ca under weak r process conditions.

$\alpha$-capture measurements with a recoil separator
Strieder, F. (Ruhr-Universit/"at Bochum) for the ERNA Collaboration
Abstract: The total cross section of $^{12}C(\alpha,\gamma)^{16}O$ and $^3He(\alpha,\gamma)^7Be$ was measured for the first time by a direct and ungated detection of the $^{16}O$ and $^7Be$ recoils. This measurement using the recoil mass separator ERNA at the 4MV Dynamitron Tandem Laboratory in Bochum in combination with a windowless He gas target allowed to collect data with high precision over a wide range of energy. The data represent new information for the determination of the astrophysical S(E) factor.

Probing dense nuclear matter in nucleus-nucleus collisions at SIS energies
Sturm, C.
Abstract: In nucleus-nucleus collisions at bombarding energies around 1GeV/nucleon baryon densities up to 3 times saturation density at moderate life times can be investigated. At these energy regime K mesons as well as light vector mesons are rare probes and predominantly produced at the high density phase. An overview of results obtained by the SIS experiments KaoS, FOPI and HADES concerning the nuclear equation-of-state and in-medium modification of mesons in dense nuclear matter will be presented.

Low-energy cross sections of the BBN reaction d($\alpha,\gamma$)$^6$Li by Coulomb dissociation of $^6$Li
Suemmerer, K. (GSI), Hammache, F. (IPN Orsay), Galaviz, D. (TU Darmstadt), Typel, S. (GSI), and the S246 collaboration
Abstract: In the context of recent precision measurements of the cosmic microwave background (CMB), Big-Bang Nucleosynthesis (BBN) has received renewed interest. Together with the recent observation of 6Li in old stars and the problems to reconcile calculated primordial 7Li abundances with those predicted on the basis of CMB results, the production of both, 6Li and 7Li in BBN has been reinvestigated. One open problem is the low-energy S-factor of the d-alpha radiative-capture reaction. Up to now, the only available experimental result [1] introduced an error of about a factor of 20 in the 6Li yield. We have therefore reinvesigated the d-alpha reaction with the help of Coulomb dissociation (CD) of 6Li at 150 MeV/nucleon at GSI. CD is the only practical way to study the low-energy S-factor (which involves l=2 multipolarity) due to the large number of E2 photons contained in the equivalent-photon flux. Preliminary results [2] indicate a drop of the S-factor as predicted by theory [3], contrary to the constant low-energy S-factor resulting from the previous study. [1] J. Kiener et al., Phys.Rev. C 44, 2195 (1991) [2] F. Hammache et al., Contr. FINUSTAR Conf., Kos (Greece), 2005, to be published. [3] A. Coc et al., Ap. J. 600, 544 (2004); S. Typel (priv. comm.).

Detonating Failed Deflagrations of Type Ia Supernovae
Plewa, T. (University of Chicago)
Abstract: Numerical models of thermonuclear supernovae must include realistic initial conditions, an element that appears exceedingly important and may prove crucial in our quest to explain the nature of those fascinating objects. Supported by recent analytic and numerical studies, we consider a simple model of Type Ia supernova in which a massive white dwarf is incinerated following the mild ignition of a thermonuclear flame at small number of isolated points located near the stellar center. In this scenario, the initial off-center deflagrations only consume a small amount of the stellar fuel and fail to unbind the star. The energy released during that early stage is, however, sufficient to expand the stellar material and accelerate the outer layers of the white dwarf. These flows interact and then trigger a detonation. The overall evolution resembles that of the previously discussed gravitationally confined detonation model and shares many of its properties. The present numerical model features a revised energy delivery scheme resulting in a weaker deflagration, longer evolutionary timescales, and stronger preexpansion of the stellar material. Several observable properties of the proposed model, including preliminary model spectra and light curves, are presented and compared against observations.

The symmetry energy in multifragmentation
Trautmann, W. (GSI Darmstadt), INDRA-ALADIN and ALADIN2000 Collaborations
Abstract: The symmetry term in the nuclear equation of state and its density dependence are of highest interest in nuclear structure but also for astrophysical applications in which nuclear matter may appear with extreme values of density and neutron-proton asymmetry. Considerable efforts are therefore presently made in order to obtain experimental information on the symmetry term from studies of nuclear reactions in which compressed and expanded states of nuclear matter may be reached. The isoscaling phenomenon and its relation to the symmetry energy in the fragmentation of excited residues produced at relativistic energies were studied in two experiments conducted at the GSI laboratory. The INDRA multidetector has been used to detect and identify light particles and fragments in collisions of 12C on 112,124Sn at incident energies of 300 and 600 MeV per nucleon. With the ALADIN spectrometer, the possibility of using secondary beams for reaction studies at relativistic energies has recently been explored. Beams of 107Sn, 124Sn, 124La, and 197Au were used to investigate the mass and isospin dependence of projectile fragmentation at 600 MeV per nucleon. Isoscaling is observed in both experiments. Symmetry-term coefficients, deduced from these data within the statistical description of multifragmentation, are near 25 MeV for peripheral collisions but decrease considerably for low-density breakups in central collisions.

Indirect methods for nuclear astrophysics
Typel, S. (GSI), Baur, G. (Forschungszentrum J\"{u}lich)
Abstract: Precise nuclear reaction rates are needed for a detailed description of the production of elements in primordial nucleosynthesis and during the hydrostatic burning of stars to constrain the astrophysical models. The relevant reactions are extremely difficult to measure directly in the laboratory at the small astrophysical energies. In recent years several indirect methods have been developed and applied to extract low-energy astrophysical S factors. Here, the methods of Coulomb dissociation, of the asymtotic normalization coefficient (ANC) and the Trojan-Horse method will be discussed. The application of these indirect methods requires a combination of experimental and theoretical efforts. This contribution focuses on the underlying reaction theories that have to be understood well in order to assess the precision and limitations of the various approaches.

Electroweak interactions in a relativistic Fermi-gas
Vantournhout K., Jachowicz N. and Ryckebusch J.
Abstract: Neutrino processes play an important role in a wide variety of astrophysical phenomena. Neutrino emissions are the driving force behind the cooling of a neutron star during the first hundreds of years after its birth. Furthermore, neutrino interactions are crucial in the final stages of core collapse supernovae. For better understanding the evolutionary stages of these events, it is necessary to have a detailed knowledge of neutrino transport properties in high density matter. Neutrino transport in supra nuclear matter has already been described in all its facets with respect to correlations in the neutron matter. RPA, molecular dynamics and Hartree analysis are some of the used techniques. Here, we will not dwell upon the correlations in nuclear matter but focus upon the differences between relativistic and Newtonian approaches. A fully relativistic description of neutrino opacity's in neutron matter shall be presented and compared with its Newtonian counterpart. For this purpose, the neutron matter is considered to be a non interacting Fermi gas in beta-equilibrium. The comparison will be founded upon differential cross sections and dynamical formfactors. The ratio of the latter two will also make the input of the hadron current in the weak interaction matrix element visible. This eventually triggers a discussion about the necessity of $Q^2$ dependent formfactors and the inclusion of a weak magnetic term in the hadron current.

Experimental Nuclear Astrophysics with AMS
Wallner A., Golser R., Kutschera W., Priller A., Steier P., (VERA Laboratory, Institute for Isotope Research and Nuclear Physics, Univ. of Vienna; Vockenhuber C. (TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada), Dillmann, I., Kaeppeler F. (Institut für Kernphysik, Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany)
Abstract: Accelerator mass spectrometry (AMS) represents a powerful technique for the detection of long-lived radionuclides through ultra-low isotope ratio measurements. In many cases, counting atoms rather than measuring decay products yields much higher sensitivities. The Vienna Environmental Research Accelerator (VERA) represents a state-of-the-art AMS facility which provides the ability for quantifying nuclides over the whole mass range. Radionuclides, like the prominent $^{26}$Al and $^{44}$Ti, can be traced in the sky as live radioactivity. Their production mechanisms are an essential key for understanding celestial evolution. Since it offers highest sensitivity, AMS at VERA is predestinated for the measurement of minute concentrations of such isotopes. In addition, e.g. explosive nucleosynthesis scenarios can be proved via supernova-produced radionuclides. Such nuclides deposited on Earth are candidates to be quantified by AMS. In general, well-established data on production rates of long-lived radionuclides, important for the various nucleosynthesis processes, are highly desired. The potential of AMS as a powerful tool for probing nucleosynthesis will be demonstrated by means of some prime examples. A lot of those production rates can be measured applying the technique of AMS to typical radionuclides of interest with half-lives between some years and up to hundred million years. In this talk, applications of AMS in astrophysics will be discussed and an overview on the recent measurement program at VERA for quantifying such long-lived radionuclides will be presented. Element abundances on bare planetary nebula central stars and the shell burning in AGB stars Werner, K. (Institut fuer Astronomie und Astrophysik, Universitaet Tuebingen) Abstract: We report on the observed properties of extremely hot hydrogen-deficient post-AGB stars. Their H-deficiency is caused by a late helium-shell flash laying bare interior stellar layers which are usually kept hidden below the hydrogen envelope. Thus, the photospheric element abundances of these stars allows to draw conclusions about details of nuclear burning and mixing processes in the precursor AGB stars. We compare predicted element abundances to results from quantitative spectral analyses performed with advanced non-LTE model atmospheres. The photoresponse of heavy nuclei - implication for nucleosynthesis Zilges, A., TU Darmstadt Abstract: The measurement of the photoresponse of atomic nuclei below and above the particle threshold enables to address challenging questions in Nuclear Astrophysics. Below the particle threshold real photon scattering is an unique tool to study the detailed distribution of electric and magnetic dipole strengths [1]. Recently, a concentration of electric dipole strength frequently denoted as Pygmy Dipole Resonance (PDR) has been observed just below the neutron separation energy in various nuclei [2,3,4]. The PDR exhausts up to 1\% of the E1 Energy Weighted Sum Rule. A similar enhancement of E1 strength has been observed in Coulomb dissociation experiments on radioactive neutron rich nuclei just above the threshold [5]. Above the particle threshold we have studied the photoresponse in (gamma,n) photoactivation experiments. Only a rather narrow energy window is relevant for the determination of reaction rates which are of crucial importance for the so called p-process to synthesize proton rich heavy nuclei [6]. We simulate a Planck spectrum of the stellar photon bath with real photons from bremsstrahlung [7]. Very recent experiments at the GSI facility use inverse kinematics Coulomb dissociation to study the (gamma,n) reaction rate of exotic radioactive nuclei too. This work is supported by the Deutsche Forschungsgemeinschaft (SFB 634). [1] U.Kneissl et al., Prog. Part. Nucl. Phys. 37, 349 (1996). [2] T. Hartmann et al., Phys. Rev. Lett. 93, 192501 (2004). [3] K. Govaert et al., Phys. Rev. C 57, 2229 (1998). [4] A. Zilges et al., Phys. Lett. B 542, 43 (2002). [5] P. Adrich et al., Phys. Rev. Lett. 95, 132501 (2005). [6] M. Arnould et al., Phys. Rep. A 500, 1 (2005). [7] K. Sonnabend et al., Phys. Rev. C 70, 035802 (2004). responsible for this tool: Joern Knoll Last modified: Sat Jan 3 21:45:14 CET 1998