G. Martínez-Pinedo

GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Hesse, Germany

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Publications (287)809.11 Total impact

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    ABSTRACT: We examine simulations of core-collapse supernovae in spherical symmetry. Our model is based on general relativistic radiation hydrodynamics with three-flavor Boltzmann neutrino transport. We discuss the different supernova phases, including the long-term evolution up to 20 seconds after the onset of explosion during which the neutrino fluxes and mean energies decrease continuously. In addition, the spectra of all flavors become increasingly similar, indicating the change from charged- to neutral-current dominance. Furthermore, it has been shown recently by several groups independently, based on sophisticated supernova models, that collective neutrino flavor oscillations are suppressed during the early mass-accretion dominated post-bounce evolution. Here we focus on the possibility of collective flavor flips between electron and non-electron flavors during the later, on the order of seconds, evolution after the onset of an explosion with possible application for the nucleosynthesis of heavy elements.
    Full-text · Article · Dec 2011
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    A. Arcones · C. Fröhlich · G. Martínez-Pinedo
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    ABSTRACT: We study the impact of the late-time dynamical evolution of ejecta from core-collapse supernovae on νp-process nucleosynthesis. Our results are based on hydrodynamical simulations of neutrino-driven wind ejecta. Motivated by recent two-dimensional wind simulations, we vary the dynamical evolution during the νp-process and show that final abundances strongly depend on the temperature evolution. When the expansion is very fast, there is not enough time for antineutrino absorption on protons to produce enough neutrons to overcome the β+-decay waiting points and no heavy elements beyond A = 64 are produced. The wind termination shock or reverse shock dramatically reduces the expansion speed of the ejecta. This extends the period during which matter remains at relatively high temperatures and is exposed to high neutrino fluxes, thus allowing for further (p, γ) and (n, p) reactions to occur and to synthesize elements beyond iron. We find that the νp-process starts to efficiently produce heavy elements only when the temperature drops below ~3 GK. At higher temperatures, due to the low alpha separation energy of 60Zn (S α = 2.7 MeV) the reaction 59Cu(p, α)56Ni is faster than the reaction 59Cu(p, γ)60Zn. This results in the closed NiCu cycle that we identify and discuss here for the first time. We also investigate the late phase of the νp-process when the temperatures become too low to maintain proton captures. Depending on the late neutron density, the evolution to stability is dominated by β+ decays or by (n, γ) reactions. In the latter case, the matter flow can even reach the neutron-rich side of stability and the isotopic composition of a given element is then dominated by neutron-rich isotopes.
    Full-text · Article · Dec 2011 · The Astrophysical Journal
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    J. Erler · K. Langanke · H. P. Loens · G. Martínez-Pinedo · P. -G. Reinhard
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    ABSTRACT: We present a systematics of fission barriers and fission lifetimes for the whole landscape of super-heavy elements (SHE), i.e. nuclei with Z>100. The fission lifetimes are also compared with the alpha-decay half-lives. The survey is based on a self-consistent description in terms of the Skyrme-Hartree-Fock (SHF) approach. Results for various different SHF parameterizations are compared to explore the robustness of the predictions. The fission path is computed by quadrupole constrained SHF. The computation of fission lifetimes takes care of the crucial ingredients of the large-amplitude collective dynamics along the fission path, as self-consistent collective mass and proper quantum corrections. We discuss the different topologies of fission landscapes which occur in the realm of SHE (symmetric versus asymmetric fission, regions of triaxial fission, bi-modal fission, and the impact of asymmetric ground states). The explored region is extended deep into the regime of very neutron-rich isotopes as they are expected to be produced in the astrophysical r process.
    Full-text · Article · Dec 2011 · Physical Review C
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    ABSTRACT: Recent neutron star mass measurements point to compact star maximum masses of at least 1.97±0.04 solar masses and represent thereby a challenge for soft nuclear equations of state, which often go hand in hand with the presence of hyperons or quarks. In this talk I will discuss such high neutron star masses regarding the nuclear equation of state from heavy ion experiments. Furthermore, I will introduce equations of state for core-collapse supernova and binary merger simulations, which include a phase transition to strange quark matter. As was recently shown, neutrino signals from supernova explosions can provide a probe for the low density appearance of quark matter. The compatibility of the latter with high neutron star masses is an interesting and important question and will be addressed in the talk.
    No preview · Article · Oct 2011
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    G. Martínez-Pinedo · B. Ziebarth · T. Fischer · K. Langanke
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    ABSTRACT: The νp process is a primary nucleosynthesis process which occurs in core-collapse supernovae. An essential role in this process is being played by electron antineutrinos. They generate, by absorption on protons, a supply of neutrons which, by (n, p) reactions, allow to overcome waiting point nuclei with rather long beta-decay and proton-capture lifetimes. The synthesis of heavy elements by the νp process depends sensitively on the luminosity and spectrum. As has been shown recently, the latter are affected by collective neutrino flavor oscillations which can swap the and spectra above a certain split energy. Assuming such a swap scenario, we have studied the impact of collective neutrino flavor oscillations on the νp-process nucleosynthesis. Our results show that the production of light p-nuclei up to mass number A = 108 is very sensitive to collective neutrino oscillations.
    Full-text · Article · Aug 2011 · European Physical Journal A
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    Q. Zhi · K. Langanke · G. Martínez-Pinedo · F. Nowacki · K. Sieja
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    ABSTRACT: Recent theoretical studies predicted that, due to nuclear correlations across the N=40 shell gap, electron captures on nuclei with proton numbers Z40 and neutron numbers N>40 would not be strongly suppressed due to Pauli blocking of Gamow–Teller (GT) transitions. This prediction has recently been confirmed by the experimental determination of the single-particle occupation numbers in 76Se and by the measurement of the 76Se GT+ strength distribution. In this manuscript we derive such occupation numbers and GT+ distributions within large-scale shell model studies. Based on the same models, we calculate stellar electron capture rates and compare them to those obtained from the experimental GT+ data.
    Preview · Article · Jun 2011 · Nuclear Physics A
  • K. Langanke · G. Martínez-Pinedo · I. Petermann · F.K. Thielemann
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    ABSTRACT: Nuclear physics plays a crucial role in various aspects of core-collapse supernovae. The collapse dynamics is strongly influenced by electron captures. Using the modern many-body theory, improved capture rates have been derived recently with the important result that the process is dominated by capture on nuclei until neutrino trapping is achieved. Following the core bounce the ejected matter is the site of interesting nucleosynthesis. The early ejecta are proton-rich and give rise to the recently discovered -process. Later ejecta might be neutron-rich and can be one site of the r-process. The manuscript discusses recent progress in describing nuclear input relevant for the supernova dynamics and nucleosynthesis.
    No preview · Article · Apr 2011 · Progress in Particle and Nuclear Physics
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    ABSTRACT: This article addresses three of the four nucleosynthesis processes involved in producing heavy nuclei beyond Fe (with a main focus on the r-process). Opposite to the fourth process (the s-process), which operates in stellar evolution during He- and C-burning, they are all related to explosive burning phases, (presumably) linked to core collapse supernova events of massive stars. The (classical) p-process is identified with explosive Ne/O-burning in outer zones of the progenitor star. It is initiated by the passage of the supernova shock wave and acts via photodisintegration reactions like a spallation process which produces neighboring (proton-rich) isotopes from pre-existing heavy nuclei. The reproduction of some of the so-called lighter p-isotopes with A100 faces problems in this environment. The only recently discovered νp-process is related to the innermost ejecta, the neutrino wind expelled from the hot proto-neutron star after core collapse and the supernova explosion. This neutrino wind is proton-rich in its early phase, producing nuclei up to 64Ge. Reactions with neutrinos permit to overcome decay/reaction bottlenecks for the flow beyond 64Ge, thus producing light p-isotopes, which face problems in the classical p-process scenario. The understanding of the r-process, being identified for a long time with rapid neutron captures and passing through nuclei far from stability, is still experiencing major problems. These are on the one hand related to nuclear uncertainties far from stability (masses, half-lives, fission barriers), affecting the process speed and abundance peaks. On the other hand the site is still not definitely located, yet. (i) Later, possibly neutron-rich, high entropy phases of the neutrino wind (if they materialize!) could permit its operation. (ii) Other options include the ejection of very neutron-rich neutron star-like matter, occurring possibly in neutron star mergers or core collapse supernova events with jets, related to prior stellar evolution with high rotation rates and magnetic fields. Two different environments are required for a weak and a main/strong r-process, witnessed by observations of low metallicity stars and meteoritic inclusions, which could possibly be identified with the two options listed above, i.e. the weak r-process could be related to the neutrino wind when changing from p-rich to n-rich conditions.
    No preview · Article · Apr 2011 · Progress in Particle and Nuclear Physics
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    ABSTRACT: We compare two classes of hybrid equations of state with a hadron-to-quark matter phase transition in their application to core collapse supernova simulations. The first one uses the quark bag model and describes the transition to three-flavor quark matter at low critical densities. The second one employs a Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model with parameters describing a phase transition to two-flavor quark matter at higher critical densities. These models possess a distinctly different temperature dependence of their transition densities which turns out to be crucial for the possible appearance of quark matter in supernova cores. During the early post-bounce accretion phase quark matter is found only if the phase transition takes place at sufficiently low densities as in the study based on the bag model. The increase critical density with increasing temperature, as obtained for our PNJL parametrization, prevents the formation of quark matter. The further evolution of the core collapse supernova as obtained applying the quark bag model leads to a structural reconfiguration of the central protoneutron star where, in addition to a massive pure quark matter core, a strong hydrodynamic shock wave forms and a second neutrino burst is released during the shock propagation across the neutrinospheres. We discuss the severe constraints in the freedom of choice of quark matter models and their parametrization due to the recently observed 2M ⊙ pulsar and their implications for further studies of core collapse supernovae in the QCD phase diagram.
    Full-text · Article · Mar 2011 · Physics of Atomic Nuclei
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    A. Arcones · G. Martinez-Pinedo
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    ABSTRACT: We present nucleosynthesis studies based on hydrodynamical simulations of core-collapse supernovae and their subsequent neutrino-driven winds. Although the conditions found in these simulations are not suitable for the rapid neutron capture (r-process) to produce elements heavier than A$\sim$130, this can be solved by artificially increasing the wind entropy. In this way one can mimic the general behavior of an ejecta where the r-process occurs. We study the impact of the long-time dynamical evolution and of the nuclear physics input on the final abundances and show that different nuclear mass models lead to significant variations in the abundances. These differences can be linked to the behavior of nuclear masses far from stability. In addition, we have analyzed in detail the effect of neutron capture and beta-delayed neutron emission when matter decays back to stability. In all our studied cases, freeze out effects are larger than previously estimated and produce substantial changes in the post freeze out abundances. Comment: 10 pages, 3 figures. Talk at Nuclei in the Cosmos XI (Heidelberg, 2010), to appear in Proceedings of Science
    Full-text · Article · Dec 2010
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    Tomas R. Rodriguez · Gabriel Martinez-Pinedo
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    ABSTRACT: We study neutrinoless double beta decay of several isotopes with state-of-the-art beyond self-consistent mean field methods to compute the nuclear matrix elements (NME). Generating coordinate method with particle number and angular momentum projection (GCM+PNAMP) is used for finding mother and granddaughter states and evaluating transition operators between different nuclei. We analyze explicitly the role of the deformation, pairing and configuration mixing in the evaluation of the NME.
    Preview · Article · Dec 2010 · Progress in Particle and Nuclear Physics
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    Tomás R Rodríguez · Gabriel Martínez-Pinedo
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    ABSTRACT: We present an extensive study of nuclear matrix elements (NME) for the neutrinoless double-beta decay of the nuclei 48Ca, 76Ge, 82Se, 96Zr, 100Mo, 116Cd, 124Sn, 128Te, 130Te, 136Xe, and 150Nd based on state-of-the-art energy density functional methods using the Gogny D1S functional. Beyond-mean-field effects are included within the generating coordinate method with particle number and angular momentum projection for both initial and final ground states. We obtain a rather constant value for the NMEs around 4.7 with the exception of 48Ca and 150Nd, where smaller values are found. We analyze the role of deformation and pairing in the evaluation of the NME and present detailed results for the decay of 150Nd.
    Preview · Article · Dec 2010 · Physical Review Letters
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    ABSTRACT: We explore explosions of massive stars, which are triggered via the quark-hadron phase transition during the early post bounce phase of core-collapse supernovae. We construct a quark equation of state, based on the bag model for strange quark matter. The transition between the hadronic and the quark phases is constructed applying Gibbs conditions. The resulting quark-hadron hybrid equations of state are used in core-collapse supernova simulations, based on general relativistic radiation hydrodynamics and three flavor Boltzmann neutrino transport in spherical symmetry. The formation of a mixed phase reduces the adiabatic index, which induces the gravitational collapse of the central protoneutron star. The collapse halts in the pure quark phase, where the adiabatic index increases. A strong accretion shock forms, which propagates towards the protoneutron star surface. Due to the density decrease of several orders of magnitude, the accretion shock turns into a dynamic shock with matter outflow. This moment defines the onset of the explosion in supernova models that allow for a quark-hadron phase transition, where otherwise no explosions could be obtained. The shock propagation across the neutrinospheres releases a burst of neutrinos. This serves as a strong observable identification for the structural reconfiguration of the stellar core. The ejected matter expands on a short timescale and remains neutron-rich. These conditions might be suitable for the production of heavy elements via the r-process. The neutron-rich material is followed by proton-rich neutrino-driven ejecta in the later cooling phase of the protoneutron star where the vp-process might occur.
    Full-text · Article · Nov 2010 · The Astrophysical Journal Supplement Series
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    Tomás R. Rodríguez · G. Martinez-Pinedo
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    ABSTRACT: We present an extensive study of nuclear matrix elements (NME) for the neutrinoless double beta decay of the nuclei $^{48}$Ca, $^{76}$Ge, $^{82}$Se, $^{96}$Zr, $^{100}$Mo, $^{124}$Sn, $^{128}$Te, $^{130}$Te, $^{136}$Xe, and $^{150}$Nd based on state-of-the-art energy density functional methods using the Gogny D1S functional. Beyond mean-field effects are included within the generating coordinate method with particle number and angular momentum projection for both initial and final ground states. We obtain a rather constant value for the NME's around 4.7 with the exception of $^{48}$Ca and $^{150}$Nd, where smaller values are found. We analyze the role of deformation and pairing in the evaluation of the NME and present detailed results for the decay of $^{150}$Nd.
    Preview · Article · Aug 2010
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    A. Arcones · G. Martinez-Pinedo
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    ABSTRACT: We use results from long-time core-collapse supernovae simulations to investigate the impact of the late time evolution of the ejecta and of the nuclear physics input on the calculated r-process abundances. Based on the latest hydrodynamical simulations, heavy r-process elements cannot be synthesized in the neutrino-driven winds that follow the supernova explosion. However, by artificially increasing the wind entropy, elements up to A=195 can be made. In this way one can reproduce the typical behavior of high-entropy ejecta where the r-process is expected to occur. We identify which nuclear physics input is more important depending on the dynamical evolution of the ejecta. When the evolution proceeds at high temperatures (hot r-process), an (n,g)-(g,n) equilibrium is reached. While at low temperature (cold r-process) there is a competition between neutron captures and beta decays. In the first phase of the r-process, while enough neutrons are available, the most relevant nuclear physics input are the nuclear masses for the hot r-process and the neutron capture and beta-decay rates for the cold r-process. At the end of this phase, the abundances follow a steady beta flow for the hot r-process and a steady flow of neutron captures and beta decays for the cold r-process. After neutrons are almost exhausted, matter decays to stability and our results show that in both cases neutron captures are key for determining the final abundances, the position of the r-process peaks, and the formation of the rare-earth peak. In all the cases studied, we find that the freeze out occurs in a timescale of several seconds.
    Full-text · Article · Aug 2010 · Physical Review C
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    ABSTRACT: We performed a 37 Cl ( 3 He , t) 37 Ar experiment at E = 140 MeV / nucleon and 0° with a resolution of 30 keV. The Gamow‐Teller (GT) strength distribution was obtained up to the excitation energy (E x ) of 14.2 MeV in 37 Ar . Under the assumption of isospin symmetry, the GT strengths in the 37 Cl → 37 Ar and 37 Ca → 37 K transitions are analogous. The obtained strength distribution was compared with the mirror 37 Ca β decay up to E x = 8.6 MeV . The overall shapes of the distributions were similar, but the details were not necessary the same. In order to understand those differences, the experimental distribution was compared with the shell model (SM) calculation using the USD interaction. The SM calculation suggests that differences at lower energies can be caused by a large tensor contribution in the charge‐exchange reaction. On the other hand, the differences seen at higher energies are due to the breaking of the mirror symmetry. The neutrino cross section for the 8 B solar neutrino source was calculated using the obtained data.
    No preview · Conference Paper · Aug 2010
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    ABSTRACT: Fragmentation reactions of relativistic 238U and 208Pb projectiles have been used to investigate the production of heavy neutron-rich nuclei approaching the r-process waiting point at A≈195. The relativistic energies, together with the use of a high resolving-power magnetic spectrometer were key conditions for the unambiguous identification of nuclei in the region of interest. Using this technique we were able to identify 73 new heavy neutron-rich nuclei expanding considerably the north-west frontier of the chart of nuclide. Moreover, we were able to determine the half lives of 13 of those nuclide. The measured values are significantly shorter than the predictions used for r-process model calculations. The confirmation of these results for r-process nuclei at A≈195 would indicate that the r-process at this point is faster than expected, leading to a larger production of the heaviest nuclei.
    Full-text · Article · Jul 2010
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    G. Martínez-Pinedo · A. Arcones
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    ABSTRACT: Core-collapse supernovae produce a hot protoneutron star that cools emitting huge amounts of neutrinos of all flavors. The interaction of these neutrinos with the outer layers of the protoneutron star produces an outflow of matter whose composition is determined by the luminosities and energies of the emitted neutrinos and antineutrinos. The presence of light nuclei like deuterons and tritons can have a big impact in the average energies of the emitted antineutrinos and consequently in the neutron-richness of the ejected matter. Recent hydrodynamical models show that the ejected matter is in fact proton-rich and constitutes the site of the νp-process where antineutrino absorption reactions catalyze the nucleosynthesis of nuclei with A>64.
    Preview · Article · Apr 2010 · Progress in Particle and Nuclear Physics
  • K. Langanke · G. Martínez-Pinedo
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    ABSTRACT: Neutrino reactions play an important role at various stages of core-collapse supernova. During infall, neutrinos are produced by electron capture mainly on nuclei and contribute significantly to the cooling of the collapsing core. After core bounce the nascent neutron star cools by neutrino emission. It is a major goal to observe such neutrinos from a future supernova by earthbound detectors and to establish their spectra. Recently it has been shown that the spectrum of electron neutrinos from the early neutrino burst is significantly altered if inelastic neutrino–nucleus scattering is considered in supernova simulations. Finally spallation reactions induced by neutrinos when passing through the outer burning shells can produce certain nuclides in what is called neutrino nucleosynthesis.
    No preview · Article · Apr 2010 · Progress in Particle and Nuclear Physics
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    B. D. Metzger · A. Arcones · E. Quataert · G. Martínez-Pinedo
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    ABSTRACT: We explore the effects of r-process nucleosynthesis on fallback accretion in neutron star (NS)–NS and black hole–NS mergers, and the resulting implications for short-duration gamma-ray bursts (GRBs). Though dynamically important, the energy released during the r-process is not yet taken into account in merger simulations. We use a nuclear reaction network to calculate the heating (due to β decays and nuclear fission) experienced by material on the marginally bound orbits nominally responsible for late-time fallback. Since matter with longer orbital periods torb experiences lower densities, for longer periods of time, the total r-process heating rises rapidly with torb, such that material with torb≳ 1 s can become completely unbound. Thus, r-process heating fundamentally changes the canonical prediction of an uninterrupted power-law decline in the fallback rate at late times. When the time-scale for r-process to complete is ≳1 s, the heating produces a complete cut-off in fallback accretion after ∼1 s; if robust, this would imply that fallback accretion cannot explain the late-time X-ray flaring observed following some short GRBs. However, for a narrow, but physically plausible, range of parameters, fallback accretion can resume after ∼10 s, despite having been strongly suppressed for ∼1–10 s after the merger. This suggests the intriguing possibility that the gap observed between the prompt and extended emission in short GRBs is a manifestation of r-process heating.
    Preview · Article · Feb 2010 · Monthly Notices of the Royal Astronomical Society

Publication Stats

7k Citations
809.11 Total Impact Points

Institutions

  • 2007-2015
    • GSI Helmholtzzentrum für Schwerionenforschung
      • ExtreMe Matter Institute EMMI and Research Division
      Darmstadt, Hesse, Germany
    • Technical University Darmstadt
      • Institute of Nuclear Physics
      Darmstadt, Hesse, Germany
  • 2003-2012
    • Catalan Institution for Research and Advanced Studies
      Barcino, Catalonia, Spain
  • 1999-2010
    • Universität Basel
      • Department of Physics
      Bâle, Basel-City, Switzerland
  • 2004-2008
    • Autonomous University of Barcelona
      Cerdanyola del Vallès, Catalonia, Spain
  • 1998-2007
    • Aarhus University
      • Department of Physics and Astronomy
      Aars, Region North Jutland, Denmark
    • California Institute of Technology
      • Department of Physics
      Pasadena, California, United States
  • 1993-2007
    • Universidad Autónoma de Madrid
      • Departamento de Física Teórica
      Madrid, Madrid, Spain
  • 2003-2006
    • IEEC Institute of Space Studies of Catalonia
      Barcino, Catalonia, Spain