SFB Colloquium

Upcoming Seminars

10. 01. 2019 at 14:00
S2 11/10

SFB Colloquium

Wolfram Weise (TU Muenchen)
TBA

TBA

07. 02. 2019 at 14:00
S2 11/10

SFB Colloquium

Michael Wiescher (University of Notre Dame)
TBA

TBA

Past Seminars

13. 12. 2018 at 14:00
S2 11/10

SFB Colloquium

Daniel Phillips (Ohio University)
Knowing What You Don't Know: Nuclear Physics, Effective Field Theory, and Uncertainty Quantification

For almost a century physicists have devoted intense attention to teasing out the nature of the nuclear force. But there remains much that we do not know about the way neutrons and protons interact, and the way that they come together to form nuclei. In this talk, I will show how two tools, effective field theory and Bayesian probability theory, can provide quantitative assessments of the impact of the things that we don't know about nuclear physics on the observables that are measured in experiments.

12. 07. 2018 at 14:00
S2 11/10

SFB Colloquium

Zsolt Poldolyak (University of Surrey)
Gamma-Ray Spectroscopy of Heavy Neutron-Rich Nuclei

Information gained on neutron-rich N~126 nuclei is essential for the understanding of nuclear structure in heavy nuclei. Studies around doubly magic systems allow direct tests of the purity of shell model wave functions. From a longer-term perspective, experiments in this region pave the way toward the proposed nuclear-astrophysical r-process waiting point nuclei along the N = 126 shell closure.

In the case of the beta decay of N~126 nuclei there is a competition between allowed and first-forbidden transitions. This is the mass region where first-forbidden (FF) transitions can be dominant, which can have profound implications on their half-lives and therefore on the r-process (A~195 abundance peak).

Recently several experiments were performed at Gammasphere and ISOLDE with the aim to study neutron-rich nuclei around 208Pb.

1.) Structure of 208Tl from the beta decay of 208Hg. 208Tl being a one-proton-hole one-neutron-particle nucleus, its excited levels give direct information on the proton-neutron interaction in the Z<82, N>126 quadrant. In addition, the existence of both negative and positive parity states at low excitation energy makes this nucleus an ideal testing ground for the study of the competition between first-forbidden and allowed beta decay.
2.) Structure of 207Tl from the beta decay of 207Hg. A large number of excited states, several of them of octupole character were observed and compared with calculations.
3.) The high-spin structure of 207Tl was studied in deep-inelastic reactions.

The talk will focus on recent results and their interpretation.

07. 06. 2018 at 14:00
S2 11/10

SFB Colloquium

Brian Metzger (Columbia University)
The Multi-Messenger Picture of a Neutron Star Merger

On August 17 the LIGO/Virgo gravitational wave observatories detected the first binary neutron star merger event (GW170817), a discovery followed by the most ambitious electromagnetic (EM) follow-up campaign ever conducted. Within 2 seconds of the merger, a weak burst of gamma-rays was discovered by the Fermi and INTEGRAL satellites. Within 11 hours, a bright but rapidly-fading thermal optical counterpart was discovered in the galaxy NGC 4993 at a distance of only 130 Million light years. The properties of the optical transient match remarkably well predictions for "kilonova" emission powered by the radioactive decay of heavy nuclei synthesized in the expanding merger ejecta by rapid neutron capture nucleosynthesis (r-process). The rapid spectral evolution of the kilonova emission to near-infrared wavelengths demonstrates that a portion of the ejecta contains heavy lanthanide nuclei. Two weeks after the merger, rising non-thermal X-ray and radio emission were detected from the position of the optical transient, consistent with delayed synchrotron afterglow radiation from an initially off-axis relativistic jet (or a shock-heated "cocoon" produced as the ejecta interacts with the kilonova ejecta). I will describe efforts to create a unified scenario for the range of EM counterparts from GW170817 and their implications for the astrophysical origin of the r-process and the properties of neutron stars (particularly their uncertain radii and maximum mass, which are determined by the equation of state of dense nuclear matter). Time permitting, I will preview the upcoming era of multi-messenger astronomy, once Advanced LIGO/Virgo reach design sensitivity and a neutron star merger is detected every few weeks.

29. 05. 2018 at 14:00
S2 11/207

SFB Colloquium

Luna Pellegri (Wits University/iThemba LABS)
Nuclear physics news from the Southern Hemisphere

The Pygmy Dipole Resonance (PDR), the low energy part of the electric dipole response in nuclei, is particularly relevant to investigate the nuclear structure and for its connections with photodisintegration reaction rates in astrophysical scenarios. Studies on the PDR are currently almost exclusively focused on spherical nuclei. For deformed nuclei several theoretical and experimental works have been performed to investigate the response of the Giant Dipole Resonance (GDR) while there are only a few on the PDR.

iThemba LABS, South Africa, is a suitable laboratory for the experimental study of the PDR. The use of the high-energy resolution magnetic spectrometer coupled to an array of gamma-ray detectors is a perfect combination to investigate the nature of the PDR in detail. In particular, since very few measurements on the PDR have been performed in deformed nuclei up to now, a research activity was started in 2015 to provide such information. A structural support was developed to couple the gamma-ray detectors (BaGeL - Ball of Germanium and LaBr detectors) with the K600 magnetic spectrometer. The installation of the structure was completed in October 2016 and the first K600+BaGeL experiment was performed to study the electric response of Sm154 excited via inelastic scattering of alpha particles. The results of this experiment together with those performed using other reaction probes will provide new insights into the role of the deformation in the excitation of the PDR.

A project to increase the gamma-ray detection efficiency of the iThemba LABS setup was recently funded by the South African National Research Foundation (NRF). This project will result in the extension of the gamma-ray detector array AFRODITE, up to 17 HPGe clover detectors, and in the construction of the African LaBr3:Ce Array (ALBA), an array of 23 large volume LaBr3:Ce. These arrays can be coupled to the K600 magnetic spectrometer and silicon detector arrays for gamma-particle coincidence measurements. This unique setup will allow for a new generation of experiments with a much-increased efficiency for detecting gamma decay compared to arrays currently available worldwide.

Preliminary results of the PDR campaign as well as an overview on the iThemba LABS facilities will be given.

19. 04. 2018 at 15:15
S2 11/10

SFB Colloquium

Francesco Cappuzzello (University of Catania)
The nuclear matrix element of 0vbb decay and the NUMEN project at INFN-LNS

The physics case of neutrino-less double beta decay and its tremendous implications on particle physics, cosmology and fundamental physics will be briefly introduced. In particular, the crucial aspect of the nuclear matrix elements entering in the expression of the half-life of this process will be deepened. The novel idea of using heavy-ion induced reactions as useful tools for the determination of these matrix elements will be then presented. The strengths and the limits of the proposed methodology will be indicated. New data from MAGNEX facility at the INFN-LNS laboratory give first evidences of the possibility to get quantitative results from experiments. Finally, the NUMEN project of INFN and the proposed strategy to this research will be sketched also in the view of the emerging technologies proposed.

08. 02. 2018 at 15:15
S2 11/10

SFB Colloquium

Kei Minamisono (NSCL)
Nuclear structure studies using lasers at NSCL/MSU

Nuclear spin, electromagnetic moments and charge radius of radioactive nuclei are determined using laser spectroscopy techniques at the BEam COoling and LAser spectroscopy (BECOLA) facility at the National Superconducting Cyclotron Laboratory located in Michigan State University. The radioactive isotopes are produced using projectile-fragmentation reactions followed by in-flight separation and gas stopping. The scheme complements the reach over isotopes of ISOL-type facilities, where many laser spectroscopy data has been obtained for selected elements. BECOLA is currently the only laser spectroscopy facility that can accept radioactive beams from the fragmentation facility, and opens up new opportunities to explore key rare isotopes that have been difficult for laser spectroscopy to access before. I will introduce the BECOLA facility, and discuss recent results for neutron-deficient nuclei at the neutron shell closures N = 20 around Ca and N = 28 around Ni isotopes.

25. 01. 2018 at 15:15
S2 11/10

SFB Colloquium

Michael Jentschel (Institut Laue-Langevin, Grenoble)
Gamma ray spectroscopy at the institute Laue-Langevin

The ILL operates one of the most intense neutron sources in the world. Although primarily used for neutron scattering there exist a long-standing history of gamma ray spectroscopy at the ILL. The availability of well collimated intense neutron beams and in-pile sample irradiation positions allowed to develop quite unique instruments and applications of gamma ray spectroscopy. The talk will start with giving an overview on the different aspects of neutron based gamma ray spectroscopy at the ILL. Amongst the operating gamma ray instruments the ultra-high-resolution gamma ray spectrometers GAMS play a particular role due to their outstanding energy resolution and dynamic range. The instruments are based on perfect crystal Laue diffraction of gamma rays produced by excited nuclei in the reactor and their operation requires one of the worlds best angle measurement devices. Accordingly the experiments contributed in the past to many different fields in physics: nuclear structure, metrology, photon matter interaction, crystallography and astrophysics. In a second part the talk will review some highlights from the past 20 years of operation of these instruments.

14. 12. 2017 at 14:00
S2 11/10

SFB Colloquium

Hans-Thomas Janka (MPI Garching)
3D Core-Collapse Supernova Modelling and Applications to Cas A and other Supernova Remnants

First three-dimensional, first-principle simulations of core-collapse supernovae have become possible in the recent past. They demonstrate the basic viability of the neutrino-driven mechanism for powering the explosions of the majority of supernova progenitors. Although a number of open questions remain to be settled, the explosion models are now sufficiently mature to strive for detailed comparisons against observations, for example considering well studied, nearby supernovae and supernova remnants. This talk will review our basic understanding of the explosion mechanism and report some results of such observational tests.

26. 10. 2017 at 14:00
S2 11/10

SFB Colloquium

Aleksi Vuorinen (Helsinki Institute of Physics)
Dense QCD matter from first principles

Neutron stars, currently probed using both electromagnetic and gravitational wave observations, contain some of the densest matter in the known universe, possibly including even deconfined quark matter. In my talk, I will describe recent efforts to understand the collective properties of high-density quark matter, using both resummed perturbation theory and the holographic AdS/CFT duality. Prospects for quantitatively constraining the observable properties of neutron stars using these results will also be discussed in detail.

13. 07. 2017 at 15:15
S2 11/10

SFB Colloquium

Kei Kotake (Fukuoka University/Japan)
Muli-messenger predictions from multi-D core-collapse supernova models (with refined neutrino reactions in progress)

We will report status of multi-messenger predictions from our 2D and 3D core-collapse supernova (SN) models. After some review about SN multi-messengers, we show that progenitor's core-compactness is a good diagnostics for predicting gravitational-wave (GW) signals and also diffuse-supernova-neutrino-background (DSNB) signals. From our 3D rotating models, we show some interesting viewing-angle effects of the neutrino and GW signals. Finally we report our on-going project to update neutrino opacities in our work-horse supernova code.

28. 06. 2017 at 11:00
S2 08/171

SFB Colloquium

Sharon McGrayne (SFB 1245 Women's Week)
From Maria Goeppert Mayer to today, and what research suggests can be done

When my first book Nobel Prize Women in Science was published in 1993, the legal barriers against women in academic science seemed to be fading into the past. But now we realize that subtle barriers are also difficult to deal with. In my talk, I'll give some examples, past and present, and describe recent research on the subject. In particular, I will draw on what I've learned from the writing a book about the present situation for women in science with Dr. Rita Colwell, microbiologist, former director of the National Science Foundation, and Distinguished Professor at the University of Maryland, College Park, and Johns Hopkins University.

18. 05. 2017 at 15:30
S2 11/207

SFB Colloquium

Paul-Gerhard Reinhard (Uni Erlangen)
Nuclear density-functional theory - from photo-absorption strength to bulk

Self-consistent nuclear models are based on energy-density functional adjusted to a reference set of nuclear data. The talk concentrates on the most widely used Skyrme- Hartree-Fock (SHF) approach comparing occasionally with the relativistic mean-field model.
The first part of the talk gives an introductory overview illustrating the wide range of phenomena which can be described by static and dynamics SHF.
The second part explains the empirical calibration of the energy functional by least-squares fits and discusses how statistical analysis, related to the least-squares method, allows to estimate extrapolation uncertainties and correlations between different observables.
The third part discusses as application response properties of finite nuclei (giant resonances, polarizability) and extrapolations to neutron matter. It works out the connections between the equation of state of bulk matter and the response observables. This way one can estimate the relation between quality of data in finite-nuclei and predictions on star matter. Particularly the dipole polarizability plays a crucial role in neutron matter.

09. 02. 2017 at 15:15
S2 11/10

SFB Colloquium

Thomas Luu ()
Applying Lattice QCD techniques to low-dimensional non-relativistic systems

I discuss the application of lattice monte carlo (MC) techniques to calculate the properties of low-dimensional non-relativistic systems. For specific applications I consider the 2-dimensional graphene and quasi 1-dimensional carbon nanotube systems at half-filling with strongly correlated electrons. I compare and contrast the use of MC techniques in lattice QCD with these low-dimensional non-relativistic systems, and show how lattice QCD techniques can be applied to calculate the quasi-particle spectrum of these systems. I discuss the limitations of this formalism, and conclude with an outlook of possible future calculations.

26. 01. 2017 at 15:15
S2 11/10

SFB Colloquium

Barbara Dietz (Lanzhou University/China)
Chaos and Regularity in the Doubly Magic Nucleus 208Pb

High resolution experiments have recently lead to a complete identification (energy, spin, and parity) of 151 nuclear levels up to an excitation Energy of Ex= 6.20 MeV in 208Pb. We present a thorough study of the fluctuation properties in the energy spectra of the unprecedented set of nuclear bound states. In a first approach we grouped states with the same spin and parity into 14 subspectra, analyzed standard statistical measures for short- and long-range correlations and then computed their ensemble average. Their comparison with a random matrix ensemble which interpolates between Poisson statistics expected for regular systems and the Gaussian Orthogonal Ensemble (GOE) predicted for chaotic systems shows that the data are well described by the GOE. In a second approach, following an idea of Rosenzweig and Porter we considered the complete spectrum composed of the independent subspectra. We analyzed their fluctuation properties using the method of Bayesian inference involving a quantitative measure, called the chaoticity parameter f, which also interpolates between Poisson (f=0) and GOE statistics (f=1). It turns out to be f~0.9. This is so far the closest agreement with GOE observed in spectra of bound states in a nucleus. The same analysis has also been performed with spectra computed on the basis of shell model calculations with different interactions (SDI, KB, M3Y). While the simple SDI exhibits features typical for nuclear many-body systems with regular dynamics, the other, more realistic interactions yield chaoticity parameters f close to the experimental values.

24. 11. 2016 at 15:20
S2 11/10

SFB Colloquium

Pierre Capel ()
Past, present and future of the eikonal description of reactions involving exotic nuclei

Away from the valley of stability, a numerous of exotic nuclear structures are encountered: shell inversions, halo nuclei,... The study of these short-lived exotic systems is mostly performed through nuclear reactions measured at Radioactive-Ion Beam facilities. To infer valuable structure information from experimental data, a reliable model of the reaction mechanism coupled to a realistic description of the nucleus under investigation is required.

The Dynamical Eikonal Approximation (DEA) is such a model for reactions involving one-nucleon halo nuclei. It has shown to provide excellent results for all kinds of observables when compared to experiments with both one-neutron (e.g. 11Be, 15C) and one-proton (8B) halo nuclei. It is hence an accurate tool to analyse reactions measured with exotic loosely-bound nuclei. However, as every model, the DEA has its own range of validity: it is mostly limited to intermediate or high beam energy. Moreover, the projectile description considered within the DEA remains simple: a valence nucleon bound to an inter core.

During this seminar, I will review the DEA, show how it compares to other, more sophisticated, reaction models, and describe its successes in the analysis of exotic nuclear structures. I will also present what is planned in the future to extend its range of validity both in the reaction part and in the description of the projectile.

03. 11. 2016 at 15:20
S2 11/10

SFB Colloquium

Xiaofei Yang (KU Leuven)
Nuclear structure studies by the measurement of nuclear spins, moments and charge radii via laser spectroscopy techniques

High resolution laser spectroscopy can access to multiple nuclear properties of ground/isomeric states of radioactive nuclei far from stability, such as nuclear spins, nuclear magnetic and quadruple moments and charge radii [1]. These fundamental properties of exotic nuclei provide important information for the investigation of the nuclear structure in different regions of nuclear chart. Currently, two complementary collinear laser spectroscopy set-ups are available at ISOLDE, Collinear Laser Spectroscopy (COLLAPS) and Collinear Resonant Ionization Spectroscopy (CRIS) [2].
Combining these two techniques, the nuclear structure in several key regions of the nuclear chart can be investigated, for example the structure of neutron-rich isotopes in the Ca region and in the Ni region, which just happens to be my research interest. Currently, several experiments are focusing on nuclear structure studies in these two regions [3-5].
In this talk, after an introduction of both the COLLAPS and CRIS techniques, I will mainly focus on my research interest on neutron-rich K[4], Sc[4] and Zn[3], Ge[5] isotopes using both experimental techniques. The results of nuclear spins, moments and charge radii of Zn isotopes, achieved from COLLAPS experiments, will be presented in details together with all the physics discussion [3]. For others, the physics motivation of each individual experiment and the status of the experiments will be introduced [4,5].
References:
[1] P. Campbell et al., Progress in Particle and Nuclear Physics 86, 127 (2016).
[2] http://collaps.web.cern.ch/ and http://isolde-cris.web.cern.ch/isolde-cris/
[3] X. F. Yang et al., Phys.Rev.Lett. 116, 182502 (2016); C.Wraith and X.F.Yang et al., in Preparation for
Phys. Let. B (2016); L. Xie and X. F Yang et al,m In preparation for Phys. Rev. C (2016) [4]X.F. Yang et al., CERN-INTC-2016-008/INTC-P-458, X.F. Yang et al.,
CERN-INTC-2015-051/INTC-P-451 ; X.F. Yang et al., CERN-INTC-2015-050/INTC-P-450 ; [5]M.Bissell,X.F.Yang et al., CERN-INTC-2016-035/INTC-P-472 ; X.F.Yang, M.Bissel et al.,
CERN-INTC-2016-036/INTC-I-170.

14. 07. 2016 at 14:00
S2 11/10

SFB Colloquium

(Argonne National Laboratory)
Laser Probing of Simple Atoms, Exotic Nuclei

The atomic structure of simple, few electron systems can be precisely calculated. Likewise, few nucleon systems can be accurately treated within ab-initio nuclear theories. Bringing these two fields together, we perform precision studies of light, radioactive isotopes that show a remarkable range of neutron-to-proton ratios. Techniques of high-resolution laser spectroscopy and of laser cooling and trapping offer unique access to precision nuclear structure and weak interaction studies of these isotopes to probe nucleon-nucleon interactions and to search for physics beyond the Standard Model. In my talk I will cover two on-going efforts in this direction: precision measurements of nuclear charge radii moving towards the proton rich Boron-8 and a beta-neutrino angular correlation measurement with laser trapped Helium-6.

Address

Technische Universität Darmstadt

Institut für Kernphysik
Theoriezentrum

S2|11
Schlossgartenstraße 2
64289 Darmstadt

Secretary

Genette Kluckner

+49 6151 16 21551
+49 6151 16 21555

Stephanie Müller

+49 6151 16 21558
+49 6151 16 21555

Next Seminar

Theorie-Seminar

on 18. 12. 2018 at 16:00
(S2 11/207)
Caroline Robin
Charge-exchange modes and weak-interaction processes in Relativistic Nuclear Field Theory
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