Seminars

Monday, Mar 18 at 11:00 AM
1200 FRIB Laboratory
Paul Gueye, Michigan State University
Another FRIB impact: Is tomography of heavy ions experimentally possible?

Abstract:  The electromagnetic probe is one of the cleanest tools to probe the nuclear matter due to its point-like nature. It has enabled some key understandings of the nuclei charge distributions, spin-dependent observables and opened a path to 3D nucleons femtography. Nuclei structures are best studied with heavy ion facilities that have unraveled and provided fundamental insights of new isotopes, with the shell model at its core for spectroscopy guidance. While many advances and discoveries have occurred, they also brought new challenges in this fascinating world of nuclear physics: we are still trying to understand how big the proton is, how far can we go on both the proton and neutron driplines, are neutron stars actually strange stars and how nucleon pairs interact inside nuclei to name a few. This talk will highlight some shortcomings of the Born approximation in electron scattering along with their relations to heavy ion studies with facilities like FRIB and the possibility to enable a 3D tomography of the nuclear matter. Another key factor in the advancement of nuclear physics is rooted in its diverse pool of scientists and engineers, an aspect that will also be highlighted.

Tuesday, Mar 19 at 11:00 AM
1200 FRIB Laboratory
Alexander Tichai, CEA Saclay
Recent advances in ab initio nuclear theory: From symmetry breaking to pre-processing tools

Abstract:  In recent years the ab initio treatment of the nuclear many-body problem has seen tremendous progress such that the A-body Schroedinger equation can be solved from first principles using realistic nuclear Hamiltonians with a sound link to QCD. However, it is yet unclear (1) how to describe genuine open-shell nuclei from an ab initio perspective and (2) how to overcome the curse of dimensionality in many-body approaches that prevents relaxing many-body approximations. Additionally, the large uncertainties arising from the input Hamiltonian make a direct comparison with experimental observations challenging, requiring extensive interaction benchmarks far away from shell closures and for large mass numbers in the future. Exploiting symmetry breaking in the many-body expansion enables for addressing nuclear observables in arbitrary open-shell systems. The recently introduced Bogoliubov extension of many-body perturbation theory serves as an example for a computationally light-weighted approach well-suited for benchmarking ground-state energetics along medium-mass isotopic chains. In a complementary way, data pre-processing techniques help resolving the computational bottlenecks one is facing in state-of-the-art many-body implementations. Two particular strategies are discussed: (i) tensor factorization and (ii) importance truncation. Following rationale (i), many-body tensors, like the Hamiltonian, are decomposed into lower-rank objects and consequently, storage requirements are decreased and, at the same time, the contraction pattern of the tensor network is optimized. Importance truncation, on the other hand, aims at an a priori selection of Hilbert space basis states which are expected to be important based on a (typically perturbative) importance measure. Due to discarding many irrelevant tensor entries the original large-scale problem can be solved in a much smaller selected model space. The combination of novel many-body expansions and innovative tools from applied mathematics allow for extending the range of ab initio applications and, thus, putting the next generation of nuclear Hamiltonians to a stringent test at a low computational cost.

Wednesday, Mar 20 at 4:10 PM
1200 FRIB Laboratory
Maxime Brodeur, University of Notre Dame
Precision measurements of mirror transitions at the Nuclear Science Laboratory

Abstract:  Despite its success, the Standard Model (SM) is currently being scrutinized at the energy, intensity and precision frontier. One probing mechanism for new physics is the unitarity test of the Cabibbo-Kobayashi-Maskawa matrix. This test requires a precise and accurate determination of the Vud matrix element, which is currently derived from the ft-value of superallowed weak decays. While superallowed pure Fermi transitions currently allow for the most precise determination of Vud, there is currently a growing interest in obtaining that matrix element from superallowed mixed transitions to test the accuracy of Vud and the calculation of isospin symmetry breaking corrections. In the past few years a research program aimed at solidifying the determination of Vud from mirror transitions was initiated using radioactive ion beams from the Twin Solenoid (TwinSol) separator at the Nuclear Science Laboratory of the University Notre Dame. The first part of the program is centered on precision half-life measurements and the second part aims at measuring the Fermi to Gamow-Teller mixing ratio ρ. Recent half-life measurements and the current development status of an ion trapping system to measure ρ in many mirror decays for the first time will be presented.

Thursday, Mar 21 at 11:00 AM
1200 FRIB Laboratory
Matthew Rizik, Michigan State University
Renormalization of CP-violating operators in perturbative QCD using the Yang-Mills gradient flow
Friday, Mar 22 at 5:30 PM
1300 FRIB Laboratory
Igor Cetkovic, Wei-Qin Claire Tang,
Advanced Studies Gateway Event: Musical Connection Beyond the Border

Abstract:  A Chamber Music Recital Featuring Igor Cetkovic (cello) and Wei-Qin Claire Tang (piano)

Monday, Mar 25 at 1:00 PM
1400 Biomedical and Physical Sciences Building
,
JINA-CEE Science Cafe - Title to be announced
Saturday, Mar 30 at 10:30 AM
1300 FRIB Laboratory
Witek Nazarewicz, Hannah Distinguished Professor
Is There an End to the Periodic Table of Elements?
Tuesday, Apr 02 at 11:00 AM
1200 FRIB Laboratory
Alessandro Roggero, UW
Theory Seminar - Title to be announced
Monday, Apr 15 at 12:30 PM
1400 Biomedical and Physical Sciences Building
Roland Diehl, MPE Garching
JINA-CEE Seminar - Gamma-ray spectroscopy from nuclei in the cosmos

Abstract:  Gamma-ray spectroscopy from nuclei in the cosmos Roland Diehl, Max Planck Institut für extraterrestrische Physik Gamma ray lines from cosmic sources display the action of nuclear reactions in cosmic sites. The gamma rays at such characteristic energies result from nuclear transitions following radioactive decays or high-energy collisions with excitation of nuclei. The gamma-ray line and its associated special continuum from the annihilation of positrons at 511~keV falls into the same energy window, although of different origin. We review the concepts of astronomical gamma-ray telescopes and cosmic gamma ray spectrometry, with the corresponding instruments and missions, including future perspectives. We then present a discussion of recent results and the challenges and open issues for the future. This includes, specifically, the diffuse radioactive afterglow of massive-star nucleosynthesis in $^{26}$Al and $^{60}$Fe gamma rays, which is now being exploited towards the cycle of matter driven by massive stars and their supernovae. Also the complex processes making stars explode as either thermonuclear or core-collapse supernovae are subject to studies through gamma-ray lines, in this case from shortlived radioactivities from $^{56}$Ni and $^{44}$Ti decays. Herein the non-sphericities that have recently been recognised as important are reflected, probably most-directly, through gamma-ray line characteristics. We will also discuss how we should relate to the above the distribution of positron annihilation gamma ray emission with its puzzling bulge-dominated intensity distribution, which is measured through spatially-resolved spectra. These indicate that annihilation conditions may differ in different parts of our Galaxy, and helps to reveal the complex paths recycling matter from nucleosynthesis sources to next-generation stars.

Tuesday, Apr 16 at 11:00 AM
1200 FRIB Laboratory
Amy Lovell, LANL
Theory Seminar - Title to be announced