Seminars

Friday, Jan 19 at 2:00 PM
Nuclear Conference Room 2025
Caroline Robin, University of Washington
Nuclear transitions of astrophysical interest in the relativistic nucleon-vibration coupling framework

Abstract:  The response of nuclei to external probes has many applications across the field of astrophysics. A precise description of neutral and charge-exchange excitations is necessary to compute the rates of various processes such as neutron-capture, beta-decay, neutrino-scattering or electron-capture, which are needed for the modeling of nucleosynthesis and stellar evolution. In this talk I will present a theoretical approach to the description of the nuclear response. This method describes the nucleus as a system of relativistic protons and neutrons interacting via effective meson exchange, and builds inter-nucleon correlations by accounting for the coupling between single nucleons and collective vibrations of the nucleus. Such correlations typically induce fragmentation and spreading of the transition strength which are essential for a precise description of giant resonances and low-energy modes, and have a great impact on the computing of decay and reaction rates. I will present calculations of various excitation modes and corresponding astrophysical rates in mid-mass and heavy nuclei. Emphasis will be put on recent calculations of Gamow-Teller transitions for beta-decay and electron-capture rates.

Friday, Jan 19 at 2:30 PM
NSCL Lecture Hall 1200
Tong LI, Graduate Assistant, NSCL
Application of Density Functional Theory in Nuclear Structure

Abstract:  COMMITTEE: Witold Nazarewicz(Chairperson),H. Metin Aktulga, S. Balasubramaniam, A. Gade H. Hergert

Tuesday, Jan 23 at 11:00 AM
NSCL Lecture Hall 1200
Amy Lovell, NSCL
Uncertainty quantification in reaction theory

Abstract:  Quantifying uncertainties within nuclear reaction theory has become more prominent over the past several years given recent improvements in the models and quality of rare isotope data. Here, I will discuss the progress that we have made quantifying parametric uncertainties in direct, few-body reaction theory. This will focus on a comparison between frequentist and Bayesian methods in order to constrain elastic scattering cross sections as well as predict the transfer cross sections that use the same potentials.

Wednesday, Jan 24 at 10:00 AM
NSCL Lecture Hall 1200
Fei Yuan, Graduate Assistant, NSCL
Addition and removal energies via the in-medium similarity renormalization group method

Abstract:  COMMITTEE: Morten Hjorth-Jensen(Chairperson), Scott Bogner, Alexandra Gade, Carlo Piermarocchi, Scott Pratt (Thesis is on display in 1312 BPS bldg. and the NSCL Atrium)

Wednesday, Jan 24 at 4:10 PM
NSCL Lecture Hall 1200
Eric Hessels, York University
Title To Be Announced
Thursday, Jan 25 at 11:00 AM
NSCL Lecture Hall 1200
Sherry Yennello, Texas A&M University
Toward Inclusive Excellence in Nuclear Science

Abstract:  The US population is made up of over 50% women. Hispanic Americans and African Americans make up over 30% of the US population. The processes by which we foster curiosity, educate our youth, encourage people into science, recruit and retain people into physics and welcome them as members of our nuclear physics community results in a much different demographic. Enabling the development of an identity as a scientist or nuclear scientist is a crucial part of mentoring young people to successful careers in nuclear science.

Wednesday, Jan 31 at 4:10 PM
NSCL Lecture Hall 1200
Ania Kwiatkowski, TRIUMF
TITAN at TRIUMF: Ion traps for precision nuclear experiments

Abstract:  TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) exploits the textbook-like conditions and versatility of ion traps, which offer sophisticated manipulation of a single ion or a cloud, for beam preparation and high-precision measurements. To test the unitarity of the quarkmixing matrix, to understand stellar evolution, and to benchmark state-of-the-art predictions of the N = 32 subshell closure in titantium isotopes require mass spectrometry. On the other hand, in-trap decay spectroscopy has focused on investigations of the double beta-decay problem and is being extended to studies of electron influence on fundamental decays. A selection of recent results will be presented as well as technical developments useful at radioactive-ion-beam facilities.

Tuesday, Feb 06 at 11:00 AM
NSCL Lecture Hall 1200
Joaquin Drut, University of North Carolina
Signal-to-noise issues in non-relativistic quantum matter: from entanglement to thermodynamics.

Abstract:  Non-relativistic quantum matter, as realized in ultracold atomic gases, continues to be a remarkably versatile playground for many-body physics. Experimentalists have exquisite control over temperature, density, coupling, and shape of the trapping potential. Additionally, a wide range of properties can be measured: from simple ones like equations of state to more involved ones like the bulk viscosity and entanglement. The latter has received much attention due to its connection to quantum phase transitions, but it has proven extremely difficult to compute: stochastic methods display exponential signal-to-noise issues of a very similar nature as those due to the infamous sign problem affecting finite-density QCD. In this talk, I will present an algorithm that solves the signal-to-noise issue for entanglement, and I will show results for strongly interacting systems in three spatial dimensions that are the first of their kind. I will also present a few recent explorations of the thermodynamics of polarized matter and other cases that usually have a sign problem, using complexified stochastic quantization.

Monday, Feb 12 at 12:30 PM
Biomedical & Physical Sciences Bldg., Rm. 1400
,
Title to be announced
Wednesday, Feb 14 at 3:10 PM
NSCL Lecture Hall 1200
Wolfram Fischer, Brookhaven National Laboratory
Head-on beam-beam compensation in RHIC

Abstract:  In a particle collider the electromagnetic interaction of one beam with the other, the beam-beam effect, is typically one of the most performance limiting effects. Operational head-on beam-beam compensation was first attempted in the 1970s in the 4-beam collider DCI but failed due to the unanticipated coherent motion of the beams. In 2015 operational head-on beam-beam compensation has been implemented in the Relativistic Heavy Ion Collider (RHIC) in order to increase the luminosity delivered to the experiments. We discuss the principle of combining a lattice for resonance driving term compensation and an electron lens for tune spread compensation. We describe the electron lens technology and its operational use, and report on measurements of the lattice properties and the effect of the electron lenses on the hadron beam. We also provide an estimate of the luminosity gain.