Seminars

Tuesday, Dec 07 at 12:00 PM
1200 FRIB Laboratory
Chien Yeah Seng, Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn
Hunting for Physics beyond the Standard Model in Beta Decays

Abstract:  Over the past few years, a series of new studies of the Standard Model (SM) corrections to the beta decay of mesons, nucleon and nuclei carried out by me and my collaborators has led to the observation of several significant anomalies in beta decays, in particular the apparent violation of the Cabibbo-Kobayashi-Maskawa (CKM) matrix unitarity. They have attracted world-wide attentions and turned beta decays into one of the most promising avenues for the search of physics beyond the Standard Model (BSM). However, the current significance level of the observed anomalies is not yet sufficient to declare a discovery, and the major limiting factor is the precision level of the SM theory inputs. In this talk I will outline a 5-year research proposal designed to systematically calculate the most important SM inputs to various beta decay processes, including the radiative corrections, isospin breaking corrections and nuclear structure corrections, to an unprecedented precision level. The success of the proposed research could increase the significance level of the existing beta decay anomalies beyond 5 standard deviations and lead to one of the earliest confirmed observations of BSM physics, of which impact to the fundamental science is far-reaching.

Wednesday, Dec 08 at 12:00 PM
1200 FRIB Laboratory
Anna McCoy, University of Washington
The Role of Approximate Symmetries in Theoretical Predictions for Nuclei

Abstract:  Ab initio methods, for which the only input is the inter-nucleon interaction, play an important role in describing nuclei for which there is limited data, particulalry in regions of the nuclear chart far from stability. However, quantitative predictions are computationally limited by the explosion in scale as the number of nulceons increases. Approximate symmetries of the nucleus can be used to combat this explosion using symmetry adapted approaches. At the same time, these symmetries can be used to gain insight into simple patterns which arise in the spectrum. I will discuss the emergences of two such approximate symmetries, SU(3) and Sp(3,R), associated with nuclear deformations, rotations and giant resonnances and how these symmetries are employed in the ab initio symplectic no-core configuration iteraction framework.

Wednesday, Dec 08 at 4:10 PM
Online via Zoom
Danielle Speller, Johns Hopkins
Looking for New Physics with Fundamental Particle Interactions

Abstract:  Some of the most interesting questions in modern physics are those regarding the nature, origin, and interactions of the fundamental constituents of matter. The answers to such questions can make a huge difference in how we understand the universe. Investigating them often involves an exciting combination of applications from many different fields - nuclear physics, particle physics, astrophysics, and more - to design and implement detectors capable of detecting tiny signals that could provide hints of new physics. In this talk, we describe a few of the questions our lab is trying to answer and how we look for physics beyond the standard model.

Thursday, Dec 09 at 12:00 PM
1200 FRIB Laboratory
Alex Gnech, Jefferson Laboratory
Fundamental Physics with Light Nuclei Using the Hyperspherical Harmonic Approach

Abstract:  Ab-initio methods provide a direct connection between nuclear physics and the underlying fundamental theory, permitting the use of nuclei as probes to study fundamental physics. In order to do this, we need to start from a nuclear model constructed from first-principles such in chiral effective field theory. Then reliable and accurate methods to solve the Schrödinger equation are needed. In this seminar we will introduce the Hyperspherical Harmonic (HH) method as the approach we used to solve the Schrödinger equation. We will focus in particular on some recent improvements that permit to treat nuclei up to A = 6. We will then show some examples on how this method, together with chiral effective field theory, has been used to study time reversal violation and β-decay in light nuclei. Finally we will briefly discuss how the HH method could be extended to treat also scattering states, opening up new frontiers for the ab-initio calculations.

Friday, Dec 10 at 12:00 PM
1200 FRIB Laboratory
Baishan Hu, TRIUMF
Ab Initio Calculations for Open Quantum Systems, Astrophysics and Beyond the Standard Model Physics

Abstract:  Background: Recent developments in effective field theory and many-body theory have pushed the limits of ab initio calculation to the 208Pb region with impressive precision [1]. This means that it becomes possible to obtain first-principles computation (with quantified uncertainties) of quantities which even reside in the heavy-mass region. The quantities include these relevant for astrophysics and searches for physics beyond the Standard Model. However, ab initio calculations for scattering and reactions are much more limited. Methods: F (Facilities, ab initio many-body method, such as in-medium similarity renormalization group, IMSRG) for R (Resonance and continuum), I (astrophysics), and B (Beyond the Standard Model) Results: I will discuss how to couple nuclear scattering states and decay channels into the IMSRG framework by using the complex-energy Berggren representation. The new IMSRG approach can describe properties of weakly-bound and unbound open quantum systems, such as limits of atomic nuclei, resonance, and halo. I will also report ongoing efforts to extend IMSRG to unify nuclear structure and reactions, especially for proton or neutron scattering and radiative capture reactions. In the second part of this talk, I will introduce some unreported strong correlations between electric dipole polarizability, binding energy, and symmetry energy parameters unlocked by large scale (range from 40Ca to 132Sn) ab initio calculations. Based on these correlations, I will show robust constraints on the equation of state of nuclear matter. Last but not least, I will present the recent ab initio calculation of nuclear responses for dark matter direct detection. Conclusion: FRIB physics needs theoretical 'FRIB'. [1] Ab initio predictions link the neutron skin of 208Pb to nuclear forces. B.S. Hu, et al. In preparation (2021).

Monday, Dec 13 at 8:45 AM
1300 FRIB Laboratory
ISNET 8 Dec. 2021,
Information and Statistics in Nuclear Experiment and Theory (ISNET 8)

Abstract:  The purpose is to maintain ISNET's mission of bringing the nuclear physics and statistical sciences communities together to report on the latest progress and to provide a vehicle for educating and enlightening the nuclear physics community in regards to the application of statistical methodologies that enable nuclear physics to reach more quantitatively rigorous scientific conclusions. The dates for the meeting are December 14th - 16th 2021, and will start Tuesday morning and end Thursday afternoon. For 2021 ISNET 8 will be an "a hybrid " meeting. All talks will be delivered on-site, but sessions will also broadcasted via ZOOM for remote participants. https://indico.frib.msu.edu/event/47/

Wednesday, Dec 15 at 11:00 AM
Online via Zoom
Andrew Sanchez, FRIB Graduate Research Assistant
Tentative Thesis Title: "Lifetime Measurements of Calcium-39 and its Mirror Symmetry"

Abstract:  Committee: Hironori Iwasaki (Chairperson), Kaitlin Cook, Sean Liddick, Dean Lee, Stuart Tessmer

Friday, Dec 17 at 2:00 PM
Online via Zoom
Arthur Choplin, University libre de Bruxelles
Non-Standard Neutron Capture Processes in Massive and AGB Stars

Abstract:  Despite considerable progresses during the last decades, the origin of trans-iron elements is not yet fully understood. These elements are thought to be produced by a variety of nucleosynthetic processes, the main ones being the so called slow (s) and rapid (r) neutron capture processes. An intermediate neutron capture process (i-process) is also thought to occur at neutron densities intermediate between the s- and r-processes. This is supported by the observation of metal-poor stars whose chemical compositions is between the s- and r-processes (the so called r/s-stars). An important challenge is to associate each nucleosynthetic process with its astrophysical source(s). In the first part of the presentation, I will discuss the synthesis of trans-iron elements in low metallicity massive stellar models. In particular, I will show how stellar rotation is expected to alter the synthesis of heavy elements both during the life and explosion of the massive star, and ultimately lead to a material with a chemical composition intermediate between the standard s- and r-processes. In the second part of this presentation, I will focus on the development of the i-process in low-metallicity AGB stars models. In both parts, I will highlight the chemical fingerprint of the discussed nucleosynthetic processes, identify key reaction rates and compare model predictions with observed r/s-stars.