If you have any questions about upcoming seminars or would like to suggest a future speaker, please contact the chair of the TUNL Seminar Committee, Julieta Gruszko.
|October 13, 2022||
Department of Physics and Astronomy, Texas A&M University - Commerce
Probing photonuclear reactions with heavy ions
Heavy ions provide strong electromagnetic fields that can be used to probe properties of interest in nuclear structure, nuclear astrophysics and particle physics. In this talk I will discuss new developments in understanding the role of the symmetry energy in the equation of state of nuclear matter, nuclear collective phenomena, QED and QCD processes, and other physics phenomena induced by photon-photon and photo-nuclear interactions in reactions with heavy ions.
|October 20, 2022||
Nuclear structure studies using photonuclear reactions with quasi-monoenergetic photon beams at HIγS
Photons provide a particular clean probe to study a variety of nuclear structure phenomena. Their interaction with the atomic nucleus is described by the electromagnetic interaction enabling the almost model-independent separation of the nuclear response from the details of the reaction mechanism.
In this talk, recent developments and experimental results obtained from photonuclear reaction studies with quasi-monoenergetic photon beams at HIγS are discussed in view of contradictory data sets when comparing data from real-photon scattering and particle-induced reactions. In addition, a model-independent approach is presented that allows the determination of photon strength functions in the photoabsorption and photon-emission channel in a single experiment testing the concept of the Brink-Axel hypothesis in the energy region below the neutron separation threshold.
|November 3, 2022||
Michigan State University
Search for the Limits of Atomic Nuclei with the Facility for Rare Isotope Beams
Nuclear science attempts to understand strongly-interacting material. The atomic nucleus, which comes in perhaps 10,000 different varieties, is the most familiar example. Many aspects of atomic nuclei including the limits in terms of neutron and proton number are not well known. The Facility for Rare Isotope Beams, FRIB, will provide access to an unprecedented range of isotopes (the varieties) of the elements up to uranium. This is possible due to FRIB’s very high-power superconducting linear accelerator that can deliver 400 kW of beam power for all stable isotopes and FRIB’s efficient isotope production and also due to the efficient separation scheme employed. The talk will review our current understanding of the limits of nuclei and present resent results. The prospects for progress at FRIB will be presented. Some of the implications of our understanding of the limits will be presented.
|November 10, 2022||
Charlotte Van Hulse
University of Paris-Saclay and CNRS/IN2P3
Study of the hadron structure in ultra-peripheral collisions at the LHC
The internal hadron structure can be studied in lepton-hadron scattering and in hadron-hadron collisions. The former interaction offers the advantage of a clean, point-like probe. The latter, in particular studied at the LHC, provides a complementary channel and the possibility to reach, with the currently existing or near-future planned facilities, higher energies and thus to study the hadron structure down to lower values of x-Bjorken. An overview of measurements in ultra-peripheral collisions at the LHC, englobing exclusive processes as well as inclusive photoproduction and sensitive to the nucleon and nucleus structure, will be presented. Where applicable parallels with measurements in lepton-hadron interactions will be highlighted.
|March 3, 2022||Raquel Castillo Fernandez
Physics Department, University of Texas Arlington
The practical beauty of neutrinos: uncovering the mysteries of the (anti)matter
Why is there more matter than anti-matter in the Universe? Do we know all the particles that constitute the Universe?
Neutrinos are the most abundant massive particle in the Universe. However, its properties have been challenging the knowledge we thought we had during the last decades. Still today, neutrinos remain as the most mysterious particle we know the existence of. We don’t know the origin of their mass, or if neutrinos can be their own anti-particle. Each neutrino property we unravel becomes a major breakthrough in science, and a new insight of new physics beyond the well stablished Standard Model. In this talk, we’ll walk through the neutrino properties and the unprecedented discoveries driven by them. In addition, we will also explore how the complexity of the interactions of this little tiny particles sculpts a precise understanding of the dynamics, from the atomic nuclei to neutron starts and the Big Bang, and how neutrino research opens new discussions and opportunities and will lead to new discoveries and a more coherent description of the Universe.
|March 10, 2022||Duke/NCCU Spring Break|
|March 17, 2022||NCSU/UNC Spring Break|
|March 24, 2022||Sam Hedges|
|March 31, 2022||Jon Engel|
|April 7, 2022||Aobo Li|
|April 14, 2022||Christian Illiadis|
|April 21, 2022||Ekaterina Korobkina|
|April 28, 2022||Spencer Axani|
|May 5, 2022||Walter Pettus|
|February 10, 2022||Miguel Marques
Laboratoire de physique corpusculaire de Caen
The neutron as a building block: a challenge for experiment and theory
Already in the early 1960s, when physicists started to move away from the valley of stability, some ambitious ones tried to put several neutrons together and create "neutral nuclei" in their laboratories. They didn't succeed, but the task was a very difficult (while fascinating) one, both from the construction and the detection points of view. Fascination overcame difficulty and other physicists kept trying to find these objects, that would defy nuclear theory as we know it, all through the XX century. Finally, in this XXI century two signals of a possible tetraneutron state close to threshold were obtained, first at GANIL and then at RIKEN, that were weak but have not been contested yet. They have triggered a lot of new theoretical calculations, as well as new generation experiments that try to reveal something that has eluded firm evidence for sixty years already. I will review some of the most exotic experiments, highlight their merits and drawbacks, and show why the present ones think they will succeed where so many others have failed. See related research in https://link.springer.com/article/10.1140/epja/s10050-021-00417-8
|February 17, 2022||Mitch Allmond
Physics Division, Oak Ridge National Laboratory
The FRIB Decay Station initiator (FDSi)
The Facility for Rare Isotope Beams (FRIB) will provide unprecedented access to exotic nuclei; approximately 80% of the isotopes predicted to exist up to uranium (Z = 92) will be produced. The FRIB Decay Station (FDS) — an efficient, granular, and modular multi-detector system designed under a common infrastructure — will have a transformative impact on our understanding of nuclear structure, nuclear astrophysics, fundamental symmetries, and isotopes of importance to applications.
The FRIB Decay Station Initiator (FDSi), led by the FDSi Coordination Committee and supported by the FDSi Group and Working Groups, is the initial stage of the FRIB Decay Station (FDS). The FDSi is primarily an assembly of the best detectors currently available in the community within an integrated infrastructure for Day One FRIB decay studies, ultimately providing a means for FRIB users to conduct world-class decay spectroscopy experiments with the best equipment possible and to transition to the FDS without interruption to the user program. The FDSi infrastructure will remain intact at FRIB, ready to receive community detectors that will nominally travel.
An overview of the FDSi and scientific program approved by the first FRIB PAC will be given.
*This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics.
|February 24, 2022||John Wilkerson - Cancelled|
|September 23, 2021||Tom Clegg
UNC Chapel Hill
Our seminar this week will be given by Tom Clegg and will provide a view of the formation and development of the nuclear physics activities amongst the Triangle area universities.
|September 30, 2021||Wei Jia Ong
Lawrence Livermore National Laboratory
Presolar grains as constraints on the origin of the p-nuclei.
There are ~30 naturally existing nuclei on the proton-rich side of the valley of stability which origin cannot be explained by neutron-capture processes. The nuclear astrophysical process (or combination of processes) that lead to the synthesis of these nuclei is not well understood or constrained. Since these p-nuclei are less abundant than the other isotopes of the same elements, astronomical spectroscopy is currently a limited source of data that can be used to constrain the astrophysical environment of origin. Presolar grains, or stellar condensates, can preserve single-event nucleosynthetic signatures from their parent star and can be exploited as a source of information on the formation of the p-nuclei. I will discuss the ongoing cosmochemical and nuclear physics efforts to investigate the origin of the p-nuclei.
|October 7, 2021||Joule Othman
UNC Chapel Hill and TUNL
The CAGE Scanner: Investigating Surface Backgrounds in High-Purity
The neutrino is an elusive particle that has challenged our models of the universe. With the discovery of neutrino oscillations, we know that neutrinos have mass, which disagrees with the Standard Model (SM) of particle physics. However, we still do not know the mechanism by which neutrinos obtain their mass. The discovery of neutrinoless double-beta decay would have a profound impact on our understanding of neutrinos and the universe. It would show that the neutrino is its own antiparticle, ie. a Majorana particle, that lepton number is not a conserved quantity, and would give us insight into the matter-antimatter asymmetry. Next-generation searches for neutrinoless double-beta decay, such as LEGEND, are working to build ton-scale experiments with the goal of discovering neutrinoless double-beta decay. To discover such a rare process, experiments must be extremely low-background to mitigate unwanted signals that may obscure the signal of interest from neutrinoless double-beta decay. This is accomplished primarily by locating experiments underground to shield against cosmic rays, using very radiopure materials, active vetos, and using pulse shape discrimination in analysis. The LEGEND experiment will operate 76Ge-enriched pointcontact High-Purity germanium (HPGe) detectors directly immersed in a liquid argon (LAr) active veto.
A significant background expected in LEGEND is from radiation interacting near the surfaces of the detectors. Thin passivated surfaces are particularly susceptible to shallowly impinging alpha and beta radiation. To help further mitigate against surface backgrounds on passivated surfaces, dedicated test stands can help us understand the detector response to surface backgrounds and develop cuts to remove them from our data, maximizing our discovery sensitivity to neutrinoless double-beta decay. In this dissertation, we introduce the Collimated Alphas, Gammas, and Electrons (CAGE) test stand, which we built to study passivated surfaces for HPGe detector geometries that will be used in LEGEND. CAGE utilizes collimated radiation sources to study the effect of shallowly impinging radiation on specific locations on the passivated surfaces of HPGe detectors. We improve on previous surface scanning systems by offering more protection from infrared (IR) shine on passivated surfaces and more flexibility in positioning the collimated source beam, most notably the ability to change the incidence angle of the source beam with respect to the passivated surface of the detector. We show that CAGE is able to operate stably and show the first results from a radial scan of a P-type Point-Contact detector using a 241Am alpha and gamma source. We present the results of a study of the risetimes of the 59.5 keV gamma from 241Am and show that certain risetime parameters can be useful in discriminating against surface backgrounds in LEGEND. We conclude by discussing the future goals of the CAGE test stand.
|October 14, 2021||DNP Meeting, no seminar this week|
|October 21, 2021||Rachel Carr
Assistant Professor, US Naval Academy
Title: Results of the Nu Tools Study: Exploring Practical Roles for Neutrinos in Nuclear Energy and Security
Abstract: For decades, physicists have used neutrinos from nuclear reactors to advance basic science. These pursuits have inspired many ideas for applications of neutrino detectors in nuclear energy and security. While developments in neutrino science are now making some of these ideas technically feasible, it has not been clear how practically they mesh with the needs, budgets, and other constraints of end users such as the International Atomic Energy Agency. In 2019, the National Nuclear Security Administration's Office of Defense Nuclear Nonproliferation R&D commissioned a community study on this question. The study, called Nu Tools, included extensive interviews with over 40 nuclear security and energy professionals. Perhaps surprisingly, these experts do see practical niches for neutrino detectors, but not in the places neutrino physicists have often seen them. This talk will review the Nu Tools study and findings, available in full at: https://nutools.ornl.gov/
|October 28, 2021||Eric Wulf
Research Physicist, Naval Research Labs
From Novel Scintillators to Germanium for Space-based Gamma-Ray Astrophysics
Terrestrial and space based gamma-ray detection has an insatiable demand for improved detectors and electronics. Two decades of Homeland Security funding has produced many new scintillators especially the elpasolites. And mass production of LIDAR systems has helped to evolve cheap and efficient Silicon Photomultipliers (SiPM). The Naval Research Laboratory is working to boost the Technology Readiness Level (TRL) of these materials and detectors to prepare them for current and future gamma-ray astrophysics missions by launching multiple satellite payloads in recent years. An overview of the dectector work and these missions will be presented.
In addition, the Compton Spectrometer and Imager (COSI) Small Explorer was selected last week for a NASA mission. The COSI readout electronics for the 16 double-side germanium strip detectors center around a 32-channel ASIC developed by NRL for silicon and germanium strip detectors. A discussion of the COSI, the ASIC, and the readout electronics effort for COSI will be presented.
|November 4, 2021||HIγS Celebration
|November 11, 2021||HIγS Celebration
Werner Tornow, Vladimir Litvinenko, Norbert Pietralla
|November 18, 2021||SESAPS Meeting: no seminar|
|November 25, 2021||Thanksgiving, no seminar|
|December 2, 2021||Leendert Hayen
Research Scientist, NCSU
The neutron as a gateway to new physics: plans and perspectives
Several anomalies currently exist within particle physics at large, compounded by open questions such as the matter-antimatter asymmetry or the nature of dark matter and neutrinos. Precise measurements of beta decays have both been at the inception of the current Standard Model and continue to be a model-independent pathway to looking for exotic physics. In the light of the current Cabbibo-Kobayashi-Maskawa non-unitarity indications, I will briefly introduce the shift in electroweak radiative corrections that initially caused it and shed light on new work. The Nab experiment at Oak Ridge National Lab measures the angular correlation between outgoing states following neutron beta decay and is is a central effort in this endeavour. I will outline its general principles and present the current status of detailed detector modeling work.
|December 9, 2021||Jon Engel|
|December 16, 2021|