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Nuclear Physics Seminar

The Nuclear Physics Seminars are held in Room 304 of the Nielsen Physics Building, at 2:25 pm. Please note that the Department of Physics and Astronomy Colloquium follows our seminars at 3:30 pm in room 307 of the Science and Engineering Research Facility (SERF).

Fall 2018 Schedule
Date
Speaker
Title
Host

August 27

Rin Yokoyama
Department of Physics and Astronomy, UTK

Recent measurements at RIKEN and their impact on the production of elements in the universe.

Rin Yokoyama

September 10

Zhengyu (Shu) Xu
Department of Physics and Astronomy, UTK

Experimental studies on the nuclear moments of the intruder 1+ isomer in 34Al.

Zhengyu Xu

September 17

Andrew Steiner
Department of Physics and Astronomy, UTK

Equation of State, Superfluidity and Superconductivity in Dense Nucleonic Matter

Andrew Steiner

September 24

Nathan Brewer
Joint Institute for Nuclear Physics and Applications/Oak Ridge National Laboratory

Search for the heaviest atomic nuclei among the products from reactions of mixed-Cf with a 48Ca beam aka 294 and the real Og

Robert Grzywacz

October 1

Marija Vostinar
Department of Physics and Astronomy, UTK

The puzzle of the unbound 13Be

Marija Vostinar

October 8

Charlie Rasco
Joint Institute for Nuclear Physics and Applications/Oak Ridge National Laboratory

Some Recent Results from the ORNL Low Energy Group

Robert Grzywacz

October 15

Noah Birge
Department of Physics and Astronomy, UTK

Looking for Beyond the Standard Model Physics in 45Ca beta decay

Noah Birge

October 22

Daniel Odell
Department of Physics and Astronomy, UTK

Regularization and Renormalization of Singular Potentials

Daniel Odell

October 29

Miguel Madurga
Department of Physics and Astronomy, UTK

Decay spectroscopy at the ISOLDE facility at CERN

Miguel Madurga

November 5

Wael Elkamhawy
TU Darmstadt

Description of 31Ne in halo EFT

Lucas Platter

November 12

Andy Castro
Department of Physics and Astronomy, UTK

Continuous Readout Upgrade of the ALICE Time Projection Chamber

Andy Castro

November 19

Nicole Vassh
University of Notre Dame

Fission and lanthanide production in r-process nucleosynthesis

Kate Jones

November 26

Evan Adamek
Department of Physics and Astronomy, UTK

TBA

Evan Adamek


Abstracts
August 27
Rin Yokoyama, University of Tennessee

Recent measurements at RIKEN and their impact on the production of elements in the universe.

RI-beam Factory (RIBF) at RIKEN Nishina Center is an exotic heavy-ion research facility in Japan. This facility is able to provide high-intensity beams of various unstable nuclei far from the line of beta stability. At the beginning of this talk, I will give some introduction to the facility and show recent researches going at RIKEN. Then, I will present a recent result from BRIKEN collaboration. BRIKEN is a high-efficiency array of 3He neutron counters designed to measure beta-delayed neutron branching ratios in the decays of very neutron-rich nuclei which is important to understand the production of elements in the universe. We measured beta-delayed one- and two-neutron emission of 86Ga and 87Ga and observed large one-neutron emission probability in 87Ga compared to the two-neutron emission, which was not expected from our shell model calculation. We found that this can be explained well by combining Hauser-Feshbach statistical model to the shell model calculation. This means that there is a strong one-neutron emission occurring even from the two-neutron unbound states in daughter nuclei. The result is the first experimental demonstration that it is important to take the competition between one- and two-neutron emissions into account to predict decay properties of very neutron-rich nuclei which may affect final abundance of elements in the universe.

September 10
Zhengyu (Shu) Xu, University of Tennessee

Experimental studies on the nuclear moments of the intruder 1+ isomer in 34Al.

An experiment has been carried out at GANIL to measure the nuclear moments of the low-lying 1+ isomer in 34Al (N=21) using the beta-NMR technique. Unlike its 4- ground state, of which the wave function is strongly mixed with 0p0h and 2p2h components, the 1+ isomer is proposed to have a dominant 1p1h configuration. Even though the excitation energy of this isomer has been reported recently, its 1p1h nature remains to be verified experimentally. In this presentation, I will present the g factor and quadrupole moment of the isomer newly determined from our recent work. The isomer's 1p1h character can be firmly identified by comparing the experimental g factor with either the effective single-particle g factor, or more complex shell-model calculations. The quadrupole moment, on the other hand, increases roughly by 50% with respect to that of the 32Al ground state (also a 1+state), suggesting an enhanced deformation induced by the 1p1h excitation across N=20. In addition, shell-model calculations of 32-34Al using several different effective interactions are compared with available experimental data in various observables, to gain a deeper insight on the neutron particle-hole excitation in this transitional region.


September 17
Andrew Steiner, University of Tennessee

Equation of State, Superfluidity and Superconductivity in Dense Nucleonic Matter.
Nuclear experiments tightly constrain the properties of the nucleon-nucleon interaction near or below the nuclear saturation density. At higher densities, however, there is considerable uncertainty because high-density matter cannot be generated in the laboratory without also creating high temperatures. Neutron star observations provide constraints on cold and dense matter which cannot be obtained from experiment. We use these observations to determine the equation of state and the nature of nucleonic superfluidity. In particular, X-ray observations of neutron stars provided gravitational wave predictions which were verified late last year. Observations of neutron star cooling are beginning to constrain the neutron-to-proton ratio in dense matter as well as the magnitudes of the neutron superfluid gaps and proton superconducting gaps.


September 24
Nathan Brewer, Joint Institute for Nuclear Physics and Applications/ Oak Ridge National Laboratory

Search for the heaviest atomic nuclei among the products from reactions of mixed-Cf with a 48Ca beam aka 294 and the real Og
The search for new decay chains of oganesson isotopes is presented. The experiment utilized the Dubna Gas Filled Recoil Separator and a highly segmented recoil-decay detection system. The signals from all detectors were analyzed in parallel by digital and analog data acquisition systems. For the first time, a target of mixed californium (51% 249Cf, 13% 250Cf, and 36% 251Cf)recovered from decayed 252Cf sources was produced and irradiated with an intense 48Ca beam. The observation of a new decay chain of 294Og is reported. Time permitting, a demonstration of the data will also be shown.


October 1
Marija Vostinar, University of Tennessee

The puzzle of the unbound 13Be
The isotopic chain of Be nuclei is particularly attractive for nuclear structure studies due to the variety of structural phenomena such as α-clustering, one and two neutron halos, breakdown of the N=8 shell gap, observed in this chain. In addition, several modern theories concerned with the evolution of the shell gaps overlap in the region of the low-mass nuclei, enhancing the importance for the experimental investigation of these isotopes. The structure of 13Be can offer insights on the N=8 shell gap, the nature of the Borromean 14Be nucleus, as well as on the influence of the continuum and the nature of the neutron-drip line. Despite its significant scientific importance, the structure of 13Be remains a puzzle. This can be observed trough the uncertainty on the position and ordering of the low-lying states remaining despite the significant number of experiments performed in the past [1]. The publication of Yu. Aksyutina et al presents a large step forward in understanding the structure of 13Be, however, it needs verification. Consequently, we performed a transfer reaction experiment at ISAC II, TRIUMF using the 12Be(d,p)13Be reaction. The beam at 9.5 AMeV interacted with the IRIS solid D2 target. At this low beam energy, the influence of the 12Be excited states is minimized, avoiding an issue highlighted by previous studies. The data are currently being analyzed and the preliminary results on the 13Be low-lying states will be presented here.



October 8
Charlie Rasco, ORNL/JINPA

Some Recent Results from the ORNL Low Energy Group
There are several detectors that have been developed or co-developed by the low energy group at ORNL, such as the Modular Total Absorption Spectrometer (MTAS) and the Beta Delayed Neutrons at RIKEN (BRIKEN) detectors. I will discuss design details of these detectors and a few of the latest measurements taken with these detectors including a precision measurement of 40K (!) and the beta-delayed neutron branching ratio of 77Cu.



October 15
Noah Birge, UTK

Looking for Beyond the Standard Model Physics in 45Ca beta decay
Although the Standard Model describes fundamental particle interactions to high precision, neutrino flavor oscillations, the observed baryon asymmetry, and complete absence of gravity from the model make it clear that there exists important physics which the model does not describe: so called beyond the standard model (BSM). The Fierz interference term for beta decay is one such observable sensitive to exotic scalar/tensor currents motivated by several BSM theories. A nonzero measurement of the Fierz term essentially manifests in the form of a distortion of the beta decay electron energy spectrum. 45Ca is a particularly appealing nucleus to attempt a measurement of the interference term, as it is an allowed, pure ground state to ground state, beta emitter. A measurement was performed at Los Alamos National Lab in 2017. A brief overview of the experiment along with some preliminary waveform data analyses will be presented.



October 22
Daniel Odell, UTK

Regularization and Renormalization of Singular Potentials
Singular potentials play a central role in a number of systems. In nuclear physics, the most singular term of the one-pion-exchange potential is an inverse cubed. In atomic physics, the van der Waals interaction which goes like the inverse sixth power dominates the low-energy behavior. I will discuss how we perform calculations with these potentials, how results differ across methods, and how our results impact power counting schemes.



October 29
Miguel Madurga, UTK

Decay spectroscopy at the ISOLDE facility at CERN
The study of exotic nuclei is at the forefront of current nuclear physics research. Large imbalances in proton-neutron numbers allow for the appearance of exotic phenomena, pushing the boundaries of our understanding of the binding nuclear potential. The ISOLDE facility provides exotic nuclei using the high energy beams from the CERN booster synchrotron to fragment a variety of target materials. ISOLDE hosts permanent experiments that allow to study nuclear masses, ground state spins and magnetic moments, and nuclear structure using nuclear reactions. Aiming to leverage the increasingly exotic beams available at ISOLDE, at intensities unsuitable for nuclear reaction or precision spectroscopy, the ISOLDE decay station (IDS) was developed and commissioned in 2014. IDS provides a collection of beta, high efficiency plastic, gamma, HPGe clovers, and neutron detectors allowing for a complete measurement of decay properties. In this talk I will present the campaign to study neutron rich nuclei using neutron spectroscopy, with an emphasis in the recent measurement of the delayed neutron emission to semi-magic 133Sn. Finally, a brief summary of current efforts to expand decay spectroscopy using polarized beams will be presented.



November 5
Wael Elkamhawy, TU Darmstadt

Description of 31Ne in halo EFT
Previous investigations of 31Ne via 1n-removal reactions on C and Pb targets revealed that it is a deformed nucleus with a significant P-wave halo component. We construct a P-wave halo effective field theory for 31Ne in order to provide an appropriate framework for its description. Within this framework, we establish correlations between different observables, which enables us to make theoretical predictions for the properties of 31Ne.




November 12
Andy Castro, UTK

Continuous Readout Upgrade of the ALICE Time Projection Chamber
The Time Projection Chamber (TPC) currently used for ALICE (A Large Ion Collider Experiment at CERN) is a gaseous tracking detector used to study both proton-proton and heavy-ion collisions at the Large Hadron Collider (LHC). In order to accommodate the higher luminosity collisions planned for the LHC Run-3 starting in 2021, the ALICE-TPC will undergo a major upgrade during the next long LHC shutdown. The TPC is currently limited to a read out of 1000 Hz in minimum bias events due to the intrinsic dead time associated with back ion flow in the multi wire proportional chambers (MWPC) in the TPC. The TPC upgrade will handle the increase in event readout to 50 kHz for heavy-ion minimum bias triggered events expected with the Run-3 luminosity by exchanging the MWPCs with a stack of four Gaseous Electron Multiplier (GEM) foils. The GEM layers will combine different hole pitches to reduce the dead time while maintaining the current spatial and energy resolution of the existing TPC. Undertaking the upgrade of the TPC represents a massive endeavor in terms of design, production, construction, quality assurance (QA), and installation. Hence, the upgrade is coordinated over a number of institutes worldwide. The talk will go over the physics motivation for the upgrade, the contribution from American institutes in the construction of Inner Read Out Chambers IROCs, and QA being performed at CERN.



November 19
Nicole Vassh, Notre Dame

Fission and lanthanide production in r-process nucleosynthesis
The observations of the GW170817 electromagnetic counterpart last year suggested lanthanides were produced in this neutron star merger event. Lanthanide production in heavy element nucleosynthesis is subject to large uncertainties from nuclear physics and astrophysics unknowns. Specifically, the rare-earth abundance peak, a feature of enhanced lanthanide production at A~164 seen in the solar r-process residuals, is not robustly produced in r-process calculations. The proposed dynamical mechanism of peak formation requires the presence of a nuclear physics feature in the rare-earth region which may be within reach of experiments performed at, for example, the CPT at CARIBU and the upcoming FRIB. To take full advantage of such measurements, we employ Markov Chain Monte Carlo to "reverse engineer" the nuclear masses capable of producing a peak compatible with the observed solar r-process abundances and compare directly with experimental mass data. Here I will present our latest results given a low entropy accretion disk wind scenario and demonstrate how the method may be used to the learn which astrophysical conditions are consistent with both observational and experimental data. Uncertainties in the astrophysical conditions also make it difficult to know if merger events are responsible for populating the heaviest observed nuclei, the actinides. Here I will discuss a potential direct signature of actinide production in merger environments which would confirm mergers capable of being a dominant source of r-process material in the galaxy. However, an r-process which reaches the actinides is also likely to host fission, which is largely experimentally uncharted for neutron-rich nuclei. The influence of fission on lanthanide abundances, and the potential for future experimental and theoretical efforts to refine our knowledge of fission in the r-process, will be discussed. The question of where nature primarily produces the heavy elements can only be answered through such collaborative efforts between experiment, theory, and observation.



November 26
Evan Ademek, UTK

TBA



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