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Nuclear Physics Seminars History

ics Nuclear
Tuesday, April 30, 2019
3:30 PM
Physics Building, Room 204
Simona Malace [Host: Donal Day]
Jefferson Lab
"On the path to extracting precision cross sections from Hall C commissioning experiment E12-10-002"
ABSTRACT:

E12-10-002 ran in Hall C in Spring of 2018 for about 3 weeks with the goal of extracting cross sections for H(e,e') and D(e,e') reactions in the deep inelastic and resonance region regimes. Our data cover a broad range in Bjorken x and we reached Q^2 values as high as 14 GeV^2. E12-10-002 will have an impact on a wide range of physics topics like Parton Distribution Functions extractions, Quark-Hadron Duality studies, F2_neutron/F2_proton at large x, modeling of H(e,e') and D(e,e') processes and moments of the F2 structure function.

In this talk I will summarize the physics motivation for running the experiment and I will also highlight the sinuous path to getting precision cross sections from measurements done with a brand new spectrometer (Super High Momentum Spectrometer) and a new data acquisition system.

ics Special Nuclear Seminar


Thursday, April 25, 2019
3:30 PM
Physics Building, Room 204
Dr. Matthias Burkardt [Host: Simonetta Liuti]
New Mexico State University
"Wigner Distributions"
ABSTRACT:

An overview of the physics of Wigner Distributions will be presented within the context of the recently established  Jefferson Lab Center for Nuclear Femtography.

ics Nuclear
Tuesday, April 23, 2019
3:30 PM
Physics Building, Room 204
Brandon Kriesten [Host: Simonetta Liuti]
University of Virginia - Physics
"Extraction of Observables from Deeply Virtual Electron Proton Scattering Experiments"
ABSTRACT:

Imaging the 3D partonic structure of the nucleon is a fundamental goal of every major nuclear experimental program, including the EIC. Ji first proposed Deeply Virtual Compton Scattering (DVCS) as a probe for understanding the spatial distribution of the partons by fourier transform of the exchanged momentum transfer between the initial and final proton. The extraction of observables from Deeply Virtual Exclusive Reactions in a clear and concise formalism, such that the various twist components and angular dependencies can be untangled, is key. We present a completely covariant description of the DVCS process that can be extended to any kinematics, either fixed target or collider. In our helicity formalism, we extract our observables such that the dependence on Q2 is clear. We can separate kinematic twist, characterized by subleading dependence on 1/Q2, from the dynamic twist, given by the Q2 suppression and azimuthal angle ɸ. Since the higher twist terms are characterized by their dependence on ɸ, it is important to understand the angular contribution arising from the kinematic variables and separate it from the characteristic angular dependence of the higher twist terms. The extension to other Deeply Virtual Exclusive Reactions, such as TCS, is in progress. From our formalism, one can extract observables important in understanding the physical properties of the proton such as the angular momentum of the quarks and gluons inside of the proton.

ics Nuclear
Tuesday, April 16, 2019
3:30 PM
Physics Building, Room 204
Matthew Roberts [Host: Blaine Norum]
University of Virginia - Physics
"The GDH Integrand of the Deuteron"
ABSTRACT:

The ultimate goal of my research is to measure for photons between 8 and 20 MeV using a frozen-spin target originally constructed at CERN in the mid 1970’s. The goal is to 1) look for a dibaryon state of the deuteron and to 2) investigate suspected deviations of the Gerasimov-Drell-Hearn integrand. In order to make sure we are as prepared as possible, we practice operation of the target in our lab. The primary goal of these practice runs or “cooldowns” is to achieve the ideal ratio of Helium-3 and Helium-4 in the target chamber of our dilution refrigerator in order to get it down to the coldest temperature possible and then to measure the polarization of the target. However, we have hit a few bumps along the way, and cannot currently do cooldowns due to our dilution fridge leaking. The primary focus of my talk will be on the steps we have taken to fix our fridge and get back to doing proper cooldowns.

ics Nuclear
Tuesday, April 9, 2019
3:30 PM
Physics Building, Room 204
Sachinthani Premathilake [Host: Kent Paschke]
University of Virginia - Physics
"Source Studies and Polarimetry for Upcoming PREX-II and CREX Experiments "
ABSTRACT:

Parity-violating electron scattering provides a clean probe of neutron densities that is model independent and free from most of the strong interaction uncertainties. The PREX-II and CREX experiments at Jefferson lab aim to measure the nucleon skin thickness in 208Pb and 48Ca via parity violating electroweak asymmetry in the elastic scattering of left and right polarized electrons. These measurement from Pb and Ca are sensitive to the existence of this neutron skin and it will provide information on nuclear structure. Knowledge of difference in proton and neutron radius or an effective neutron skin thickness is required in order to calibrate the equation of state for neutron rich nuclear matter.

I will discuss how we are getting ready for the upcoming 2019 runs of both experiments, especially focused on source studies and polarimetry studies.

ics Nuclear
Tuesday, April 2, 2019
3:30 PM
Physics Building, Room 204
Christopher Jantzi [Host: Gordon Cates]
University of Virginia - Physics
"Probing neutron spin framework with polarized 3He"
ABSTRACT:

Two types of functions used to describe the electromagnetic structure of nucleons include “form factors”, which describe the spatial distribution of charge and magnetism within the nucleon, and “structure functions”, which describe their longitudinal momentum distribution. We explore form factors by exclusive scattering of high energy leptons with the nucleus or focusing on elastic channels in our analysis; we explore structure functions by inclusive scattering with the nucleus. When exploring the electromagnetic structure of the neutron, 3He is an ideal target for quasi-elastic scattering because the proton-proton wave-function is dominated by the spin-zero, S-state (by approximately 90%). Thus, scattering leptons from a polarized 3He target is a reasonable approximation to scattering from a polarized, free neutron.

My talk will focus on the polarizable 3He targets used in two experiments at Jefferson National Laboratory: one experiment explores the neutron electric form factor, GE­n, and the other experiment explores the neutron structure function, A1n. I will discuss my work in the filling and characterization of these targets as well as optimizing these targets for future experiments at higher beam energies.

ics Nuclear
Tuesday, March 26, 2019
3:30 PM
Physics Building, Room 204
Adam Zec [Host: Kent Paschke]
University of Virginia - Physics
"Simulations and Polarimetry for the PREX-II and CREX Experiments"
ABSTRACT:

The PREX-II and CREX experiments are both parity-violating electron scattering experiments which seek to probe the weak form factor of the nuclei of 208Pb and 48Ca respectively by measuring an asymmetry between the scattering of left- and right-handed electrons. These experiments seek to constrain models of nuclear theory by measuring the radius of a “neutron skin” in neutron-rich nuclei. There are a number of experimental challenges associated with these very high luminosity, high precision measurements. I will discuss how we will meet these challenges in the upcoming 2019 runs of both experiments.

ics Special Joint Nuclear and High Energy Seminar


Thursday, February 28, 2019
2:00 PM
Physics Building, Room 204
Oleg Denisov [Host: Dustin Keller]
COMPASS experiment
"A New QCD Facility at the M2 beam line of the CERN SPS (COMPASS++/AMBER)"
ABSTRACT:

Possibility to use high intensity secondary beams at the SPS M2 beam
line in combination with the world’s largest polarized target, liquid hydrogen,
liquid deuterium and various nuclear targets create a unique opportunity
for universal experimental facility to study previously unexplored aspects
of meson and nucleon structure, QCD dynamics and hadron spectroscopy. 

High intensity hadron (pion dominated) beams already made COMPASS the
world leading facility for hadron spectroscopy and  hadron structure
study through Drell-Yan production of di-muon pairs. High intensity
muon beams, previously used for unique semi-inclusive and exclusive
hard scattering programs, make possible proton radius measurement in
muon-proton elastic scattering and further development of polarized
exclusive hard scattering program.
  
Upgrades of the M2 beam line resulting in high intensity RF-separated
anti-proton- and kaon-beams would greatly expand the horizon of experimental
possibilities at CERN: hadron spectroscopy with kaon beam, studies
of transverse momentum dependent quark structure for protons, pions and
kaons, precise studies of nuclear effects and for the first time measurements
of kaon quark—gluon substructure.

ics Nuclear
Tuesday, February 19, 2019
3:30 PM
Physics Building, Room 204
James Maxwell [Host: Kent Paschke]
Jefferson Lab
"Probing Polarized Nuclei to Explore the Structure of Matter"
ABSTRACT:

Since the failure of classical mechanics at subatomic scales, understanding the spin of fundamental particles has been central to the investigation of the most basic workings of matter. Beyond a key property for study, spin has become an indispensable instrument for experimental discovery in the form of polarized beam sources and scattering targets. As physicists have turned from the successful description of the weakly bound, perturbative regime of QCD toward unraveling the mysteries of confinement and the glue, ever-improving polarized tools are as crucial as ever. This talk will give an overview these tools, emphasizing solid polarized targets for leptonic probes of QCD, covering their operation, development and upcoming experimental use. With the promise of a nuclear physics facility for e-N collisions on the horizon, I will discuss a new technique to produce a polarized He3 beam source. Finally, a new search for exotic glue in the nucleus using polarized targets and sources will be introduced.

ics Special Nuclear Seminar


Thursday, February 7, 2019
3:30 PM
Physics Building, Room 204
Dustin Keller [Host: Kent Paschke]
University of Virginia
"UVA Solid State Polarized Target Program"
ABSTRACT:

The UVA solid polarized target group has been a hub for scattering experiment
polarized target research for the last 30 years.  Solid state polarized targets provide
high polarization and high density for many types of fixed targets employed by nuclear
labs worldwide.  Dynamic nuclear polarization and other RF techniques are
used to enhance the polarization of the cryogenically cooled solid
material to improve the figure of merit of the experiment.  An overview of
the technology and techniques is given with an emphasis on recent
developments.  Some future experiments are discussed providing examples of
implementation of this research which make it possible to access many spin-dependent
degrees of freedom used to test fundamental prediction of QCD.


 

ics Nuclear
Tuesday, May 1, 2018
3:30 PM
Physics Building, Room 204
John Matter [Host: Nilanga Liyanage]
UVA- Department of Physics
"The Search for Color Transparency at 12 GeV at JLab"
ABSTRACT:

Color Transparency (CT) refers to a prediction of QCD that at high momentum transfer Q^2, a system of quarks, each of which would normally interact very strongly with nuclear matter, could form a small color-neutral object whose compact transverse size would be maintained for some distance, passing through the nuclear medium undisturbed. A clear signature of CT would be a dramatic rise in nuclear transparency with increasing Q^2. The existence of CT would contradict traditional Glauber multiple scattering theory in its domain of validity, which predicts constant nuclear transparency. CT is also a prerequisite to the validity of QCD factorization theorems, which provide access to generalized parton distributions that contain information about the transverse and angular momenta carried by quarks in nucleons. The E12-06-107 experiment in JLab's Hall C will look for a signature of CT in electron-proton scattering with carbon-12 and liquid hydrogen targets. Data for Q^2 between 8 and 14 GeV^2 were taken in early 2018 in JLab's Hall C, a range over which nuclear transparency should differ appreciably from conventional Glauber calculations.

 

ics Nuclear
Tuesday, April 24, 2018
3:30 PM
Physics Building, Room 204
Sina Tafti [Host: Gordon Cates]
UVA - Department of Physics
"1. Toward Spin-Polarized Nuclear Fusion: MRI of Laser-Polarized He-3 Permeating Through Polymer-Shell Tokamak Pellets 2. A Novel Method of Defining Emphysema Index Using MRI of Laser-Polarized Noble Gases in the Lungs"
ABSTRACT:

I will share two applications of spin-polarized noble gas imaging using magnetic resonant imaging. To date, self-sustained fusion energy production has not been achieved since the energy spent in containing the plasma favorable for fusion reaction surpasses the energy outcome. Spin-polarized fusion (SPF) promises a 50% boost in fusion cross section between deuterium and tritium (or He-3). However, SPF has not been experimentally tested in a reactor for several logistical challenges related to delivery of polarized fuels to the plasma.

In collaboration with General Atomics and JLab, we propose to optimize and measure polarization survival of spin-polarized He-3 during permeation into polymer-shelled inertial-confinement fusion (ICF) pellets, a crucial step toward achieving SPF. Granted that adequate polarization survival into the pellets is achieved, the SPF reaction of D and 3He will be tested in the General Atomics D-III D Tokamak which would be the very first experimental demonstration of SPF in a fusion energy reactor.

CT has been the golden standard imaging technique to characterize and quantify emphysema, however, it exposes the body to ionizing radiation. An alternative image based method of characterizing emphysematous lung tissue is by having the patient inhale spin-polarized noble gas (He-3 or Xe-129) and image the gas inside the lungs. Since diffusion of the gas molecules inside the lungs are constrained by the microstructure of the lungs, how far gas molecules travel can tell us about regional tissue destruction due to emphysema. Here we introduce a novel method of defining emphysema index based on apparent diffusion coefficient maps acquired using a diffusion-weighted MRI pulse sequence.

ics Nuclear
Tuesday, April 17, 2018
3:30 PM
Physics Building, Room 204
Caryn Palatchi [Host: Kent Paschke]
UVA - Department of Physics
"Polarized Electron Source for the MOLLER Experiment"
ABSTRACT:

The MOLLER experiment at Jefferson Laboratory will be part of a new generation of ultra high precision electroweak experiments. It will measure the Moller (electron-electron scattering) parity-violating asymmetry, providing an unprecedented precision on the electroweak mixing angle. To achieve such small uncertainties, innovative techniques in the electron source are required to switch the beam helicity more quickly than previously achievable. A key technology is the Pockels cell in the laser optics of the polarized electron source. RTP crystals have been demonstrated to achieve almost an order of magnitude faster transition times than commonly used KD*P crystal cells and are promising for the future Moller Experiment. 

Nuclear Physics Seminars
Kent Paschke (Chair)

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