Nuclear Physics Seminars History

Nuclear
Tuesday, February 11, 2020
3:30 PM
Physics Building, Room 204

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"The Lead Radius Experiment (PRex-II)"


Siyu Jian , University of Virginia - Department of Physics
[Host: Nilanga Liyanage]
ABSTRACT:

The RMS radius of the neutron distribution in a heavy nucleus RN provides an important test of nuclear theory. Furthermore RN is used in the determination of the density dependence of symmetry energy of neutron rich matter; this dependence is an important input in neutron star structure, heavy iron collision and atomic parity violation experiment calculations. In the past hadron scattering experiments with with pion, proton or anti-proton beams have been used to determine the neutron radii of heavy nuclei. However, these measurements suffer from uncertainties associated with the probe particle and the target nucleus. Electron scattering provides a model independent probe of nuclear radii. However, in electron scattering, the measurement of neutron distribution in a nucleus is much harder than the measurement of the proton distribution since the neutron is uncharged. Because the neutron weak charge is much large than that of the proton, PRex-II used the parity violating weak neutral interaction to probe the neutron distribution in the 208Pb nucleus, thus measuring the RMS neutron radius with high accuracy. The PRex-II experiment was performed from June to September 2019 in Jefferson lab experimental hall A using the High Resolution Spectrometer (HRS) pair. This seminar presents the details the PRex-II experiment as well as the preliminary results from HRS Optics calibration measurements and from the Gas Electron Multiplier (GEM) detectors used for obtaining high rate calibration data.
 

Nuclear
Tuesday, November 19, 2019
3:30 PM
Physics Building, Room 204

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"A new comparison of the F2A/F2p and F2A/F2n structure function ratios "


Narbe Kalantarian , Virginian Union University and Jefferson Lab
[Host: Simonetta Liuti]
ABSTRACT:

Using electron scattering data from SLAC E139 and muon scattering data from NMC in the DIS region, we determine the F2A/F2p and F2A/F2n structure function ratios, spanning 0.07 < xB < 0.7 and 1 < Q2 < 200 GeV/c2 and 0.006 < xB < 0.6 and 1 < Q2 < 55 GeV/c2, respectively. This region is of particular relevance to studies of EMC Effect. Assuming no Q2 dependence, we compare the structure function ratios for isoscalar nuclei and study non-isoscalar nuclei with the possibility to look for flavor dependence. This talk will present the results of the mentioned ratios for isoscalar nuclei using the new F2n global data from the CTEQ-JLab Collaboration.

Nuclear
Tuesday, September 10, 2019
3:30 PM
Physics Building, Room 204

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"The Muon g-2 Experiment at Fermilab"


Chris Hong , University of Virginia - Physics
[Host: Dinko Pocanic]
ABSTRACT:

The Muon g-2 experiment at Fermilab (E989) is addressing the known, but not yet understood incompleteness of the Standard Model (SM) theory by measuring the anomalous magnetic dipole moment, am, defined as (gm-2)/2. To be able to test the SM predictions, the experiment aims to reach the precision of 0.14 ppm. At Fermilab a intense proton beam is passed through a target where pions are produced; after a long delay virtually all pions decay into muons, which are stored in a muon storage ring. Evaluation of am requires the measurement of the muon spin precession frequency in the storage ring and, of the mean magnetic field the stored muons experience. I will introduce the experiment, its basic measurement techniques, and will focus on the magnetic field measurement, my thesis topic. The basic method relies on the free induction decay (FID) signals from NMR probes. Of particular interest is understanding and quantifying the possible interference between the electrostatic beam focusing quadrupoles and the FID signals in the 378 "fixed" NMR probes mounted all around the storage ring.

Nuclear
Tuesday, April 30, 2019
3:30 PM
Physics Building, Room 204

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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.

Special Nuclear Seminar


Thursday, April 25, 2019
3:30 PM
Physics Building, Room 204

 Slideshow (PDF)
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"Wigner Distributions"


Dr. Matthias Burkardt , New Mexico State University
[Host: Simonetta Liuti]
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.

SLIDESHOW:
Nuclear
Tuesday, April 23, 2019
3:30 PM
Physics Building, Room 204

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"Extraction of Observables from Deeply Virtual Electron Proton Scattering Experiments"


Brandon Kriesten , University of Virginia - Physics
[Host: Simonetta Liuti]
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.

Nuclear
Tuesday, April 16, 2019
3:30 PM
Physics Building, Room 204

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"The GDH Integrand of the Deuteron"


Matthew Roberts , University of Virginia - Physics
[Host: Blaine Norum]
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.

Nuclear
Tuesday, April 9, 2019
3:30 PM
Physics Building, Room 204

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"Source Studies and Polarimetry for Upcoming PREX-II and CREX Experiments "


Sachinthani Premathilake , University of Virginia - Physics
[Host: Kent Paschke]
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.

Nuclear
Tuesday, April 2, 2019
3:30 PM
Physics Building, Room 204

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"Probing neutron spin framework with polarized 3He"


Christopher Jantzi , University of Virginia - Physics
[Host: Gordon Cates]
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.

Nuclear
Tuesday, March 26, 2019
3:30 PM
Physics Building, Room 204

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"Simulations and Polarimetry for the PREX-II and CREX Experiments"


Adam Zec , University of Virginia - Physics
[Host: Kent Paschke]
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.

Special Joint Nuclear and High Energy Seminar


Thursday, February 28, 2019
2:00 PM
Physics Building, Room 204

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"A New QCD Facility at the M2 beam line of the CERN SPS (COMPASS++/AMBER)"


Oleg Denisov , COMPASS experiment
[Host: Dustin Keller]
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.

Nuclear
Tuesday, February 19, 2019
3:30 PM
Physics Building, Room 204

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"Probing Polarized Nuclei to Explore the Structure of Matter"


James Maxwell , Jefferson Lab
[Host: Kent Paschke]
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.

Special Nuclear Seminar


Thursday, February 7, 2019
3:30 PM
Physics Building, Room 204

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"UVA Solid State Polarized Target Program"


Dustin Keller , University of Virginia
[Host: Kent Paschke]
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.


 

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