Nuclear Physics Seminars

Join Zoom Meeting: 
https://virginia.zoom.us/j/3993936949
Meeting ID: 399 393 6949

Tuesday, October 6, 2020
3:30 PM
Online, Room via Zoom
Note special room.

 Add to your calendar

"The Color Propagation Program in Hall B"


Dr. Michael H. Wood , Canisius College
[Host: Dustin Keller]
ABSTRACT:

Hadronization is the process of a liberated quark traversing the nuclear medium and its formation into a color neutral object.  This talk will focus on the color propagation experiments in Hall B to study the hadronization process.  Hall B is one of the four experimental areas at the Thomas Jefferson National Accelerator Facility (JLab). The original experiment used deep inelastic electron scattering to liberate a quark from a bound nucleon and the CLAS6 detector to count the multiplicity of produced hadrons and measure the transverse momentum broadening in order to understand the hadronization process.   The experiment ran during the CLAS6 period (1997-2011) before the JLab energy upgrade to 12 GeV.  For CLAS12, new reconstruction software, file format, and analysis framework have been developed.  With a grant from the DOE, my students and I developed software to convert the CLAS6 files into the CLAS12 format where I have used the new analysis framework to data mine the old data.  Preliminary color propagation results for protons and mesons will be presented.

Join Zoom Meeting: 
https://virginia.zoom.us/j/3993936949
Meeting ID: 3993936949

Tuesday, September 29, 2020
3:30 PM
Online, Room via Zoom
Note special room.

 Add to your calendar

ABSTRACT:
The proton is commonplace in the world but contains rich information about how matter is constructed by the strong force.  It is described by the parton picture, namely a system made of quarks, antiquarks and gluons, when it is observed in short range such as high-energy scattering.  The proton is the best object to investigate the dynamics of the strong force (i.e. QCD) since it is the simplest stable system bound by the strong force.  Particularly the antiquarks in the proton are of great interest because they are all dynamically created by the strong force.  They are thus sensitive to mechanisms beyond the simple quark model where the proton is composed of only three quarks.

SeaQuest is a fixed-target experiment using the 120-GeV proton beam at Fermilab.  It detects the Drell-Yan process in proton + proton and proton + deuteron scatterings; quark + antiquarks -> gamma^* -> mu^+ + mu^-. It primarily aims at measuring the flavor asymmetry of light antiquarks, namely the difference between antiup and antidown quarks in their distributions in the proton.  Several mechanisms that can induce this asymmetry have been theoretically proposed.

In this seminar, the physics motivation and the measurement principle of SeaQuest are explained.  Then the detector construction, data analysis and experimental results are presented.
Nuclear
Tuesday, February 11, 2020
3:30 PM
Physics Building, Room 204

 Add to your calendar

"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

 Add to your calendar

"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.

Show More...

To add a speaker, send an email to dmk9m@Virginia.EDU Include the seminar type (e.g. Nuclear Physics Seminars), date, name of the speaker, title of talk, and an abstract (if available). [Please send a copy of the email to phys-speakers@Virginia.EDU.]