Nuclear Physics Seminars

Joint Nuclear/HEP seminar


Wednesday, April 28, 2021
4:00 PM
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"Joint Nuclear/HEP seminar - Please see the HEP Schedule"


Manolis Kargiantoulakis , Fermilab
[Host: Craig Group and Dinko Pocanic]
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Tuesday, April 27, 2021
3:30 PM
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"Implementation of Polarization Effects in Geant4 Simulations of Neutron Elastic Scattering"


Thomas Krahulik , University of Virginia - Department of Physics
[Host: Blaine Norum]
ABSTRACT:

Geant4 is a software toolkit for simulating how particles interact with matter. It has a wide range of applications across diverse fields, with an emphasis on the simulation of physics experiments and events. It is an important tool in the preparation and analysis of many nuclear and particle physics experiments. The software is constantly evolving with the field, as a network of Geant4 working groups optimizes the structure of the code and the accuracy of the physics. In some aspects, the software is still a work in progress, leaving some gaps in its ability to simulate all experiments. One such piece of physics that is missing from the software is accounting for spin polarization in low energy neutron scattering. Spin-polarized neutrons scattered from nuclei will exhibit a left-right asymmetry in their scattering distribution. This behavior is not included in the Geant4 classes that handle low energy neutron scattering. Including the calculations for this left-right asymmetry is a key component of utilizing Geant4 for simulating polarized neutron experiments. In this talk, I will describe our work on implementing polarization effects for elastic neutron scattering in Geant4 and demonstrate some proof-of-concept results of the effect these modifications can have on simulations.

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Tuesday, April 20, 2021
4:00 PM
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ABSTRACT:
Electromagnetic form factors describe the spatial distribution of electric charge and magnetization of the nu-cleon. Quarks are the charge carriers in nucleons, and so, these form factors describe the spatial distributionof these quarks and act as direct probes to their principal dynamics. Electron scattering experiments are thetool of choice for measuring these nucleon form factors. Modern developments in high luminosity and po-larized electron beams, in combination with new polarized targets, recoil polarimeters, and large-acceptancedetectors, are advancing the strides in form factors measurements. The Super BigBite Spectrometer (SBS)at Jefferson Lab (JLab) is the next big step. The upcoming series of experiments on the SBS at JLab willmeasure nucleon form factors at Qmomentum-transfer values at upwards of 13.5 (GeV/c/)2, and will utilizemultiple measurement and experimental techniques. For instance, Gen and Gen-RP will both measure theform factor ratio of the neutron, but using two varying techniques (double polarization and recoil polarime-try, respectively). The primary components on the SBS to detect and track charged particles are gas electronmultiplier (GEM) detectors. Our research group at UVa has developed two configurations of GEM detectorsfor the SBS. One GEM configuration is currently being installed onto the SBS apparatus and the second isnearing its completion in our Detector R&D Lab at UVa.
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Tuesday, March 30, 2021
3:30 PM
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"Jlab SBS Program to Measure Nucleon Elastic Electromagnetic Form Factors at High Q2 and “Gas Electron Multiplier” Detectors"


Anuruddha Rathnayake , University of Virginia - Department of Physics
[Host: Nilanga Liyanage]
ABSTRACT:

In the fall of this year in September, the Jlab Hall-A SBS program is sched-uled to start running. The primary goal of the program is to measure elastic-electromagnetic form factors of the nucleon with high precision at high Q2 values. The knowledge of the electromagnetic form factors are essential for our understanding of the structure of the nucleon. The concept of the Hall-A SBS (Super Bigbite Spectrometer), which has a large solid angle acceptance ( 75 msr) and the capability to operate at high luminosity, relies on Gas Electron Multiplier (GEM) detectors for particle tracking. In this talk, I will talk about how the GEM detectors will be used in the SBS program, and the commissioning activities of the UVA-built GEM detectors that are underway at the Jefferson Lab, in order to make them ready for the upcoming experiments. Also, I will briefly talk about the Jlab-SBS program with a special focus on its very first experiment - GMn : precision measurement of the magnetic form factor of the neutron up to Q2 = 13.5 (GeV/c)2 using the ratio method.

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Tuesday, March 23, 2021
3:30 PM
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"Phenomenology of nucleon 3D structure"


Filippo Delcarro , University of Pavia
[Host: Dustin Keller]
ABSTRACT:

TMDs are fundamental objects in the study of three-dimensional structure of nucleons. However, due to their nonperturbative nature, they cannot be directly computed and have to be extracted from experimental measurements. In this talk we will present the formalism and methodology involved in this analysis and give an overview of the most recent results.

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Tuesday, February 23, 2021
3:30 PM
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"TMDs: a transverse look at hadrons "


Andrea Signori , University of Pavia
[Host: Dustin Keller]
ABSTRACT:

In this talk I will outline some fundamental properties of transverse-momentum-dependent distributions (TMDs), in particular their role in exploring the structure of hadrons in 3D momentum space. I will also focus on some open issues, and on the possibilities to deepen our understanding of hadron structure and hadronization by combining the potential of fixed-target and collider experiments.

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Meeting ID: 399 393 6949

Tuesday, October 6, 2020
3:30 PM
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"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.

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Tuesday, September 29, 2020
3:30 PM
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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

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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.

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