Nuclear Physics Seminars

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Tuesday, October 12, 2021
3:30 PM
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"Scattered Spectra from Non-linear Compton Effect"


Geoff Krafft , JLAB, Accelerator Division
[Host: Blaine Norum]
ABSTRACT:

Compton famously studied frequency shifts in the scattering of electromagnetic radiation in his Noble-prizewinning work. The so-called Compton effect provided one of the earliest experimental verifications of the existence of separate, individual photons in beams of electromagnetic radiation. Recently, prodded by the desire to construct intense narrowband sources of x-rays or gamma rays, photon sources based on the scattering of laser radiation from relativistic electron beams have been built and operated. Most present devices operate in regimes where linear (first order QED) calculations of the spectrum of the scattered radiation apply. In the future, however, when more intense lasers are available, non-linear Compton scattering obtains. A group at Old Dominion University has developed new methods allowing this more general case to be calculated precisely. After reviewing spectrum calculations in the context of some existing and contemplated Compton Sources, several new predictions involving non-linear Compton scattering will be presented. In particular, we have demonstrated through calculation that proposed performance enhancements in Compton sources by frequency chirping extend to the highest harmonics emitted from the source and are remarkably insensitive to being degraded by electron beam thermal effects.

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Tuesday, May 25, 2021
3:30 PM
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"N3LO extraction of the Sivers function from SIDIS, Drell-Yan, and W/Z boson production data"


Alexey Prokudin , Penn State University
[Host: Dustin Keller]
ABSTRACT:

I will talk about a global fit of the available polarized Semi-Inclusive Deep Inelastic Scattering (SIDIS), polarized pion-induced Drell-Yan (DY) and W/Z boson production data at N3LO and NNLO accuracy of the Transverse Momentum Dependent (TMD) evolution, and extraction of the Sivers function for u,d,s and and for sea quarks. The Qiu-Sterman function is determined in a model independent way via the operator product expansion from the extracted Sivers function. I will also show the study of the applicability region, the impact of the unpolarized distributions' uncertainties, the universality of the Sivers functions, positivity constraints, the significance of the sign-change relation, and provide the comparison with the existing extractions.

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]
VIDEO:
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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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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.]