Nuclear Physics Seminars

Nuclear
Tuesday, May 17, 2022
3:30 PM
https://virginia.zoom.us/j/7615450175, Room via Zoom
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"Extraction of Compton Form Factors from DVCS experimental data"


Liliet Calero , UVA - Department of Physics
ABSTRACT:

Over the last 20 years, there has been intense experimental activity dedicated to the measurement of observables to help build a 3D description of the nucleon. Generalized parton distributions (GPDs) describe complementary aspects of the structure of hadrons, providing qualitative and quantitative information about the partonic structure and dynamics such as orbital angular momentum. The formulations of the Deeply Virtual Compton Scattering (DVCS) cross-section are parametrized in terms of Compton Form Factors (CFFs) which are convolutions of GPDs with coefficient functions computed from perturbative QCD. The CFFs are extracted from DVCS experimental data taken at Jefferson Lab, including the most recent Hall A data. The analysis consists of a local fitting technique where the CFFs, ReH, ReE, and ReHtilde are determined independently in each kinematic bin for the unpolarized beam-target configuration at twist-2 approximation using the formalism developed by A.V. Belitsky, D. Müller, and A. Kirchner (BKM02 and BKM10). Significant systematic studies were done to optimize the local fitting procedure. The resulting CFFs are then used to train and regularize the neural network to obtain a global behavior of the CFFs with minimal model dependency. This procedure is tested and systematically studied using pseudo data generated with kinematics mimicking the experimental data.

Nuclear
Tuesday, May 10, 2022
3:30 PM
PLSB, Room 030
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ABSTRACT:

The SpinQuest experiment (E1039) is a transversely polarized fixed target experiment at Fermi National Accelerator Laboratory designed to measure the sea-quark Sivers functions via the Drell-Yan process and the gluon Sivers function via the J/$\psi$ process. An unpolarized beam of 120-GeV protons will interact with a transversely polarized proton or deuteron target which will produce Drell-Yan and J/$psi$ dimuon events. Those muons will be detected in the spectrometer which allows for the extraction of the single-spin transverse asymmetry. Fast online monitoring is necessary to scan the quality of the incoming data and the general health of the experiment. Machine learning techniques can be used to speed the reconstruction of dimuon events on a spill-by-spill basis, and monitor the measured asymmetry over a longer period of time. Additionally, slow controls information can be integrated, allowing for automation of diagnostics and quality checks during the experiment, potentially reducing the overall systematic error of the experiment.

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Meeting ID: 959 1387 9831      Password: 981282

Tuesday, April 5, 2022
3:30 PM
Physics Building/Online, Room 313/Zoom
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ABSTRACT:

The Super BigBite Spectrometer (SBS) physics program at Jefferson Lab provides a large acceptance apparatus to precisely measure the proton and neutron form factors. The neutron electromagnetic form factors, \(G_E^n\) and \(G_M^n\), give important insights into the nucleon structure. The GMn experiment took place in fall of 2021, measuring \(G_M^n\) by colliding electrons on a liquid deuterium target, and extended the \(Q^2\) coverage from 5.0 to 13.6 GeV\(^2\). The GEn-II experiment will take place in August 2022, measuring \(G_E^n\) by colliding a polarized electron beam with a polarized \(^3\)He target, will extend the \(Q^2\) coverage from 3.5 to 10.2 GeV\(^2\). In both experiments Gas Electron Multiplier (GEM) based trackers will precisely measure the scattered electrons. GEM detectors are capable of rates higher than 500 kHz/cm\(^2\) with position resolutions of 70 \(\mu\)m. The proper running of these detectors is critical to the success of the SBS experiments. At our highest \(Q^2\) point we expect to be able to calculate the form factor ratio with an accuracy better than \(\Delta (G_E^n/G_M^n) = 0.20\), which corresponds to \(\Delta G_E^n = 3 \times 10^{-4}\) with accurate measurements of \(G_M^n\). This would greatly increase our understanding of the neutron in a region where no data is available.

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Tuesday, March 29, 2022
3:30 PM
Online, Room via Zoom
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"Nuclear or Human Physics?"


Paul Guaye , Facility for Rare Isotope Beams (FRIB) at Michigan State University
[Host: Prof. Kent Paschke]
ABSTRACT:

Nuclear physics is a fascinating field that allows to probe the interactions between nucleons inside the nucleus using fundamental particles such as the electron or much larger and heavier objects like ions as magnifying glasses, allowing us to extract information about the how, why and what is happening inside nuclei. Yet, scientific discoveries have historically been rooted in the desire for some to take on a quest to tackle the unknown, often with relentless commitments and efforts, and sometimes bold actions that have proven to unravel new pathways. This talk will provide some brief review on the role and successes of (basic and applied) nuclear physics as they pertain to my journey in becoming a nuclear physicist, as well as establishing bridges to under-represented groups.

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Tuesday, March 15, 2022
3:30 PM
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"Lattice QCD and TMDPDF evolution "


Michael Wagman , Fermilab
[Host: Prof. Dustin Keller]
ABSTRACT:

Lattice QCD can provide nonperturbative information about the three-dimensional structure of hadrons including TMDPDFs and their evolution. I will present recent exploratory lattice QCD calculations of the Collins-Soper kernel describing the rapidity evolution of quark TMDPDFs. I will also discuss the outlook for achieving lattice QCD predictions of the Collins-Soper kernel, and eventually complete lattice QCD predictions of TMDPDFs, with controlled systematic uncertainties and phenomenologically relevant precision.

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Meeting ID: 983 9819 1458  Passcode: 088847

Tuesday, March 1, 2022
3:30 PM
Zoom and in-person, Room Online / Physics Room 204
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"Towards a unified framework for the description of neutrino-nucleus interactions"


Professor Omar Benhar , INFN and Universita`
[Host: Prof. Donal Day]
ABSTRACT:

I will outline the main problems involved in the interpretation of the flux-averaged neutrino-nucleus cross sections--the understanding of which is critical for the determination of neutrino oscillation parameters--and argue that the theoretical approach based on factorisation provides a unified framework, allowing to take into acount all relevant reaction mechanisms in a consistent fashion.

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Tuesday, November 16, 2021
3:30 PM
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"Transverse spin asymmetries in J/psi production at COMPASS"


Jan Matousek , Charles University
[Host: Dustin Keller]
ABSTRACT:

Transverse spin asymmetries that are observed in hadron production in DIS can be explained in the transverse-momentum-dependent (TMD) PDF approach as arising from correlations between the spin and the intrinsic transverse momentum of quarks and the spin of the parent nucleon.

These correlations should give rise to transverse spin asymmetries for example in the production of Drell-Yan muon pairs in the scattering of pi- off transversely polarized protons. The same effect could appear in J/psi production, though the magnitude depends on the production mechanism. COMPASS has collected data with pi- beam and transversely polarized NH3 target and the analysis of the J/psi production is in progress. The production of J/psi in muon-proton scattering on the other hand can proceed via the photon-gluon fusion process, gamma* g -> c cbar. Measurement of this process thus allows to access the gluon TMD PDFs. COMPASS has measured this process with transversely polarized proton target and the results will be presented.

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Meeting ID: 956 6888 8640        Passcode: 232075

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.

VIDEO:
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Tuesday, May 25, 2021
3:30 PM
Online, Room via Zoom
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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
Online, Room via Zoom
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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
Online, Room via Zoom
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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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Meeting ID: 247 041 6971
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Tuesday, April 20, 2021
4:00 PM
Online, Room Via Zoom
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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
Online, Room viz Zoom
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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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Meeting ID: 399 393 6949
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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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Meeting ID: 399396949
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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.]