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Meeting ID: 941 6160 2774

Passcode: 360588


Tuesday, June 7, 2022
3:30 PM
Online, Room via Zoom
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"Global extraction of quark unpolarized Transverse Momentum Distributions at N3LL"


Chiara Bissolotti , Argonne National Laboratory
[Host: Ishara Fernando]
ABSTRACT:

Transverse Momentum Distributions (TMDs) are three-dimensional maps of hadrons in momentum space and generalize the well-known concept of collinear Parton Distribution Functions (PDFs). TMDs are crucial in understanding the 3D spin and momentum structure of the nucleon and other hadrons, and information on their functional form can be obtained, for example, from Drell-Yan and Semi-Inclusive Deep Inelastic Scattering (SIDIS).

In this seminar I will discuss the state-of-the-art status of unpolarized TMD extractions, focusing on the results obtained by the Pavia group and in particular on the most recent global TMD extraction that reaches the perturbative accuracy of next-to-next-to-next leading log.

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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https://virginia.zoom.us/j/95913879831?pwd=VDY2ZmhENHo3STd4cWkydHUreURqdz09
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
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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
Online, Room via Zoom
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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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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.]