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Axel Schmidt (George Washington University)3/18/24, 9:00 AM
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Eric Voutier (Université Paris-Saclay - CNRS/IN2P3/IJCLab)3/18/24, 9:05 AM
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Joe Grames (JLab)3/18/24, 9:15 AM
In this presentation I will review the baseline design for Ce$^+$BAF and explain the R&D Plan for the next few years.
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Carlos Hernandez-Garcia (Thomas Jefferson National Accelerator Facility)3/18/24, 9:45 AM
A photogun to generate high intensity, high polarization electron beam with unprecedented kC lifetime is being developed at JLab. The proposed Ce+BAF polarized positron source will require > 1 milliampere CW with > 90% polarization electron beam at 120 MeV. To be practical for a user program, a photogun operating at 1 milliampere should deliver ~ 2 kC high polarization beam for a month without...
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Silviu Covrig Dusa (Jefferson Lab)3/18/24, 10:45 AM
I will give an update about the positron target effort at Jefferson Lab.
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Vaclav Kostroun (Xelera Research LLC)3/18/24, 11:15 AM
The very large power in electron beams needed to generate positrons and the accompanying enormous power densities preclude solid targets unless some complicated means of heat removal is implemented (e.g., cooled high-speed target rotation). A promising alternative is to use a windowless target and a liquid metal converter. Two liquid metals that have desirable properties for such a converter...
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Andriy Ushakov (JLab)3/18/24, 11:45 AM
The concept of generation and capture of polarized positron beams for the CEBAF upgrade is presented. In order to provide the highly polarized positron beam and the high current low polarized positron beam for nuclear physics experiments, the positron source requires a flexible capture system with an adjustable energy selection band. The simulation results of the positron beam generation in a...
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Amy Sy (Jefferson Lab)3/18/24, 2:00 PM
Degraded electron beams are electron beams with enlarged emittance due to multiple scattering in thin targets. This talk describes the effort to generate degraded electron beams in CEBAF to measure the machine acceptance and better understand the transport of large phase space beams, with first measurements expected later this year. We will also discuss the potential use of degraded electron...
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Raffaella De Vita (Jefferson Lab)3/18/24, 2:30 PM
Simulations of beam particle interaction in the target have been used to estimate the background affecting the experiment, optimize the detector configuration, and determine the maximum acceptable luminosity. Lessons learned from CLAS12 background simulation studies will be discussed.
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Juan Sebastian Alvarado (IJCLab)3/18/24, 3:00 PM
Deeply Virtual Compton Scattering (DVCS) is a privileged channel to study the structure of the nucleon as their experimental observables let us access information about Generalized Parton Distributions (GPDs). In general, the identification of DVCS events relies on the detection of only two final state particles as the kinematics of the third one can be reconstructed from conservation laws....
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David Mack (JLab)3/18/24, 4:00 PM
In Bhabha scattering, the virtual exchange of a dark boson would interfere with photon exchange to produce amplitude level effects in the yield and polarized-beam asymmetries. I will overview such resonant effects in half a dozen Bhabha scattering observables, then summarize which few may be appropriate for proposals that would still be competitive a decade from now.
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Xuangong Wang (University of Adelaide)3/18/24, 4:30 PM
We investigate the corrections to the beam asymmetries in parity-violating electron scatterings arising from charge symmetry violation, strange quark, and charm quark distributions. Based on the parton distributions from the NNPDF Collaboration, these corrections could lead to $(1$-$2)\%$ uncertainties in the extraction of the weak couplings $g^{eq}_{AV}$ and $g^{eq}_{VA}$, and as large as...
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Jan Bernauer (Stony Brook University / RBRC)3/18/24, 5:00 PM
The extraction of form factors, radii and related quantities have been
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an important focus of research in the last decades. The research
intensity has increased with the proton radius puzzle about a decade ago, and more recently with results on the gravitational form factors. But the field is much wider, including also weak form factors, other radii and a multitude of particles beyond the... -
Andrew Puckett (University of Connecticut)3/19/24, 9:00 AM
One of the principal motivations for accelerating positrons in CEBAF is to perform direct measurements of positron-proton elastic scattering observables, toward a conclusive resolution of the long-standing discrepancy between extractions of the proton electromagnetic form factor ratio based on cross section measurements and double-polarization observables, especially polarization transfer....
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Peter Blunden (University of Manitoba)3/19/24, 9:30 AM
In this talk I will discuss beam and target normal single-spin asymmetries in electron--proton elastic scattering. Our calculation of the imaginary part of two-photon exchange amplitudes considers resonance intermediate states of spin-parity 1/2± and 3/2± and mass W<1.8 GeV. The latest CLAS exclusive meson electroproduction data are used as input for the transition amplitudes from the proton...
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Christian Weiss (Jefferson Lab)3/19/24, 10:00 AM
Two-photon exchange gives rise to distinctive spin effects in electron/positron-nucleon scattering, which can be observed in inclusive or exclusive (elastic/inelastic) measurements. We report about recent progress in computing the transverse target single-spin asymmetry in ep scattering the resonance region, using systematic methods based on the 1/Nc expansion of QCD [1, 2]. We discuss the...
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Hervé Dutrieux (College of William & Mary)3/19/24, 11:00 AM
The connection of experimental data, notably in the DVCS channel, to generalized parton distributions (GPDs) faces a notoriously difficult deconvolution problem. I will present an impact study of the plausible impact of the positron beam on the extraction of Compton form factors, and discuss how this is a very useful data to consolidate the extraction of GPDs.
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Pierre Chatagnon (Jefferson Lab)3/19/24, 11:30 AM
For the past 25 years, many JLab experiments have been dedicated to determining the Generalized Parton Distributions (GPDs), especially by measuring Deeply Virtual Compton Scattering (DVCS) observables. The GPDs describe the correlation between longitudinal momentum fraction and transverse position of partons in the nucleons. GPDs also give access to the Gravitational Form Factors (GFFs)...
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Wally Melnitchouk (Jefferson Lab)3/19/24, 12:00 PM
We discuss opportunities with positron beams for the study of parton distribution functions of the nucleon in deep-inelastic scattering and related processes. Specific topics include the flavor separation of the unpolarized PDFs as well as the spin-dependent distributions.
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Dipangkar Dutta (Mississippi State University)3/20/24, 9:00 AM
Axial structure of the nucleon with positron capture at medium energies
A medium energy polarized positron beam would enable the extraction of the axial form factor $G_A(Q^2)$ of the nucleon and its four-momentum transfer square ($Q^2$) dependence, using the weak capture reaction in deuterium ($ \vec{e^+} + {^2H} \rightarrow 2p + \bar{\nu}_{e}$). A polarized positron beam with beam energies...
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Whitney Armstrong (Argonne National Laboratory)3/20/24, 9:30 AM
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Stinson Lee (George Washington University)3/20/24, 10:00 AM
Semi-inclusive meson production is used to access transverse momentum dependent distributions (TMD) or partons in a nucleon. We investigate a role of two-photon exchange (TPE) for this process. Such calculations require a model of nucleon structure. At the first step, we perform separation of hard and soft photon exchange. Soft photon exchange is demonstrated to be model-independent due to a...
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Nicole d'Hose (IRFU, CEA, Université Paris-Saclay)3/20/24, 11:00 AM
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Michael Kohl (Hampton University)3/20/24, 11:30 AM
Inspired by the proton radius puzzle, the MUon Scattering Experiment (MUSE) at Paul Scherrer Institute (PSI) in Villigen, Switzerland, was introduced to provide new information by simultaneously measuring elastic scattering of electrons and muons, as well as positrons and antimuons from a liquid hydrogen target. MUSE aims to provide precise cross sections with extractions of the electric form...
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Cynthia Keppel (Jefferson Lab)3/20/24, 2:00 PM
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Douglas Higinbotham (Jefferson Lab)3/20/24, 2:45 PM
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Douglas Higinbotham (Jefferson Lab)3/20/24, 4:00 PM
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