Bulletin of the American Physical Society
APS April Meeting 2020
Volume 65, Number 2
Saturday–Tuesday, April 18–21, 2020; Washington D.C.
Session L12: MiniSymposium: Nuclear FemtographyFocus Live

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Chair: Latifa Elouadrhiri, Jefferson Lab Room: Maryland B 
Sunday, April 19, 2020 3:30PM  3:42PM Live 
L12.00001: The FrameIndependent Spatial Coordinate $\tilde{z}$: Implications for LightFront Wave Functions, Deep Inelastic Scattering, LightFront Holography, and Lattice QCD Calculations Gerald A. Miller, Stanley J. Brodsky A general procedure for obtaining frameindependent, threedimensional lightfront coordinatespace wave functions is introduced. The third spatial coordinate, $\tilde{z}$ , is the conjugate to the lightfront momentum coordinate $x={k^+\over P^+}$ which appears in parton distributions. These lightfront wave functions are used to derive a general expression for the quark distribution function of hadrons as an integral over the spatial separation $s= \tilde{z} \tilde{z'}$, the frameindependent longitudinal distance (the Ioffe time) between virtualphoton absorption and emission in the forward virtual photonhadron Compton scattering amplitude. The integrand, $g(s,x)$ of the quark distribution contains a factor of $\cos{s x}$ which remains significant for very large values of $s$ at small $x$, thus demonstrating that the spatial extent of a proton in the longitudinal direction can be very large  a key feature of the Ioffe time. Specific examples using models derived from lightfront holographic QCD exhibit a large extent in $\tilde{z}$. [Preview Abstract] 
Sunday, April 19, 2020 3:42PM  3:54PM Live 
L12.00002: Extraction of Compton Form Factors from Deeply Virtual Exclusive Reactions Brandon Kriesten, Simonetta Liuti Imaging the 3D partonic structure of the nucleon is a fundamental goal of every major nuclear experimental program, such as the Electron Ion Collider (EIC).~ Ji first proposed Deeply Virtual Compton Scattering (DVCS) as a probe for understanding the spatial distribution of the partons by fourier transform of the exchanged momentum transfer between the initial and final proton. The extraction of observables from deeply virtual exclusive reactions in a clear and concise formalism was a necessity. We recently presented a completely covariant description of the DVCS process that can be extended to any kinematics, either fixed target or collider. In our helicity formalism, we extract observables such that the dependence on Q\textasciicircum 2 is clear. Using a generalization of the Rosenbluth method, we present an extraction of Compton Form Factors from current JLab DVCS data. With our formalism and pseudodata of an EIC, we hope to show predictions of what such a machine will do for our understanding of the physical properties of the proton. [Preview Abstract] 
Sunday, April 19, 2020 3:54PM  4:06PM Live 
L12.00003: The Generalized Polarizabilities of the proton HAMZA ATAC, Nikolaos Sparveris, Michael Paolone, Ruonan Li The Generalized Polarizabilities (GPs) are fundamental quantities of the nucleon and they are essential for a complete understanding of the nucleon structure. The GPs can be explored through measurement of the Virtual Compton Scattering reaction. Similar to how the elastic form factors describe the charge and magnetization distributions, GPs give access to the polarization densities inside the nucleon. Recent results from JLab and MAMI and future prospects will be discussed in this talk. [Preview Abstract] 
Sunday, April 19, 2020 4:06PM  4:42PM Live 
L12.00004: Challenges and Opportunities in Nucleon and Nuclear Femtography Invited Speaker: Charles Hyde Deeply virtual exclusive scattering (DVES) offers the exciting possibility of imaging the spatial distributions of quarks and gluons in the nucleon and in nuclei, referred to as Nuclear Femtography. These processes are studied via the reactions $ l +{}^Z\!A \to l + M + {}^{Z'}\!A,$ where $l$ denotes an electron or muon, $^Z\!A$ denotes a target nucleon or nucleus, and $M$ is a final state meson or gammaray. The CenterofMass frame of the exchanged virtual photon and the target define a preferred longitudinal axis. In high energy scattering, the lepton kinematics define the lightcone momentum transfer to the struct parton, and the net transverse momentum transfer to the target is Fourierconjugate to the parton's spatial coordinate. The longitudinalmomentum and transversespatial distribution of partons is dependent upon their spin polarization. These degrees of freedom are accessible with polarized leptons and polarized targets (beams, or fixed). I will review the experimental requirements and prospects for nuclear femtography , including the past programs at HERA and HERMES, the ongoing programs at Jefferson Lab and COMPASS, and the proposed Electron Ion Collider (EIC). [Preview Abstract] 
Sunday, April 19, 2020 4:42PM  4:54PM 
L12.00005: Transverse distributions of the pion cloud of the proton Mary Alberg, Ethan Purcell, Enrique Sanchez, MacQuarrie Thomson The pion cloud of a proton is generated by its fluctuations into pion/baryon pairs. For fastmoving protons, this cloud is contracted into a disk transverse to the proton's longitudinal momentum. We construct a twobody light cone wave function $\psi (y, k_\perp)$ to represent a fluctuation in which a pion has longitudinal momentum fraction $y$ and transverse momentum $k_\perp$. We then use a 2D Bessel transform to calculate the transverse spatial probability distribution $\rho_\pi(y,b) $ with $b$ the transverse position coordinate. We compare our results to the expected spatial extent of the cloud, $\sim 1/m_\pi$, and to other theoretical transverse spatial distributions. [Preview Abstract] 
Sunday, April 19, 2020 4:54PM  5:06PM Not Participating 
L12.00006: Exclusive pion electroproduction at Hall A Jefferson Lab Bishnu Karki Generalized Parton Distributions (GPDs) provide simultaneous spatial and momentum distribution of quarks and gluons inside the nucleons. GPDs can be accessed experimentally through hard exclusive processes like Deeply Virtual Compton Scattering (DVCS) or Deeply Virtual Meson Production (DVMP). Experiment E1206114 completed its data taking at the end of 2016 in Hall A at JLab. Main goal of this experiment is to measure the DVCS and exclusive π 0 electroproduction crosssections at various Q2 for three Bjorkenx in valence regime. These result will provide stringent test of QCD factorization in hard exclusive processes over a wide range of Q2 achieved with upgraded CEBAF to 12 GeV. I will show the most recent results for exclusive π 0 electroproduction at high Bjorkenx(0.60). [Preview Abstract] 
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