Bulletin of the American Physical Society
APS April Meeting 2020
Volume 65, Number 2
Saturday–Tuesday, April 18–21, 2020; Washington D.C.
Session B11: Few-Body Nuclear PhysicsOn Demand
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Sponsoring Units: DNP GFB Chair: Maxim Mai, George Washington University Room: Maryland A |
Saturday, April 18, 2020 10:45AM - 10:57AM |
B11.00001: $\omega$ photoproduction within a novel unitary isobar model Shahab Razavi, Kanzo Nakayama The $\omega$ photoproduction off proton is analyzed within a novel unitary isobar model constructed based on the recent work by Razavi and Nakayama [Phys. Rev. D 100, 114036], where the full complex phase structure of the meson-baryon as well as the meson photoproduction amplitudes have been exposed. In this model unitarity is preserved through the so-called generalized Watson's factor. Moreover, apart from the usual $u$ and $t$-channel Feynman diagrams, we include a generalized contact current in the driving potential in the background amplitude, which guarantees the local gauge invariance of the resulting full amplitude by satisfying the Ward-Takahashi identity. The analysis considers the currently available high-precision cross section as well as the nine independent spin observables data, especially from the CLAS Collaboration. [Preview Abstract] |
Saturday, April 18, 2020 10:57AM - 11:09AM |
B11.00002: A new comparison of the F2A/F2p and F2A/F2n structure function ratios Narbe Kalantarians, Holly Szumila-Vance, Cynthia Keppel Using electron scattering data from SLAC E139 and muon scattering data from NMC in the DIS region, we determine the F2A/F2p and F2A/F2n structure function ratios, spanning 0.3 lt xlt 0.8 and 1 lt Q2 lt 200 GeV/c This region is of particular relevance to studies of the EMC Effect. The structure of the free proton is well known from numerous experiments, but the free neutron structure function has remained difficult to access. Recently, the free neutron structure function has been extracted in a systematic study of the global data within a parton distribution function extraction framework and is available from the CTEQ-Jefferson Lab (CJ) Collaboration. In this talk, we leverage the recent global free neutron extraction to introduce a new method to study the EMC Effect in nuclei by re-examining existing data and by now determining the magnitude of the medium modifications to the free neutron and proton structure functions, independently. We further examine the nuclear effects in deuterium and their contribution to our interpretation of the EMC Effect. This talk will summarize the results of the mentioned ratios for the SLAC E139 nuclei using the F2n global data from the CJ Collaboration. [Preview Abstract] |
Saturday, April 18, 2020 11:09AM - 11:21AM Not Participating |
B11.00003: Nucleon Polarisabilities from Few-Nucleon Systems: An Update Harald W. Griesshammer Low-energy Compton scattering probes the nucleon's two-photon tesponse to electric and magnetic fields at fixed photon frequency and multipolarity. It tests the symmetries and strengths of the nteractions between constituents, and with photons. For convenience, this energy-dependent information is often compressed into the two scalar dipole polarisabilities $\alpha_{E1}$ and $\beta_{M1}$ at zero photon energy. These are fundamental quantities, and important for the proton charge radius puzzle and the Lamb shift of muonic hydrogen. Combined with emerging lattice QCD computations, they provide stringent tests for our understanding of hadron structure. This talk reports new results for elastic Compton scattering from the deuteron in Chiral Effective Field Theory with an explicit $\Delta(1232)$ degree of freedom ($\chi$EFT). These extend the previous formulation to one higher order in the chiral counting, reducing the residual theoretical uncertainties from about 5% to about 1%, and provide more accurate polarisability values. I also elaborate on promising extensions to heavier nuclei which take full advantage of the numerical power of modern few-nucleon methods. [Preview Abstract] |
Saturday, April 18, 2020 11:21AM - 11:33AM Not Participating |
B11.00004: Inelastic Compton Scattering on the Deuteron Junjie Liao Nucleon structure is a challenging and unsolved problem in Quantum Chromodynamics (QCD). Detailed information of it can be parameterized by Compton scattering in terms of two parameters: the electric (α) and magnetic (β) dipole polarizabilities. χEFT, a low energy approximation of QCD, has been successfully applied in analysis of elastic Compton scattering off protons and deuterons, and to determine α and β to a desired degree of accuracy. It is a reliable method to handle these channels as well as a wide variety of hadronic interactions, since it provides a consistent model-independent framework with controlled uncertainties. This work aims to extend the application of χEFT to describe inelastic Compton scattering on the deuteron, and extract nucleon scalar polarizabilities α and β for purpose of interpretation of data gathered by the High Intensity Gamma Source (HIγS). [Preview Abstract] |
Saturday, April 18, 2020 11:33AM - 11:45AM On Demand |
B11.00005: Efficient excited state preparation for linear response Chenyi Gu, Alessandro Roggero, Alessandro Baroni, Thomas Papenbrock, Joseph Carlson Quantum computing holds a huge potential in simulating the dynamics of quantum systems. We are interested in the preparation of excited states, which is a necessary step in studying quantum dynamics problems, and we describe two different strategies. The first strategy approximates the Hermitian excitation operator $O$ by $\sin(\gamma O)/\gamma$, valid for small $\gamma$, using the time evolution operator and one additional qubit. The second strategy performs the excitation operation in an exact way using the linear combination of unitary (LCU) algorithm. We apply these two strategies to a toy version of the nuclear $n(p,d)\gamma$ reaction. [Preview Abstract] |
Saturday, April 18, 2020 11:45AM - 11:57AM Not Participating |
B11.00006: Quantum Monte Carlo calculations of electron scattering from A=3 and 4 nuclei Lorenzo Andreoli, Saori Pastore, Stefano Gandolfi, Joseph Carlson In this talk, I will present ab initio Quantum Monte Carlo calculations for the scattering of electrons off $A=3,4$ nuclei, in the quasielastic regime. Adopting the Argonne $v_{18}$ realistic two-nucleon interaction, we use a propagation in imaginary-time to evaluate the short-time response of nuclei. This approach consistently accounts for two-body physics, both in the nucleon-nucleon interaction and the electromagnetic currents. It is also used to study scattering channels involving nucleons in back-to-back kinematics, for nn, pp and np pairs, currently tested at, e.g., JLab. I will present results for both longitudinal and transverse response functions as well as response densities. [Preview Abstract] |
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