Bulletin of the American Physical Society
86th Annual Meeting of the APS Southeastern Section
Volume 64, Number 19
Thursday–Saturday, November 7–9, 2019; Wrightsville Beach, North Carolina
Session H01: Puzzle of Proton Charge Radius |
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Chair: Ashot Gasparlan, North Carolina A&T State University Room: Holiday Inn Resort Causeway/Masonboro |
Saturday, November 9, 2019 8:00AM - 8:30AM |
H01.00001: Status of the MUSE Experiment at PSI Invited Speaker: Lin Li The MUon Scattering Experiment (MUSE) at Paul Scherrer Institute (PSI) has been developed to address the proton-radius puzzle. The experiment will measure elastic electron-proton and muon-proton scattering data with positively and negatively charged beams in a four-momentum-transfer range from 0.002 to 0.08 GeV$^2$. Each of the four sets of data will allow the extraction of the proton charge radius. In combination, the data test possible differences between the electron and muon interactions and additionally two-photon exchange effects. The status of the experiment will be discussed. [Preview Abstract] |
Saturday, November 9, 2019 8:30AM - 9:00AM |
H01.00002: Proton Radius from Jefferson Lab PRad Experiment Invited Speaker: Xinzhan Bai A new measurement of the proton charge radius was recently released by Jefferson lab PRad collaboration. The PRad experiment (E12-11-1061\footnote{Spokespersons: A.Gasparan(Contact), H. Gao, M. Khandaker, D. Dutta}) was performed at Jefferson Lab in Hall B to investigate the proton charge radius puzzle. This experiment was designed to measure electron-proton elastic scattering cross section in an unprecedented low region of momentum transfer squared ($Q^2 = 2\times10^{-4} -0.06 ~ (GeV/c)^2$), with sub-percent precision. PRad experiment utilized a non-magnetic calorimetric electron detection method using a pair of large GEM detectors with high spatial resolution, a hybrid calorimeter (HyCal) with high energy resolution, and a gas flow windowless target to reduce the background from target cell walls. To better control the systematic uncertainties, the e-p elastic scattering cross section was normalized to the well-know M\o ller scattering process, which was measured simultaneously within the similar kinematics and detector acceptance. In this talk, we will present the details of the experiment and the proton charge radius result. [Preview Abstract] |
Saturday, November 9, 2019 9:00AM - 9:30AM |
H01.00003: Deuterium Charge Radius Experiment (DRad) at Jefferson Lab Invited Speaker: Jingyi Zhou High precision muonic deuterium spectroscopic measurements found a significantly smaller (7$\sigma$) deuterium charge radius compared to the CODATA recommended value, creating the ``deuterium charge radius puzzle''. In order to investigate this, the DRad experiment (Jefferson Lab PR12-17-009) was proposed to measure the $e-d$ elastic scattering cross section in a very low momentum transfer squared region ($\rm{Q}^2 = 2\times10^{-4} - 5\times10^{-2}~\rm{(GeV/c)}^2$), with a sub-percent proposed precision. The designed setup of the experiment will be largely based on that of the PRad experiment (Jefferson Lab E12-11-106), with an addition of a low energy Si-based cylindrical recoil detector within the windowless gas flow target cell for the rejection of the quasi-elastic background, and a second layer Gas Electron Multiplier (GEM) detector to improve the tracking capability for a better beam-line background rejection and reductions of other systematic uncertainties. The absolute $e-d$ elastic scattering cross section will be normalized to that of the well-known M$\o$ller scattering process, which will be measured simultaneously within similar kinematics and detector acceptances. In this talk, we will present the design of the experimental setup and preliminary projected results. [Preview Abstract] |
Saturday, November 9, 2019 9:30AM - 10:00AM |
H01.00004: New Instrumentation for Future High Precision Proton and Deuteron Radius Experiments Invited Speaker: Kondo Gnanvo Recent results of from high precision measurements of deuteron rms charge radius using spectroscopy of muonic deuterium show \textasciitilde 7$\sigma $ discrepancy with the previously world-average CODATA values and \textasciitilde 3.5$\sigma $ smaller than with ordinary deuterium spectroscopy, adding a new ``\textit{deuteron charge radius puzzle}'' to the extensively discussed ``\textit{proton charge radius puzzle}'' in the nuclear physics community. We propose to conduct two high precision electron scattering cross section experiments on windowless hydrogen (PRad-II) and deuterium (DRad) targets to extract proton and deuteron charge radius at very low scattering angles. Both experiments will use an upgraded version of the experimental setup of the previous proton charge radius experiment (PRad) successfully conducted at JLab in 2016. In the present talk, after a brief introduction to the physics motivation of DRad and PRad-II experiments, we will present the PRad-II and DRad experimental setup with a focus on the new instrumentation. We will discuss the addition of a second tracking layer, based on the state-of-the-art Micro Pattern Gaseous Detector (MPGD) technologies in addition to the existing PRad GEM layer in order to improve vertex reconstruction of the scattered electrons. We will also introduce the new idea of silicon-based cylindrical proton recoil detector inside the target cell for the control of the inelastic electro-disintegration background process in the DRad experiment and for tagging the recoil proton to cleanly identify very forward angle ep events in the PRad-II case. Finally, we will describe the small angle calorimeter installed downstream to the main setup to achieve the very low Q$^{\mathrm{2}}$ values required by the two experiments. [Preview Abstract] |
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