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 Nuclear Tuesday, April 18, 2017 3:30 PM Physics Building, Room 204 Xinzhan Bai [Host: Nilanga Liyanage] UVA- Physics Department "PRad experiment at Jefferson Lab" ABSTRACT:The proton charge radius is one of the most fundamental parameter in physics. Precise knowledge of its value is critically important in various physics field. Recent high precision measurement of proton radius using the spectroscopy method of muonic hydrogen atom demonstrated a much smaller value, which is more than 5 standard deviations away from the widely accepted CODATA value. This fact triggered the well known “proton charge radius puzzle”.  In order to investigate this puzzle, the PRad experiment was performed in 2016 at Jefferson Lab in Hall B. This experiment aims to extract the electric form factor in an unprecedented small four-momentum transfer squared region, from  $$2 \times 10^{-4}$$ to $$10^{-2} (GeV/C^2)$$, with sub-percent precision. The PRad experiment utilizes a pair of large area, high spatial resolution GEM detectors, and a non-magnetic calorimeter (HyCal). PRad experiment has superior ways to control systematic errors, the e-p elastic scattering cross-section will be normalized to the well known moller scattering process, which is simultaneously measured with similar kinematics and the same appratus, this greatly reduces the uncertainties from luminosity, detector efficiency and acceptance, etc; and PRad covers a large $$Q^2$$ range in one experimental setting. With the data in low $$Q^2$$ region, we hope to reach sub-percent precision and model independent extraction of proton charge radius. In this talk we will present the detailed experimental method and setup, and the current data analysis status.