High-precision measurement of the proton elastic form factor ratio mu pGE/GM at low Q super(2)

• Published in: Physics letters. B Vol. 705; no. 1-2; pp. 59 - 64
• Main Authors: Zhan, X, Allada, K, Armstrong, D S, Arrington, J, Bertozzi, W, Boeglin, W, Chen, J-P, Chirapatpimol, K, Choi, S, Chudakov, E, Cisbani, E, Decowski, P, Dutta, C, Frullani, S, Fuchey, E, Garibaldi, F, Gilad, S, Gilman, R, Glister, J, Hafidi, K, Hahn, B, Hansen, J-O, Higinbotham, D W, Holmstrom, T, Holt, R J, Huang, J, Huber, G M, Itard, F, De Jager, CW, Jiang, X, Johnson, M, Katich, J, De Leo, R, LeRose, J J, Lindgren, R, Long, E, Margaziotis, D J, Beck, SMay-Tal, Meekins, D, Michaels, R, Moffit, B, Norum, B E, Olson, M, Piasetzky, E, Pomerantz, I, Protopopescu, D, Qian, X, Qiang, Y, Rakhman, A, Ransome, R D, Reimer, P E, Reinhold, J, Riordan, S, Ron, G, Saha, A, Sarty, A J, Sawatzky, B, Schulte, E C, Shabestari, M, Shahinyan, A, Shneor, R, Sirca, S, Solvignon, P, Sparveris, N F, Strauch, S, Subedi, R, Sulkosky, V, Vilardi, I, Wang, Y, Wojtsekhowski, B, Ye, Z, Zhang, Y
• Format: Journal Article
• Language: English
• Published: 03.11.2011
• Subjects: Charge; Deviation; Electric charge; Form factors; Hydrogen storage; Lamb; Unity
• ISSN: 0370-2693
• DOI: 10.1016/j.physletb.2011.10.002

We report a new, high-precision measurement of the proton elastic form factor ratio mu pGE/GM for the four-momentum transfer squared [inline image]. The measurement was performed at Jefferson Lab (JLab) in Hall A using recoil polarimetry. With a total uncertainty of approximately 1%, the new data clearly show that the deviation of the ratio mu pGE/GM from unity observed in previous polarization measurements at high Q super(2) continues down to the lowest Q super(2) value of this measurement. The updated global fit that includes the new results yields an electric (magnetic) form factor roughly 2% smaller (1% larger) than the previous global fit in this Q super(2) range. We obtain new extractions of the proton electric and magnetic radii, which are [inline image] and [inline image]. The charge radius is consistent with other recent extractions based on the electron-proton interaction, including the atomic hydrogen Lamb shift measurements, which suggests a missing correction in the comparison of measurements of the proton charge radius using electron probes and the recent extraction from the muonic hydrogen Lamb shift.