학술논문
High Precision Measurement of the Proton Elastic Form Factor Ratio $\mu_pG_E/G_M$ at low $Q^2$
Document Type
Working Paper
Author
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, C. W.; Jiang, X.; Johnson, J.; Katich, J.; de Leo, R.; LeRose, J. J.; Lindgren, R.; Long, E.; Margaziotis, D. J.; Beck, S. May-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.; Sirca, S.; Solvignon, P.; Sparveris, N. F.; Strauch, S.; Subedi, R.; Sulkosky, V.; Vilardi, I.; Wang, Y.; Wojtsekhowski, B.; Ye, Z.; Zhang, Y.
Source
Phys. Lett. B 705 (2011) 59-64
Subject
Language
Abstract
We report a new, high-precision measurement of the proton elastic form factor ratio \mu_p G_E/G_M for the four-momentum transfer squared Q^2 = 0.3-0.7 (GeV/c)^2. 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_p G_E/G_M from unity observed in previous polarization measurements at high Q^2 continues down to the lowest Q^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^2 range. We obtain new extractions of the proton electric and magnetic radii, which are ^(1/2)=0.875+/-0.010 fm and ^(1/2)=0.867+/-0.020 fm. 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.
Comment: 12 pages, 3 figures
Comment: 12 pages, 3 figures