Polarization transfer observables in elastic electron-proton scattering at Q2=2.5, 5.2, 6.8, and 8.5 GeV2

Puckett, A. J. R. et al. (2017) Polarization transfer observables in elastic electron-proton scattering at Q2=2.5, 5.2, 6.8, and 8.5 GeV2. Physical Review C, 96(5), 055203. (doi: 10.1103/PhysRevC.96.055203)

Abstract

Purpose: The GEp-III and GEp-2γ experiments were carried out in Jefferson Laboratory’s (JLab’s) Hall C from 2007 to 2008, to extend the knowledge of Gp E/Gp M to the highest practically achievable Q2 given the maximum beam energy of 6 GeV and to search for effects beyond the Born approximation in polarization transfer observables of elastic ep scattering. This article provides an expanded description of the common experimental apparatus and data analysis procedures, and reports the results of a final reanalysis of the data from both experiments, including the previously unpublished results of the full-acceptance dataset of the GEp-2γ experiment. Methods: Polarization transfer observables in elastic ep → ep scattering were measured at central Q2 values of 2.5, 5.2, 6.8, and 8.54 GeV2 . At Q2 = 2.5 GeV2 , data were obtained for central values of the virtual photon polarization parameter of 0.149, 0.632, and 0.783. The Hall C High Momentum Spectrometer detected and measured the polarization of protons recoiling elastically from collisions of JLab’s polarized electron beam with a liquid hydrogen target. A large-acceptance electromagnetic calorimeter detected the elastically scattered electrons in coincidence to suppress inelastic backgrounds. Results: The final GEp-III data are largely unchanged relative to the originally published results. The statistical uncertainties of the final GEp-2γ data are significantly reduced at = 0.632 and 0.783 relative to the original publication. Conclusions: The final GEp-III results show that the decrease with Q2 of Gp E/Gp M continues to Q2 = 8.5 GeV2, but at a slowing rate relative to the approximately linear decrease observed in earlier Hall A measurements. At Q2 = 8.5 GeV2 , Gp E/Gp M remains positive but is consistent with zero. At Q2 = 2.5 GeV2 , Gp E/Gp M derived from the polarization component ratio R ∝ Pt/P shows no statistically significant dependence, as expected in the Born approximation. On the other hand, the ratio Pl/P Born l of the longitudinal polarization transfer component to its Born value shows an enhancement of roughly 1.7% at = 0.783 relative to = 0.149, with ≈ 2.2σ significance based on the total uncertainty, implying a similar effect in the transverse component Pt that cancels in the ratio R.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Hamilton, Dr David
• Authors: Puckett, A. J. R., Brash, E. J., Jones, M. K., Luo, W., Meziane, M., Pentchev, L., Perdrisat, C. F., Punjabi, V., Wesselmann, F. R., Afanasev, A., Ahmidouch, A., Albayrak, I., Aniol, K. A., Arrington, J., Asaturyan, A., Baghdasaryan, H., Benmokhtar, F., Bertozzi, W., Bimbot, L., Bosted, P., Boeglin, W., Butuceanu, C., Carter, P., Chernenko, S., Christy, M. E., Commisso, M., Cornejo, J. C., Covrig, S., Danagoulian, S., Daniel, A., Davidenko, A., Day, D., Dhamija, S., Dutta, D., Ent, R., Frullani, S., Fenker, H., Frlez, E., Garibaldi, F., Gaskell, D., Gilad, S., Gilman, R., Goncharenko, Y., Hafidi, K., Hamilton, D., Higinbotham, D. W., Hinton, W., Horn, T., Hu, B., Huang, J., Huber, G. M., Jensen, E., Keppel, C., Khandaker, M., King, P., Kirillov, D., Kohl, M., Kravtsov, V., Kumbartzki, G., Li, Y., Mamyan, V., Margaziotis, D. J., Marsh, A., Matulenko, Y., Maxwell, J., Mbianda, G., Meekins, D., Melnik, Y., Miller, J., Mkrtchyan, A., Mkrtchyan, H., Moffit, B., Moreno, O., Mulholland, J., Narayan, A., Nedev, S., Nuruzzaman, , Piasetzky, E., Pierce, W., Piskunov, N. M., Prok, Y., Ransome, R. D., Razin, D. S., Reimer, P., Reinhold, J., Rondon, O., Shabestari, M., Shahinyan, A., Shestermanov, K., Širca, S., Sitnik, I., Smykov, L., Smith, G., Solovyev, L., Solvignon, P., Subedi, R., Tomasi-Gustafsson, E., Vasiliev, A., Veilleux, M., Wojtsekhowski, B. B., Wood, S., Ye, Z., Zanevsky, Y., Zhang, X., Zhang, Y., Zheng, X., and Zhu, L.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Physical Review C
• Publisher: American Physical Society
• ISSN: 2469-9985
• ISSN (Online): 2469-9993
• Published Online: 06 November 2017
• Copyright Holders: Copyright © 2017 American Physical Society
• First Published: First published in Physical Review C 96(5):055203
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher