Search for Effects Beyond the Born Approximation in Polarization Transfer Observables in $\overrightarrow{e}p$ Elastic Scattering

Journal Article · Tue Mar 01 00:00:00 EST 2011 · Physical Review Letters

DOI:https://doi.org/10.1103/PhysRevLett.106.132501· OSTI ID:1015435

Meziane, M.; Brash, E. J.; Gilman, R.; Jones, M. K.; Luo, W.; Pentchev, L.; Perdrisat, C. F.; Puckett, A. J. R.; Punjabi, V.; Wesselmann, F. R.; Ahmidouch, A.; Albayrak, I.; Aniol, K. A.; Arrington, J.; Asaturyan, A.; Ates, O.; Baghdasaryan, H.; Benmokhtar, F.; Bertozzi, W.; Bimbot, L. ; Bosted, P.; Boeglin, W.; Butuceanu, C.; Carter, P.; Chernenko, S.; Christy, 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.; Goncharenko, Y.; Hafidi, K.; Hamilton, D.; Higinbotham, D. W.; Hinton, W.; Horn, T.; Hu, B.; Huang, J.; Huber, G. M. ; Jensen, E.; Kang, H.; Keppel, C.; Khandaker, M.; King, P.; Kirillov, D.; Kohl, M.; Kravtsov, V.; Kumbartzki, G.; Li, Y.; Mamyan, V.; Margaziotis, D. J.; Markowitz, P.; 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.; Nuruzzaman,; Nedev, S.; Piasetzky, E.; Pierce, W.; Piskunov, N. M.; Prok, Y.; Ransome, R. D.; Razin, D. S.; Reimer, P. E.; Reinhold, J.; Rondon, O.; Shabestari, M.; Shahinyan, A.; Shestermanov, K.; Širca, S.; Sitnik, I.; Smykov, L.; Smith, G.; Solovyev, L.; Solvignon, P.; Subedi, R.; Suleiman, R.; Tomasi-Gustafsson, E.; Vasiliev, A.; Vanderhaeghen, M.; Veilleux, M.; Wojtsekhowski, B. B.; Wood, S.; Ye, Z.; Zanevsky, Y.; Zhang, X.; Zhang, Y.; Zheng, X.; Zhu, L.

Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, $$G_{E}/G_{M}$$, obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange (TPEX) contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, we report measurements of polarization transfer observables in the elastic $$H(\vec{e},e'\vec{p})$$ reaction for three different beam energies at a fixed squared momentum transfer $Q^2 = 2.5$ GeV$^2$, spanning a wide range of the virtual photon polarization parameter, $$\epsilon$$. From these measured polarization observables, we have obtained separately the ratio $$R$$, which equals $$\mu_p G_{E}/G_{M}$$ in the Born approximation, and the longitudinal polarization transfer component $$P_\ell$$, with statistical and systematic uncertainties of $$\Delta R \approx \pm 0.01 \mbox{(stat)} \pm 0.013 \mbox{(syst)}$$ and $$\Delta P_\ell/P^{Born}_{\ell} \approx \pm 0.006 \mbox{(stat)}\pm 0.01 \mbox{(syst)}$$. The ratio $$R$$ is found to be independent of $$\epsilon$$ at the 1.5% level, while the $$\epsilon$$ dependence of $$P_\ell$$ shows an enhancement of $$(2.3 \pm 0.6) %$$ relative to the Born approximation at large $$\epsilon$$.

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Contributing Organization: GEp2γ Collaboration
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1015435
• Report Number(s): JLAB-PHY-10-1280; DOE/OR/23177-1541; arXiv:1012.0339; PRLTAO; TRN: US1102846
• Journal Information: Physical Review Letters, Vol. 106, Issue 13; ISSN 0031-9007
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
BORN APPROXIMATION
CROSS SECTIONS
ELASTIC SCATTERING
FORM FACTORS
MOMENTUM TRANSFER
PHOTONS
POLARIZATION
PROTONS